View Full Version : how to tie the overall system together?
So I'm going to pursue 2 variable speed heatpumps (A-S/Trane 13 Seer?) for cooling and heating (when above 40 degrees). I haven't figured out the total usage yet, but I have learned that electricity is 12.5 kwh in my area and heating oil is approx. $2.75 / gallon. Based on other posts, it seems that some $$ can be saved here using the heat pumps until gets cold enough to switch back over to my oil-fueled boiler. My question is, how can the 2 systems be tied together so I don't have to manually turn on/off based on the latest temperature reading come next winter? I've read of thermostats from Honeywell and Inifinity (is that Carrier?) and one description has a Honeywell Vision Pro IAQ matched up with a gas furnace and a heatpump. Can something like this be used in my above scenario between oil boiler and 2 heatpumps? Any recommendations on the best controller? And it would seem that the installer I would go with needs to demonstrate good experience here as installation is paramount? Thanks!!
05-21-2007, 01:45 PM
Depending on the type of boiler you have you may be able to install hot water coils on the upstream side of the heat pump air handler and use the hot water from the boiler to “supplement” the heat pumps just as the typical heat pump uses electric strips. The heat pump would run at any time there is a call for heat and when the heat pump could not provide enough heat then the hot water would circulate to supplement. Under this scenario you would get the maximum benefit of the heat pump and cheaper supplemental heat than electric heat strips.
If you can’t add hot water coils then using your existing hot water heat system as a secondary heat system can be done too. In that case the heat pump would operate down to some point (probably around 35*F) and then be locked out below that temp.
Either one of these setups can be done by the right contractor. They can also help you figure out the economic break point for switch from the heat pump to the oil boiler based on your cost of electricity and oil.
05-21-2007, 03:27 PM
You really don't have a problem. If your oil burner is forced air, as I assume it must be, you simply set up the system as a "dual fuel" system. Any good installer can make this happen for you. The controls are simple to install. Your heat pump is just and outside condensor with an indoor coil, just like any other air conditioning device. It only requires an air handler to make it function, which is exactly what your furnace is...Wait. You said boiler. In that case, you will have to install a central system for the heat pump. Still the changeover to the boiler can be accomplished using a dual fuel approach. Be sure you have a professional with a good understanding of what you want to accomplish.
thanks for the posts. i actually just met with a contractor and he seemed to think it would be an easy thing to do (i.e., tie the two "systems" together with a single thermostat so that I don't have to intervene every time it drops below a certain temp and then raises back above, etc.). hopefully i'm on my way to an air conditioned home finally, which will be very nice in about 1 month...
Will each variable speed heat pump air handler have it's own separate duct system??
Or didn't you mean variable speed heat pumps ,as in VS indoor units??
Each air handler will have its own duct system (one in attic supplying 2nd floor, and one in basement supplying 1st floor and basement).
Unfort. I don't understand you 2nd question, though no doubt it's because I don't know that much about this stuff (am interested in learning).
oh and interestingly, i spoke with a Trane guy today who said controlling both heat pump and boiler with one thermostat would be easy, and I just spoke to a Carrier guy who said it was impossible (even with a fancier series, according to him it would have to be a Carrier heat pump + a Carrier boiler, and not my existing boiler).....so the process goes??
05-21-2007, 08:48 PM
ANY boiler will work with ANY heat pump. That Carrier dealer is out to lunch.
I sell TRANE and CARRIER. There is absolutely no reason to think the boiler needs replacing. Either brand will give you good quality, warranties, and performance. Choose the guy you trust the most and go with him. Always ask the tough questions and scrutinize the answers carefully.
On another note: Carrier gives me the best support. Trane gives me the best pricing.
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