# Using Mixing Valve on Tank to Maximize Buffer Use and Pellet Boiler Runtime



## velvetfoot (Jan 15, 2016)

Something that ticks me off is when the pellet boiler is running and one or no zones are on, the flow is to the buffer tank.  This means that very cool water is returning to the boiler and the protection valve comes into play, big time.  Meanwhile, the boiler, which modulates down to 30%, is cranking at 100% to satisfy the the tank.  

My goal is to only charge the tank with excess heat.  

I am thinking that if I have a mixing valve on the tank return and set it on the high side, say 170, water will only start flowing to the tank when it gets over 170. The pellet boiler water temperature is set manually, say 160, but will continue to run to 181 or so, modulating down until it shuts itself down.  I have it set up so that any time the boiler runs, it runs until it shuts itself down.

Anyway, in my plan, the boiler alone will be supplying the loads, modulating down to 30% as it goes past 160, and when the it reaches the tank mix valve temperature of 170 (or whatever), incremental amounts of cold water will be injected into the loop to keep it at 170.  Gradually tank temperature will increase until the boiler shuts down, unless the modulating boiler matches the load.

My big idea requires 4 check valves and a mixing valve.  I'm not sure it would work or if it'd be worth it.

Comments?


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## __dan (Jan 15, 2016)

No, No, No,

Without looking at the details, the factory wiring diagram for the Windhager which would be my first step...

Somewhere on the Windhager there are two terminals that when closed give the boiler a call for heat and tell it to fire. Opening those terminals and the boiler gets told to turn off and most likely goes through a programmed cycle shutdown procedure (burning off the remaining fuel, moving the remaining boiler hot water out to the tank / loads. I know where to start, confirming these assumption first, where the boiler gets the call for heat, and how the boiler shutdown proceeds when the call for heat is satisfied.

If the boiler call for heat is not presently tied to the indoor thermostats and DHW aquastat (you are saying the boiler runs when there is no call for heat) possibly there is a change you may make (your electrician makes) that may be simple.

Somewhere there is a call for heat and if it's not tied to your zone stats, the next place it would be is the buffer tank aquastat  (the buffer would be always max hot at the tank aquastat setting and the boiler runs even with no house load until the buffer tank aquastat is satisfied (this is what I read in your post).

The simple change would be to add a set / sets of contacts controlled by any load that opens the call for heat circuit when all loads are satisfied and closes the call for heat circuit when any load calls (load dry contacts in parallel).

I would check this first and if the call for heat is only the buffer tank aquastat, keeping it always hot, yes the change will result in a noticeable drop in pellets consumption.

I did not try to follow if the double checks would do anything, cannot say it's not obvious, but any plumbing change I would make would be a change to primary secondary loops with OAT reset of the injection pump and mixing down of the secondary distribution temp. If you have conventional baseboard that expect and need the higher boiler or primary loop water temp, this change would be expensive and not necessarily advised. If you had radiant heat loads, this change would be strongly advised and probably necessary for the system to work comfortably without overheating the living spaces.

Look at opening the call for heat circuit when there is no call for heat ...


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## velvetfoot (Jan 15, 2016)

Unless I misinterpret, I guess our general objectives seem to differ.

My objective is minimal start/stops.  Start/stopping is not efficient and increases wear.  To achieve this objective I use a buffer tank to absorb excess heat, provide heat for some while without re-starting and a head start while starting, and provide dhw.

Your objective seems to be to eliminate the buffer tank and its standby losses completely, providing heat to zone and dhw loads directly, at low temperatures. I guess this would be nice, but I don't think practical for my loads


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## __dan (Jan 15, 2016)

No, same objective different method.

Scenario 1. Make change

No call for heat at the zones opens the boiler call for heat terminals at the Windhager. The boiler continues to run in a programmed shutdown cycle where remaining fuels in the fuel chamber is cleanly burned off and remaining boiler heat is transferred out to the loads, the boiler circ and the burner firing, two independent variables.

Scenario 1 the boiler burns its remaining shutdown energy and deposits it into the buffer tank with the loads off. The buffer tank is still cooler and can absorb the remaining heat usefully by raising its temp and lowering the boiler's.

Scenario 2. Current

No call for heat, the boiler continues to fire as long as the buffer tank aquastat is closed and it may be set high. 175 or 180. The buffer tank aquastat opens at 180 and dumps the boiler call for heat circuit. The boiler continues to run while it burns clean the remaining chamber fuel and dumps the remaining hot water out to the loads.

But now the loads are off and the buffer tank is at 180. It cannot store any remaining 180 boiler water, only boiler water above that temp, which will be created as the boiler continues to run after receiving the shutdown signal.

So the boiler has run longer every cycle but the heat produced has only gone up the stack or to standby losses, with very little of the scavengeable off cycle energy quantity being stored or used.


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## velvetfoot (Jan 15, 2016)

__dan said:


> boiler continues to fire as long as the buffer tank aquastat is closed


No, once the boiler fires based on a buffer tank aquastat, the boiler is latched and continues to fire until its internal control turns itself off, gracefully, with a 13 minute burnout pump run, discharging its heat to the buffer.

I am trying extract only EXCESS heat from the boiler, while extending its runtime.


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## __dan (Jan 16, 2016)

If I recall the buffer tank also has the DHW coil in it, the Tarm USA Energy Tank? Then for DHW you would want the buffer tank hot all the time and the thing to look at is the tank aquastat setpoint, lowering that. The tank aquastat gives the boiler fire / shutdown signal. The burner and boiler circ each independently have there own shutdown sequence, continuing to run for a few more minutes purging heat / flue gas.


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## velvetfoot (Jan 16, 2016)

__dan said:


> If I recall the buffer tank also has the DHW coil in it, the Tarm USA Energy Tank?


Yes.



__dan said:


> Then for DHW you would want the buffer tank hot all the time and the thing to look at is the tank aquastat setpoint, lowering that.


Yes.  I try to get away with as cool a launch temperature as possible to stretch out the buffer tank and still provide enough dhw while the boiler is warming up.  I also turn off the zones if the top of tank temperature gets too low-sort of priority.



__dan said:


> The tank aquastat gives the boiler fire / shutdown signal.


The tank give the boiler fire signal.  Shutdown signal is internal to the boiler.  I want to stretch out run times.




__dan said:


> The burner and boiler circ each independently have there own shutdown sequence, continuing to run for a few more minutes purging heat / flue gas.


Right.

Again, my goal in this thought exercise is to stretch out run times of the boiler, using the buffer to store ONLY minimal excess heat produced by the boiler.


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## Kristen (Jan 17, 2016)

Just curious: why not charge Buffer fully? Is this because you are burning pellets (in this scenario) rather than, more commonly, logs? so you want to conserve what is, presumably, a more expensive fuel and is probably being used because you are away / not able to load the Log boiler? (But I'm guessing !!)

Here I aim to charge the buffer fully on each burn, and to have the boiler go out just as the buffer is fully charged.  To achieve that I dumped excess heat into the house (if the buffer will be charged before boiler has finished its burn AND house thermostat is already satisfied). but we only burn logs ... I'm considering how we might add a second, smaller, boiler for "when we are away" but we don't have main's gas and adding a tank for Gas or Oil would be a huge job - it would have to be sited far from the house, dig up drive to lay pipe, etc.


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## velvetfoot (Jan 17, 2016)

Kristen said:


> Just curious: why not charge Buffer fully?


That is indeed my aim, but not at 100% power-more like 30%.  (The pellet boiler modulates down to 30%.) Currently, if one or all of the zones are not operating, the tank is being charged at 100% power and, to begin with, a fairly long time at a little more than than the return temperature of 130F provided by the boiler protection valve, and the resultant lower flow to the zones.  If I recirculate around the tank with a mixing valve, I can get high temperature faster because there is no water going to the tank-just to the load.  When the boiler temperature gets to a certain point, it starts modulating down.  It would be after that point that I would begin to open flow to the tank.  It would be slow, so that the return temperature wouldn't change drastically, and the tank would charge slowly, only with excess heat, and the pellet boiler operating at 30%.  Unless there is more big load demand: then the boiler temperature would drop and flow to the tank would be cut off, boiler could modulate up to match the load, until things get hot again, and then flow is again diverted to the tank.

There are big difference between your setup, and all the other the wood boiler people, is that the pellet boiler is continuously fed with fuel and is not batch burn, can modulate to a fairly high degree, and that your storage is huge compared to mine.  For 'you guys', it's mostly a matter of managing heat flow from the large tank, where I do have a small 109 gal tank, I also have to coordinate the pellet boiler.  Actually, it could be looked at that the tank is coordinated with the pellet boiler, which is I guess where I'm at.

Oh, and my oil tank is in the basement.


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## maple1 (Jan 17, 2016)

*I'm considering how we might add a second, smaller, boiler for "when we are away" but we don't have main's gas and adding a tank for Gas or Oil would be a huge job - it would have to be sited far from the house, dig up drive to lay pipe, etc.*

My solution was an electric boiler. Takes up next to no space, no chimneys or fuel supply piping needed. It does need a hefty power supply - think mine is on a 100a. breaker. But mine is oversized a bit at 18kw - I could get by with a 12kw, which could be fed by a 60a breaker.

Easy & cheap to install - but expensive to run. So might not be the best solution if it will be needed frequently. Ours is typically used only 2 days a year. It feels very nice to not have an oil tank in the house anymore.


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## Kristen (Jan 17, 2016)

velvetfoot said:


> That is indeed my aim, but not at 100% power



Thanks, I've got it now - I think .  Priority is for heat to the radiators; once the return temperature from them is approaching that when the boiler will modulate then start mixing "cold" water from the buffer. This keeps the boiler at best-temperature for longest and, presumably, means that the boiler is burning for the length of time that you want / need the radiators to be hot (or, failing that, a "decently long time") which will be more efficient than stop/start cycles.  As you rightly say, with a large buffer things change; as soon as the top of my buffer is at a reasonable temperature I can heat the house ... its then many hours until the buffer is fully hot, so my boiler is running efficiently whether I'm heating the house as well, or not (up until the point where the buffer is fully charged, but the boiler still has logs that are not completely burnt).

I may have misremembered but I thought you had a twin-boiler which allowed burning either Pellets or Logs?



velvetfoot said:


> my oil tank is in the basement



No longer allowed in the UK. My tank used to be indoors too, we removed it when we put the log boiler in and I suspect if we had not then by now the oil delivery people would have, finally, told me they couldn't fill it any more. But that would have made for an easy standby oil boiler - I could have had a much lower kW boiler; the original boiler had to have enough kW to heat the water going around the radiator loop, whereas with my buffer tanks a smaller boiler could run 24/7 to get the tanks up to temperature, and the tanks would provide the "surge" power when the radiator circuit came on and all the water in the radiators and pipes was cold.



maple1 said:


> My solution was an electric boiler



I do have some immersion heaters in my storage tanks, but I hadn't considered them as a heat source, only a "limp along" if the boiler broke. Perhaps I should re-think that ...



maple1 said:


> mine is oversized a bit at 18kw



I have 2 x 18kW heaters in my tank. That is close to the total power that the house has available, so I would have to turn off all significant power consumption equipment when using them.  Actually I've never used them, as they were for emergencies only, perhaps I should try that. I can do a cost-benefit calculation of the capital cost of installing an additional boiler, to use only once-in-a-while, and the cost of electricity to run the immersions. I have Solar PV here, so it might be that I am currently exporting some electricity on sunny winter days which I could, instead, dump through my immersions.  My 60kW Log boiler runs for about 6 - 8 hours, so I assume that is 360 - 480 kWH.  If I use 2 x 18kW immersions presumably they will have to run for 10 - 13 hours.  Overnight our electricity is GBP 0.06 per kWH so I suppose that would be GBP 21 - 27 per day, but I don't know how to guesstimate how much Oil would be needed in a nice, shiny, new boiler to generate 360 - 480 kWH of heat? Then I could work out how many days it would take to get a payback on the electricity.


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## velvetfoot (Jan 17, 2016)

Kristen said:


> Thanks, I've got it now - I think


Yes, you have it.  Whether it really makes enough difference to make it worth all the piping changes is another matter entirely.


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## velvetfoot (Jan 17, 2016)

Kristen said:


> I may have misremembered but I thought you had a twin-boiler which allowed burning either Pellets or Logs?


Just pellets.  I do have a wood burning insert which heats a part of the house and isn't always on, requiring flexibility on the pellet boiler's part.


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## __dan (Jan 18, 2016)

velvetfoot said:


> Just pellets?  I do have a wood burning insert which heats a part of the house and isn't always on, requiring flexibility on the pellet boiler's part.



Buffer/Energy/DHW tank aquastat, lower the setpoint to the point where you still get sufficient hot water production. 140 to 150 F may work and if not, the problem will be insufficient DHW production under load.

Setback, during setback, open the buffer tank aquastat so it will not call for heat during setback but does call for heat when the setback house load calls. When the house load is satisfied it should dump the buffer tank call for heat in setback.

Setback, adjust the setback time earlier so it has recovered from setback at the time when you want heat, ie, begin setback prior to the time you want heat adding time,starting earlier, so the house has recovered at the time your demand for heat returns to normal. ~ 1.5 to 2 hours earlier.

Windhager HWS setpoint. You have previously mentioned reducing this. The caveat is that as you reduce this you may run the boiler in its condensing range where it will make a mess. Take a picture of your clean shiny boiler as it is the last time it will be this clean if you accidentally run the boiler in condensing range.

Ideally this would be adjusted in auto with OAT reset with a low limit to prevent condensing. If the boiler does not have this built in, you may manually try to lower it. Flue gasses will condense in the boiler and flue if the boiler operating temp falls below ~ 140 F. My guess is that 160 F or above would be OK but if you tried to adjust HWS setpoint to the 150 to 160F range, flue gas condensation is possible and will make a mess.

No changes to the boiler's auto burner shutdown and boiler circ shutdown sequence. These continue to run when the heat call has been dumped to purge remaining heat/flue gas from the boiler.


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## velvetfoot (Jan 18, 2016)

__dan said:


> Buffer/Energy/DHW tank aquastat, lower the setpoint to the point where you still get sufficient hot water production. 140 to 150 F may work and if not, the problem will be insufficient DHW production under load.


I have aquastat sensors at a point 1/3 of the the way from the top as well as the top of the tank.  I start the boiler when 1/3 is at 129.  I stop zone circs when top of tank is 125.  The Energy Tank is efficient.  So far, so good.  No complaints yet.



__dan said:


> Setback, during setback, open the buffer tank aquastat so it will not call for heat during setback but does call for heat when the setback house load calls. When the house load is satisfied it should dump the buffer tank call for heat in setback.


This might a short duration.  My goal is long run times for the pellet boiler.



__dan said:


> Setback, adjust the setback time earlier so it has recovered from setback at the time when you want heat, ie, begin setback prior to the time you want heat adding time,starting earlier, so the house has recovered at the time your demand for heat returns to normal. ~ 1.5 to 2 hours earlier.


A quicker setback recovery would be enabled by my plan of closing off the buffer tank as much as possible while the pellet boiler is running.  Heating up the tank's cold bottom water is a deterrent to quick recovery.  



__dan said:


> Windhager HWS setpoint. You have previously mentioned reducing this. The caveat is that as you reduce this you may run the boiler in its condensing range where it will make a mess. Take a picture of your clean shiny boiler as it is the last time it will be this clean if you accidentally run the boiler in condensing range.


Reducing the external temperature supply temperature helps a lot to stretch things out because the boiler modulates down.  I currently have it set at 156.  I have a Caleffi Thermix mixing valve supplying 130F minimum to boiler return.  Note that 130 is when the valve starts opening, and that it is fully open at 148.  Please note this is a pellet boiler. No mess seen as yet.



__dan said:


> No changes to the boiler's auto burner shutdown and boiler circ shutdown sequence. These continue to run when the heat call has been dumped to purge remaining heat/flue gas from the boiler


Yes.


I'm wondering how my piping scheme would work.


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## velvetfoot (Jan 30, 2016)

Looking at some charts I made on https://www.hearth.com/talk/threads/pellet-boiler-cycle-monitoring.152539/ , it looks like the boiler goes about a hour and a half from modulate start to 30%, even on low or no load.  I think taking the tank out of the mix for as long as possible could shorten this up.  To that end, I bought a mixing valve and controller.  Now I have to figure out how to best install it.  The valve and actuator is by Johnson Controls, bought on ebay.


Controller:  
http://www.supplyhouse.com/Honeywel...ure-Inputs-2-Analog-Outputs-1-Sensor-Included

Valve/Actuator:
http://www.ebay.com/itm/Johnson-Con...A-2-1-1-4-Valve-Actuator-AC-24V-/272055797954


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## velvetfoot (Feb 1, 2016)

They came in the mail.  The valve looks pretty well put together for $99 on eBay.  cv=29
I'm really not sure I'll ever install them because of the uncertain benefits, hassle and risk, but at least I have them.


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## velvetfoot (Feb 1, 2016)

I thought I'd throw in a chart from that other thread.  My idea is for a faster rise to temp and associated decrease in power output-pushing the 30% load start to the left, if you will, and stretching out the time on.


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## Sparky978 (Feb 1, 2016)

I like that Honeywell controller. Is it backlit? Thats what I don't like about the Ranco sometimes hard to read without backlight.


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## velvetfoot (Feb 1, 2016)

I believe it is backlit; I haven't powered it up yet.  The same unit comes in various configurations.  Mine has provision for two sensors and two analog controls.  Some others include relays, or even outdoor reset, all for more money, natch.  I'm still trying to puzzle out the piping diagram.


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## velvetfoot (Feb 6, 2016)

Report from the basement:  One or two zones on and the buffer tank valved off, the boiler modulated beautifully to approximately the set temperature of 156. Maybe 46% for one zone at steady state.  With two zones on it was 90% plus or so, and modulating nicely.  When the one zone dropped out the temp went up and output was modulating down.  Anyway, with one zone on and the buffer tank isolated, it modulated beautifully - no buffer tank required.

When both zones went off, the cold water from the bottom of the buffer tank came into play again, the water temperature went down 10 149 or so and the modulation went up to the high 90's%.  It's going up just to heat the darn buffer tank.  Although it's a two-pipe setup, and the zones have first crack at the boiler water, the cold water still has a big impact on the return temperature especially with only one zone on.

Anyway, I'm still trying to talk myself into actually doing this (in the summer, of course.)


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## TCaldwell (Feb 6, 2016)

Shouldn't be too much work to cut the 3 way valve into your return, draw it out first, get the fittings, pipe, I'll bet you'll find yourself doing it I no time!


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## velvetfoot (Feb 6, 2016)

Of course, now that I actually have it in my hands, things might move along faster.  Still not this winter...too many things to go wrong.


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## velvetfoot (Feb 8, 2016)

__dan said:


> Setback, during setback, open the buffer tank aquastat so it will not call for heat during setback but does call for heat when the setback house load calls. When the house load is satisfied it should dump the buffer tank call for heat in setback.



You gave me an idea, although it's probably the opposite. 
To recover from an overnight setback, a fully charged buffer tank, rather than a nearly depleted one, at start of recovery would be helpful.  So, maybe, if I had more control over things, the boiler could be made to charge the tank during certain time intervals with a tank temp was somewhat more than usual, for faster recovery.


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## velvetfoot (Feb 10, 2016)

Another recovery thought.  I isolated the tank this morning while one zone recovered from a 6 degree setback.  Without the massive cold water returning from the tank, (the bottom was at 110), the supply temperature got hot quick and heated the zone quicker than if the tank was involved.  

I turned up the thermostats and had both zones running for a while.  It's great to see things working nicely with a load, delivering hot water to the baseboards, modulating nicely, all without the tank involved. Direct from boiler to zones!

Delivery of hot water quickly (relatively) for reset, and then modulate down and divert hot water to the tank while maintaining the hot water in the loop for delivery to a calling baseboard.  I think I like it.

Because of the low distribution system and boiler water volume, I'm supposed to be able to do away with the boiler protection valve, keeping the boiler pump off until a suitable temperature (135).  Not sure of what the benefit would be to remove, except for less head loss and maybe natural convective flow during a power outage.

The issues for me are setback recovery, as I've said, and another building source - my wood insert.  So, it has to have the 'oomph' to power back from setback, and the ability to heat only one zone, gently.  I think keeping the tank out of the equation for 'power' and using the tank for 'gentle' might help.

Still talking myself into an off-season project.

edit:  Just would like to say that at high supply temps, response times to the baseboard are almost gazelle like.
edit2:  At the high end, 176, the loss of one zone led to boiler burnout. The margins aren't much at that set temp, with a high temp of 176, so it'd be better to set it (external) at something less.


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## __dan (Feb 10, 2016)

Here's a thought.

Without looking at your plumbing diagram, the zone circ / circs for the baseboards, if you have something like a standard 007, you could try replacing that with an ECM circ with fixed temp sensing. Then the circ sensor would go on the baseboard's return pipe / header and be set to something like 130 -140 F.

If it fits your application, it would be one of the easiest changes you could make. At cold start, the circ would max to achieve HW return of 130 F, but would quickly ramp down as setpoint is met. So you would have a variable load, high when you need it in the beginning so the boiler starts out firing hard, then quickly lightens up but stays on at a lower load, giving time for the boiler to turn down.

I cannot understand how the DHW tank does not become fully mixed with boiler water at the end of the cycle. But this way, the boiler circ should be flowing lots more than the load ECM circ, so the tank should see that flow. Sizewise, the tank should be invisible to the boiler, like putting an ice cube in a pot of boiler macaroni.

You do need to take out the loading unit, disconnect the zones / DHW tank, and fire the boiler, as making steam, condensate, popping the relief valve, seems to be the only thing that will keep you happy.


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## velvetfoot (Feb 10, 2016)

I am using four  B&G Ecocirc Varios for zones and boilers.  Alas, they are ECM but not auto in any way, but are infinitely adjustable manually.
As I've noted, I feel that the cold water coming back to the boiler from the tank, ~105 at start of cycle, keeps the boiler from warming up.




__dan said:


> I cannot understand how the DHW tank does not become fully mixed with boiler water at the end of the cycle.


The sensors on the outside of the tank generally show a 5* difference between top and bottom.  So, ending up with something like 179 and 174.


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## velvetfoot (Feb 14, 2016)

Good morning to fool around with this since it was -19F.
I tried lowering the boiler feed pump speed just a tad, and that may, or may not, have boosted temp.
Still, long recovery time from setback with low return temperatures.  Would be nice if the zones were given priority and the tank was out of the loop.


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## velvetfoot (Feb 16, 2016)

This is what I'm currently thinking.   When a  baseboard loop starts, the slug of cold water in the pipe takes little while to come back to the return header.    I'm not sure where to put the mixing valve controller temperature sensor, before the zone return tees or after.  The slugs of water are pretty transitory, and I don't know how fast the mixing valve would react.  Before the return tees might result in a more smooth control, but I'm not sure.


I'm also a little unsure of the type of the two check valves I figure I'll need.  I used a spring check valve on my oil boiler supply and that seems to work well.  The system came with Taco FloChks on the zone supplies.  I'm thinking spring check valves.


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## __dan (Feb 16, 2016)

What I'm reading still makes no sense.

The response time of that type of valve, if it is a mixing type, is very slow. It will start moving almost immediately, but if the PID is tuned for hydronic, I would not expect it to settle into the final position for five or more minutes. If it's doing hydronic mixing, the controller will be slow to avoid hunting.

If it's something that is just driven open and driven closed, the cycle time could be just a few seconds.

The normal strategy in your application is to prioritize DHW, meaning the zones are off until some condition, DHW is satisfied or, maybe better with the pellet burner, boiler return temp is above setpoint.

I cannot see the 110 gal of tank being any kind of significant load that prevents you from getting heat to the zones. Even in a cold start first thing in the morning, the tank water is probably warmer than either the boiler or the baseboard water. So, what load can the tank present. It would actually give a shot of warmer water to the system, reducing the cold start time.

Also the DHW tank was part of a factory recommended and supported install. If the tank was part of the factory requirements in their installation instructions and not just a recommendation, removing it with the valve would constitute a code violation and may void your warranty, insurance. Code are adopted by State law, so it would be a violation of that requirement of the State law. What if you needed the insurance to pay and then explained to them how you disabled something the factory required then fired the boiler. Do you think you are covered for that?


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## velvetfoot (Feb 19, 2016)

Five minutes is a long time.  This would point to using this control would avoid the effect from where the zone returns tie in, dumping in periodic slugs of cold water, in my baseboard case.

As I've said, I have a reverse indirect tank and don't operate the zone pumps below a certain temperature to assure dhw.

I've observed the temps and the boiler return temp is lowered for a significant time before the boiler gets to, say, 168, even with a boiler protection valve in place. 

When the temp of the tank gets cold enough the pellet boiler fires.

A rough calculation of 60 degree rise of the tank, 120-180 gives me 60,000 btus.

You know, I'm not sure if anything you've said is helpful at all.  I'll leave it at that.


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## velvetfoot (Feb 19, 2016)

On a more hopefully helpful note, I've started reading the Honeywell controller instructions.  While mine is modulating outputs only, the models with relays can do *150*  degree differential!  That's more than the Rancos and Johnson Controls models usually cited here.


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## velvetfoot (Feb 19, 2016)

Upon reading some more, the two check valves might be dispensed with.  The controller has a terminal block on it called 'digital input' that's a dry contact that when closed, puts all modulating outputs to zero %.  So, a relay can sense if the pellet boiler is 'off', and then close the tank bypass, which will allow flow from the tank to heat the zones.

My current plan is to have it serve as a mixing (rather than diverting) valve on the return, for hopefully better response.

It talks about throttling range and integral settings and recommends keeping derivative at zero.  This is what it says about integral and throttling range settings:

NOTES:
1.       The Integral time is factory set for 400 
seconds. This is a good middle range and 
should satisfy many applications. The integral 
time can be increased for applications where 
sensed response is slow, and can be 
decreased for applications where sensed 
response is fast (e.g. discharge air control).
2.       As a starting point, an optimal integral time for 
discharge air typically ranges from 12 to 200 
seconds. An optimal integral time for room 
control typically ranges from 60 to 2,500 
seconds. The purpose of integral action is to 
reduce or eliminate the offset from setpoint 
during steady state control that is often seen 
in proportional only control.
3.       Keep in mind that control is most sensitive to 
throttling range. Adjust the throttling range 
first before any adjustment to integral time. 
Adjust throttling range to be as wide as 
possible to start since this will provide the 
most stable control. Remember that the 
integral will eliminate the steady state error so 
you do not need to have a small throttling 
range to have accurate control. (Integral 
action allows for controlling to a setpoint even 
with a wide throttling range)


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## velvetfoot (Feb 20, 2016)

Several other interesting things about the controller:

-The output can be set to a minimum percentage.  I'm thinking in case I want the top of the tank to gain some heat earlier for dhw purposes, or if the boiler run times are getting too long .


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## velvetfoot (Feb 22, 2016)

Well, I managed to hook it up electrically.  Wasn't entirely intuitive for me but got it working.  What they call 'digital input' also worked.  While 100% modulated,  (100% bypassed), like if the return temperature is below X*, when the dry contact 'digital input' leads are joined, it goes back to 0% modulated (free flowing through the tank).  This would allow reverse flow without check valves and extra pipe, so that the tank can heat the zones when the boiler is off.

I have to say the display is bright. It never dims or shuts off though.  They could've put a timer on it like my boiler, I think.


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## velvetfoot (Mar 19, 2016)

I just piped up the valve and I'm filling things back up now. Hopefully, no leaks.  Knock on wood.


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## velvetfoot (Mar 19, 2016)

Came home from movies-small leak, only right near the tank.  Crap.  Draining tank.  Hopefully can drain water from pipe w/o taking apart.  Crap.


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## TCaldwell (Mar 21, 2016)

How's it going?


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## velvetfoot (Mar 21, 2016)

I hate to jinx it, but good.  There, I said it.  I drained things again, tried to isolate the tank, sucked some more water out of the bottom of the tank with a shop vac, applied a little flux to the outside of the leaking joint, heated and added solder.  Filled things up, repressurized and, knock on wood, no leaks.

I also relocated the Spirovent closer to the heat source; I had to move it anyway since it was near the tank and was interfering with new piping.

I've mounted the actuator on the valve and  the controller on the wall.  I've powered the controller up and installed the temperature sensor on the pipe a relatively short distance downstream of the valve.

I've checked the control voltages coming out of the controller and it seems right:  controller shows 100% bypass, 10 volt output, valve SHOULD stem rotate all the way clockwise.

This morning I will read up some more on wiring up the actuator (really don't want to burn anything out), and also what my preliminary controller settings will be; hopefully the settings won't be a long drawn out thing.  I'll complete the wiring this morning and fire up the oil boiler and see what happens.

Pictures might be difficult because of close quarters, but I'll try.

What's a shame is the beautiful and expensive glued-together 1" thick foam insulation doesn't remove that easily.  I do have some spare pieces though.

Anyway, you asked.


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## TCaldwell (Mar 21, 2016)

Just installed a 3 way mix valve ( shunt valve) on my system to accommodate outdoor reset, will get into that with another thread. The valve/ actuator is a belimo 0-10vdc with a 100 sec stroke speed, the controller is a Tekmar 423 reset module, there aren't adjustable pid parameters, rather tekmars own learning algorithm, I'm surprised how precise the control actually is. Once dialed in you'll be happy.


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## velvetfoot (Mar 21, 2016)

Not happy now.  Leak started again as it was heating up.  Very depressed.  Right at tank.  I might try one more time.  I really don't want to break it open, and not sure of how to proceed if I do.  Very bummed.

When it was heating up the controller it was doing its job but maybe working the valve a little too hard, I don't know.


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## TCaldwell (Mar 21, 2016)

Shark bite fitting?


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## velvetfoot (Mar 21, 2016)

Do you think one more round of attempting to add solder would not be successful?


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## TCaldwell (Mar 21, 2016)

Doubtful, l would take it apart clean up fitting/pipe and re sweat. Your almost home to testing something you have put a lot of effort into.


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## velvetfoot (Mar 21, 2016)

Yeah.  It's going to be a pain to take things apart though.


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## TCaldwell (Mar 21, 2016)

Cut the pipe in the middle, between the valve and tank fitting, unscrew witch side is leaking weather from the valve or tank, put it in a vice, heat and remove the bad joint from the fitting, clean it up and resweat. Then screw fitting back in and connect with a sweat coupler


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## maple1 (Mar 21, 2016)

Yep. Been there. Looks like a fix that starts with a recip saw, and ends with a sweat coupling.

Edit: Although it does look like a tight spot. Which might mean more than one cut & coupling.


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## velvetfoot (Mar 21, 2016)

Thing is, it's so tight there might not be enough length for a slip coupling.   I'm also reluctant to unscrew the adapter from the tank-who knows if that might not leak.  I might try sweating again tomorrow, but I'm not optimistic.


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## Bob Rohr (Mar 21, 2016)

velvetfoot said:


> Thing is, it's so tight there might not be enough length for a slip coupling.   I'm also reluctant to unscrew the adapter from the tank-who knows if that might not leak.  I might try sweating again tomorrow, but I'm not optimistic.




You may end up over-heating the thread dope and create a leak there.  best to start over, once you have a bad spot inside a sweat fitting, desoldering is almost impossible.

Do you have a union connection in there somehow?

Perfect spot for a press fitting and tool


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## velvetfoot (Mar 21, 2016)

I was thinking of a union, but they've leaked on me too.


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## TCaldwell (Mar 22, 2016)

Possibly cut the valve out on the other 2 legs far enough away so as not to damage pipe dope when you reassemble with sweat couplings after leaking leg fix. If you didn't want to consider re sweating legs or can't cut the 2 legs far enough from the valve, I'd consider shark bites


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## maple1 (Mar 22, 2016)

I have unions in my system in strategic (I think) places, made putting some things together easier & hopefully anything I will have to do in the future easier too.

I also have had issues getting them to not leak. So I got a tube of some siliconey type stuff, that I found in the automotive section of the local Canadian Tire store, that is meant for sealing things like carb bowls. Actually, I guess I already had it here from doing some work on bike carbs. I forget what it's called, I think something 'moto' related, but it stays soft & flexible & is meant to allow easy disassembly. I just put a little thin skin coat of it on the union sealing surfaces, then tighten. Never had one drip from them after using it, and I did end up taking some of the apart & reassembling in a couple places to do other things later with no issues.

EDIT: Just ran down stairs & checked - it's Permatex MotoSeal 1, has a pic of a MX bike on the package.


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## velvetfoot (Mar 22, 2016)

I can't imagine the fun if it was iron pipe.


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## TCaldwell (Mar 22, 2016)

Possibly cut the valve out on the other 2 legs far enough away so as not to damage pipe dope when you reassemble with sweat couplings after leaking leg fix. If you didn't want to consider re sweating legs or can't cut the 2 legs far enough from the valve, I'd consider shark bites


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## TCaldwell (Mar 22, 2016)

Sorry for the duplicate


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## velvetfoot (Mar 22, 2016)

I'm gonna try re-sweating one more time.  Not expecting much, but hoping.


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## velvetfoot (Mar 22, 2016)

Seems to be holding after heatup on oil

Didn't get a good fill.  Control not that good.  Have to fool around with settings.  I wish I knew what I was doing there.  Might try relocating the sensor.  I'm hoping the high cv of the valve isn't a factor, as Bob indicated in another thread.


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## TCaldwell (Mar 23, 2016)

Johnson Controlls has good tech help


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## velvetfoot (Mar 23, 2016)

TCaldwell said:


> Johnson Controlls has good tech help


That's good to know, alas, the controller is by Honeywell.
setpoint, Throttling range, proportional, integral, derivative...ai yai yai.


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## TCaldwell (Mar 23, 2016)

Oops


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## velvetfoot (Mar 23, 2016)

Things can change quicker in my application than your room warming.


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## TCaldwell (Mar 23, 2016)

Stronger proportional, shorter integral?


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## velvetfoot (Mar 23, 2016)

I relocated the sensor right after the valve outlet and it works like a charm, even with default setting of 400 seconds for Integral, 20 F for throttling range and 0 for derivative.

Alas, now the boiler pump is heating up the two zones without the zone pumps being on, pumping through the zone pumps and the swing checks.  I turned it down and the boiler temp went up and it turned off.  I can't win for trying.


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## TCaldwell (Mar 23, 2016)

Maybe zone valves right after the circ discharge


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## velvetfoot (Mar 23, 2016)

I wonder if I could replace the zone Taco flo check valves, which go to each zone, with zone valves?  They wouldn't be needed with the zone valves in place, no?

The basis of my system is a typical old school layout where the zone pumps pump to return.  The boiler pump I added also pumps to return.

I'll run it some more (on oil).    I am running it now with bypass closed and so far it seems to be running as it was, knock on wood. 

I will have to use what Honeywell calls the "digital input", which will send the valve to 0% (bypass) upon a signal, which will have to be when the oil boiler is off and the heat is coming from the tank.  That is, the flow changes direction and the mixing valve has to be open to the tank when extracting heat from it.

If my current no-bypass run looks okay, next time I'll try it with the mixing valve "in the mix".  Perhaps the constant seeking previously (before I learned the secret) had something to do with it.  Or, it's flow resistance of the valve or something.


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## velvetfoot (Mar 23, 2016)

I went through another cycle, this time with the mixing valve operational.

I have to say, it really kept the return temp at 160 setpoint pretty well.  

As far as the heat bleed, I previously had to turn down the boiler pump (infinitely variable but not auto ecocirc vario) because of that problem.  On this cycle, despite the 160 return, the boiler temp kept climbing, so I bumped the boiler pump speed up a bit from 3.5 to 4.5 (on a scale of 1-7).  That brought the boiler temp down and it continued to run until the buffer tank was nicely filled.

It was definitely heating the house though, even with the zone circs turned off.  I have temp sensors on the in/out of both zones, and it was doing a differential of maybe 40 (180/140), maybe less !  Without the zone circ!  So yes, a couple of zone valves are in my future.

Again, I guess I could replace the flo checks if they weren't needed-not sure if there is room for both (see picture), and access is tight.  How about if I put them on the return?  Very accessible, and it would stop the loop.  I guess there would be some ghost flow, but would that be big?

Can anyone recommend a zone valve?


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## velvetfoot (Mar 27, 2016)

While I'm waiting for two Taco Zone Sentry valves to arrived, I managed to add a couple of relays to sense current in the pellet and oil boilers and close and open the Digital Input terminals of the Honeywell controller.  When contacts are closed, Digital Input sets output to 0%, which opens valv e to tank, which allows zones to be heated by the tank.  When either boiler is on, contacts open, and the Controller sets the % output according to the setpoint.  100% is all tank bypass, and 0% is no tank bypass.

Here are a couple of pictures of the tank bypass mixing valve and input tee.


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## velvetfoot (Mar 31, 2016)

I installed the two Taco Sentry zone valves, the check valve and relocated the Spirovent.
Not leaking yet, but haven't heated up yet (tomorrow).
I added another 40va transformer; the valves are efficient on holding, but it supposedly takes 11 watts while charging (about 30 seconds).  The capacitor provides the valve closing energy.   Anyway, the existing zone valve controller's 30va transformer is powering the mixing valve and its controller.  The new transformer powers the zone valves and the thermostats.
The thermostats switch on the zone valves, and end switches on the zone valves switch on their respective pumps via the original pump controller.
Here are a couple pics.  Please excuse the mess, crappy looking solder joints, etc.


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## TCaldwell (Apr 1, 2016)

Looks nice, now your a full fledged member of the point of no return club. This is the type stuff you get done when the wife goes on vacation.


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## velvetfoot (Apr 1, 2016)

TCaldwell said:


> This is the type stuff you get done when the wife goes on vacation.


No kidding.  

In the "Nothing's Easy" department, there seemed to be pressure creep after I refilled.  I set the pressure down on the Watts makeup valve and bought a replacement at the plumbing store.  It seems like it might be holding now.  I'm not crazy about replacing it:  the original plumber seems to have used some kind of hardening plumbers dope on the threads.  Thankfully, on the Watts, one end is a union.  I just rather not take the chance, so I'll keep looking at the gauge and cross my fingers.

Still haven't heated it up yet.


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## velvetfoot (Apr 1, 2016)

Heated it up.  Still hunting.  I'm worried that B. Rohr's post about having too big a Cv for a Mic valve might be a factor.  Still messing with I and D.


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## Beagle Dad (Apr 1, 2016)

The CV of your valve should be in the range of 0.7 to 1.0 times the maximum expected flow. This will give a 1 to 2 psi pressure drop across the valve at full flow.  CV= USGPM/ SQRT(pressure drop across valve at full flow).
​


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## velvetfoot (Apr 1, 2016)

The valve is Cv is 29.2.  The pipe is 1.25".
Here is my pump curve.  I have the setting at 5.  I have no idea what my head loss is to find flow.  It pumps through a loop with 2 check valves, a thermomix boiler protection valve, a spirovent, the tank, and not that much pipe-maybe 25 feet.
From the curve below, using pump setting 5, the middle of the curve would be 6 gpm.
I guess that would mean the cv would be way high?
I don't think I'll ever replace it, so I guess I'm screwed.
I always thought bigger (cv) was better.


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## velvetfoot (Apr 2, 2016)

Other than the control issues, which is big. I think I might have done a bad move in relocating the spirovent where I did-now it seems the zones won't clear the air as well as before-plus the tank top will see the same hot water as closer to the boiler, except when recirculating.  Perhaps another spirovent?  Also thinking of changing swing check to spring.

I'm thinking of not commenting on this thread anymore since it really highlights my dumbassedness.


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## TCaldwell (Apr 2, 2016)

Is the actuator removable from the valve, if so in the long it might be the least cost fix. Would think a 3/4 valve with a cv between 5 and 8 would do it?


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## velvetfoot (Apr 2, 2016)

I did another heatup and fooled around with settings again.  At some point it became stable at 400I, 0d, 20 degree throttle range.   Earlier it was oscillating at the same settings.  Weird.


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## Beagle Dad (Apr 2, 2016)

velvetfoot said:


> I did another heatup and fooled around with settings again.  At some point it became stable at 400I, 0d, 20 degree throttle range.   Earlier it was oscillating at the same settings.  Weird.



If you find the valve hunts too much try reducing the effect of the proportional gain which I think translates to increasing the throttling range. This should cause the control to be mostly from the Integral which will result in the valve lagging behind the error between the setpoint - measured value.


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## TCaldwell (Apr 2, 2016)

watch the controller output to see if it seems to hunt around a certain output range, i have noticed that when the supply and mix temps have a large delta and the valve output is under 15% it will hunt. The best operating valve range for me seems to be from 25% and up.


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## velvetfoot (Apr 2, 2016)

Other than the control issues, which is big. I think I might have done a bad move in relocating the spirovent where I did-now it seems the zones won't clear the air as well as before-plus the tank top will see the same hot water as closer to the boiler, except when recirculating.  Perhaps another spirovent?  Also thinking of changing swing check to spring.

I'm thinking of not commenting on this thread anymore since it really highlights my dumbassedness.


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## velvetfoot (Apr 2, 2016)

I'm gonna comment anyway.

Came home, boiler on, at some point in its cycle.  Rock steady at 160.  I don't get it.  I'll see if I can monitor a cycle from the start again.

A comment from previous messing about with derivative:  while it seemed to help keep the temp closer, the recirc % varied wildly, exercising the valve a lot.  Right now, the recirc % varies a percent or two.  It's great-I wish I could bottle it.


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## velvetfoot (Apr 2, 2016)

Beagle Dad said:


> If you find the valve hunts too much try reducing the effect of the proportional gain which I think translates to increasing the throttling range. This should cause the control to be mostly from the Integral which will result in the valve lagging behind the error between the setpoint - measured value.


Yes, I noticed that increasing the throttling range from 10 to 20 degrees in my previous run helped.  I still can't fully explain how it started working though, though I shouldn't complain too much.  I'm sure things will mess up on the next observed run.


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## velvetfoot (Apr 2, 2016)

TCaldwell said:


> watch the controller output to see if it seems to hunt around a certain output range, i have noticed that when the supply and mix temps have a large delta and the valve output is under 15% it will hunt. The best operating valve range for me seems to be from 25% and up.


And the previous run for me it seemed to thrive and a wide supply/mix delta-buffer tank bottom still cold, boiler around 178 or so.  When mine was oscillating, it would go from high to low percentages and the temps would be plus or minus at least 5 degrees.


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## velvetfoot (Apr 2, 2016)

Worked fine for another tank heatup. 
Will try pellet boiler soon.


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## velvetfoot (Apr 3, 2016)

Just noticed that the speed control on one of the Ecocirc Vario pumps doesn't work.  Seems to be stuck on high.  Great.


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## velvetfoot (Apr 3, 2016)

Did quick and dirty fix involving a 1/16" hex wrench and some clear plastic tape to keep the water out and allow seeing the power on indicator light.

I moved the sensor 6 feet down the return pipe from the mix valve and after the zone circ return connections.  The effect of the cold water that has been lying in the distribution pipes is big time - bringing the return temp down to past throttling range and closing off the tank completely while the boiler returns back to temperature. 

The valve still controls well, even after those big hits.  It takes somewhat of a while to bring it back, and it always seems to be a degree or two above setpoint, never below.  

My pellet boiler and baseboard output are pretty well matched, so that's why recovery from a double zone hit can take a while, I suppose.


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## velvetfoot (Apr 16, 2016)

Beagle Dad said:


> If you find the valve hunts too much try reducing the effect of the proportional gain which I think translates to increasing the throttling range. This should cause the control to be mostly from the Integral which will result in the valve lagging behind the error between the setpoint - measured value.


This does seem to be key.  It was oscillating again and increasing the throttling range from 20 to 40 smoothed it right out.


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## velvetfoot (Apr 26, 2016)

Another note on the Honeywell controller.  If there's enough ambient light you can disconnect the lead to the display leds and still read it.  The leds are pretty bright, as I've said before.


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