Replace 1 of 2 A/C's with heat pump in CT?

[rblakenyc]

I have a 4600 sf house just outside Hartford ct that has two Lennox A/C units (10acb36 and 42) and oil furnaces. The 3 ton a/c compressor, serving the downstairs, has seized and since it is 14 years old I'm leaning towards replacing with a new unit (rather than just a dry-charge replacement with uncertain coil or other issues).

One firm has suggested we consider a heat-pump (XP17 - though I think XP14 might make more sense with existing furnace?) and I was wondering how much utility I might get by having just the one heat-pump with my oil as both back-up on that unit (right?) and upstairs serviced with still working 10acb42/furnace.

I hope I've given sufficient info for opinions. I might ad that my wife likes it 72-74 degrees all year round and keeps widows closed due to allergies. Also add that I have 4 fireplaces that i need to do a better job of sealing during the winter.


Thanks for thoughts and clarifying questions.

Rick

[jtrammel]

I would definitely get a heat pump instead of straight ac, it's only a few dollars more and should save a pretty good amount of oil bc in milder weather (~35F and up) the heat pump will be much more efficient and still keep your house comfortable it will still be more efficient at lower temps but most set them up to run down to 35f then use back up furnace at lower temps. As for the higher seer unit you won't achieve that seer unless you have a variable speed blower in the furnace so the 14 seer would be a better match imo

[rblakenyc]

Thank you! I wasnt sure if it would be odd to have just the one heat pump. Should I question an installer who recomended higher seer units since I wont achieve the benefit? Maybe there was another reason to recommend the signature series over the elite (quieter) but doesnt make sense that he would...

[jtrammel]

Also the price difference between 14 seer equip and anything 16 seer and up is a pretty significant increase. I wouldn't think they are trying to scam you or anything just ask them why and what the pros of that unit are. If you think it's worth the extra $ then go for it, if not I'm sure the contractor will work you up a quote on another unit. The higher seer units have 2 speed, variable, or 2 independent compressors so that in milder weather it uses less power to operate and doesn't cool the house quickly and shut off and by short cycling like this it won't remove the humidity as well. They are also quieter usually and have a few other details that the lower seer units don't. You usually won't see a reasonable Return on investment by going from 14 seer to 16+ but some people are willing to spend the extra for better comfort and bells and whistles.

[BaldLoonie]

You would need new variable speed furnace to get over 14. I can't picture any reasonable ROI in your climate. XP14 or similar makes more sense.

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[skippedover]

The actual efficiency of the AC/HP combination is something that is very difficult to predict with a non-matched combination. So in reality, if it isn't a matched set, meaning all parts of the mechanical items, including outdoor unit, indoor coil and blower, then there are no ratings published that can produce a document you can show someone and claim that efficiency. However, some manufacturers do submit efficiency data for indoor coil and outdoor unit without a blower. The assumption in those cases is that the system is being installed on a non-variable speed product and therefore the actual efficiency is lower. But even that is not always correct. For example, you could have an oil furnace where someone has installed an ECM blower motor to improve the electrical efficiency of the furnace. Adding AC or HP to that unit will inherently have a higher efficiency than if the blower motor was the original PSC motor. In addition, even with a V/S-ECM motor, if the duct system is under sized, you could get a lower energy efficiency due to the higher amps drawn by the ECM motor trying to operate against excessively high static pressures.

So in the end, the actual efficiency you get from your house and equipment combination isn't really something anyone for which anyone can actually print a rating paper with any guarantee that it reflects your actual operating conditions. All of that said, sometimes there are more features and benefits available on higher SEER/EER/HSPF units than are available on lower rated units.

Finally, when it comes to heating with a heat pump, the SEER and EER ratings are not really the important rating. It's the HSPF rating that is the best indicator of efficiency and that can be higher with lower efficiency equipment or higher efficiency equipment. So check out that number and you might also want to entertain the idea of installing an ECM motor along with the HP for your oil furnace and enjoy the higher efficiency (assuming you don't suffer from high static, which should be checked before installing the new motor) even if you can't get a certificate that claims what efficiency you're actually getting.

[54regcab]

Heat pump/oil systems would also give you options as the price of oil fluctuates. You would simply change the balance point that the system switches from heat pump to electric as the price of oil/electric varies.

[rblakenyc]

Thanks for all the advice. Gives me some solid questions to ask the two solif pro's I have quoting the job. I will let them guide me on realized advantages of more expensive equipment based on on site evaluation. The HP sounds like a unanimous vote in favor so I will plan on going that route. Thanks again.

[54regcab]

Pull the rate schedules from your local electric and oil suppliers. Found out how much each heat source costs and determine where the switchover point should be. Some utilities give discounts once you use a preset amount of KWH per month. Our electric company gives 1/2 price power once you get to 600KWH, which most people running heat pumps would get to.