OK, it's the first time we've been in this house with 0 deg temps and I realize I'm living on borrowed time with ~15 YO heat pump but...it finally stopped blowing out warm air. Thermostat is @70 but it's currently 55 on first floor. We've had some A/C problems but mostly do to worn out contacts, blow fuses, etc. Heat has never been an issue, even below freezing (just not THIS cold). Am I hitting a temp limit or is there something easy to check out first? Oh yeah, I mean my wife since I'm out of town. Nice timing, huh? Thanks a bunch!

 

Is a lot of what runs now?? Are all breakers on and ok.Can she go to AUX or EM on the tstat and get the blower and heat? Ed

 

All breakers look ok, nothing was tripped. Of course, I can't tell on the outside unit. Everything else looks functional as well. Strong air, but just not warm. Switched to EM but the air didn't get warmer, although overall the house has warmed up a few degrees (we finally hit 32 outside). Never used EM before so this might be something to check out later. The compressor stopped, as expected, while the air handler stayed on, with only cold air. Switching back, the air *feels* warmer. The insulated line from the compressor feeding the air handler is only room temp, while the cold line is pretty cold. We're now adding other heaters to try and compensate, but I guess I have two questions: is there a lower temp limit associated with heat pumps? If not, am I just looking at frozen line situation because of the age/ability of my pump? (where a newer pump wouldn't experience this) I should probably start saving $$$ for a replacement.

 

I think it's about 20 degrees a heat pump becomes fairly useless, hence the "emergency" heat...

I'd check those auxilary heaters to see if they are working.

 

Its hard to say what here. When you went to EM the strip heaters in the unit should have turned on and it should have got warm air. You could be low on freon also that big copper line should be hot when the outdoor unit is running unless it in defrost mode. It should work, Id say you need an amprobe and start to ring it out to find whats out.
You said 15 years YES thats about the life on the units but I know of one AC that 39years old now. Then you have to think a heat pump run 2 times more than an AC. So when I say 15 years for an AC thats about 7 1/2 years for a heatpump. So that way you have been doing real good on the run time here. ED

 

I know of a Sanyo heat pump that cuts out the compressor at 19F and restarts at 29F. I also know of York units that have a cutout thermistor at 10F. Your unit might be like this but not necessarily... If the outdoor unit is running including the fan motor, it's most likely out of gas or low. The insulated pipe just outside the unit should be warm..

 

Thanks for the replies! Well, the insulated line is finally warming up both at the compressor outside and at the air handler. It looks like several things could have happened: one, I reached the low temp limit and it couldn't go any further (as it seems to work at 32F) or two, by shutting it off and back on, I might have jump started/unclogged something/other. However, the EM is still an issue. Nothing kicked on at all, so someone needs to come out as I'm not sure where the strip heaters are. I guess I should consider myself lucky to have lasted this long on it. It's been well serviced and my home inspector said it was in very good shape, well above air flow and temp delta norms (this was A/C).

 

Most installation manufacturers use the 37th parallel as a guide for installations. south of this the primary concern is cooling...above is heating. If you are in the cooing zone you don't have to have the supplemental heaters...although they are good in a pinch if the heat pump fails...
Problem is, most people don't know it's failed till they get the electric bill!
Make sure you have 1/2" insulation on the piping, or it will loose it's heat to the surrounding air before it gets a chance to heat your home.....