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Convert forced air to hot water heating?
I'm thinking about converting from forced air to hot water heating and I
wonder if this is a crazy idea.
Here's our situation:
6000 square foot home on 3 floors, built 1903, in eastern Massachusetts.
We've put a lot of money and effort into insulation and weather sealing,
but still it is an old, leaky house.
We currently have two separate forced air systems, one for the ground
floor and one for the two upper floors. The ground floor is heated by a
Lennox 100kBTU/hr gas furnace. This is insufficient to our needs. We
turn down the first floor thermostat to 50F at night when we're not
using it. On a cold winter day (say low 0F, high 20F) it will take
maybe 6 hours to get back up to the daytime setpoint of 65F.
For upstairs we have a Lochinvar 150kBTU/hr high-efficiency gas boiler
which provides DHW through a storage tank with heat exchanger and
heating through a hydronic air handler. We have separate
air-conditioning units for the two floors with outside compressors and
heat exchangers in the furnace and air handler.
It's nice to have A/C available, but we don't use it much. We use the
upstairs unit maybe 15 days per year and the downstairs unit maybe 5
We often have quite a lot of our upstairs closed off, so we don't need
to heat or cool it. This works poorly because shutting off vents is not
very effective. Thus my interest in hot water heat, which would be much
easier to control. Presumably it would also not dry our bedroom air so
much in winter. The downstairs is open plan so there is no issue of
closing off rooms there.
The only equipment that is in good shape is the boiler and the DHW
tank. Everything else is old and needs replacement. The downstairs
A/C is not working. The downstairs furnace heat exchanger has a small
rust hole. The upstairs A/C works (but it's 35 years old) except for
the system that collects condensate water, which instead drips all
over everything else. So the hydronic heat exchanger is badly rusted.
This seems like a good time to think carefully about what we want. My
thought was to run the hot water from the boiler around the upper
floors for heating, and use the upstairs ductwork only for cooling.
I'm imagining either individual thermostats to control hot water in
each room or at least manual valves to shut off the rooms we don't
need heated. But maybe this would be insanely expensive.
For downstairs heat, I guess we just need a new gas furnace. But
I wonder whether there's some way to have a single air-conditioning
system, or at least a single compressor, that could be used for both
upstairs and downstairs. We don't use A/C all that much and we
certainly don't need to cool upstairs and downstairs simultaneously.
This is my first post to the Heating Help forum. It looks like a great
resource. Thanks so much for your help.