Need new A/C. Should we go with a heat pump?

14 years ago

Our AC needs to be replaced (the date on the condenser is 1986. We get our heat from an oil burner the blows forced hot air. The date on that is also from the 80's. Our oil tank is buried in the front lawn and probably dates from when the house was built in 1960. We live in Northern NJ in a raised ranch house with lots of trees around us. We have lots of shade in the summer and sun in the winter.

My question is: As long as we have to replace the AC, should we go with a heat pump?

Thanks,

Zella

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Comments (5)

garyg
14 years ago
Need to know your delivered electric rate, in cents per kw-hr. Delivered = generation + transmission + distribution.

You can install a heat pump for primary heat, and use your old oil furnace as back-up / auxillary heat to the heat pump. You will have a "dual fuel" system.

Since you will be using the old existing furnace blower, I wouldn't get any higher than a 14 SEER heat pump. You don't have a variable speed motor in the old oil furnace blower to take advantage of higher SEER systems.

You need a good thermostat like the Honeywell Vision Pro 8000 Series w/outdoor temp sensor. This ties the sytem controls together and allows you to take advantage of the switchover temperature from the heat pump to the oil furnace. Start at 32F and see how it goes.

Get your duct work checked and make sure you have no air flow issues.

Good luck.
zellalamb
Original Author
14 years ago
Thanks so much for your reply.

Our current rate is: 1-600 usage .167355/kw-hr
601 and up is .224749/kw-hr (I had to call our utility to find that out)

An amendment to my question is that our furnace blower is actually the original, from the early 60's.

Before I received your reply, I asked our AC contractor about the "dual Fuel" system and the guy told me it couldn't be done with oil heat because it "burns too hot"????? Now I'm trying to figure out if I'm the complete idiot or if he is. Your reply has helped me lean toward the latter.
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srercrcr
14 years ago
The HP is merely the air conditioning running in reverse, so instead of expelling heat you're capturing heat, and there's not alot of heat in the air in the winter. So around about the lower 40s outside your secondary heat will kick in, either oil, gas, or electric strip heaters, the latter making the meter spin into orbit). Many folk find the HP heat cycle not comfortable because it does not blow HOT air in the primary mode, more of steady warm air. If you are fussy about drafts, could be an issue. I recommend HPs in southern climes where cold snaps are the exception rather than the rule. In the cooling mode HPs are no more efficent than regular units, theyre commonly made with the same parts except related to reversing the direction.
garyg
14 years ago
Your electric rates are extremely high. Guessing you are in the upper Northeast. I pay 15 cents per kw-hr in Maryland, no tiered rates.

Compare the cost of 1 million btu's of heat for heat pump vs oil furnace.

Oil furnace w/oil at $3 per gallon, 80% efficient furnace:
(1,000,000 / 139,000 btu per gallon) x $3 / .8
= $26.98

Heat pump with electricity at $.22 kw-hr, C.O.P. = 3.25 at 40F ambient:
(1,000,000 / 3414 btu per kw) x $.22 / 3.25
= $19.82

The heat pump is 26% cheaper for the same 1 million btu's if you pay $3 gallon for oil and your oil furnace is 80% efficient. Insert your actual oil price and furnace efficiency for a more accurate cost comparison. As ambient temps rise from the 40F example, the C.O.P. (Coefficient of Performance) of the heat pump rises, and it is even cheaper to operate.

The heat pump can indeed be used with an old oil furnace, they just can't run at the same time (furnace temps are too high). Same goes with a heat pump and gas furnace.

The only time the furnace will run along with the heat pump is when the pump is in a defrost cycle. The furnace will run to temper the cold air from the indoor coil, while the outdoor coil gets hot refrigerant to defrost it.

The VisionPro 8000 Series t-stat will run the heat pump as primary heat, then if the heat pump can't keep up with the indoor setpoint, it will turn the heat pump off and run the oil furnace to setpoint. You can also determine the switchover temp with the VisionPro if you have an outdoor temp probe for the t-stat.

The contractor has to be comfortable with the heat pump install with an oil furnace. Maybe he doesn't do too many pumps in your area.

Good luck.
Bellgirl
3 years ago
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Need new A/C. Should we go with a heat pump?

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Need new A/C. Should we go with a heat pump?

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