Heat Pump Ice Up

[condojack]

Have a Lennox heat pump that ices up on me. Have replaced defrost board & checked out refg charge. There does not seem to be a sensor connected to board, and the wiring diagram is un-readable. Fan speed is OK, reversing valve is OK. Can not get it to go into defrost cycle by itself. Need advise & a wiring diagrtam for Lennox HP HP22-411-3P. Also does anyone know what manufacter handles parts for Air Pro heat pump, can not find any in my area.

[iwannahelp]

It has a defrost thermostat. It has two, one is for defrost(which is the one you want) and the other is for discharge temp. of compressor(don't mess with that one). Really can't go into much detail since I don't think it is allowed on here, but I know for a fact that is does have a thermostat.

[condojack]

Thanks iwannahelp I will check that out, I wish I had wiring diagram.

[davefr]

Thanks iwannahelp I will check that out, I wish I had wiring diagram.

Have you tried searching? Lennox makes some of their technical installation manuals public. Go to the installation manual section vs the owners manual section.

http://www.lennox.com/owners/archived-docs.asp

[condojack]

Thanks Davefr for the info, will give them a try.

[Msully]

As I recall on this unit it is strictly time based defrost. Defrosts according to jumper setting and terminates on thermostat.

[condojack]

MSully thanks for the imput, will put it to good use.