I live in an off-grid solar powered home in Lakes Region, NH. For DHW and radiant underfloor heating (RUH) we have a 1200+ gallon tank (concrete with insulation and liner) with is heater in summer by solar thermal and excess solar electricity. In winter we need more heat and we have a wood boiler which can lift temperature up 30 - 40 degrees in a day. Both we and wood boiler are getting old, and we can’t find people willing to repair it.
In winter, the tank loses about 10-15 degrees a day on cloudy days (sunny days raise the temperature, but it can be cloudy for days on end). As long as its above around 105 degrees, we are fine; that’s warm enough for a shower. But that’s not warm enough for RUH.
My wife would like to use a fossil fuel, like propane, to heat the tank.
We actually rarely use the RUH as our woodstove keeps us warm on the main floor of our house, but our guestroom in basement is too cold without it being on. I have been thinking of getting either a tankless water heater or a propane boiler (not sure of the difference). My plan is to set the thermostat so that whenever it gets down to 110 degrees, the propane heat brings the water up to 120 degrees. That way we can run radiant heat if we want it and system will just keep coming back to 120 degrees if we draw it down.
In winter, the tank loses about 10-15 degrees a day on cloudy days (sunny days raise the temperature, but it can be cloudy for days on end). As long as its above around 105 degrees, we are fine; that’s warm enough for a shower. But that’s not warm enough for RUH.
My wife would like to use a fossil fuel, like propane, to heat the tank.
We actually rarely use the RUH as our woodstove keeps us warm on the main floor of our house, but our guestroom in basement is too cold without it being on. I have been thinking of getting either a tankless water heater or a propane boiler (not sure of the difference). My plan is to set the thermostat so that whenever it gets down to 110 degrees, the propane heat brings the water up to 120 degrees. That way we can run radiant heat if we want it and system will just keep coming back to 120 degrees if we draw it down.
Is a propane boiler or a propane Hot Water Heater better for this purpose? I imagine it will take several hours to heat the tank up to 120 degrees. Will a THWH cope with extended burn times. What kind of boiler? It seems to me a combi unit does NOT make sense as our radiant tubing pulls from our warm tank, and warming water from 110 to 120 degrees is a lot less than warming it from 55 to 120 degrees if we used combi unit. How do I find a non-combi propane boiler? Will it let me program it to cut off when tank water (i.e incoming water) hits 120 (the loop would run into tank and come back from tank). I’ve asked my plumber, but this unique heating system has him stumped, and me too as to upgrading it to make it easier on my wife and I. Any thoughts?