I want to install a hard start capacitor into my Carrier Air V ac. I been told that it is a psc motor so it would take a Supco # SPP6E capacitor. I looked at my capacitor that has 3 terminals with 2 tabs and they all have wiring on them except for 2 terminals that don't have anything on them . Those 2 terminals are marked herm and fan . The instructions I've read say one wire of the capacitor goes to herm and the other goes to the con. So I need some help on that, Thanks

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RV A/C usually has TWO "Run" capacitors. Permanent Split Capacitor = PSC. The MicroFarad (uF) rating for the Compressor (HERM) capacitor is around 40uF and the Fan (FAN) around 5uF. Your unmarked terminal would be the Common (COM).You have two-way capacitor that provides capacitance for HERM and FAN in one. They are interchangeable with two individual capacitors of the correct value, just the COM of both need to be jumpered together.I found a Carrier Service Manual and suggest you download it. Starting Section 4, are wiring diagrams and you can see that HERM/FAN capacitor. It has a PTC device across the HERM and COM terminals.What bothers me is that I read your OP to read that you are NOT finding a wire on COM already. Is that true, or do you in fact already have wires on all three sets of terminals FAN, HERM, and COM/Unmarked?Is there a wiring diagram inside your Carrier unit? Does it match the manual I linked?

Followup - In this picture, there are three sets of terminals. By "set" I mean within a black insulator.In your A/C, does each "set" have at least one wire on it? I think you'll find a PTC Device across HERM and COM. If that's how yours is, check the SUPCO instructions against that information.

I didn't know what to do with mine either. They had that El Cheapo PTC thermister across the run capacitor where the supcro would go so I disconnected it and hooked the supcro there. It helped starting with my Yamaha 2400 a lot.Seems to me if you left the PTC thingey hooked up it would effectively short out the supcro making it worthless. Maybe thats why they didn't help for some people?

j-d wrote:Followup - In this picture, there are three sets of terminals. By "set" I mean within a black insulator.In your A/C, does each "set" have at least one wire on it? I think you'll find a PTC Device across HERM and COM. If that's how yours is, check the SUPCO instructions against that information.Yes on my capacitor it has at least one wire to each set of terminals. What I was trying to say that on the herm terminalthere is only one wire going to it so I can run a wire from the hard start capacitor to the empty one. The only other terminal that has a empty one is the one marked fan.

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Fuller_Johnson
Explorer II
Apr 11, 2014
I didn't know what to do with mine either. They had that El Cheapo PTC thermister across the run capacitor where the supcro would go so I disconnected it and hooked the supcro there. It helped starting with my Yamaha 2400 a lot.

Seems to me if you left the PTC thingey hooked up it would effectively short out the supcro making it worthless. Maybe thats why they didn't help for some people?
j-d
Explorer II
Apr 11, 2014
Followup - In this picture, there are three sets of terminals. By "set" I mean within a black insulator.

In your A/C, does each "set" have at least one wire on it? I think you'll find a PTC Device across HERM and COM. If that's how yours is, check the SUPCO instructions against that information.
j-d
Explorer II
Apr 11, 2014
RV A/C usually has TWO "Run" capacitors. Permanent Split Capacitor = PSC. The MicroFarad (uF) rating for the Compressor (HERM) capacitor is around 40uF and the Fan (FAN) around 5uF. Your unmarked terminal would be the Common (COM).

You have two-way capacitor that provides capacitance for HERM and FAN in one. They are interchangeable with two individual capacitors of the correct value, just the COM of both need to be jumpered together.

I found a Carrier Service Manual and suggest you download it. Starting Section 4, are wiring diagrams and you can see that HERM/FAN capacitor. It has a PTC device across the HERM and COM terminals.

What bothers me is that I read your OP to read that you are NOT finding a wire on COM already. Is that true, or do you in fact already have wires on all three sets of terminals FAN, HERM, and COM/Unmarked?

Is there a wiring diagram inside your Carrier unit? Does it match the manual I linked?
1492
Moderator
Apr 11, 2014
Moved from Forum Technical Support

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