Supco Hard start capacitor on Coleman A/C

Golden_HVAC wrote:
As a general rule, yes you must have at least the minimum voltage rating of the replacement capacitor as the expected running voltage in the system. So a 120 volt compressor will see upwards of 175 volts at it's run capacitor, thus the minimum rating of 370 volts.

That said, a start capacitor with relay to take that compressor out of the circuit once the compressor is running must be properly sized. Oversize it and the correct "Drop out" voltage will not be obtained in time or at all. So a start relay that works great on a 220 volt compressor and drops out the capacitor at 190 volts on the start to run winding will work great with 200 - 250 volts input to the compressor. However move it to a 120 volt compressor, and it will never drop out, unless it has a back up timer circuit to take the start capacitor out of the circuit after a certain time has gone by. The SPP6E does have a electronic timer, and anyone putting this 220 volt capacitor on a 120 volt circuit is doing so hoping that the timer keeps working. The capacitor has a maximum working volt rating around 300 - 370 volts, so that is not a problem, the problem is the minimum voltage to drop out the start capacitor is well above what a 120 volt compressor will run at.

The SPP4E is the correct start capacitor for a 120 volt compressor, and will drop out at the correct voltage, even if the time circuit fails.

You present your reasoning very logically and understandably. I am taking your advice to use the less-suggested SPP4E for a greater margin of reliability (i.e.timer failure).

Thanks for sharing your expertise with us!

Pop

Beyer wrote:
I have a 1996 camper with a Coleman A/C. I bought the Supco SPP6E. My A/C has 2 round capacitors, one small and one large. The small one has 2 wires and the large has 3 wires. Which one do I replace? Both?
Pics:

http://i1372.photobucket.com/albums/ag321/beyer25/Mobile%20Uploads/image_zpsf3f66b5c.jpg

If the additional capacitor isn't fully functional, say with compressor restart with head pressure still....

wwest wrote:

like2rok wrote:
When i start it cold, then go to Eco Mode On, then RPM's are slightly higher than when it warms up and slows down even more. It IS Much Slower than Eco Off which wastes fuel overnight when the AC only needs to run a few minutes per hour. On this thread Please Refrain from suggesting the easy fix of Eco Off.
The entire purpose of spending $1000+ on this Inverter Generator is the Fuel Economy/quiet operation and I refuse to settle with Eco Off as a solution.

I will keep this thread updated on the attempts to modify eco idle speed or rejetting.

FYI I have the Whynter GREEN ARC-110WD AC with dual hoses that specs state 9.5amps maximum current

Simple. You need to add a TDR, Time Delay Relay, and a heavy electrical load (***)to your A/C.

The idea is that the relay delays providing power to the compressor for 2-3 seconds, initially providing a connection to the new "load". A/C switch "demands" cooling, the load comes on line, the genset revs up to speed, then the TDR switches the AC to the compressor.

*** 2 500W halogen bulbs.

An AC typically draws 3X the running load at compressor startup, maybe even 5X at times, high head pressure.

X2 for piggybacking the existing capacitor. That's what my instructions said to use. Paralleling two capacitors simply adds the capacitance of each together, unlike resistors. I also used the SPP6E and it did had the desired effect. I was able to start my 13.5k ac with my EU2000i Honda.

ScottG wrote:
General rule for capacitors; voltage rating of a cap is not important as long as it is greater than what your using it for. It's like having a higher rated wire insulation.
In this case the voltage rating has no impact on the operation of the capacitor and its circuit.
It's the capacitance value that is critical.

As a general rule, yes you must have at least the minimum voltage rating of the replacement capacitor as the expected running voltage in the system. So a 120 volt compressor will see upwards of 175 volts at it's run capacitor, thus the minimum rating of 370 volts.

That said, a start capacitor with relay to take that compressor out of the circuit once the compressor is running must be properly sized. Oversize it and the correct "Drop out" voltage will not be obtained in time or at all. So a start relay that works great on a 220 volt compressor and drops out the capacitor at 190 volts on the start to run winding will work great with 200 - 250 volts input to the compressor. However move it to a 120 volt compressor, and it will never drop out, unless it has a back up timer circuit to take the start capacitor out of the circuit after a certain time has gone by. The SPP6E does have a electronic timer, and anyone putting this 220 volt capacitor on a 120 volt circuit is doing so hoping that the timer keeps working. The capacitor has a maximum working volt rating around 300 - 370 volts, so that is not a problem, the problem is the minimum voltage to drop out the start capacitor is well above what a 120 volt compressor will run at.

The SPP4E is the correct start capacitor for a 120 volt compressor, and will drop out at the correct voltage, even if the time circuit fails.

While the SPP6E has a electronic circuit to take the start capacitor out of the circuit after a time delay, it is NOT the correct capacitor for the task at hand. The "Drop out voltage" for a 120 volt compressor is about 130 volts, then the start capacitor stops being in the circuit with the run capacitor. In your case, you are installing the 190 - 277 volt SPP6E with a drop out voltage well above 180 volts, so it will only drop out on the timeout relay.

If you disconnected the run capacitor that has the red and yellow wires going to it (in the picture above) then the compressor probably will not run at all. The SPP6E and SPP4E are designed to add to the run capacitor, not replace it.

IF you are still having difficulty starting the compressor with the generator, my suggestion is to measure the capacitance of the factory capacitor, or replace it with one that is 5 mfd higher rating, and about the same voltage rating.

IF you have a volt meter, you will be surprised what voltage is read across the red and yellow wires. You normally will find about 135 to 155 volts. Yes even the two brown wires going to the outside fan should read about 135 - 155 volts when only 110 - 120 volts is applied to your RV power cord. This is normal. Even measuring your home 220 volt A/C unit capacitor will read about 250 - 300 volts, perhaps more.

So the SPP6E will work, but it is not the product designed for 120 volt compressors. It is designed to drop out at 180 volts, for compressors using more than 190 volts input power. It is only the electronic time delay that keeps the capacitor from staying in the circuit all the time, and burning up the compressor with high amperage that it is not rated to use. The SPP4E will drop out at 120 - 130 volts across the capacitor, something that will happen in your system, even with only 108 volts applied to the compressor run winding.

Fred.

Chris Bryant wrote:

Beyer wrote:

So, if I replace both of my capacitors (start and run) with the new Supco, how should the wiring look on that?
The Supco has 2 wires and the old "large" capacitor has 3 wires and the "small" capacitor has 2 wires.

It should piggyback off the large capacitor- it will not replace anything.

Just to be clear- the large capacitor has 3 wires, but only 2 actual connections, just a couple of wires to the same connection. This is a separate compressor and fan capacitor, most now use a single combo capacitor which has "herm" "Fan" and "Com" terminals.

Going to try this tonight. Going to hook the new Supco up to the terminals on top of the large existing capacitor.

Beyer wrote:

So, if I replace both of my capacitors (start and run) with the new Supco, how should the wiring look on that?
The Supco has 2 wires and the old "large" capacitor has 3 wires and the "small" capacitor has 2 wires.

I replaced only the smaller start capacitor (it was badly corroded) and PTCR with the SPP6E. The two connections were made at the larger capacitor, to the same two terminals as the original capacitor and PTCR wires.

Beyer wrote:

So, if I replace both of my capacitors (start and run) with the new Supco, how should the wiring look on that?
The Supco has 2 wires and the old "large" capacitor has 3 wires and the "small" capacitor has 2 wires.

It should piggyback off the large capacitor- it will not replace anything.

Just to be clear- the large capacitor has 3 wires, but only 2 actual connections, just a couple of wires to the same connection. This is a separate compressor and fan capacitor, most now use a single combo capacitor which has "herm" "Fan" and "Com" terminals.

On my Coleman MachIII AC the SPP6E was piggybacked to the existing capacitor(s). It didn't replace anything. In my case, the Supco package had the instructions right on it and the electrical cover had the wiring diagram. It works GREAT by the way.

Dutch_12078 wrote:
The SPP6E works fine on my Dometic/Duo-Therm 13.5 A/C's. The capacitance of the SPP4E and the SPP6E are the same, and I went with the recommendations of RV Tech Chris Bryant in choosing the 6E's. The packages I bought show the voltage rating as "90-277VAC". On my A/C's, the smaller round black capacitor is the compressor start capacitor in series with a Cera-Mite PTCR. Both were replaced by the SPP6E. The larger three terminal capacitor is the run cap for both the compressor and fan motors. My Honeywell digital thermostats prevent "instant" A/C restarts anyway, so that's not an issue.

So, if I replace both of my capacitors (start and run) with the new Supco, how should the wiring look on that?
The Supco has 2 wires and the old "large" capacitor has 3 wires and the "small" capacitor has 2 wires.