frost on suction line

[Anthony Alderman]

I found this frost on the foam sleeve on suction line in the crawlspace. I've never seen this before and don't know if it's a problem soooo HELP!
I cant find any info on this.
Thanks Tony

[Jim Luttrall]

Frost on the suction line means only ONE thing, the suction line is less than 32 degrees.
No it is not normal for air conditioners, but don't get too excited, yet.
What was the indoor and outdoor temperature and was the A/C set to an unusually low setting.
Next question, was there sufficient air flow.

[Anthony Alderman]

Sorry should given more info...
Heat pump
outside temp 38
inside at 68
heat pump was running

[Vern Heiler]

Sorry should given more info...
Heat pump
outside temp 38
inside at 68
heat pump was running

Anthony, it sounds like the transfer valve has the unit in cooling mode. The heat you are seeing inside the house is from the heat strips. I have seen this before. In the case I saw it was due to shorted wiring at the thermostat. Heating bills were through the roof!

[Anthony Alderman]

how would you check that?

[Vern Heiler]

how would you check that?


The technically exhaustive way is to look for 24v on the Orange control wire. Normally has 24v when in the cooling mode and 0v when in the heating mode. This is not always the case depending on mfg. but most often.
The quick and dirty is to switch from heat to cool and listen for the transfer. The gas line (large) should become warm when in the heat mode, cold when in the cooling mode.

[Anthony Alderman]

Thanks Vern
I will see about that. How long do I need to wait between switching between heat to cool?

[Vern Heiler]

Heatpumps switch between heat and cool on the fly everytime they go into defrost. There is no need to wait.

[Anthony Alderman]

Thanks Vern

[David Bell]

also look for a new thermostat,,,very often people change stats and don't know whether orange or blue wire activates reversing valve. By the looks of that suction line the coil is probably a block of ice