Carrier Infinity defrost problem

[Pirlbeck]

In April of 2006 I had a Carrier Infinity heat pump installed to replace a 15 year old heat pump. It worked great for summer cooling, but almost from the start of the heating season last year, I felt the outdoor unit spent way too much time frosted up. I am not home a lot, but it seemed like a high percentage of the time when I was at home, it was frosted up. I had the installer come out and check it several times and they could find no problems and set the defrost timer to 30 minutes. I still felt it was frosted up too much, but just put up with it. This past weekend it got to the point where it would not defrost at all and by Monday morning the outdoor unit was a huge block of ice.

Here is some info on the unit.

The outdoor unit is a 38YDB048-311
The indoor unit is a FE4ANB006000

The thermostat software version is CESR131339-10

Here are a few of the heat pump settings.

Defrost- 30min
Quiet shift-off
Elec heat lockout-none
Hi coil latch-none
Hi heat latch-off

In checking the run/fault history I found the following:

HP 01/06/2007 temp sensor out of range 52 times as of last Sunday, now at 55 times
HP 10/27/2007 hi pressure switch open 3 events

Under heat pump faults I found:

lo pressure switch open 1 event
hi pressure switch open 1 event

And this morning for the first time I found this:

Outdoor air temp fault- 3 events.

On the advice of the distributor techs, the service man came out yesterday and ohm tested the outdoor temp sensors and said they both test OK, Using the thermostat control, he manually defrosted the heat pump and he says it defrosts just fine. I am not sure he feels that there really is a problem.

When I got home last night the unit had pretty good frost build up on it. I kept an eye on it off and on through the night and I never did see it defrost and it is pretty much solid frost this morning. I am located in Iowa and the temps here this morning are about 15 degrees, not sure of the humidity.

Sorry about the lenght of this.

What is causing the "events" and the failure to auto defrost? Any thoughts on all of this?

Thanks!
Pat

[second opinion]

Are there any other dealers that can look at your system? At 15 degrees there should not be a lot of moisture in the air to cause the coil to freeze over. A thirty minute defrost intervall is short.

Did his service ticket give you any pressures and temperatures? You may have a charge issue and a defrost issue.

[Pirlbeck]

Thanks for your reply!

At this point I am willing to give the installing dealer more time to figure this problem out. They have done a lot of work for me at my home and business and I have always been very satisfied. Also, this is a very rural area (town of 250) and I am not sure if there are any Carrier dealers in the area that would have any more experience then these guys.

I do not know if he tested any pressures and temperatures . We kept an eye on it all morning and it never did defrost, so it must not be going into the defrost cycle at all, as it defrosted fine yesterday when it was put into defrost via the thermostat interface. Any ideas on why it would not go into defrost on it's own?

Any other thoughts?

Thanks!
Pat