[DrJosh]

Hi. My heat pump fan motor died. I got a replacement motor and capacitor but the wiring is a bit different for the new parts and I was hoping you could help me sort it out. The old capacitor had three terminals while the new one has only two.

In the old setup, there were 5 wires to deal with:

brown:  motor -------------------> cap (terminal labeled "fan")
purple: motor -------------------> cap (terminal "0" or something like that)
black:  motor -------------------> circuit board (contactor?)
orange: cap (terminal "herm") ---> somewhere else
red:    cap (terminal "0") ------> somewhere else

By "somewhere else" I mean this wire goes somewhere other than the cap or the motor, so it doesn't seem too important for this job. If it is, let me know and I'll happily provide more info...

The new motor has two wiring diagrams printed on it. The first is:

brown/white --------> cap
brown --------------> cap
purple (common) ----> L1
black --------------> L2
green --------------> ground

The second is labeled "optional 3 wire connection":

brown/white ---> insulate
brown ---------> cap
purple --------> cap ----------> L1
black -------------------------> L2

So my questions are:
-What are L1 and L2?
-The optional 3 wire connection looks more similar to the old setup--should I wire it this way?

Any help would be greatly appreciated! :)

[hvac1000]

I figure your heat pump motor is 220/240 volts.

The easiest way is to just

Use the two brown to go to the new capacitor.
Use L1 and L2 to power the motor up from the load side of the contactor so when the unit turns on and the contactor makes the connection the new motor will also come on.

By wiring this way you prevent having to mess with the wires for the compressor Orange/Red. The old capacitor is also powering the compressor and needs to be hooked up to it just as it is now.
You can remove the wires from the original capacitor that were used for the old fan motor if you wish or just tape up and leave alone. That is your option.

NOTE: if there is a short green wire make sure it goes to ground which is the unit metal.

[DrJosh]

Thanks for your swift reply! I appreciate your expertise.

I'm still not clear on what "Use L1 and L2 to power the motor..." means.

Black: motor ----> contactor (as before)
Purple: motor --->?

I guess the contactor is L2. What's L1? What do I connect purple to?

There is a little green wire coming off the motor. I'll be sure to secure it to the unit chassis. Thanks again.

[hvac1000]

You need to hot legs to power up the motor. L1= Line one 120 volts and L2=Line 2=120 volts. When wired to a 220/240 volt motor both lines of 120 are used to get the 240 volts needed so the motor will run.

On the contactor there are two power terminals for the power in and 2 for the power out. The power in comes from the house or disconnect for the unit. The two for the power out (out after activation by the 24 volt control circuit). The two for the power out are used to run the compressor and the condenser fan motor which you are replacing so blcak to one side and purple to the other side of the contactor. They will be put on the same side that is also used now for the compressor.

NOTE: There are probably an extra wire or so that feeds the old condenser fan motor circuit. If you know what you are doing those can be eliminated IF NOT let them alone and just attach the purple and black.

[DrJosh]

I was finally able to take another look at the unit and try to apply
Your advice. However I'm still not clear on how to proceed. To
Make things a little clearer I took some pics:





As you can see I reinstalled the old cap and reconnected red and
Orange as per your advice. In the old setup the brown and purple
Wires ran from the fan motor to the cap terminals and the black
Wire ran from the fan motor to the black "ZETTLER" box on the
Circuit board (right). In my previous posts I assumed this was the
Contactor but maybe that was wrong?

Anyway would it be bad if I just forgot about the new cap (5uF) and
Connected everything as before? Old cap is 7.5uF.

How would you rig this up? Again, I thank you for your time.

Josh

[hvac1000]

Post the brand name

Post the exact model number

I need to see the wiring diagram for this unit and with the above info I will try to look it up. I believe the top of the contactor is the side you want to use to power the motor I want to be sure.

The answer to your question is NO you need to use the capacitor that was sized for the new motor. While the difference is small (7.5 to 5) the long term problem could cause motor failure.

[DrJosh]

Old motor
Emerson K55HXFHD-7740
RPM 825
Volt 200-230
Hz 60
Amp 1.9
Ph 1
HP 1/4
Thermally protected

I got the replacement motor through Grainger. Told them the
Old model number and they sold me the following replacement:

New motor
Dayton 4M226J
RPM 825
Volts 208-230
Hz 60
Amp 1.6-1.9
Ph 1
HP 1/4
Protection auto

[hvac1000]

Brand name of unit

Exact model number of unit

The motors make little difference it is the units brand and exact model number I need. I need to be able to follow the units wiring diagram not the motors since I know how the motor works but I do not know for sure how the motors wiring is incorporated into the unit due to the circuit board

[DrJosh]

Oh, sorry about that. Here's the unit info:

Date: 4/98
Model#: Trane TWR042C100B2
Min circuit ampacity - 28.0 amps
rec. fuse/breaker - 40
Max fuse/breaker - 45

[hvac1000]

Here is the wiring diagram for your unit.With this and the info I supplied in my other posts you should be able to wire your unit. If not then I suggest you contact a local HVAC professional to help you since I cannot wire it from here.

Note: The one motor leed has to go on to the circuit board and attach to the black Zettler relay. If the relay or circuit board is damaged or defective it will also need to be replaced. This is the defrost control for the heat pump and must be used if the heat pump is to function correctly.

[DrJosh]

A little follow-up: last week I installed the new motor according to the "optional 3-wire connection" indicated in my first post (integrates well with the original wiring diagram). It's been working great!

[hvac1000]

As long as you got it working that is all that counts. I am sure you used a new capacitor on your install.

[harvestpride]

If you used the grainer motor replacement that Dr. Josh was so kind in sharing. All the wire colors should match. There is a brown and white wire you will not use. Tape this wire off.

Thanks Dr. Josh!! Just did mine today and it works like a champ. $120 motor with shipping.

[harvestpride]

All the wire colors should match. You will not used the brown and white wire. Tape this off. Works great!

[harvestpride]

All the wire colors should match. You will not used the brown and white wire. Tape this off. Works great!

[BR14648]

I hooked up my cental a/c with the new capacitor and it works great! You are the best!
Linda