| Author | Message | ||
     Ratbuell |
So, I have an Armstrong Air heat pump in the house with an Ecobee3 thermostat. I'm familiar enough with everything to have set it up (and tested it to verify) that the compressor runs efficiently and heats the house down to 24 degrees ambient; I have the thermostat set to allow the aux electric heat only below that temp. Currently, it's 6 degrees and aux heat has been on for approximately 24 hours. For the first time since I got this house (~6 years), it can't keep up. Setting is 72; actual is 68. My semi-educated guess is, part of my heat grid has gone bad. I'm too lazy to get up and check my manuals at the moment but I want to say I have a 10kW heat grid, which through research would mean a pair of 5kW elements. It's blowing warm air, so I'm guessing one of the elements has gone bad. Earlier tonight, I did change filters. The old one looked good enough and was only 2 mos old, but I did note increased airflow at the vents after the change...so I suppose it may have been restricted enough to allow the element to burn out. Now, I'm more than a little familiar with electrical work - from 800A 3-phase panel installations to component-level repairs, I've done 'em all at one point or another. I'm finding "re-string" kits for these elements for not a lot of money, but they say "professional installation required". Disclaimer? Is it as simple as hook one end to the card, string it through the insulators, cut to length, and connect the other end to the card? http://www.myhvacparts.com/store/electric-furnace- re-string-kits.php I'm not skeered of electrical work but I don't want to miss something obvious in an HVAC scenario and light my vents on fire. And yes, before I order anything I will be verifying all my model numbers and ratings with my paperwork. I've been installing ceramic tile flooring today and (at 6'4") that's a LOT of bending, and my back doesn't want to come off the heating pad just yet... | ||
| Doz |
Got a similar thing going on at my moms house. Best thing I can do is to check that all breakers are good.And checking that the larger of the two lines coming off the pump is hot. Other than that-I'm lost. (Message edited by doz on January 22, 2019) | ||
| Hughlysses |
Joe- a bad element sounds like a likely candidate, but is it possible the unit just can’t keep up at 6 degrees F? | ||
| Aesquire |
My Mitsubishi is struggling to keep up, and I didn't get the aux resistance heaters. So my propane boiler is working near continuously. Yesterday was 2 f winter. | ||
| Hootowl |
If one of the elements burned out, it should be open. Ohm it out and see. | ||
| Ratbuell |
Yeah, I have to grab my meter from the apartment I'm rebuilding. It's on the list for this afternoon - today is paintpaintpaint...and more paint, in the apartment. Can't install the kitchen till the tile floor is grouted; can't grout till the adhesive dries. Hurry up and wait... I did lower the compressor threshold to 5 degrees to see if that can help out, and at least get me some cycle time instead of con$tant-on aux heat. My meter is about to spin off the damned wall! | ||
| Doz |
My moms unit was calling for emergency heat but someone had disconnected the wire to the heating elements. It's an older Carrier unit and it probably is not very efficient due to age but at least its giving her the heat she needs.(now that I reconnected the heaters) But I have heard many years ago that heat pumps don't do so well in extreme cold conditions. | ||
| Aesquire |
It's simple math. They pump heat from outside, to inside. ( or the other way around for cooling ) When there is less heat outside, it takes more energy to pump it. Depending on the individual unit, they can produce heat down to -13 F. That's what the brochure on my Mistubishi says. But my experience is it's are working hard when it gets below about +15 F, and in my house can't keep up below Zero F. There's a reason some spend the big bucks to suck heat out of the ground, or a pond, that never gets below freezing. It's more efficient. It's also more expensive. I Opted not to buy the electrical resistance back up heat, as the heat pump is the "substitute" ( or booster ) for the Propane boiler underfloor water heating system. The heat pump is cheaper than propane, and propane is cheaper than hot wires. | ||
| Ourdee |
I just use hot wires. Woe is me = warm is me. | ||
| Ratbuell |
21 degrees ambient now. Aux heat off, compressor on, house nice and toasty! | ||
| Rparnel1 |
10kw is the minimum needed. 15 or 20 KW is more appropriate for whole house heating. System probably just cant keep up. You can measure the current draw to see if you have a burnt element or kill the power and ohm out the elements | ||
| Fast1075 |
The skinny: Air over heat pumps go over the curve at around 30 degrees, regardless of what the propaganda says. Water source units are immune to temperature. Auxiliary heat is your friend. If you know the KW size of the heater, access the power to the air handler and do an amp draw. The blower motor draws less than 5 amps. For rule of thumb, 5KW heat string draws (depending on actual voltage) about 20 amps. 7.5kw about 35, and a 10kw about 40 amps. If you are only drawing the 5 or so amps, it is likely to be from a control issue. If you have an ODT limit (keeps aux heat from working above XXX degrees)in the outdoor unit (required in some places by code), it could be whacked. The test, if the heaters are not working is to check the control voltage where the thermostat wires hook up in the air handler. If you have 24 volts between Red and white wires (should have said "R" and "W") and the heater is not working, you have a heater problem. If you don't have 24 volts, you have a control problem. (Message edited by fast1075 on January 23, 2019) |
