Evap coil freezing

[rpope904]

I am in HVAC, but only on test and balance side. I have no exp. with repair, and so on.. In my house, we moved in a month ago, the condenser was missing, the old owner had a new one installed. I never even bothered looking at it, but wasn't happy due to the house never being cooled off below 78. I figured it was undersized. The wife who parks in the garage said she had heard water in the unit, and tried to pull the filter out but it was soaked, so I finally got into it yesterday. The evap coil was frozen solid, so I put it into heat pump to melt the ice, and dry it up some.. Afterwards, I strapped my temp probe on the coil, closed the unit back up and dumped it into cooling, and the temp on the coil went to 26.5, which is def. too low, and again, it iced up which explains why the house never got cool.

Now, before I go after the guy who installed the condenser, should I? My concerns with this are, that when he installed it the first time, it ran for a week and then the compressor locked up on a brand new unit, he replaced the compressor, not the entire condenser and now this problem, which I know could be a number of things, from a line problem to low charge (which I want to know why, if it is a low charge why he didn't properly charge the unit) or an over sized compressor.

[skippedover]

:callpro:

[jpsmith1cm]

:callpro:

:ditto:

Ask around and find a good one.

[beenthere]

I'd call him and have him check it out. Its under his 1 year labor warranty.

[sktn77a]

Could be a whole host of things - airflow set wrong, dirty filter (sounds like you removed that), low refrigerant charge, miswired thermostat, etc, etc. Call the guy back and tell him it still isn't working correctly.

[KaseSchool]

Most definitely call your installer back. If they are worth anything, they also want to make things right. When the condenser was installed, was a new coil installed also?

[Shophound]

You're a test and balance guy - you know why you're testing for proper airflow delivery to each room, correct?

It won't hurt for you to know why proper airflow across a cooling coil is also important. The less airflow across a coil occurs (assuming a proper refrigerant charge), the greater likelihood the coil will freeze. Why? When you move less air over a cooling coil, you reduce the amount of total heat transfer that occurs between the air, the coil, and the refrigerant. What hasn't changed is (again, assuming a normal refrigerant charge) the capacity of the compressor to pump refrigerant. If heat transfer to the refrigerant in the evaporator is reduced via low airflow, the compressor drops the refrigerant pressure lower, which lowers the temperature that it boils at, which reduces the surface temperature of the evaporator. Any moisture on that coil will at some point freeze.

Break out your balometer and test the supplies in your house. Other than that you'll need an EPA certified tech to get gauges on the system and see what's going on.

Have you changed your air filter lately? And if so, how clean is the cooling coil and indoor blower wheel?