# boiler, buffer, backup, DHW and loads



## Bob Rohr (Mar 2, 2013)

I think this concept, designed by John Siegenthaler  www.hydronicpros.com covers most of the functions that many want.

The boiler is protected from low return temperature by a variable speed circ.  I like this for high output boilers especially.  Less cost and less pressure drop compared to large loading units, this could be an ECM pump for additional energy savings.  Actually all the circs could be ECM which are mandated in Europe now for all heating pumps.

I believe with a swing check, and generously sized boiler piping, the boiler would thermo-siphon for over-heat protection, remove any spring checks from the pump!  It seems to work well in the loading units with a swing ck.

The controls could be very simple.  The wood boiler runs it's own pump P-1, all seem to have a relay output for that function.  The load circ P-2 could be a brand with the logic built on, or run by an inexpensive solar differential control, just about all brands and models of solar controllers have variable speed functions built in nowadays.

The buffer tank serves as a hydraulic separator and a fairly good air removal point for the boiler.  as well as a dirt separation function.

Boiler back up with a mod con has some buffer space for small micro zones.  Loads could be removed from the tank with reset temperature controls MV-1.

DHW is via a 30 plate HX.  I have proven this method on my own system for a year now.  I've found the  Harwil Q8-N flow switch works perfectly and triggers at 1/2 gpm flow.  Protect the DHW temperature with a listed 3 way thermostatic valve.

DHW backup could be a small tankless gas or electric.  if I were to buy a new mod con boiler I would use a brand with them DHW HX built in.  So boiler back up and DHW from one unit.  Really back up could be oil, gas, LP, electric, heat pump, any source you chose.  Back up DHW could also be a small electric HW heater too.

There are trade offs on any system design, this simple to plumb option shows a one tank concept that covers most options that customers want, with Caleffi components of course 

Thoughts, suggestions?


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## ewdudley (Mar 2, 2013)

As usual, Siggy disregards maintenance of storage tank stratification as a goal when integrating DHW.  A preferable design would be the European approach of putting a DHW coil in the top of the storage tank with an internal reverse chimney to guide spent DHW to the correct thermocline. 

Of course all-radiant all the time is nice because it makes integration of heating loads with storage foolproof.  The choice of a motorized three-way seems extravagant with the price of temperature controlled ECM loop injection pumps coming down so nicely.

I like the variable speed temperature controlled P2.  Is it controlled only by return temperature?  And if so is supply temperature an arbitrary function of P1 flow and instantaneous boiler heat output?

Connecting the fossil fuel boiler directly to storage as a buffer and hydro separator works quite well, it seems that may are reluctant to take that approach.

--ewd


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## Bob Rohr (Mar 2, 2013)

ewdudley said:


> As usual, Siggy disregards maintenance of storage tank stratification as a goal when integrating DHW. A preferable design would be the European approach of putting a DHW coil in the top of the storage tank with an internal reverse chimney to guide spent DHW to the correct thermocline.
> 
> Of course all-radiant all the time is nice because it makes integration of heating loads with storage foolproof. The choice of a motorized three-way seems extravagant with the price of temperature controlled ECM loop injection pumps coming down so nicely.
> 
> ...


 

We have looked at DWH coils in the top of the tank.  They add considerable cost and the ones we looked at had fairly low DHW output.  Much too low for the typical US house hold, same with the early Euro designed tankless heaters that hit the US shores.  Some of the brands tested had stainless steel corrugated coils and they pin holed from the treated water common in the US, cholorides or cholorine is not a common water treatment where those tanks come from 

The rest of the world is much more DHW consumption are. 2 gpm is plenty of DHW flow for a Euro family.  In the US we need 5 gpm or more, some tubs have 7 gpm fillers!

A heat exchanger with two "moving" flows is a better method from my experience, a coil in stagnate conditions will not transfer as well as a plate type HX and it is servicable when the HX is external.  External HXers allow you to buy a fairly inexpensive "off the shelf" insulated tank, or former LP tank for the storage vessel.


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## ewdudley (Mar 2, 2013)

Bob Rohr said:


> We have looked at DWH coils in the top of the tank.  They add considerable cost and the ones we looked at had fairly low DHW output.  ...



Pfft.  My neck and collar cost $40 and the coil itself was $150 for a nominal 7 gpm 'tankless coil' [edit: actually it's labeled 5 gpm, from Diversified Heat Transfer].  Supplies shower and washing machine simultaneously and continuously.  I set it up to supply preheat flow for an electric tank but it turned out it supplies plenty on its own.


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## Armaton (Mar 2, 2013)

Which coil do you have Eliot? Even tho I have my flatplate already, may be a better fit to put a coil in the top of my separator. Save a pump also.


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## kuribo (Mar 2, 2013)

Bob Rohr said:


> I think this concept, designed by John Siegenthaler www.hydronicpros.com covers most of the functions that many want.
> 
> The boiler is protected from low return temperature by a variable speed circ. I like this for high output boilers especially. Less cost and less pressure drop compared to large loading units, this could be an ECM pump for additional energy savings. Actually all the circs could be ECM which are mandated in Europe now for all heating pumps.


 
How about the line of thermostatic boiler protection valves from Regulus? They make a line of three way thermostatic valves for boiler protection that have large Cv and very reasonable pricing. They make a 1-1/2" (Cv ~ 25) and  2" valve (Cv ~ 38) (TSV6, TSV8) that are priced around $100 and $120, respectively. They claim these are suitable for boilers up to 340,000BTU/hr output. That doesn't include shipping, but even with, seems it would be a lot cheaper and simpler option that the pumps, sensors, and controllers, never mind the electricity costs.


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## kuribo (Mar 2, 2013)

ewdudley said:


> Pfft. My neck and collar cost $40 and the coil itself was $150 for a nominal 7 gpm 'tankless coil'. Supplies shower and washing machine simultaneously and continuously. I set it up to supply preheat flow for an electric tank but it turned out it supplies plenty on its own.


 
The only coils I could find were over $400 each. Can you provide a source for these at $150?


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## ewdudley (Mar 2, 2013)

kuribo said:


> The only coils I could find were over $400 each. Can you provide a source for these at $150?


Ebay and patience.


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## kuribo (Mar 2, 2013)

Ah....ok. Thank you.


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## ewdudley (Mar 2, 2013)

kuribo said:


> Ah....ok. Thank you.


But now that you mention it, it took ten months to find and $30 per month electricity in the meantime for hot water.  I've seen them new for less than $500 so looks like rewards of patience weren't so grand.


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## kuribo (Mar 2, 2013)

They don't look to complicated- wonder how hard it would be to make one...


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## ewdudley (Mar 2, 2013)

Armaton said:


> Which coil do you have Eliot? Even tho I have my flatplate already, may be a better fit to put a coil in the top of my separator. Save a pump also.


I needed one for DHW and another for hot tub.  I moved one from my coal boiler to the buffer tank and got another like it so the mounting would be the same for both.  It's a six hole 5.25 maybe 5.375 inch diameter bolt pattern that seems to be pretty common, with what looks to be plain old 4.00 inch pipe for a neck.  The flange is about 6.5 inch OD.


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## lotawood (Mar 2, 2013)

Will the P1 pump lower the head of P2 at all?  
I need to upgrade to a boiler protection valve.  This approach looks better than a danafoss or termovar.
A bumble bee is close to my gpm.


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## ewdudley (Mar 3, 2013)

lotawood said:


> Will the P1 pump lower the head of P2 at all?
> I need to upgrade to a boiler protection valve.  This approach looks better than a danafoss or termovar.
> A bumble bee is close to my gpm.


At $190 an ECM Bumble Bee (model HEC-2) would be wonderful for a return temperature control application, but according to their sheet it only controls increasing-deltaT with increasing-flow, or increasing-temperature with increasing-flow.  For return temperature control we need decreasing-temperature with increasing-flow, which it doesn't claim to do.  It's possible they left it out of the documentation, or perhaps they've figured it out and have added the functionality in the meantime, or I maybe I've got it wrong, so might be worthwhile to research it further.

It can be done correctly, inexpensively, and reliably with a PID controller and bang-bang injection. Such a two-pump solution is working well for me, one pump recirculates boiler supply to return, and another injects system return into the loop with a PID controller and bang-bang modulation.

Return temperature control is accomplished by injecting into a boiler recirc loop with an injection pump under PID bang-bang control. With an 80 second cycle, 105 degF system return water, and a 160 degF return temperature setpoint I'm seeing a 10 degF swing in return temperature with boiler discharge temperature steady at 170 degF. Pumps were salvage, controller $40, relay with pedestal $12.

Push a button and you can set the return temperature anywhere you want it. Since supply temperature follows return temperature, setting return temperature according to desired supply temperature can be used to avoid the two-laps-through storage problem where tanks fill with 160 degF water on the first lap and recirculate to 180 degF on the second lap. This is important for me during a couple weeks in January when there are zones that need 180 degF water to do the job.  Again, these benefits could be achieved more efficiently and with little less complexity with a variable speed temperature controlled ECM pump if and when they become available economically with the correct operating modes for this application.

(Then again as kuribo points out above, there are now affordable mixing valves with monster Cvs available.  If and when there is an affordable ECM temperature control pump with an increasing-flow decreasing-temperature mode we could have a single pump solution with adjustable supply temperature, and be done with it.)

There's a supply side sensor that kicks in a second pump when storage is hot and extra flow is required, and for fail-safe redundancy.  Pump check valves are IFCs, but wouldn't have to be.


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## BoilerMan (Mar 3, 2013)

ewdudley said:


> But now that you mention it, it took ten months to find and $30 per month electricity in the meantime for hot water. I've seen them new for less than $500 so looks like rewards of patience weren't so grand.


 
Good logic there, EW.

Ebay and time is good at almost all things money saving.

TS


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## jebatty (Mar 3, 2013)

> Connecting the fossil fuel boiler directly to storage as a buffer and hydro separator works quite well, it seems that may are reluctant to take that approach.


 
This is my arrangement with my Tarm and 1000 gal storage, and Deep Portage does nearly the same with a 4000 gal storage/hydraulic separator. At DP both a Wood Gun E500 and a Garn WHS 3200 charge the storage, but the storage is a "load" off a primary loop and a supply to the primary loop. Works extremely well.

DP also is re-doing a Froling with a 1600 gal tank o operate as storage/hydraulic separator.


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## lotawood (Mar 3, 2013)

ewdudley said:


> At $190 an ECM Bumble Bee (model HEC-2) would be wonderful for a return temperature control application, but according to their sheet it only controls increasing-deltaT with increasing-flow, or increasing-temperature with increasing-flow. For return temperature control we need decreasing-temperature with increasing-flow, which it doesn't claim to do. It's possible they left it out of the documentation, or perhaps they've figured it out and have added the functionality in the meantime, or I maybe I've got it wrong, so might be worthwhile to research it further.


 
What would be an example of a variable speed setpoint circulator?  That is P2 on the first post.  

Would the bumble bee, on a set point of 160 degrees, go slower under 160 and faster above 160.  Or do I have it backwards? 

A PID sounds like a good alternative as well.  I need to get one for another part of my system.


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## ewdudley (Mar 3, 2013)

lotawood said:


> What would be an example of a variable speed setpoint circulator?  That is P2 on the first post.
> 
> Would the bumble bee, on a set point of 160 degrees, go slower under 160 and faster above 160.  Or do I have it backwards?
> 
> A PID sounds like a good alternative as well.  I need to get one for another part of my system.



The Bumble Bee is a variable speed setpoint (or deltaT) circulator, but reading the sheet on the Bumble Bee all I can see is 'direct acting' control, where if setpoint is 160 pump speed increases below 160 and decreases or stops above 160.  It's hard to believe that they can't be configureed for 'reverse-acting' control but I'm not seeing it.

Taco makes conventional motor '00' series variable speed units that do explicitly provide both direct and reverse acting control, but they don't offer the efficiency and wide range of precise flow rates available with an ECM pump like the Bumble Bee.

http://www.taco-hvac.com/en/product...Circulator/products.html?current_category=193


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## Blue Tornado (Mar 3, 2013)

Concerning the Taco Bumblebee HEC-2.

In the instruction sheet at he bottom of page 5 is a diagram for the plumbing and sensor location as "boiler protection". It appears that using one bumblebee on boiler loop (as diagrammed in OP) and one for primary loop to storage (as diagrammed in OP) is an ideal alternative to a loading unit.

Add a third to your shelf as backup and it is gold. At $200 per pump it is a close initial investment as a loading unit.


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## ewdudley (Mar 3, 2013)

Blue Tornado said:


> Concerning the Taco Bumblebee HEC-2.
> 
> In the instruction sheet at he bottom of page 5 is a diagram for the plumbing and sensor location as "boiler protection". It appears that using one bumblebee on boiler loop (as diagrammed in OP) and one for primary loop to storage (as diagrammed in OP) is an ideal alternative to a loading unit.
> 
> Add a third to your shelf as backup and it is gold. At $200 per pump it is a close initial investment as a loading unit.


The OP uses P2 as an injection pump into the boiler loop and requires a reverse-acting control, i.e., more injection causes lower return temperature to boiler.  Again, I don't see that the HEC-2 offers reverse-acting control.  Hopefully this is just a defect in the documentation, or the reverse-acting control will be available in future versions.

Diagram No. 1b: Boiler Protection By-Pass on page 5 of the HEC-2 sheet shows ... well I'm not sure just what it shows.  P1 sensor is labeled as 'Supply Sensor', but it's on the return port of the boiler, which should be our first clue that not a lot of thought has gone into this setup.  P1 can run as fast as you please but if the other pump flow is too much or too cold then the whole scheme fails at providing return temperature protection to the boiler.


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## lotawood (Mar 3, 2013)

ewdudley said:


> Diagram No. 1b: Boiler Protection By-Pass on page 5 of the HEC-2 sheet shows ... well I'm not sure just what it shows. P1 sensor is labeled as 'Supply Sensor', but it's on the return port of the boiler, which should be our first clue that not a lot of thought has gone into this setup. P1 can run as fast as you please but if the other pump flow is too much or too cold then the whole scheme fails at providing return temperature protection to the boiler.


 
That is what I thought when I saw that.

Blue tornado:  I was aiming for something cheaper that a boiler protection valve.  I read of a few people having problems.  But I got to say that was more with a danafoss than a termovar.  I have 1.5 inch pipe and the BPV get pricey or are not available.


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## kuribo (Mar 3, 2013)

Check out the Regulus 1-1/2" and 2" thermostatic three way valves. HIgh Cv and low prices. Simple solution.


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## __dan (Mar 3, 2013)

The P2 variable speed injection pump could be a standard Taco IFC wet rotor circ and use an external three thermistor variable speed injection pump controller. Outside temp sensor (for reset), boiler HWS temp sensor (for target setpoint), and boiler return water temp sensor (for boiler low return temp protection). The (Tekmar) controller calculates target HWS setpoint but only enables and ramps up the circ after the boiler return thermistor reads return water above the protective low limit temp setpoint. Boiler return temp sensor is shown on the drawing.

The ECM circ is very different internally, with internal sensors and inverter VFD. Not directly compatible with the Tekmar standard wet rotor circ controllers, but as the market matures I'm sure this functionality will be carried over to the ECM circ controllers.


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## maple1 (Mar 3, 2013)

Good lord, that wiring setup makes mine look not as bad as I thought it looked.


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## kuribo (Mar 3, 2013)

Simple enough.....


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## Blue Tornado (Mar 3, 2013)

WOW... Wild looking control room there.

I am thinking that this diagram is doable with the bumblebees. Not the most economical way to go but still seems to me it is workable.

Both pumps wired to go on from boiler controller at 180 or so. Notice sensor locations as per Taco install sheet.
Hope the upload goes well enough.


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## __dan (Mar 3, 2013)

Yep, thought you guys would like that. The crowd here keeps asking how to wire circs with extension cords. Looking at the bumblebee documentation, page 5:

http://s3.pexsupply.com/product_files/Taco - HEC-2 - Install Instructions.pdf

shows *this* ECM circ is a single thermistor control. So, for the P1 system circ it will vary pumping to maintain setpoint boiler return temp. However, as the P2 variable speed storage charging circ, this unit does not incorporate boiler return temp protection and could easily overpower the P1 system circ, driving low temp storage water into the boiler return. The ECM VS storage injection pump would need two thermistors minimum to do setpoint VS injection pumping with boiler return protection, ramping up load only as allowed by keeping boiler return water temp, BRWT, above setpoint.


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## Blue Tornado (Mar 3, 2013)

It would seem to me that the P1 would also ramp up to meet its setpoint as P2 ramps up. They are equal pumps. Just my thoughts without experience in this field, yet.


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## __dan (Mar 3, 2013)

Blue Tornado said:


> It would seem to me that the P1 would also ramp up to meet its setpoint as P2 ramps up. They are equal pumps. Just my thoughts without experience in this field, yet.


 
If the system has been running (boiler firing) 2+ hours with hot storage, loads returning hot, yes. In the first hour or two with cold storage and initial demand at max, the boiler could be struggling and get hit at the return with 90 to 100 deg water in volume from storage. As shown, with no P2 boiler return protection, P2 will initially go to full speed, ramping max up to the setpoint of its sensor (sensing temp below setpoint). Because it is sensing max load. P2 is supposed to stay off until *a* BRWT sensor enables P2, then P2 is supposed to ramp slowly up, limited by the BWRT sensor staying above the low limit protective setpoint. As the BWRT increases, P2 may increase, sending more to the load and more return to the boiler. It is cold start protection. The bumblebee HEC 2 does not have this functionality, but I'm sure an ECM pump with integral BWRT protection will come to market. I'm going to check the specs of the Grundfoss Alfa.

In setpoint mode with the sensor at the boiler return, P1 will actually slow as the return becomes hotter and less supply mix tempering is required


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## Floydian (Mar 3, 2013)

I sure do love my lk810 loading unit, despite the cost. Isolation ball valves, unions, temp gauges, insulation package all in one. Pretty simple.

And it shouldn't be too long before we see ECM pumps on loading units as an option on this side of the pond. The lk810 eco has a 3 speed Alpha(50 Hz).

Fewer pumps and less power usage sound good to me.

Noah


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## __dan (Mar 3, 2013)

Drawing is very close to my as built but it is closer to my idea of a reference design. I don't know if I will get enough heat passively from the storage as shown but I do know I get enough straight from the Froling supply header, when the Froling is firing. I have a circ there and disabled it, I do not have to pump through, plenty heat rises.

Primary concerns, fast heat from repeated cold starts bypassing storage at startup. Direct isolated, and heat trapped loops do not heat up idle piping. Mod con boiler would have OAT reset and DHW priority call built into the boiler, so, taps directly into the loads. Using OAT reset built in the mod con boiler and bypassing storage increases efficiency, lowers RWT, boiler firing turns down and goes off earlier every firing cycle.

Drawing shows the LK 810 loading unit which will close off flow to the boiler as return temp drop below 150 F or so, reducing boiler standby loss while drawing from storage (but I could redraw it to show the BWRT protection built into the pump controllers).

Tried to show a hydraulically separated flow between DHW and storage to maintain stratification, DHW has a high flow and high return water temp while storage would want to come off and return slowly. Since electrical is my thing and not heat, this last part is the one I would like heat engineered (can I take heat from storage slowly and passively as shown?). Indirect over plate and frame because water soluble minerals in the cold water supply, when heated will cause mineral precipitation either in the tank or on the HX plates. Low grade service techs in the future will cut and replace the plate and frame HX rather than clean it, just like they will chop the ECM circs and replace with old style PSC. Codes and reference designs will have to change to make a market in this.

Lastly, This is the only thing I would consider when building new (in cold climates). Found the link in another thread here. Insulated envelope totally surrounding the foundation, Heat that radiantly and there's most of your storage and distribution problems solved, very simply.

http://www.nauglerhouse.com/foundation.html

Fresh drawing in the last hour for your viewing pleasure.


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## Willman (Mar 4, 2013)

Can't comment on the control or electrical end of your install but wonder how the long length of horizontal smoke pipe works out? Any ash issues?


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