Lennox package coil icing up

[lees8110]

Hi all,

Got to attend a unit with regards to complaints the coil is icing up. (In heating mode) Its a Lennox package Lha model,

I dont suspect the unit to be low on gas as I serviced it not so long ago,

Just wondering if anyone can tell me how the defrost cycle is determined on these units before I get there.

Cheers
Lee

[lees8110]

Well, in this case just for anybodies future reference

It was a pipe temperature sensor (s6) had to sense 256psig/2 degrees to send the signal to a small pcb defrost timer card, (cmc), this sending the signal out to relay (k4) this activating the heat pump solenoid every 30, 60 or 120 minutes depending on setting.

In this case it was the defrost timer card (cmc) that happened to be faulty.