AC / Supco assistance needed

j-d wrote:
That's great information, Denny. I like it when a new motor comes with a new capacitor. Some motor brands seem to make it a policy to include one, others don't seem to think it's necessary.
I saw a website that explained how the properly matched capacitor is best, by telling the downside of too much and too little capacitance. Only about RUN caps, but still useful information.
Do you happen to have a link to that site?

Don't have a link it's just things I know from being in the business for years and to many hours in classrooms.

Denny

This Page is pretty good about capacitor matching, but again it's mostly run capacitors.
It includes the durability rating (classes) of capacitors too. Helps to know what you're buying.

That's great information, Denny. I like it when a new motor comes with a new capacitor. Some motor brands seem to make it a policy to include one, others don't seem to think it's necessary.
I saw a website that explained how the properly matched capacitor is best, by telling the downside of too much and too little capacitance. Only about RUN caps, but still useful information.
Do you happen to have a link to that site?

All motors are close to a dead short when power is first applied (locked rotor curent), the only resistance is the wire in the windings. The start windings have smaller wire so they have more resistance than the run windings. The difference in the resistance splits the phase causing a rotating magnetic field that pulls on the rotor, when a run cap is in the start circuit it splits the phase even further increasing the torque or the magnetic pull on the rotor. When a start cap is introduced into the start circuit it splits the phase even more but it can only be in the circuit for a split second because it can't take the current like a run cap. After the motor starts the rotation of the motor induces what's called inductive reactance or induced resistance reducing the current draw to the rated running current.

When they design split phase motors they calculate just how much capacitance the run cap has to be and what size start cap should be used for optimal starting efficency along with how long the starting relay will hold the start cap in the circuit. If it drops out to fast it hurts the starting time and if it stays in to long the motor current goes up not down and will cause start cap failure. Supco can't make enough units to match all the different size compressor motors out there, they are one size fits all and aren't matched to your compressor windings like the factory caps and relays are. When I used to buy replacement compressors they would come with new run caps and start caps and relay for a reason, in many cases if it was a warranty compressor I would have to sent the old caps back with the compressor or no warranty.

Like I said I did it for a living and worked on 1000s of split phase compressors and if you don't use the right parts they don't work right but its your money so do whatever you want. But I think you better look at your generator not your ac unit.

Denny

Awhile ago, my daughter's side-by-side home fridge-freezer went warm. We could hear compressor trying to start, klix-on opening, closing than another start attempt. With their cheapest-of-the-cheap Harbor Fright clamp-on, I found it was at LRA. Took the little Start Module off wondering if it was bad. When I shook it and a sand-like material came out (probably a disintegrated PTCR), I decided testing time was over and a parts run was in order. Not too many appliance parts shops in ANC, but "K Appliance" had a SUPCO device. Might have been URCO210 "3N'1", but when I installed it the compressor started and it's run since around 1999. The K man mentioned that older appliances can destroy the start assist because their winding resistance increases over the years, amperage along with it.
Just read where SUPCO has Potential Relay Hard Start Kits. These are Three-Wire "True" potential relay units, which should provide better results than "E-Series" and the PTCR stuff. LINK
They show it as equivalent to the "5-2-1" units we've mentioned.

My understanding of LRA... Is the amps needed to unlock the rotor and start it moving..The rotor being locked in place by the pressure against it.. ?
How close the needed current is to the listed value is determined by facts like age and compressor "Head Pressure"

j-d wrote:
I don't know, can only wonder, if an A/C requires the full LRA current on startup. Maybe it does. Or, is LRA only a troubleshooting aid to determine if the compressor is actually stuck?

. . .

Agreed, LRA is supposed to be the current at just the point of stopping the compressor--worst case scenario. However, after making inrush current measurements on a number of a/c units with my inrush-capable, Mastech MS2108 clamp-on meter, I've found the startup/inrush readings with this meter have consistently been very close to the LRA. I'm sure these inrush readings would vary widely from one make/model of clamp-on to another; however, for comparison purposes (when using the same meter) the readings are definitely helpful in determining whether your hard-start kit is actually working or not. Or, whether the inrush current of a given a/c will exceed the inrush capability of a previously tested generator.

FWIW, through quite a bit of testing over the last 6 months (using this same meter) I've determined the inrush threshold for successfully starting various a/c units with one/two EU2000i's, an EU3000i, and Champion 3100 (75531i) with the ECO mode, both on and off. Surprisingly, I've found the Champion 3100 is able to supply more inrush current than a paralleled pair of EU2000i's (both compared with ECO mode on and off).

I don't know, can only wonder, if an A/C requires the full LRA current on startup. Maybe it does. Or, is LRA only a troubleshooting aid to determine if the compressor is actually stuck?
From what I read here:

1. PTCR is the bare-bones approach to hard start assist. Like "I crank my car for the count of three and it usually starts" which disregards the possibility it needs to crank longer, or would have started sooner.

2. Device like SPP6e (in my thinking) can feel to see if the engine fired. May not have started, but the "E Class" gets a little feedback from the compressor.

3. A true Potential Relay Assist is like having a dashboard tachometer. It can "see" the compressor running and takes the Start Capacitor out of circuit just then. Some RVP/Coleman units have a Potential Relay. The "5-2-1" Start Assist claims to have an electronic Potential Relay. If it does, it'd be better than SPP6e and way better than SPP6 or an OEM PTCR kit.

I don't know a way to see which is best without trying them, at least SPP6e vs. 5-2-1. The average clamp-on AC Ammeter isn't quick enough to capture the peak inrush current.

The LRA for your Coleman is 58 amps. That's pretty high for a 9.2k btu unit. Out of curiousity, what kind/size of generator are you trying to power your a/c with? If you can get your LRA/inrush down in the very low 50's (with a hard-start kit or a different unit altogether), you'll dramatically increase your chances of starting/running it with a single Honda EU2000i (ECO mode on) or Yamaha EF2400iSHC. I've found the inrush threshold for successfully starting/running an a/c unit with one EU2000i (ECO mode on) is approx. 50-51 amps.

Photos of the model sticker: