Heat pump and electric plenum issues?

[tadder52]

Hey all,

I'm in Northern MN just bought a a 1400 ft2 house plus a basement it was built 1997 good quality windows, doors, and well insulated. I have a Bryant heat pump with an electric plenum assistance with propane backup heat.

Earlier in the season when it was 10-30 degrees I started to notice my fan was running constantly. It had two different fan speeds it seems. One seems on high which would run for most the time about 80% of the time. I would hear the tstat click and I would confirm that the house has gotten up to temp. As soon I would walk across the room to confirm this I could here the fan click on to the lower speed and run for 5-10 minutes then the tstat would click again and the fan would immediately jump up to the high speed again and run for the next 50 minutes.

Since it has gotten real cold -5F for a high the tstat automatically switched over to running the propane backup. Which blows much warmer air out of the vents than the heat pump/electric plenum ever did.

Is my electric heat helping at all? Is this how it should run? What should be the difference in temperature of the air coming out of the vents for both types of heat?

If you need anymore information or details please don't hesitate to ask. I'm capable with circuits and not afraid to trouble shoot, but I thought I would ask here before calling out a technician and getting that bill right after the holidays.

Thanks,
MB

 

[Milton Shaw]

Most heat pump quit giving enough heat about 35 or so outside based on what the design was set up as. The two speeds for the fan I think would be going when the tstat calls for more than 2 degrees of heat. The electric plenum heat would be an emergency back up heat only I would think, and be 3 times as expensive to operate as the heat pump.. Is the tstat set to fan on all the time, otherwise it should turn off instead of just changing speeds.

 

[tadder52]

The fan is set to auto.

 

[zmaxmotorsports]

Have you had the heat pump and furnace serviced?

 

[tadder52]

Have receipts from previous owner having both the ac and heat gone through in April. I was hoping it was something I was missing, or just not experienced in that I was over looking. Guess it's time to get the check book out.

 

[frankush]

Power to the electric heating coil is probably bypassed once the propane kicks in. You should try and determine the sequence of operation for all the units. My guess is once the outside temp drops too low for the heat pump to provide adequate heat, the electric coil is energized. If the stat signals an even bigger temp drop, the electric heat then gets shut down and the propane kicks in. I'd be willing to bet it's running properly. If you do have someone come out, ask what the sequence is. It's a great troubleshooting aid.

 

[tadder52]

That's the way I understand it. Heat pump, then electric assistance, then propane. I know when it's super cold out the propane will and does kick on. It's been doing that for the last two weeks. I think in the last two weeks we've had a high above zero maybe 4 days. The propane, and switch over is working correctly. I am trying to figure out the heat pump when it's warmer out.

 

[zmaxmotorsports]

Ive never seen a hp with heat strips and a furnace back up.

 

[jvitez]

What should be the difference in temperature of the air coming out of the vents for both types of heat?

We have geothermal heat, open loop, feeding 4 fan coils so it's a forced air system. The air feels only slightly warm when the heat pump is providing 100% of the heat. In the rare instance when a backup electric plenum heater turn on in one of the fan coils, the air finally feels definitely warm but still less than a fuel burning furnace.

I suspect when your heat pump can't keep up, the plenum heater turns on and the fan kicks up to high speed. Before paying for a service call, can you google any online manual for your specific model of heat pump? It might have the information you need.

 

[DEnd]

First of all the Furnace either electric or propane should put out warmer air than the heat pump. The output air temp from lowest to highest should be heat pump, electric, propane.

What it sounds like to me is that the heat pump may have been sized for the A/C load and not the heat load. Typically the BTU per hour is lower on the heating side of a heat pump. Remember a heat pump works by pumping heat and it's a lot easier to pump heat when the temps are higher as there is a much lower chance of the coils freezing over. Also in your climate you need more heat than A/C.

At the design temp (of your heat pump only) your heat pump should be running 100% of the time. The design temp is the temperature at which heat gain (in the summer) or heat loss (in the winter) of the house equals 100% of the output of the heat pump (or there about). If you have a two speed heat pump at this temp the Heat pump should run on high (and will likely have a high AHU fan speed as well), pretty much 100% of the time. After this point the Electric heat should kick on to Supplement heat output, and this will likely kick on and off depending on needs. Once the heat pump is no longer able to provide heat the propane will likely kick on.

For your piece of mind I would have a tech come out and service the system and confirm it is operating as designed. It sounds to me like it is operating correctly, but I have no experience with such a system to know for sure.