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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a old Lennox defroster circuit board that as failed

Customer Question

I have a old Lennox defroster circuit board that as failed (see picture). I can not find an match for this? It uses two input sensors, ambient temperature sensor and coil sensor. Unfortunately the model numbers on our old heat pump have faded and are unreadable. But the heat pump still works fine! I just need a defroster board. There is a number on the board I have; it is: EIA232D Is there a kit that will replace it?
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Take a look at this board and see if it looks like your board

Customer: replied 1 year ago.
No, I am attaching a picture.
Expert:  airheatman replied 1 year ago.

Got any idea how old unit is or do you have a picture of unit? That one was an upgrade for the old Hp7,8,9 and 10

Customer: replied 1 year ago.
you mean a picture of the entire packaged unit?
Expert:  airheatman replied 1 year ago.

Yes, picture might help me identify

Customer: replied 1 year ago.
here's a pdf on it that's a match to the unit.
Expert:  airheatman replied 1 year ago.

Take a look at this upgrade kit and tell me if you have those RST and HOLD terminals

Expert:  airheatman replied 1 year ago.

This shows to be the replacement for the CHP10 packaged unit

Customer: replied 1 year ago.
Hmmm....interesting...would you be kind enough to look at this picture of my unit and see if indeed it looks like a CHP 10 to you?
Expert:  airheatman replied 1 year ago.

It does to me. I can not see all the letters by your terminals, The AC plus and AC minus are labeled 24v and Com on new board.

Customer: replied 1 year ago.
Let me help clarify: The letters by the four terminals on my existing board are: "R" "R" "AC" & "+AC" The two R terminals go to a 24 volt relay (the part # ***** this relay is midland ross 23C100) , the "AC" terminal goes to a yellow wire that ends up on the 24 volt control transformer, the last remaining wire goes to the reversing valve ( I think?) . Do you think this replacement board kit will be able to work with my existing system which ONLY has four wires?
Expert:  airheatman replied 1 year ago.

Is it possible that that wire you think goes to reversing valve may go to a high pressure switch on refrigerant line?

Customer: replied 1 year ago.
no, because cause at some time in the past, one of the hvac guys cut the wires on high pressure switch, perhaps originally it went to the this valve? Also, there's be added "delay on make timer" that's been added at one time in the past. What's so frustrating is that the wiring diagram on side of the unit has peeled away. I would really like to get a wiring diagram of how this beast was originally wired. Can you provide this diagram?
Expert:  airheatman replied 1 year ago.

Doesn't look like anything I have goes back that far on wiring diagrams.Will se what I can come up with

Customer: replied 1 year ago.
That would be great! Please email me anything you find ***@******.*** Thank you so much for your time. Would I be able to pick up this conversation with you later? Any ideas on cost for follow up? same price as this time? What's the hours you work? etcetera, etcetera
Expert:  airheatman replied 1 year ago.

WE can continue here tomorrow,If I find anything, I will respond here.We can leave the question open until we are done.

Customer: replied 1 year ago.
thank you again and good night
Expert:  airheatman replied 1 year ago.

Good night

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