[pvteacher]

I have an older York Heat Pump. When outdoor temperatures drop below freezing the outdoor unit stops running and the thermostat shows the red emergency heat light flashing five times like a pattern. Our electric bills have been astronomical, with the last one reaching 851.00 for one month. When I reset the circuit breaker during above freezing temperatures, the heat pump runs again, until the temperatures drop again. Can you help?

[hvac1000]

Usually there is a thermostat located in the heat pump that turns it off at 35 degrees or below since a Heat Pump does not work well at low temperstures. With a 851.00 bill you need On Site service or your next bill will be just as high. Something is causing the breaker to trip and unless you know how to repair heat pumps it is best left to a professional. Sorry.

[dac122]

On some York's there is a Low Temp Cut Off (LTCO) jumper that will cut over to EM heat. On my aging York the LTCO jumper was set surprisingly high from the factory, so I set it much lower and let me and my thermostat decide best.

So it could just be that, but if power cycling the system is making it work for a while then I might suspect a fault somewhere.

Get a tech over and have him check out the system, and educate you on any inner workings such as LTCO, Balance Point (BP) and interactions with your thermostat.

[Missouri Bound]

HVAC... you say a heat pump turns off at 35 degrees or below? That is 100% incorrect. Where did you get that information? You either don't own a heat pump or live in a warm climate. Heat pumps aren't as efficient in temperatures below freezing, that is true. But they don't shut off when it gets cold, they just rely on aux. heat to back them up when they can't keep up.

[hvac1000]

Missouri Bound what is your problem. I said what I said and there is info to back that up. If you are in the HVAC biz then you should know that many different areas with many different 2nd stage fuels will use different balance points. When you calculate the proper balance point you must take into consideration many different operating parameters.

Heat pumps do save energy costs but they are expensive to operate on a repair cost per hour usage basis. This is just one item that most people fail to enter into there calculations when selecting a design balance point for the change over to the next available heat source. Sure you can let the heat pump run all winter if you wish but at some point it will not be efficient to run based upon proper calculations.

We must remember that most heat pump systems need to run the electric resistance heat during the defrost period in order to temper the air blowing through the home and this costs extra bucks no matter how you look at it. The colder it is outside the more the heat pump will go into the defrost mode and the longer that defrost mode will take. This also has to be taken into consideration when calculating the balance point.

We have a unit at the university that has been running in our chamber for some time. It is a two stage complete variable speed unit with a projected 28.5 SEER. The HSPF (heating seasonal performance factor) has not been calculated at this time. This unit will operate down past -20 F but at a much higher wear rate than would be acceptable to the manufacturer. What this means to all the uninformed is that while hear pumps can work at much lower temperatures than 35 degrees you have to do all the calculations to see if operation below that point is economical not only for energy usage but from equipment longivity also.

Most manufactures list a preferred balance point in there literature. There are also other variables to consider but I am not going to go to all the details since I am sure you know them all.

Here is a link to a guy that has done a bit of energy testing and there is a bit of interesting reading there.

Energy Testing & Consulting - Properly Sizing a Heat Pump

BTW If your heat pump runs all the time no matter how cold the temperature gets I am happy for you. Eventually you will figure it all out or you will be making unnecessary repairs due to longer than economically efficient run times.

[Missouri Bound]

PV, sorry it took so long to come back. After HVAC's tongue lashing I thought I better do some research before I expounded on the issue. Heat pumps are designed to run in all temperature conditions, with back up heat being called upon when the heat pump simply can't keep up. This is true of all electric systems. However, as HVAC eluded to there is a balance point issue. This is only relevant with duel fuel systems. Every heat pump here runs throughout the winter. You have a problem and again as HVAC has stated correctly, you need service. Resistance heat only will generate those bills that you are experiencing. Get it fixed while you can afford to pay for the repair.