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When do Indirect water heater's pencil out?
I have an old house with a natural gas forced air furnace/ground source geo combo.
I added a garage last fall with an mudroom/porch to attach it to the house. I installed radiant pump at the time, but not a heat source. I recently put an HTP boiler in my shop and am happy with it, so I'm probably going to hang one in the garage as well. Heating off the existing furnace is not feasible due to layout.
One option I cam up with was to put the boiler in the basement and install an indirect water heater. On one hand, my current tank water heat has a date of 1994 on it, so I'm sure I'm running on borrowed time. But I looked at my natural gas bill's and the gas only portion of the bill, (exluding the fixed customer charge) ranges from $5-12 in the non heating months (we have a gas stove as well).
So let's say I use $200 of ng to heat my water. If I raise my efficency from .6 to .9 I'm only saving $70 per year. I would also have to assume that $10-20 of that would go to pumping cost. So if I save $60 per year and it cost me an additional $1000 to install, it takes 16 years to break even. Not to mention I have another $300 in materials to get the hot water out to the garage.
I think I'll hang the boiler in the garage and see how long my 22 year old rheem will run. Now to get rid of that condensate water....