HVAC Question

Mabrins

I've got a house with forced oil radiant heat. The oil system is probably as old as the house (1950s). We also have an AC system that's about 25 years old. The house is a brick cape cod, and is about 1700 sq. ft., with 12 windows. The house has ducts for the AC running to all rooms upstair and downstairs (on the ceilings); the upstairs is a finished attic. I'd like to have a heat pump installed that replaces the AC, and will kick over to the oil heat when the temperature dips. Is there a hybrid system that will work with my current oil furnace? Should I get a packaged system or split? What should I anticipate for this installation cost? Any specific product recommendations? Also, I live in Richmond, VA; would this type of system be overkill? Any other suggestions or advice are appreciated! Thanks!

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sammy37

Stay with the split setup. They make simple controls that would shut the heat pump down and switch over to your oil system but I'm not sure you would want that, seems like the radiant setup would take forever to warm up and electric backup heat may be cheaper to operate.
How are your electric rates?
Cant really give a price on what it would cost to do the job, every city/state has different rates. Around here where I am, it would probably run from 3500 bucks on up, depending on the contractor and brand of equipment you buy.
You will also want a contractor that will do a load calculation to determine the proper size of unit you will
need.

Mabrins

Well we currently have a oil heat system that I'd forced to radiators throughout the house. We want to get a heat pump so isn't that electric heat?

Doc Holliday

heat pumps utilize the same refrigerant used for cooling as for heating during that mode. the refrigerant reverses flow now rejecting heat inside versus on cooling mode the heat is rejected outside. Ever put your hand over the outdoor fan on the condenser on a hot Summer day and felt how hot the air was? Now that's simply reversed.

Secondary heat or auxilary/emergency would be whatever else you have. Many times indeed it is an electric air handler coupled to the heat pump so yes, you could have electric heat if you went that route but many times gas and propane or oil is used as secondary as well. It's all up to you and what you want and what you are willing to pay for.

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Thanks.

sammy37

Yes it's electric but your heating with a compressor and refrigerant, much more efficient than trying to heat with resistance heat, (heating elements).
However, when the heat pump goes into defrost, it will also need some electric backup heat to warm the air during the defrost cycle.

Technow

Heat pump is electric heat. Doing a conversion from AC to Heatpump typically takes some electrical work because the airhandlers are 240 volts where the old ones were only120. Oil radiators don't back a good heatpump backup because it takes too long to heatup (like during a 5 minute defrost)

We have done many conversions, but typically just convert the house to all electric.

JScotty

You don't have to change the wiring unless youy switch to an electric furnace. However as you mention a radiator system won't work as a good backup since it won't heat up before the defrost ends. However it could still be used, but he is going to get cold air from his vents until the defrost ends. But he could also have a gas or oil forced air furnace installed & he wouldn't have to switch to a 240 circuit.

And depending on how his electric is set up that may be the best option. Usually houses with oil/gas furnaces tend to have 100 amp service. A 20 kw furnace will pull almost 90 amps by itself, so usually the entire electric service (all the way to the weather head outside, including the entire electric panel) has to be replaced. If this is the case a forced air gas or oil furnace can be easily be installed much cheaper than electric.

Mabrins

Any idea on a rough ballpark to install heat pump (not hybrid) with new electric? I just closed on this house and its my first purchase. I know I need to call an HVAC company but just wanted to get an idea.

Technow

There is no way to give a ballpark....too many factors.

Here is one from near St. Mary's hospital...it still has the oil boiler....but its not needed anymore.

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Mabrins

So what if I want to do away with oil and just have an electric heat pump for heat and AC?

Technow

Not a problem, just have to realize heatpump heat is not like boilers and furnaces. The thermostat will still read 70...but heatpumps move lots of air which has a tendency to feel colder even though its still 70.

JScotty

Depending on where you live that might not be a good idea. You have to realize how a heat pump works. It makes heat from the outside air. As the outside air gets cooler the heat pump makes less heat. Also since it's colder outside your house actually requires MORE heat to keep up.

So at a certain outside temp (the actual temp depends on the sizing of the HP, your house insulation, setpoint etc) your heat pump will no longer be able to heat the house to a reasonable temp. This is why they install "backup heat" on heat pumps. If the temp drops much below freezing it won't keep up & you'll need a 2nd heat source.

If you're going to do that just leave the oil heat as is. Like I said above you'll get about 5-10 minutes of cold air when your HP defrosts, but then the heat will come back on & warm you back up. If it gets too cold outside & the unit can't maintain it will fire your oil to keep the house warm. So you'll have the oil boiler you'll just really only use it when it's really cold outside.

JScotty

I'd say that regardless of backup heat. If you like hot air from your vents you won't like a heat pump. I love them, if I feel cold I bump it up 2 degrees. It's cheap so who cares