Print

[MTJAG]

Your diagram doesnt' match my setup.  My heat exchanger mounts directly before my propane boiler on the manifold return "cold" line of the existing propane boiler.   Also, what is that extra pump for between the heat exchanger and your common manifold?   

[mingom]

Not sure.  trying to figure that out.  Thats what the clamp on aquastat at the heat exchanger is wired to via a taco SR 501 zone switching relay.

[MTJAG]

after looking again at your diagram, it seems something is amiss.  Did your return line from your zones originally run back into your propane unit?   

My setup has my original install of the propane system and zone as a completely closed loop.  My install of my OWB is also a closed loop and the two systems are "connected" by the heat exchanger.
However, on my original propane/infloor heat system, the return line from the zones came back into the propane furnace.  On your diagram, it's not clear that is the case.  According to my understanding of your diagram, both the propane furnace and the OWB feeds a common manifold that feeds your zones.  Then, the return line from your zones flow back to the OWB.  The feed loop on your propane unit comes from where?  As long as your propane furnace has cool water coming back from the zones, it will fire...does that make sense?

[RSI]

It looks to me like the gas boiler is off on it's own loop sort of. If I am looking at it right no water will flow through the gas boiler.

It appears that a Tee was added to the return line and a fitting was added to the supply manifold.

If that is how it was installed, I would put it back how it started and put the plate heat exchanger in series with the return line going into the gas boiler.

If you want to be able to control the heat so as much doesn't go out to the boiler if you had to run the gas burner I would put the plate heat exchanger on a secondary loop with it's own pump and feed both supply and return from the plate loop into the return line just before the gas boiler.

[mingom]

The confusion is my fault.  There is also a common manifold on the return side that ties into both the propane unit and runs out as the cold side to the heat exchanger

[mikenc]

Dosen't match my set up either. I have oil boiler. My supply from owb goes to one side of heat exchanger then out of heat xkchanger back to OWB. Other side is then piped into oil boiler. It is piped with reverse flow. Oil boiler water never mixes with owb water.Piping of oil boiler is piped with with tee in return from house going into HX then out of hx back to boiler. A valve is between tees for by pass of hx when i only use oil boiler.Return line from hx to boiler has pump which runs 27/7. A tee is in oil boiller supply going into return hw  to give constant flow through oil  boiler. Will try to post pics later.

My existing oil boiler system has not been changed at all. Only hx was added to heat it with OWB.
Your propane system should remain a closed loop pressurized. Owb will be open loop not presurized.





[attachment deleted by admin for space issues]

[mingom]

Possibly my drawing is wrong, but they systems are completely seperate.  Hot water in from OWB, transfers heat through HX, cold returns to OWB.  Cold Enters HX from propane system, exits warm from HX.  The fluids never mix.  I think I drew it wrong, they only interface through the heat exchanger.

[Ridgekid]

do they cross flow?  (like though my DHWX?)

http://outdoorwoodfurnaceinfo.com/forum/index.php?action=media;sa=media;in=159;preview

[mikenc]

Maybe I just looked at it wrong. will try to post pic
Do you have a pump circulating water through HX on propane boiler side all the time. All return piping from house should go through HX before going back to Prop Boiler.

[attachment deleted by admin for space issues]

[mingom]

Did a little research last night, looking into the system a little more.  I had made a mistake.  Hot side of HX goes to cold side of manifold of system, cold side is fed from hot side of system through the circulator I've been mentioning.

[mikenc]

Does your pump on propane boiler side run all the time circulating water through HX. If so it should keep your boiler close to same temp as your OWB.

[mingom]

It does, as long as the aquastat is satisfied. If not, it'll shut off the circulator I believe.  Starting to get a better understanding of how the system works, just not why I'm still burning propane.  I'm afraid it could be heat loss in the underground lines, but I'm not sure.  My OWB has been pushing to get its temps up over 175 this morning, so I'm also wondering if its not transferring the heat well at the boiler.  Does a creosote build up prevent the water temps from coming up at all?

[mikenc]

Only if your flue is clogged keeping owb from comming up to temp. I Would try letting pump run constant to keep prop boiler up to temp all the time. If your operating control on prop boiler is set to close to acutual water temp of OWB it will call for heat when a load is placed on boiler causing prop boiler to fire.

You should have a by pass from prop boiler supply going back to HX inlet to circulate water and maintain boiler temp at all times. You make need a check valve in return to HX before tee so water has to go through HX instead of flowing other direction based on your piping.

[mingom]

Aquastat is set to 75 degrees so the pump never shuts off.  There is a taco check valve after the circulator so that it can't feed backwards

[mikenc]

Aquastat is set to 75 degrees so the pump never shuts off.  There is a taco check valve after the circulator so that it can't feed backwards

Not sure of your piping arrangement but check valve after pump will not stop flow from going wrong way at HX if you have by-pass from supply to hx inlet. Pump should be in hx outlet or at least that is how i piped mine. so you are pulling water through hx instead of pushing. Will work either way but mechanical engineers say to pull through equip instead of pushing through.