Coleman H/P Defrost Issues

[dgunt]

I have a customer that has a Coleman 18SEER 2 Stage 3Ton heat pump. The issue that I am having with the unit is that it wouldn't defrost the bottom 1/4 of the coil. The unit is sitting up on a snow stand that is 18" off the ground. I have weighed the charge out and re-weighed the correct charge back into the system. I have switched the defrost board on it. I have checked the defrost sensor to see if it was out of range (ohms out fine). What I notice when I was there last time was that the top part of the coil would heat up to 110F and the bottom part had a hard time getting up to 80F after 10mins in defrost. Has anyone had defrost issues with the Coleman or York 18SEER units?? Also I have check the reversing valve to see if it was leaking by and there is only a 1F difference between in and out on the suction side in heating and defrost mode.

[Saturatedpsi]

If you're satisfied the system is running right, and if the bottom quarter is ice (instead of frost), have you tried "manually" removing the ice with water, assuming it ain't 15˚ ambient? It may have just gotten behind for whatever reason.

[ksefan]

In heat pump mode is the discharge line temp 125 plus outdoor ambient?

[uniservice]

Might call Tech Support, see if they recommend relocating sensor. I recall a manufacturer doing that back some time ago, but I don't remember who,,,,,,,,solved the problem on that one.

[bruced]

What is your sub-cooling? Weighed charges wont do it!

[behappy]

I have a customer that has a Coleman 18SEER 2 Stage 3Ton heat pump. The issue that I am having with the unit is that it wouldn't defrost the bottom 1/4 of the coil. The unit is sitting up on a snow stand that is 18" off the ground. I have weighed the charge out and re-weighed the correct charge back into the system. I have switched the defrost board on it. I have checked the defrost sensor to see if it was out of range (ohms out fine). What I notice when I was there last time was that the top part of the coil would heat up to 110F and the bottom part had a hard time getting up to 80F after 10mins in defrost. Has anyone had defrost issues with the Coleman or York 18SEER units?? Also I have check the reversing valve to see if it was leaking by and there is only a 1F difference between in and out on the suction side in heating and defrost mode.

I remember reading a post from Mr. DigiCool that this problem ( with UPG equipment) is common in your area. I would contact Coleman....

[dgunt]

Thanks for all the replies. I called tech support and the guy I was talking to said I should check the charge. So What I ended up doing was adding some more gas to the system to get the discharge temperature up around 170F in defrost mode. What I also did was speed the indoor fan up some. The reason for that was because I checked the speed on electric heat and it was low compare to the flashes I was getting on the board. Knock on wood haven't heard anything back yet.