Hard start A/C capacitor worth getting?

My A/C unit is a Dometic 15,000. Any particular hard start model I should want over another?

tvman44 wrote:
If you are trying to run the A/C on a marginal generator it will help a lot. :)

I do believe that this is the case. According to SUPCO, the SPP6 is the better model to use versus the SPP6E for this application. However, SUPCO also told me that they do not recommend their product for this usage since a generator that is marginal for running an AC is still marginal while using the hard start capacitor which may not be healthy for either the generator or AC. However, this sounds like CYA advice that a company lawyer said to say! There are also success stories from folks using the SPP6E, so really I don't know which is "better".
I put the SPP6 in my AC before its first trip out so I don't have a before/after anecdote. Our Yamaha 2400 is still marginal for running the AC when we are at high elevation and/or the temps are really high.

There is NO QUESTION that a large start cap reduces voltage drop at start up and restarting on high head pressures. Every cap start compressor I own, every transformer, every inductive load has oversize starting capacitors. So I guess you can call this an " affirmative recommendation?

May depend on the unit. I have an older Coleman (90) and over the years I noted that starting the compressor seemed to take more juice to kickstart -it was due for new capacitors so I upgrading to a Supco hard start capacitor and it made a positive difference - under $15 so money isn't an issue.

Good point on Coleman units. Ours has an OEM start kit consisting of a "Potential Relay" and a Start Capacitor. The Parts List will show those parts even if they are NOT on your specific unit. Dealers/Servicers can look up the Model Number and see what it left the factory with. Best way for most of us is Climb Up and Look. If it has only (approximate values) 7.5uF Fan and 45uF Compressor (may be marked HERM) in separate capacitors or a single dual capacitor (Coleman seems to generally use separate ones) then there's no Hard Start Kit.
The Start Cap has to get OUT of the circuit once the Compressor is running. Cheapest way is with a PTCR device. In the popular SUPCO brand, that'd be model SPP6 for an RV-sized A/C.
Better is an electronic version that tries to approximate Potential Relay performance. In SUPCO it's SPP6e and probably the most popular one here.
The Potential Relay is supposed to be better and there's a kit that I just heard about and available at Amazon as is SUPCO
If my A/C did not have a Start Kit, I would add one. Either SUPCO SPP6e or that "5-2-1 CSR U1" listed in the Amazon link. I keep spare Fan, HERM, and SPP6e on board. I don't want to be without A/C for the sake of something I can fix easily.

I bought one for my 2012 camper with a Coleman Mach air conditioner, but then discovered that Coleman had already installed one. I'm not sure when they started that, but you should look before you buy.

Sounds like I'll be installing one. :) Any particular brand, style, strength, etc.....?

I installed a hard start cap on one of my two 19 year old roof A/C's to replace a badly corroded OEM start cap. I immediately noticed that the 7KW generator didn't "grunt" anywhere near as much starting that A/C as it did starting the other one. Both now have SPP6-E hard starts installed.

Installed one and it wasn't really expensive, wasn't hard to install and allowed my generator to continue running without stalling when the ac tried to cycle. Is it worth it, absolutely!

If you are trying to run the A/C on a marginal generator it will help a lot. :)