I'd like to replace it with a gas tank heater for lower fuel costs, and it seems Bradford is a reliable brand. While researching the costs of a Bradford with a power vent, I came across a new old stock Combicore M2-C-TW75T10CN unit for $1000.
In my area a 40gal NG heater from Home Depot is $400, and the local supply house quoted me a 50gal NG heater with power vent for $800.
For space heat I have a 1976 Burnham gas boiler with 3 zones of baseboard. It works ok, but it can't quite keep up on the coldest days of 0-10F. My 1500sqft 1961 split level has single pane windows, poor insulation, and cathedral ceilings. My heat loss is probably roughly 65-75kbtu with a 70F delta.
My question is:
If I'm spending $700-800 on a water heater, does it make sense to get this Combicor unit for $1000 and use the heat exchanger as the primary heat source for my baseboard heating, keeping the Burnham for backup? Can it even be done in a simple way?
I'm thinking that even with only 82% efficiency the CombiCor would be better than the Burnham, and that the two units can be plumbed in parallel with a manual power switch and zone valve to keep the Burnham out of the loop 95% of time. I don't have a problem flipping a switch manually to bring the Burnham online on days when the CombiCor can't keep up. Since that would only be 5% of the time, it seems that they could just share the heating load 50/50 with no fancy balancing, just a Y junction in the heating loop.
I can commit to $1000 plus 3-4 hours of plumbing but not much more.
Thanks for your input.