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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8512
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I installed a Thermal Zone heat pump model TZPL4242B with

Customer Question

I installed a Thermal Zone heat pump model TZPL4242B with matching coil with a 20 yr old Lennox air handler. The thermostat is a Honeywell model T8011R 1026 (2). It has wired attached to terminals G,C,R,y/W1,W2 E and O. I am uncertain what to attach to the 5 wwire on the Thermal Zone.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.


Tell me if this is what you have or not please, I do not understand about the '5 wire'. Please elaborate.

Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip icon at the right end of the toolbar at the top of this dialog box,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip icon, look for the '+attach files' link at left of your send button.

I can mark it up with trouble shooting instructions. You will need a multi meter ($30 at a hardware store) and some experience working with appliances, let me know a lot about your skill sets in those regards.

We can go from there.

Customer: replied 1 year ago.
I attached a picture of the thermostat wiring. I am a technician andinstall many a/c units. Heat pumps I am somewhat familiar with. have all test equipment needed and 26 years repair experience. From what I understand the cond unit reversing valve is energized in heat mode. The wires at the condensing uni are :Red, Purple heat relay,Yellow cooling relay, Blue, and brown 24 v common. This is from info from another tech to another customer's question on justanswers.
Expert:  Phil replied 1 year ago.

Hello again,

I must be very direct here. This is close to worst wiring mess that I have ever seen, not only are the thermostat connections non standard, but the free hand mark ups on the thermostat will not work either... the system controls will need to be rewired from *scratch.

To do that I will the photo's I asked for in my previous post.

I will give those photo's I need a look, if I can see a quick fix I will provide it, if not I will ask for a very substantial extra... in the range of $150, or I can opt out at your option.

Get me those pictures, we can go from there.

Customer: replied 1 year ago.
I don't have the pics from the air handler although I can get that. I would disregard the hand written notes and go with what the thermostat terminals operate. From what I understand the new unit uses 24v in heat cycle to operate the eversing valve and the lennox may have done that in the cool cycle.
Expert:  Phil replied 1 year ago.

I will wait until I get the pictures, we can go from there.

Customer: replied 1 year ago.
here is the schematic from the heat pump
Expert:  Phil replied 1 year ago.


I also need photo's of the air handler wiring diagram where the thermostat wires land inside the house, and a photo of the printed circuit card that shows the thermostat wiring there, same on the outside unit.

You are working with a total mess there, I need to see the totality of it... seeing just parts here and there doesn't help me sort this out for you... even then its a long shot.


Customer: replied 1 year ago.
I will get the air handler pics for you. The hand written notes on the thermostat are simply the color wire they ran to that particular terminal/ is still C. R is still R It's not that much of a mess as I see it, just a matter of interpreting what terminals need to be connected to the outdoor unit. I believe the diagram inside the cover of the outdoor unit is the same as the schematic I sent you but will take a picture of it for you.
Expert:  Phil replied 1 year ago.

They also ran wire to and from the wrong terminals, as well as having the color code incorrect...the 24 volts has to be rewired entirely, 100% from scratch.

This is not slightly screwed up, it is completely screwed up...I have found over my half century in this business that it is virtually always better to start from scratch, even in cases not half as bad as this.

Customer: replied 1 year ago.
Diagram for cond. unit
Customer: replied 1 year ago.
Model of air handler
Customer: replied 1 year ago.
Thermostat connections to air handler
Customer: replied 1 year ago.
24v connections air handler opposite t'stat connections
Customer: replied 1 year ago.
another view of 24v connection board
Expert:  Phil replied 1 year ago.

Hello again, thanks for the great pictures.

This is the install manual for your thermostat

see page 4

This is something that will take a few hours to sort out online here, but that a well qualified, and long experienced HVAC tech could wire for you in less than 30 minutes

We can go from there any way you wish. if you want to hire this done, tell me which direction you are from the center of the nearest city...I can probably locate one or two well rated companies for you in that case.

Customer: replied 1 year ago.
The thermostat info is great! I'm going to look it over and think I can get it going. If not I have 2 competitors I work with to bail me out. Now that I know what the thermostat terminals do, it shouldn't be bad. I'll let you know how I make out and give you positive feedback. Thanks again.
Expert:  Phil replied 1 year ago.

Thats good, I will put up the rating box now, stay in touch for anything else you need on this, rating does not close the question or increase your charges, but it does fund my ongoing ability to follow up on these sorts of questions.