Sorry Blackhat, another HVAC thread

[Snipe Hunter]

I ran into an Aqua Therm furnace yesterday in a home inspection. MFG. by First Co, 2011. Trane condenser, 2011. I have never seen one before. The evaporator coil is in the bottom of the air handler, fan in the middle and a hot water coil in the top. The hot water coil is fed from a 45 gallon gas water heater which also feeds the rest of the house 1400sq ft house, 2 bath.

Simple enough system. Are their downsides to this type of heating system? Upsides? Are they cost/energy efficient?

[barnowl]

My son's house in VA has a similar system, with the horizontal air handler in the attic, and water heater in the garage.

[blackhat]

Don't see many exactly like that here. A residential water heater barely puts out enough heat for a 2 car garage up here. It's a simple and fairly cheap way to build. Like any other system, there's pros and cons. Big drawback is that if it's sized too tight you could be stuck choosing between having heat or hot water. Water quality also plays a part. In extreme cases, a coil could have a massive biological growth during the off season that gets dumped into the tap water at the first heat call. Many jurisdictions won't  allow such systems because of that risk. I can expand more when I'm on a keyboard instead of my phone.

[Snipe Hunter]

Yuk. Thanks!........................

[blackhat]

Lots of builders here were throwing in floor tubing in the concrete basement floor and running it from the conventional tank style water heater.  That had the same water quality issues I mentioned above so when it got canned, they added a small heat exchanger and isolated the fluid in the floor.  Sold the houses as having in floor heat in the basement.  A warm basement floor slab is a nice feature and was pulling a premium dollar.  Problem was they didn't insulate below the slab and the floor was sucking up heat faster than the water heater could produce it.  Never had hot water at the taps in winter.  Water heater burner never shut off and water heater would die in 3 or 4 years.  The same package tied into a tankless works moderately well.  Fairly well if a flow switch shuts off the heat exchanger pump when the house is drawing hot tap water.  Now you are starting to talk a fair piece more money for equipment and install.

Air handlers are semi popular here but are in 2 different types of systems.  Some use a hot water coil for main floor heating, or multiple coils in the duct branches for heat zoning, basement and attached garage with in floor radiant and an indirect water heater tank, all driven by a condensing high efficient boiler.  That can produce a very efficient and comfortable system with air conditioning, humidification and dehumidification, air filtering and air purification if wanted.  The boiler can also be used to heat a pool or hot tub.  The other one that is gaining a bit of favour is a geothermal or air source heat pump system for heat and ac and a boiler and coil to pick up when the geo system sizes out.  You can also add all the bells and whistles previously mentioned if your pockets are deep enough.  They are even more efficient.

Tank style water heaters are not very efficient and as mentioned, have limitations on the amount of heat they produce.  They are pretty cheap to buy, a positive considering the decreased life expectancy of the appliance.