Topping off the tank

[RJP Electric]

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

 

[WoodNotOil]

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.

 

[mwk1000]

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.

 

[WoodNotOil]

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.

 

[DaveBP]

Kitchen table science at its finest!

 

[mwk1000]

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 ?

 

[WoodNotOil]

Back to the original topic. . . I think this control by Azel (broken link removed to 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)

 

[DenaliChuck]

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

 

[DenaliChuck]

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?

(broken link removed to https://www.azeltec.com/customer/product.php?productid=16170)

 

[chuck172]

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.

 

[WoodNotOil]

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?

 

[chuck172]

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

 

[WoodNotOil]

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?

(broken link removed to https://www.azeltec.com/customer/product.php?productid=16170)

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.

 

[leaddog]

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

 

[chuck172]

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?

 

[WoodNotOil]

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?

 

[jebatty]

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.

 

[chuck172]

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

 

[WoodNotOil]

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.

 

[chuck172]

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.

 

[WoodNotOil]

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!

 

[mpilihp]

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,

 

[oilbegone]

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

 

[WoodNotOil]

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!

 

[WoodNotOil]

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.