NC4AB
ArboristSite Member
The oil furnace was propably sized with some safety factor. (Hopefully it does not run 24x7)
Your system will be limited by the weakest (smallest) link. Bear with me on the numbers and feel free to PM me if you need clarification:
If you have the standard Taco 009 pump on the H4 the maximum flow the pump can do is 10 gpm (with 0 back pressure).
Not seeing how many elbows and fittings are on your system I will take a guess that it is ~300 equivalent feet of pipe worst case (100 ft supply + 100 ft return + 100 ft for fittings). From previous experience 6 gpm in a 1" PEX gives ~ 5.5 feet of pressure drop per 100 ft of pipe so the pressure drop would be 16.5 feet. The 009 is good for ~20 feet of head at 6 gpm so you would be OK.
You are correct that at reduced flow your return temperature will be lower so you will be transfering more heat. Say you have your stove water temperature set at 180F and drop the return to 120F = 60 F drop which is still going to provide you with ~100F degree air which works out magically to ~ 180,000 btu/hr.
On the air side of the heat exchanger you are going to have to be honking some air through the exchanger to get 180,000 btu /hr. Assuming the house is set at 65 F with 100 F exit air temp you will need to move ~4,800 cfm through the air side of the heat exchanger.
I hope that your load is not a continuos 180,000 btu/hr because if it is you will be feeding the stove 24 x 7.
Good luck !!
Your system will be limited by the weakest (smallest) link. Bear with me on the numbers and feel free to PM me if you need clarification:
If you have the standard Taco 009 pump on the H4 the maximum flow the pump can do is 10 gpm (with 0 back pressure).
Not seeing how many elbows and fittings are on your system I will take a guess that it is ~300 equivalent feet of pipe worst case (100 ft supply + 100 ft return + 100 ft for fittings). From previous experience 6 gpm in a 1" PEX gives ~ 5.5 feet of pressure drop per 100 ft of pipe so the pressure drop would be 16.5 feet. The 009 is good for ~20 feet of head at 6 gpm so you would be OK.
You are correct that at reduced flow your return temperature will be lower so you will be transfering more heat. Say you have your stove water temperature set at 180F and drop the return to 120F = 60 F drop which is still going to provide you with ~100F degree air which works out magically to ~ 180,000 btu/hr.
On the air side of the heat exchanger you are going to have to be honking some air through the exchanger to get 180,000 btu /hr. Assuming the house is set at 65 F with 100 F exit air temp you will need to move ~4,800 cfm through the air side of the heat exchanger.
I hope that your load is not a continuos 180,000 btu/hr because if it is you will be feeding the stove 24 x 7.
Good luck !!
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