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drumming102's avatar
drumming102
Explorer
Jun 03, 2017

Hard Start Capacitor install issues

Hey guys,

I have a dometic AC unit on my Passport 2920BH. It's like a polar ice 2 or something like that (13.5). It also has a 5-6 sec delay compressor start after fan.

I purchased a Supco SPP6 https://www.amazon.com/gp/product/B008FM8X3Q to install on the run Capacitor.

When I cracked open the electrical box I found only 1 capacitor instead of an expected 2. Are they combined? The wiring diagram almost makes it look like they are.



Well I hooked up the relay side (with the extra prong) of the SPP6 to the red wire post and the other to the white (As per the schematic) and it seems like my genny takes an even bigger hit when it starts and stumbles more. Is my cap bad? AM I reading the diagram wrong?





I even tried reversing the SPP6 wires

"Help me RV.net forums, you're my only hope"

Genny is a 3100 Champion inverter. It runs the AC but just trying to make the start a little easier on it.
  • j-d's avatar
    j-d
    Explorer II
    Jun 03, 2017
    I wonder if that "spooling up" remark is valid for both the constant speed and the inverter generators...

    I noticed the pics you posted show the SPP6 label different from the SUPCO site.

    From what I've heard, the compressor can't start if the start assist capacitor fails to get out of the circuit. So your idea of a bad SPP6 might have something going for it.
  • j-d's avatar
    j-d
    Explorer II
    Jun 03, 2017
    There's debate over the best "hard start kit." Not talking "soft start" like Micro Air that's much more effective and much more expensive.

    Basic Hard Start is Capacitor and PTCR like SPP6.

    Then there's Electronic that's a little smarter like SPP6e.

    Better is a "Potential Relay" that does a better job of determining compressor's starting status.

    Our gurus here think the "e" series does a better job than PTCR, but SUPCO defends PTCR. They claim it gives the generator more time to spool up and help start the compressor.
  • drumming102's avatar
    drumming102
    Explorer
    Jun 03, 2017
    j-d wrote:
    From the diagram and the pictures, you have a two-in-one Run Capacitor. The Compressor runs on HERM and COMMON. Chances are only HERM (Compressor) and FAN are marked, and COM is the third one.
    The SPP6 has two wires that go to HERM and COM. Doesn't matter which is which. The SPP6 contains a Start Capacitor and a Positive Temperature Coefficient Resistor (PTCR) to take it out of circuit when it thinks the compressor is up to speed.

    You diagram shows the equivalent starting device labeled "Comp Start Assist" with its Red and White wires going to HERM and COM on the two-in-one RUN capacitor.

    IF IF IF the Comp Start Assist was an option and it's NOT already there, then you can add SPP6. If it's already there, DO NOT add SPP6 as a second one.


    Yea there is NO other cap installed. the diagram just helps you with installing one like this if you want. My SPP6 must be junk then.
  • j-d's avatar
    j-d
    Explorer II
    Jun 03, 2017
    From the diagram and the pictures, you have a two-in-one Run Capacitor. The Compressor runs on HERM and COMMON. Chances are only HERM (Compressor) and FAN are marked, and COM is the third one.
    The SPP6 has two wires that go to HERM and COM. Doesn't matter which is which. The SPP6 contains a Start Capacitor and a Positive Temperature Coefficient Resistor (PTCR) to take it out of circuit when it thinks the compressor is up to speed.

    You diagram shows the equivalent starting device labeled "Comp Start Assist" with its Red and White wires going to HERM and COM on the two-in-one RUN capacitor.

    IF IF IF the Comp Start Assist was an option and it's NOT already there, then you can add SPP6. If it's already there, DO NOT add SPP6 as a second one.

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