# Topping off the tank



## VeggieFarmer (Oct 4, 2008)

1) What sort of storage-tank temperatures are people achieving? I've read talk of 170 to 175 in some other posts but have only managed 162 F myself, after a half dozen fires. I'm hoping to reach 170 after I insulate the boiler-to-tank pipes (25 foot run, losing 6 to 8 degrees along the way.) Any other tricks out there?

2) Any consensus on how much to push the gasifier once the fan starts modulating? On the one hand, having the wood smolder between fan bursts seems inefficient, but on the other, once the boiler is hot, it seems a shame not to try to push the storage temp. as high as possible.

3) Any simple control method for preventing the boiler circulator from pulling heat back out of the storage tank as the fire goes out? In the case of the EKO-40, the circulator comes on at 60 C and stays on as long as the water temperature stays above 60 C. If the storage tank has been pushed to 72 C, the circ. will pump heat out of the tank for hours until either the fuel light come on or I remember to turn off the fan/power. Seems like there ought to be a better way.


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## Nofossil (Oct 4, 2008)

VeggieFarmer said:
			
		

> 1) What sort of storage-tank temperatures are people achieving? I've read talk of 170 to 175 in some other posts but have only managed 162 F myself, after a half dozen fires. I'm hoping to reach 170 after I insulate the boiler-to-tank pipes (25 foot run, losing 6 to 8 degrees along the way.) Any other tricks out there?
> 
> 2) Any consensus on how much to push the gasifier once the fan starts modulating? On the one hand, having the wood smolder between fan bursts seems inefficient, but on the other, once the boiler is hot, it seems a shame not to try to push the storage temp. as high as possible.
> 
> 3) Any simple control method for preventing the boiler circulator from pulling heat back out of the storage tank as the fire goes out? In the case of the EKO-40, the circulator comes on at 60 C and stays on as long as the water temperature stays above 60 C. If the storage tank has been pushed to 72 C, the circ. will pump heat out of the tank for hours until either the fuel light come on or I remember to turn off the fan/power. Seems like there ought to be a better way.



Good questions. This is what happens when theories meet the real world. I'm assuming that you have a heat exchanger in the system - perhaps an unpressurized tank? I have the exact same issues, although I've reached 170 a few times. Usually, I end with a tank top closer to 160. I didn't appreciate the heat exchanger issue when I built the system. As the storage gets closer to the boiler output temp, the heat exchanger's effective heat transfer capacity drops off pretty dramatically. That's the main reason I now recommend pressurized storage where practical.

I tend to build my fires in the late afternoon or evening. Part of my thought is that when the storage starts to get hot, it would be helpful if the house called for heat once in a while. That's more likely when it's dark and cold outside.

Idling is really bad when you're in the earlier phases of a burn - when a lot of wood gas is being produced and moisture is being driven out of the wood. Later in the burn, you're mostly oxidizing charcoal. The efficiency hit for idling is pretty minimal then, and I expect a bit of fan cycling in the last hour or so of a burn.

As to your last question, the answer is 'no', at least with my limited skills. I've never found a simple solution to that problem. You need to be able to compare two temperatures and make a control decision based on the difference. I ended up with a computer to do that for me.

The only thing I can think of that falls into 'simple' would be to put the EKO on a timer. It would take some experimentation, but perhaps you could estimate closely enough so that you could have it shut down somewhere close to the right time.


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## steam man (Oct 4, 2008)

[3) Any simple control method for preventing the boiler circulator from pulling heat back out of the storage tank as the fire goes out? In the case of the EKO-40, the circulator comes on at 60 C and stays on as long as the water temperature stays above 60 C. If the storage tank has been pushed to 72 C, the circ. will pump heat out of the tank for hours until either the fuel light come on or I remember to turn off the fan/power. Seems like there ought to be a better way.[/quote]

The solution I use is what nofossil mentioned:comparing two temperatures. I only have a wood stove with heat exchangers right now but I use a solar differential controller to compare the heat at the wood stove exchangers to the storage tank. I use about a 20 deg start and shut it down at about 5 deg differential. This way the boiler has to be higher than the storage for the circ to run. If you wired it in series with your 60c controller it should work fine. Mine does. You can probably get what you need for under 150 bucks.

Mike


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## jebatty (Oct 4, 2008)

> What sort of storage-tank temperatures are people achieving? ....how much to push the gasifier once the fan starts modulating?



Hitting the 160-165 is pretty easy. I can get to the 175 area with cycling of the draft fan, which works best as nofo says towards the end of the burn, definitely not the early part. My plate hx on the high end will achieve just about a 5* temp differential between water in from boiler and temp out to storage. The main issue is that the Tarm draft fan shuts down at about 185 and that is as high as it can be set. If it could be set higher, then higher temps could be delivered to storage. However, I honestly don't need higher than 165.



> Any simple control method for preventing the boiler circulator from pulling heat back out of the storage tank as the fire goes out?



I use a timer. With a full load of pine (my primary wood), 8 hours on the timer is about right. The load is usually done burning in about 6 hours, and the extra time is just to make sure. If it did shut down a little early, all that would be left would be charcoal embers and that would not pose any problem. A little issue here, though, too. The timer I have been using is an electronic digital timer, and if we have a power glitch, it shuts off. Not good if it shut down 1 hour into the burn. I will be getting a mechanical timer.


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## Reggie Dunlap (Oct 4, 2008)

Steam Man- I have that problem. As the boiler comes down in temp it cools off the tank until the aquistat shuts off the circulator. I manually turn up the aquistat  as the fire is dying to prevent this, but you have to be there.

I don't know of any control that will work.


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## steam man (Oct 4, 2008)

Reggie Dunlap said:
			
		

> Steam Man- I have that problem. As the boiler comes down in temp it cools off the tank until the aquistat shuts off the circulator. I manually turn up the aquistat  as the fire is dying to prevent this, but you have to be there.
> 
> I don't know of any control that will work.



Simply put, the circ stays on because of the heat coming back from the storage tank. It doesn't see a positve heat output from the boiler and doesn't know the difference. I use Tekmar, Thermomax, and Resol controllers. I would suggest maybe a simple Tekmar differential controller, maybe a model 155, http://www.tekmarcontrols.com/prod/155.shtml. It uses thermisters for sensing. Obviously there are others out there that will work.

Mike


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## deerefanatic (Nov 4, 2008)

nofossil said:
			
		

> Good questions. This is what happens when theories meet the real world. I'm assuming that you have a heat exchanger in the system - perhaps an unpressurized tank? I have the exact same issues, although I've reached 170 a few times. Usually, I end with a tank top closer to 160. I didn't appreciate the heat exchanger issue when I built the system. As the storage gets closer to the boiler output temp, the heat exchanger's effective heat transfer capacity drops off pretty dramatically. That's the main reason I now recommend pressurized storage where practical.



Hey Nofo, I get 172 at the top and 156 out the bottom with my flat plate routinely.  Course, 70 plate flat plates can do that for you.... And I'm getting plenty of idling at the end (about 40% on time, and 60% off time for the stove fans)


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## Nofossil (Nov 4, 2008)

deerefanatic said:
			
		

> Hey Nofo, I get 172 at the top and 156 out the bottom with my flat plate routinely.  Course, 70 plate flat plates can do that for you.... And I'm getting plenty of idling at the end (about 40% on time, and 60% off time for the stove fans)



I recently hit a tank top temp of 178, but the middle and bottom were only 162 and 160 respectively. Lots of idling is the price to pay in trying to get maximum tank temp through a heat exchanger.


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## pybyr (Nov 4, 2008)

nofossil said:
			
		

> deerefanatic said:
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I'm still in the spot of acquiring and assembling parts (with the zeal of a man who cancelled his oil deliveries and does not want to freeze or starve)-- but

with a tank that is not temp-limited like the liner types-

and with a 150mbtu boiler,

and with a 5"x12"x70 plate HX, and,

with 4 way valves for counterflow across both sides of the plate HX, and,

once I get the initial shakedown bugs out of my system,

I aim to eventually "put the boots to" my tank, in the extreme, in hopes of pushing the tank as close as I can to boil without either hitting actual boil in the tank or getting cavitation in the circulator on the unpressurized side of things

time will tell, and suggestions are welcomed!


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## WoodNotOil (Nov 4, 2008)

I am glad to see I am not the only one getting a lot of idling near the top end.  My experience is similar to deerefanatics through my flat plate hx (but I only have 30 plates).  I get the temp up between 160-169 usually.  I haven't crossed over the 170 mark yet and don't intend to until I am certain my top tank temp reading is accurate.  I don't want to exceed the limits of my EPDM liner.  I end up with a stratification of 18-20*.  I like seeing others data for comparison.


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## Blevesque (Nov 4, 2008)

I'll second the tekmar control. I just picked up the 156, although its not installed yet I think it's going to make my system operate much better. Right now I have my Tekmar 374 reset control jumped out to run the wood boiler pump all the time. If i didn't the 374 shuts everything done when there is no call for heat. When the 156 is hooked up this will keep the wood boiler pump running to try and achieve the diff. in the tank until the fire dies down and shuts the pump off. Then when there a call from the house the 374 will call the pump back on. Last night I was able to get 186 in the tanks. Next I have to work on someway to shut the combustion fan off when the fire starts to die. If anyone has a cheap solution other then a timer switch let me know.


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## free75degrees (Nov 4, 2008)

I am getting to 175 at the top with no idling, which I am thrilled with.  I was a little worried about my HX, because it is a configuration that isn't exactly like anybody else's who I have heard of.  I have 4 coils of 1/2" copper in parallel, each one is about 85 feet total.  I just got all three of my sensors working (Dallas semiconductor 1 wire sensors interfaced to a ts7800 arm SBC).  The highest energy storage I have achieved is 176 at the top, 165 in the middle and 145 at the bottom.  I confirmed the top temp with a mercury lab thermometer.  Now that I have all 3 sensors working I plan to push the limit to see how much energy can cram in.

For the 3rd question, I don't know of a simple solution.  I am planning on doing something lik nofo where he compares the boiler output temp to the tank temps to decide whether to keep charging the tank.


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## mpilihp (Nov 4, 2008)

steam man said:
			
		

> [3) Any simple control method for preventing the boiler circulator from pulling heat back out of the storage tank as the fire goes out? In the case of the EKO-40, the circulator comes on at 60 C and stays on as long as the water temperature stays above 60 C. If the storage tank has been pushed to 72 C, the circ. will pump heat out of the tank for hours until either the fuel light come on or I remember to turn off the fan/power. Seems like there ought to be a better way.



The solution I use is what nofossil mentioned:comparing two temperatures. I only have a wood stove with heat exchangers right now but I use a solar differential controller to compare the heat at the wood stove exchangers to the storage tank. I use about a 20 deg start and shut it down at about 5 deg differential. This way the boiler has to be higher than the storage for the circ to run. If you wired it in series with your 60c controller it should work fine. Mine does. You can probably get what you need for under 150 bucks.

Mike[/quote]

Hi Mike could you explain how the solar differential controller works?  Where are the sensors and how its configured?  Sorry im new to the concept and I cant wrap my mind around it.  Your saying the boiler output has to be higher than the storage for the circ to run.  Is this circ the wood boiler circ or one just for circulating to the storage?  IE I have a aqusat on the wood boiler that at 170D to start and run, with the Diff set to 5 which I think means it will shut off at 165.  IE start running at 170 and above and stop running at 165 deg.   Are you putting a sensor on the output pipe of the wood boiler and as long as the temp of the water in the pipe there is hotter than the storage temp it will allow the circ to run?  so would I put this in series with the aqustat on my wood boiler that activates the wood boiler circulator??  Or would it just replace this aqustat?

Sorry for the confusing questions..

~ Phil


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## Hansson (Nov 4, 2008)

I can reach 220 in the top of the tank and 203 in the bottom of the tank.
My boiler don't have the modulating fan thing. The boiler stops the fan when the temp is to high

I now some people here are modifying the temp sensors on the Orlan Super to reach higher temperatures.


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## steam man (Nov 5, 2008)

mpilihp said:
			
		

> steam man said:
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Hi Mike could you explain how the solar differential controller works?  Where are the sensors and how its configured?  Sorry im new to the concept and I cant wrap my mind around it.  Your saying the boiler output has to be higher than the storage for the circ to run.  Is this circ the wood boiler circ or one just for circulating to the storage?  IE I have a aqusat on the wood boiler that at 170D to start and run, with the Diff set to 5 which I think means it will shut off at 165.  IE start running at 170 and above and stop running at 165 deg.   Are you putting a sensor on the output pipe of the wood boiler and as long as the temp of the water in the pipe there is hotter than the storage temp it will allow the circ to run?  so would I put this in series with the aqustat on my wood boiler that activates the wood boiler circulator??  Or would it just replace this aqustat?

Sorry for the confusing questions..

~ Phil[/quote]

This thread has been around.  No problem. The problem with the aquastat is that it only sees the boiler temp. On at 170-of at 165. Say you heated the tank up during a cycle to above 165. As long as it stays there it just keeps circulating back to the boiler. If the boiler is not generating a positive heat output, it will stay at whatever temperature water the tank is sending to it until the water cools below 165 and the circ shuts off. Now the tank has given up its heat to the boiler. If you use a differential controller to measure both the boiler and the tank, you can shut the pump off while it still has a slightly positive heat output which is before the tank starts to give up heat to the boiler. The Tekmar 155 is pricey but there are other differential controllers that may work and are are used for wood boilers. A good controller can be programmed for minimum boiler temp, maximum tank temp, and other variables. It can just replace the aquastat. Note that they are not used for safety shutdown devices so that has be a consideration when installing. In that case a series wiring may be all that is needed. The sensors need to be where you can measure accurately with a good response. Probably at the outlet pipe close to the boiler. The tank temp most likely near the lower part inside a well.
I know mine works flawlessly.

Mike


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## NHFarmer (Nov 5, 2008)

I have built the same HX as Free75.With the Tarm Solo 40 I have been able to get the top of the tank to 170* with no problem.So far,one burn per day is all I need to meet my needs.I am sure it will be different once it really gets cold,but so far it has been working great!


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## Nofossil (Nov 5, 2008)

NHFarmer said:
			
		

> I have built the same HX as Free75.With the Tarm Solo 40 I have been able to get the top of the tank to 170* with no problem.So far,one burn per day is all I need to meet my needs.I am sure it will be different once it really gets cold,but so far it has been working great!



I only ever do one burn per day. On cold days, though, the burn could be 12 hours.


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## NHFarmer (Nov 5, 2008)

nofossil said:
			
		

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Boy would that be nice


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## free75degrees (Nov 6, 2008)

nofossil said:
			
		

> NHFarmer said:
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How many refills do you need to keep it going 12 hours?  I was a bit suprised at how quickly I go through 1 full load of wood - about 3 hours at full gasification.  Is this normal?  Should I be reducing my primary air?


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## NHFarmer (Nov 6, 2008)

Free75 I also go thru a full load in about 4 hours if I don't top it off half way into the burn.I do cut my wood 16"long and that does leave some empty space in the firebox.I was thinking that was why I had such short burn times


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## chuck172 (Nov 12, 2008)

Has anyone come up with another solution to prevent the wood boiler circulator from removing heat from storage as the fire dies down? I believe so far the only options are a timer, a differential control, manually turning up the aquastat.


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## pybyr (Nov 12, 2008)

chuck172 said:
			
		

> Has anyone come up with another solution to prevent the wood boiler circulator from removing heat from storage as the fire dies down? I believe so far the only options are a timer, a differential control, manually turning up the aquastat.



I am hoping- when I get that far- to put a thermal switch on the stack, so that once the fire goes out, that thermal switch, by way of a relay, kills power to the boiler's blower and the boiler's circulators.  My plan is to have a temporary-on timer with a push-button switch to briefly override the temp switch for when the fire is first lit and getting started.


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## chuck172 (Nov 12, 2008)

I'd think you would need more precise control. If the storage tank is 180*, the controller should stop circulation to the tank if under that temp. But in my case still feed zones which call for heat till I hit a low limit of about 140*


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## Nofossil (Nov 13, 2008)

free75degrees said:
			
		

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I get about 5 hours on a really full load, plus another hour or two of cool down where there's still heat being generated. I'll refill every three or four hours as needed. On a typical winter day I'll do an initial load that's good for an hour or so, then a three hour load, and then one last three hour load at bed time.

My control system is differential on steroids. I'll actually select loads and circulator speed to keep the boiler outlet temp in the range that I need. As the storage tank gets hot, I'll slow the circ to raise the boiler outlet.


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## mwk1000 (Nov 13, 2008)

This has been an excellent place to learn. I am glad I found it before I finished my install. I would never have caught the reverse heat drain.  Until after I was done of course ! I will be adding the tekmar to my design. My plans look similar to much that I have seen here. I built an 8x6x5 ( Inside dimensions ) tank in my basement with the boiler in the garage. I have a HX 5x12-70 with a pump each on the tank and the boiler side. I will add the teckmar to the two input sensors on the HX and when the tank and boiler temps flip ( or get to close ) I can shut down the tank side pump. I'll leaved the boiler circuit alone. It will pump but it should cool down normally without stealing from the tank

This tip.

The paraffin wax on top for evaporation I liked.

The stability of polystyrene ( That one may cost me some rework since that is what I used ) I have a couple of chunks of my materials in a boiling pot for the last 12 hours to see how they do at 190 and I'm hoping for the best. FYI the pink home depot stuff expanded and got soft at 212 but the blue was a MUCH better. It did distort but only slightly at boiling for 1 hour. So far no distortion of either at 190. I'm torn since 12 hours does not = 10 years. But I was planning on a 175 tank temp 180 tops if I could hit it. I may loose some capacity by lowering the temps, There is OSB over the Insulation so if the boiling blocks look ok tonight I'm going to run with it.

Some of the code clearances -- I'm in Michigan and someone mentioned an 18" off the floor requirement.

I was planning 1 burn per day based on my BtU  calcs for the house and tank and boiler. The discussions here make me think it might happed. The house is 84,000 BTU / hr at -15 so I figured on the tank for 16 Hours.

Thanks to all for the comments you have saved me some future grief I am sure.

my stuff:

EKO 60, DIY tank at 1500 usable gal 60 foot run of 1" Pex-al-pex to garage based boiler. two zones using an air exchanger in existing furnaces draw from tank side of HX. Tank is done, Chimney is done, Line set is run and insulated. Setting Boiler and plumbing to lineset and chimney is next ....


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## RJP Electric (Nov 13, 2008)

chuck172 said:
			
		

> Has anyone come up with another solution to prevent the wood boiler circulator from removing heat from storage as the fire dies down? I believe so far the only options are a timer, a differential control, manually turning up the aquastat.



I gave this one some thought too in the past. You already have a aquastat on the tarm that opens on temp decrease (or closes on temp rise no matter how you look at it)
You could put another one in series with it by the bottom of the tank or return pipe that will open on temp increase.
With that said you keep your tarm set at the origional temp setting and will work as normal, when tank is charged and set at 160* it will open the circuit and stop your pump


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## WoodNotOil (Nov 13, 2008)

MWK1000

Polystyrene is supposed to be only good up to 165* (http://www.engineeringtoolbox.com/insulation-temperatures-d_922.html).  It would be worth picking up some polyiso (300* limit) and putting a layer of that in over the polystyrene.  I went with all polyiso due to the higher R value and high temp limit, but I think even 1/2" polyiso would probably protect the polystyrene enough.


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## mwk1000 (Nov 13, 2008)

WoodNotOil said:
			
		

> MWK1000
> 
> Polystyrene is supposed to be only good up to 165* (http://www.engineeringtoolbox.com/insulation-temperatures-d_922.html).  It would be worth picking up some polyiso (300* limit) and putting a layer of that in over the polystyrene.  I went with all polyiso due to the higher R value and high temp limit, but I think even 1/2" polyiso would probably protect the polystyrene enough.




Yes, I caught that yesterday and did some digging and testing of my own, From a materials safety report I found this:

Polystyrene is a thermoplastic and, by definition, has a well-defined temperature at which the polymer softens. The upper temperature limit before cellular polystyrene foam softens, as specified in the ASTM Specification C 578 [13], is 74 °C. 

Mehta et al. [18] reported that similar polymer polystyrene beads when exposed to elevated temperatures collapsed about 110 to 120 °C. The collapsed beads melted at 160 °C and began to vaporize above 275 °C [18].

Flammability
Standard Reference Material 1453 is a commercial grade of expanded polystyrene foam that does not contain fire-retarding additives. It is an organic thermoplastic material that is combustible and, at elevated temperatures melts (> 160 °C, [18]). For safety, do not expose the material to sources of ignition.

Solvents 

Polystyrene is soluble in many organic solvents such as chlorinated and aromatic hydrocarbons,esters, and ketones. The aromatic chemical structure of polystyrene is inherently water repellant.

As noted in Appendix D, the material is very insensitive to low levels of humidity. Ultraviolet Degradation When exposed to sunlight (ultraviolet radiation), polystyrene degrades as evidenced by discoloration of the surface. To minimize degradation


I boiled it at 212 and 190 to see what "softens" means. I'll try to put up the picture as it says a lot. It holds up at 190 with no detectable softening after 12 hours in the top of the boil pot. It's pretty clear that the Dow ( Blue ) holds up better than the Owens ( Pink ) material at 212. I have 7/16 OSB between the 60 Mil EDPM and the foam.


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## WoodNotOil (Nov 13, 2008)

You can see how it goes, but remember "the fastest way to do it, is to do it right the first time."  I think you need to pull the liner and put some polyiso under it.  Just my $0.02

On another note, how did you like working with cement blocks?  Did you backfill them all and rebar?  When I did mine it felt like it took me forever!  I would pour it in a form if I had it to do over.


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## DaveBP (Nov 13, 2008)

Kitchen table science at its finest!


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## mwk1000 (Nov 13, 2008)

Yes, I hear you and I'm not the type to want to "wing it".  I'm figuring out if there is a way to be sure ( Short of pulling it ) . I have the deck on it now so it will be a bigger pain to pull it.  As for the Kitchen table science, it beats maybe ... Kinda... Should ... Never hurts to have some actual proof for your decisions. If it winds up being some hokey fix then I'm just going to pull it and add the extra. I would never be able to stand knowing it was rigged.

Also, it was a lot of work toting in 5 gal buckets of cement, It is pinned to the walls and floor with rebar and cement/rebar filled to the top. It took me longer than I was planning as well.


I am getting a good feel for the upper end of Tank temperature, What is the low end to still be useful. I have water-> air exchanger 20"x20" in the furnace and was wondering what the low end was that people were using ?


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## WoodNotOil (Nov 13, 2008)

Back to the original topic. . . I think this control by Azel http://www.azeltec.com/catalog.0.html.0.html#DST-777 is made to accomplish the same thing as the Tekmar 156.  Thoughts?  I think it is a little bit less expensive and it uses line voltage instead of needing a 24vac transformer like the Tekmar.  It also displays the temp from both sensors, so no separate tank theremometer would be needed for a top of tank reading.  It says it can be used for tank heating.  Would it work as well as the Tekmar?

I didn't know controls existed for this application.  This is exactly what I have been looking for.  Does anyone know of any other brands for comparison?

Edit: The Azel DST-7772 is actually $155 making it just a few dollars more than the Tekmar 156 which is $150.  However as I said above the Tekmar needs a 24vac transformer which would add to the cost.  (unless you already have one in your setup)


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## DenaliChuck (Nov 14, 2008)

Might the "simple differential control" at the bottom of this web page be modified to run any pump?  At $86 it is inexpensive...

http://www.sssolar.com/pumps.asp


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## DenaliChuck (Nov 14, 2008)

Good find WNO!

I just looked at their site and saw there is a model that has four sensor inputs, two relay outputs and can control two pumps.  Seems like this would be a good controller for those (like me) that might plumb in a solar collector since the one controller could control the wood boiler circ and a solar collector circ.

Do I understand this correctly?

https://www.azeltec.com/customer/product.php?productid=16170


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## chuck172 (Nov 14, 2008)

I'm a little confused about the circulator differential controller. I would like to be able to stop the wood boiler hw from circulating through the storage tank when the storage tank is hotter. I now  use the boiler circ. pump to satisfy the heat loads of my zone valves. When the boiler drops below its aquastat temp,(140*) I use the storage tank. If the differential control cuts off the wood boilers circulator pump, it couldn't heat the zones.


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## WoodNotOil (Nov 14, 2008)

Chuck

I think in the setup originally mentioned (and mine as well) the wood boiler circ runs giving heat to the regular system (zones etc.) and a separate circ runs to charge storage.  It is that separate circ that we want to shut off as the temp of the wood boiler drops below the temp of storage so we don't give heat back from storage after charging.

The Pump Control Model 2W2 Delta you mentioned looks interesting, but I can't tell how you set the actual temps.  Are you able to change them?


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## chuck172 (Nov 14, 2008)

Yeah, I guess its back to the timer for me!


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## WoodNotOil (Nov 14, 2008)

DenaliChuck said:
			
		

> Good find WNO!
> 
> I just looked at their site and saw there is a model that has four sensor inputs, two relay outputs and can control two pumps.  Seems like this would be a good controller for those (like me) that might plumb in a solar collector since the one controller could control the wood boiler circ and a solar collector circ.
> 
> ...



If you look at the brochure http://www.azeltec.com/images/dst7772instruction.pdf you will see that it can control two pumps but can only have two sensors.  The 777S and 777D only have one sensor and that is why we would need the 7772 to get the differential.  The price isn't too bad when you consider that it is only the cost of two inexpensive aquastats.  Many aquastats even cost that much but can't accomplish what this thing does.  I have an Azel single stage that controls my floor with a sensor which is what gave me the idea of looking for something in this brand.  As I said before I like the 120vac and two temp display of it over the Tekmar.

Chuck - One of these controls could also trigger a zone valve.  Would that help with your charging? I am not sure how your system is piped.


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## leaddog (Nov 14, 2008)

http://www.termoventiler.se/default.asp?webb_ID=110&webbsida_ID=56&u1_ID=189&u2_ID=195    This might work to shut off the pump when the boiler is lower than storage tank temp so it doesn't pull from tank
leaddog


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## chuck172 (Nov 14, 2008)

The Tarm has a low limit setting to control the fan. It is triggered not by water temp but by stack temperature. I wonder if it can also be used to shut down the pump?


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## WoodNotOil (Nov 14, 2008)

I guess that would be another approach to it.  Find out when the fire dies down and stop the pump.  However, the tank might reach temp before the fire dies out and then the pump would keep running.  How much does one of those cost?  Are there other brands of them?  Where can you buy them?


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## jebatty (Nov 14, 2008)

chuck172 said:
			
		

> The Tarm has a low limit setting to control the fan. It is triggered not by water temp but by stack temperature. I wonder if it can also be used to shut down the pump?



I see no reason why it could not, other than if the current draw exceeds the rating of the Tarm control circuit. But in that event, and maybe regardless out of caution, use the low limit control to operate a 120v relay coil, and the relay contacts control the fan and the circulator. Good idea.


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## chuck172 (Nov 14, 2008)

I think it would work!
It would do what the Laddomat  Flue thermostat control does.


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## WoodNotOil (Nov 14, 2008)

My Tarm Solo 40 does not have a flue thermostat that controls anything.  Is that something you added?  I have a stack thermostat but it doesn't control anything.  From my understanding the fan comes on and off based on the water temp.  If the fire goes out, it just keeps blowing until I go down and turn it off.  Clarify please.


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## chuck172 (Nov 14, 2008)

Don't you have a lo-limit thermostat? It has a probe that you insert horizontally into the firebox. The tarm manual says to set the lo-limit to 140* no storage, or 190* with storage.


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## WoodNotOil (Nov 14, 2008)

I don't think I got one or maybe my installer didn't put it in.  I will check the manual and see what I've got.  That would turn the fan off at the low limit right?  That would be helpful!


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## mpilihp (Nov 14, 2008)

Any thoughts about this pump controller that DenaliChuck posted earlier, its for solar setup being used as a diff controller for topping off a storage tank?

http://www.sssolar.com/pumps.asp

See at bottom of page,


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## oilbegone (Nov 14, 2008)

woodnotoil this is a picture of the low limit probe that is in the smoke box on my solo 30. On top of the boiler insulation there is a silver wire that goes to the upper right corner of the picture with the coiled wire on the end. The probe is inserted just below the wing nut.

I guess in the picture it looks black


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## WoodNotOil (Nov 15, 2008)

I do have one after all!  However, in my manual it had you "Place the longest probe under the insulation on top of the boiler.  This long probe controls the fan low limit which should be set at 60C."  I didn't think I had anything in the smoke box.  I had forgetten about the probe altogether after the install was complete.

The reason mine wasn't working was that it was set to 140C not 60C.  The installer must have misread the dial or something and thought it was Faren.  It works now that it is set correctly even though it is just on top of the boiler.  Strange that your manuals said to put it in the smoke box (I assume from your picture it is in the hx tubes?).  Should I move mine? Does the hx tube cover have a hard time sealing with the wire in it?  Thanks guys for pointing this out to me!


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## WoodNotOil (Nov 15, 2008)

mpilihp said:
			
		

> Any thoughts about this pump controller that DenaliChuck posted earlier, its for solar setup being used as a diff controller for topping off a storage tank?
> 
> http://www.sssolar.com/pumps.asp
> 
> See at bottom of page,



I still can't see any way to set the temp point and differential on it or to keep track of temps at all.  Also, those look more like snap switches than probes.  On snap switches you can't change the temp setting and they aren't very accurate.  I think the Tekmar and Azel units previously mentioned are the best bet for topping off the tank.


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## chuck172 (Nov 15, 2008)

Woodnotoil, Yes you should put it in the smokebox, you have storage. There is a small horizontal hole, below the access plate on the right side,(facing the boiler). The long probe gets inserted in there.
Set the low limit to 190*F


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## chuck172 (Nov 15, 2008)

I wired a 110vac relay to the low limit switch. To the relay I wired  the circ. pump in series. I'm gonna see if I can use the low limit switch to turn off the pump when the fire dies down. It would save buying a differential control.
A problem with this might be if the boiler goes into idle, will the firebox cool and keep the pump off?


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## WoodNotOil (Nov 15, 2008)

Any particular position in there or does it just dangle?

If you have a 110vac tester light you could hook it up to your relay first and watch what it does throughout different parts of a burn cycle.  That should answer you question about idling.  Let me know how it turns out.  If it works it might save a bunch of us from buying more expensive controls.


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## DenaliChuck (Nov 15, 2008)

I've got to say it is great to be able to learn from everybody here!


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## DaveBP (Nov 15, 2008)

> Yes you should put it in the smokebox, you have storage. There is a small horizontal hole, below the access plate on the right side,(facing the boiler). The long probe gets inserted in there.
> Set the low limit to 190*F



I also have a Tarm Solo 40 but I'll be blessed if I can find in the manual where it says to put the low limit sensor in the smoke box. It just says if you have storage you'll have to mount it differently. Thanks, Chuck172. I'm not going to get mine running probably until I don't need it in the spring, but boy am I following this forum and taking notes.


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## 2.beans (Nov 15, 2008)

i installed 24 volt fast acting zone valves on  tank supply line and and one on a cross over/bypass return line. used a sensor in the tank so when the tank hits my desired temp lets say 175* the controller shuts the supply and opens the bypass which returns the water back to the boiler also it shuts off the power to the draft door and wont let it open until the tank drops to my desired differential.  this stops the tank water from mixing. also these valves act like check valve and stop the thermosyphoing . also if the wood boiler starts to creap up in temp the valves open and act as a dump zone sending some cold water from the bottom of the tank to the boiler to cool it down. ive set up three seton boilers like this and seems to be working good so far. now i need to minimize the the circulation on the house side supply and return (next project). heres some pics of my father inlaws valves supply and return tank temp gauges and controller.


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## chuck172 (Nov 15, 2008)

DaveBP-On page 28 of the Alternate Instructions that came with the Tarm Manual:
Insert the longest sensor probe in the sensor well that is  on the right hand front side of the smoke box.


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## mpilihp (Nov 15, 2008)

Hi 2.beans, what is the controller your using to turn your valves open/closed to storage?  Can you post a diagram and wiring of your setup??

Thanks

~ Phil


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## oilbegone (Nov 15, 2008)

In the picture I have the probe in the hole in the front of the smoke box you just can't see it because the insulation is in the way. The coil resting on the wing nut just helps keep the probe in the place. My installer made the same mistake about the low limit dial not reading in Fahrenheit thanks to this forum and all the great information I was able to figure out what the problem was.


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## jebatty (Nov 16, 2008)

Tarm low limit sensor: we must have different instructions depending on our boiler design. On pg 28 of the instruction manual for my Tarm 40 the following is stated:

"Place the longest probe under the insulation on top of the boiler. This long probe controls the fan low limit which should be set at 60 degrees C. The placement and setting of this probe will be different if you have a heat storage system."

I changed the low limit setting to 90C as I have storage.

No mention is made of putting the probe in the smoke box.


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## 2.beans (Nov 16, 2008)

mpilihp said:
			
		

> Hi 2.beans, what is the controller your using to turn your valves open/closed to storage?  Can you post a diagram and wiring of your setup??
> 
> Thanks
> 
> ~ Phil


i use a ranco etc controller.the wiring is pretty simple, the picture attached shows the load contacts at the bottom of the controller there is a NO C NC. you put 24 volt input to C then NC goes to the supply zone valve and NO goes to the bypass zone valve.i didnt take it apart to check this but its easy to set up with a volt meter. you get your supply voltage from a 24 volt transformer and run the red wire to the ranco controller from the ranco controller to the zone valve and the white to the zone valve for the neutral. the ranco in the picture is a dual stage 211000-000. all you need to bypass a tank is a single stage 24 volt model 112000-000.{ it shows in the picture 120 volt on the upper part of the controller but on a 24 volt one its 24 volt.} i hope i didnt make something easy seem confusing.


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## deerefanatic (Nov 16, 2008)

I will address the question asked earlier as to how cool you can run your tank water........

I can keep the house warm down to about 135F water temps. Beyond that, the furnace runs alot and not much heat comes out.. PLus, at night, I probably couldn't get away with less than 145F water.......

I too have a 20x20 air coil in my furnace.....


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## free75degrees (Nov 16, 2008)

jebatty said:
			
		

> Tarm low limit sensor: we must have different instructions depending on our boiler design. On pg 28 of the instruction manual for my Tarm 40 the following is stated:
> 
> "Place the longest probe under the insulation on top of the boiler. This long probe controls the fan low limit which should be set at 60 degrees C. The placement and setting of this probe will be different if you have a heat storage system."
> 
> ...



When I got my manual they gave me a few extra pages of "alternate" instructions because they knew I would be installing a tank.  One of the pages was page 28 with the difference on where to put the probe.  If they didn't think you were installing a tank they might not have given you the alternative pages.  Or maybe the alternates are a newer thing they are giving out.

However, I never figured out the alternate location for that probe so i just put it under the insulation.  Why is it better for it to be in the smokebox when you have a tank?


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## chuck172 (Nov 16, 2008)

jebatty said:
			
		

> Tarm low limit sensor: we must have different instructions depending on our boiler design. On pg 28 of the instruction manual for my Tarm 40 the following is stated:
> 
> "Place the longest probe under the insulation on top of the boiler. This long probe controls the fan low limit which should be set at 60 degrees C. The placement and setting of this probe will be different if you have a heat storage system."
> 
> ...



Jebatty, Check #8


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## rickh1001 (Nov 16, 2008)

I'm kind of late to the party on this thread, but it is an interesting one.  For those of us with EKO's and the RK-2001UA controllers (and perhaps the other models as well), the minimum temp for the circulator on can be adjusted.  The factory default is P144 (on at 144 deg F).  However, I set mine to the maximum of P160.  So if the boiler drops below 160F, the boiler circ will be off, letting me use the storage tank down to about 140F or so with the plenum heat exchangers I am using.  I also have had no problem charging my 500 gal pressurized tank to 175-180 deg, by setting the EKO target temp to 190F.  So at least when I run out of fuel, the tank will retain the water at 160F without further losses to the EKO.  Not a perfect solution to the basic problem, but at least it minimizes the impact in an easy way.


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## mpilihp (Nov 16, 2008)

2.beans said:
			
		

> mpilihp said:
> 
> 
> 
> ...



Hi 2beans thanks, I do better with pictues, here is a sketch of how you have your controller hooked up I think.  Can you fill in the blanks for the controls of each zone valve, IE what contact type NO or NC each is connected to??  Im thinking both zone valves A and B are on a NO contact and C is on a NC contact correct? 

Sensor is set at 175 deg on the tank?  

I can see how this stops charging the tank when it reaches 175 degs, but how does it monitor the temp of the wood boiler and allow charging when the wood boiler temp is hotter than the tank, or if the wood boiler dies before the tank is fully charged, how does this shut off the tank and keep it from being charged with colder water??

http://i103.photobucket.com/albums/m132/mjenphil/WoodBoiler/Storagetankcontrol.jpg

~ Phil


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## oilbegone (Nov 16, 2008)

WoodNotOil said:
			
		

> Back to the original topic. . . I think this control by Azel http://www.azeltec.com/catalog.0.html.0.html#DST-777 is made to accomplish the same thing as the Tekmar 156. Thoughts? I think it is a little bit less expensive and it uses line voltage instead of needing a 24vac transformer like the Tekmar. It also displays the temp from both sensors, so no separate tank theremometer would be needed for a top of tank reading. It says it can be used for tank heating. Would it work as well as the Tekmar?
> 
> I didn't know controls existed for this application. This is exactly what I have been looking for. Does anyone know of any other brands for comparison?
> 
> Edit: The Azel DST-7772 is actually $155 making it just a few dollars more than the Tekmar 156 which is $150. However as I said above the Tekmar needs a 24vac transformer which would add to the cost. (unless you already have one in your setup)




Last night I heated the tank up to 173 and in the morning it was 160, the circulator had been running all night and dropped the temperature in the tank that much. The house temperature had risen from 67 to 70 just from the heat given off, the thermostat was set back to 62 for the night.
These two controllers look like good solutions to the problem and I will eventually get one of them. The wife wants a humidifier first but that is another topic. My electrician installed a separate on off switch for the wood boiler circulator. If I am home when the fire dies out it can be switched off. My question is will it cause a problem if I build the next fire without turning it back on?


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## 2.beans (Nov 17, 2008)

mpilihp said:
			
		

> 2.beans said:
> 
> 
> 
> ...


ill send you a pm  tomorrows , nice picture.


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## 2.beans (Nov 17, 2008)

i have minute before work, you only need two zone valves, the one on the boiler return you can gat rid of. if your boiler has a dump zone hooked to it you set the dump higher then your tank set point. you use the tank as your dump zone by hooking the dump zone control (24 volt) wire to the tank supply zone valve. so as long as your boiler is putting out higher temp then your tank set point it will still charge your tank and then isolate your tank if its colder.


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## mpilihp (Nov 20, 2008)

Hi 2.beans thanks im still wondering if there is a simpler way.

In the simpliest pressurized storage setup  by Nofo, couldnt there be a threeway valve at the fill point of the tank on top  and it configured as a diverter valve set to only allow water at a min temp of say 170 deg (this value up for discussion) that way when the wood boiler sends water at a lower temp than we want to charge the storage with it will return to the wood boiler.  IE tank gets charged to 170 or above and doesnt get sucked back down by the wood boiler running as it cools off.

Now there would need to be one-way flow check valves to only allow water into the top of the tank through the 3-way valve and there would need to be a bypass line that goes past the 3-way valve with a one-way check valve to only allow water to flow out from the top in this bypass line.  This would be how it would draw hot water out of the top of the tank for heating.

Im sure the diff controllers are a better method to get the most heating out ofthe wood boiler but I like simplicity.  5-10 years from now I dont want to have to deal with dead electronics and have to try and figure them out again and be able to set it back up.....

~ Phil


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