During heatpump defrost - will indoor air blow cold or warm?

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Old 01-22-15, 11:52 AM
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During heatpump defrost - will indoor air blow cold or warm?

I live in the Central VA, USA & recently my Trane XR16 (17 beginning 2013) heat pump went into defrost mode during a couple of icy rain/ 28-29F degree days.

The outside unit fan didn't spin but there was noise eminating from it & some steam coming out - so I gathered it was defrosting.

Also, noted that my Trane TAM8 air handler was blowing out cool air at this exact same moment. This lasted for about 7-8 mins before the HP kicked back in & spun warm air again.

Questions are:

1) should I be feeling cool or warm air during this defrost cycle?
2) if my aux 5KW heat strips are being used as part of the defrost cycle, would that explain why I am not feeling warm air during defrost?
 
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Old 01-22-15, 02:10 PM
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The AUX heat should be turned on automatically when the outside unit is in defrost mode. My upstairs unit has electric AUX heat and it feels warm during defrost. My downstairs unit has a propane furnace for AUX heat and it blows warm air during defrost.
 
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Old 01-22-15, 02:25 PM
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All of the "symptoms" you've described are normal. You may experience cold air delivery during defrost. Say 10 minutes maximum.

If you have auxiliary heat strips, they will temper the cold air during defrost, but it won't always be warm.

So long as you have regular service and the charge is correct you're probably fine.
 
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Old 01-23-15, 07:21 AM
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Thank you DMCman & MrTech.

I think the key phrase to manage my expectations are:
If you have auxiliary heat strips, they will temper the cold air during defrost, but it won't always be warm.


Knowing that the house temps during defrost cycles possibly won't feel as warm as non defrost cycles (i.e. a couple of degrees below desired set point) - Will allow us to make other arrangements during these small 'down times'.
 
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Old 01-23-15, 03:29 PM
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5kw is something like 17000 btu if i remember correctly. That's maybe enough to properly temper the air if your heatpump is 1.5 ton.
 
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Old 01-24-15, 12:39 PM
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5kw is very small. What size HP do you have.
 
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Old 01-24-15, 01:52 PM
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I wonder what the BTU difference is of the defrost compared to the normal AC. The outside fan is not running which would reduce the BTUs but the coils are very cold with frost or ice on them which would increase the BTUs.
 
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Old 01-26-15, 12:39 PM
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airman.1994
5kw is very small. What size HP do you have.



I have a 3 Ton XR16 covering 3k sq ft.

I am going back to check with my installer to verify the size of the heat strip again.
 
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Old 01-26-15, 03:05 PM
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I'd have a 15kw heater on this. Even in defrost 15kw would be putting out warm heat. May I ask who put this in? Post initials
 
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Old 01-26-15, 08:56 PM
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airman.1994
I'd have a 15kw heater on this. Even in defrost 15kw would be putting out warm heat. May I ask who put this in? Post initials



Verified it is an 8KW strip.
During defrost cycle this evening with outdoor temps hovering around freezing, my register reading was 68* with t-stat setpoint @ 71*.

If I wanted to replace it with a 15KW how much should I be budgeting for?
F.H&P in Richmond. Did load calc & blower door test was also done.
So house is tight , if that matters in strip spec-ing.
 
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Old 01-26-15, 11:46 PM
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You may have a burned out element. A technician would check the current draw with a clamp on amp meter but you could check if it's burned out by running emergency heat. If you don't get warm air in emergency heat then your element is probably burned open.
 
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Old 01-27-15, 06:23 AM
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8kw is very small for 3tons in central VA. If this is less than a year old it should be under warranty, so I would call in a service call with the company just to make sure there isn't another issue. Saying that as long as you didn't spec the heater I would fight them the entire way. force them to put in the correct heater. Id only pay the difference between the two heaters.
 
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Old 01-27-15, 08:55 AM
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airman.1994's
8kw is very small for 3tons in central VA. If this is less than a year old it should be under warranty, so I would call in a service call with the company just to make sure there isn't another issue. Saying that as long as you didn't spec the heater I would fight them the entire way. force them to put in the correct heater. Id only pay the difference between the two heaters.


Hmmm...coming up on 2 years since move in.
So not sure they will go for it since i signed the paperwork on the install & deployment.

But I'd definitely am not feeling warm air @ a 68* register reading on a 71* setting in 30* outdoor.
Wonder what that will be in 10* outdoor??
 
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