Watercoil in stack of OWB

[NC4AB]

Scott is right, 18 degrees is low for a temperature drop across the hot water coil.

You might want to check to see if the coil is undersized for your house heat load. The standard TACO pump on a Hardy H2 is good for a nomimal flow of ~ 5 gpm which combined with your 18 degree temperature drop only is allowing ~ 45,000 btu/h of heat transfer into the air.

 

[hondaracer2oo4]

Well here is the story. This is our first year in the house and when we bought the house the current heating unit is/was a FHA oil fired 200k btu with a 2 gph nozzle! I took one look at that thing and figured that the house was going to be VERY difficult to heat. So I went out and bought the Hardy from a guy out in New York selling it because of a repair gone bad. I got it for $500 bucks but needed to replace a section on the back that he had repaired a bung that was leaking and used a mig welder with mild steel wire which leaked something awful. So my brother in law, who is a welder, tig welded a new piece in place for me. After that I started calling around asking about what I should run for lines and a pump. My water to air HX which is a 24x24 in my plenum. I got every answer under the sun and everyones reasoning behind their answer was 'Because I know and I have been doing it for a long time'....Right! So I did the heat loss calculations myself and came up with the need for Dual 1 inch pex lines running each way with a minimum of 12 gpm to keep me in the 20 degree drop range. So I ran dual 1 inch pex lines each way with a Bell and Gossett NRF 36 3 speed pump. When I installed everything I tested the flow on speed 1 and got 10 gpm! I didn't have a container big enough to test the pump on speed 3 but I think I am getting somewhere in the range of 13 gpm on speed 3. I get 1 degree of heat loss from the boiler to the house over a 100 foot run. When the house isn't calling for heat the water will actually lose 7 degrees just flowing through the HX. Anyways I built the system right figuring I didn't want to do it again.

 

[4b316]

stack water heater

We have a pipe about 19 inches long with copper pipe around the outside with another piece of pipe around the out side of the copper(5/8,s).This is a manafactured piece.We have not used it yet as we are concerned with the pipe freezing.If I would of thought quicker,i might of pumbed it into my OWB fill tube and used it to help warm the incoming water and also help keep the boiler water up to temp.we have a taylor 450.I might still try it next year when we relocate the stove closer to the garage so that we can heat both

 

[hondaracer2oo4]

That sounds interesting. Was it made as a flue heat recovery system? I would love to see some pictures of it. I don't think that you would have any issues with freezing pipes if you insulated the exposed piping well since the return line should flow through it the water temp should be in the 150 range at least.