Bryant HP defrost problem

[yarnik]

I'm working on a Bryant Heat Pump, model #657ANX042000AANF in Phoenix. Last night it got down in the 20's. Complaint is that there is cold air blowing in heat mode during the night. I jumped defrost board - it cycles, reversing valve OK, outdoor fan motor stops. Problem is that indoor fan motor continues to run. There are no heat strips on unit to need the indoor fan motor. I disabled the timer for now so that defrost does not run (the jumper was set to 90 min).

Does this sound like a problem with the board?

[racingfan]

I'm not sure that you have a problem. All units that I'm aware of always run the indoor fan during defrost, thus the minimal need for supplemental heat.

[chillbilly]

Are you saying you have a split system heat pump that does not utilize a second stage of supplemental heat?
If the indoor unit is not equipped with supplemental heat strips, the indoor fan will continue to run during defrost cycle with no supplemental heat.
That sucks.

[dna]

"G" and "Y" terminal are still being energized at thermostat, even thru a defrost cycle. Is the wire heavy enough going to air handler to support some resistance heat?

[markj]

Sounds like its working right to me. New install or been there awhile?
You Phoenix sure don't like cold weather. I used to visit my parents there. We would be headed for the golf course in the morning. 5o and sunny. I had on shorts and a wind shirt. People going to work wold have on gloves, hats and winter coats. i guess its all in what you get used to.
My guess is that it rarely goes into defrost and the customer only noticed it when it got that cold. Heat strips woild be nice for the homeowner if the heatpump would fail in cold weather, if you ever get any.

[yarnik]

The unit is 10 years old, and there is no supplemental heat (it's not a split system). Is it OK to leave the defrost timer disconnected? It was set to 90 minutes, so I don't think it went into defrost that often. We don't get many wet days when frost really could form on the condenser.

I don't think the owner wants higher electric bills, so I'm thinking that heat strips aren't an option.

Thanks for your help.

[erc tech]

It will never fuction correctly without heater kit installed. Mid 20's HP can't keep up, Also you will have cold blow during defrost cycle.

[jrbenny]

How did you disable the timer? Did you simply pull the jumper for the timer from the board? If so, the timer is still functioning at 90 minutes. The 90 minute place holder is a dummy terminal.

The unit is working fine as others have noted. You just need supplemental heat to temper the air during the defrost cycle.

[yarnik]

I did pull the jumper from the board (forgot that the 90 min post went nowhere). I guess I'll need to strongly recommend a supplemental heat strip kit. Thanks much for your help. Before long, it will be 110 degrees in Phoenix and we won't have to worry about electric heating.

Take care.

[lentz]

The unit is 10 years old, and there is no supplemental heat (it's not a split system). Is it OK to leave the defrost timer disconnected? It was set to 90 minutes, so I don't think it went into defrost that often. We don't get many wet days when frost really could form on the condenser.

I don't think the owner wants higher electric bills, so I'm thinking that heat strips aren't an option.

Thanks for your help.

During Defrost
You are going to have room temperture air coming out of the ducts if you do not have any strips. Body temmperture is in the 90's and circalatin air is in the 70's. It does feel cool. Might have to add another wire to unit just for strips. Rain had nothing to do with frost building up on the outside unit. It could help get rid of it.

[BaldLoonie]

Defrost is cooling mode. You will have 50° air coming out with no strips during defrost

Also rain outside in 30° adds to frosting problems. That means the air is 100% RH and very likely to frost a coil. That's what we've had here all weekend

[jarrett hvac]

Are you saying you have a split system heat pump that does not utilize a second stage of supplemental heat?
If the indoor unit is not equipped with supplemental heat strips, the indoor fan will continue to run during defrost cycle with no supplemental heat.
That sucks.

yes sir, you are correct. The Bryant Heat Pumps will run the fan in defrost and the heat pack should energize or furnace should come on if it is a dual fuel. I can't think of any reason that a heat pump would be installed without a heat pack or in a dual fuel application.

[fixitmanmc]

disconnect od sensor wire

[Airmechanical]

I'm working on a Bryant Heat Pump, Last night it got down in the 20's. Complaint is that there is cold air blowing in heat mode during the night defrost cycles valve OK, outdoor fan motor stops. Problem is that indoor fan motor continues to run. There are no heat strips on unit to need the indoor fan motor. I disabled the timer for now so that defrost does not run (

1) indoor fan should always run during defrost cycle

2) its gonna blow COLD air during defrost cycle (unless aux.heat available)

3) if ya disconnect the defrost board its gonna freeze up

4)if ya lower the timer (jumper) to 30 or 60 minutes, defrost cycle (time)
will be shorter, although there will be more cycles per day

if it was a variable speed a/h you could
slow down rpm during defrost (i'll elaborate in pro forum)



.

[Airmechanical]

delete!


.

[jarrett hvac]

this is incorrect, during defrost with no strip or auxillary heat
you will have approx 50 degrees supply air temp. assuming
inside temp is 70 degrees




.

correct, in defrost is goes into a/c mode

[chillbilly]

yes sir, you are correct. The Bryant Heat Pumps will run the fan in defrost and the heat pack should energize or furnace should come on if it is a dual fuel. I can't think of any reason that a heat pump would be installed without a heat pack or in a dual fuel application.

Ouch. If the high voltage wiring at the indoor unit can handle at least some supplemental heat, I would install it.