My trailer has a Dometic Duo-Therm Brisk Air 13,500 BTU air conditioner. The original configuration has a starting capacitor for the compressor motor connected across the Common and Motor leads of the dual run capacitor (the cap also is the run cap for the condenser fan motor). This starting cap is 43-52 uF (micro Farads) and has a PTCR positive temperature coeficient relay on one terminal to remove it from the circuit. The PTCR has a heating element that is heated by the current passing through and opens to take the starting capacitor out of the circuit. The need for the PTCR to cool and put the starting cap back into the circuit is the reason an immediate restart of the compressor isn't possible.
I removed the starting cap and the square wafer-shaped PTCR and installed a Supco SPP6E relay and start capacitor. This is 88-106 uF, and has an electronic voltage sensing potential relay. "The voltage sensing method monitors start winding developed voltage and actuates an electronic potential relay to disengage the start capacitor. The electronic potential relay is inherently more reliable and precise than the older type mechanical potential relay." All these parts are found inside the steel terminal box under the shroud on the roof of the RV.
I measured the power line with a digital voltmeter and ammeter, and due to the sampling time I probably missed some peaks. I was powered from my Honda EU2000i running fast on a cool day.
Original start condition--16 amps and 85 volts
Supco SuperBoost hard start cap--12 amps and 110 volts, and faster starts.
So, the Supco SPP6E is an advantage, but may not be the panacea for a small generator and a hot day.
I'm free of prostate cancer for 5 years now.
All men over age 50 should get an annual PSA blood test. Mine had a low reading, but the yearly jump was significant. The biopsy showed cancer just entering the aggressive stage. Dr. Hackenslash removed it.
I carry three Supco's on my service truck.
Thanks for taking the time to post the results.
Jim and Sue Osbern,
08 Ford Super Duty 3/4 PSD 4x4 lariat Crew Cab. '07 3400RL Montana, Maytag's with 220 dryer, Satdome, Rear A/C unit, Digital amp Gage, Vena tank monitor, Rear camera, 3,000W. Inv, Roto chocks, air bags My Mod's
I appreciate you posting this information. I don't really know enough about electricity to completely understand it but I have a friend who will. I recently bought a Kipor 3500tc generator and it won't start my A/C. I think it's probably very nearly there, so my friend may be able to interpret your post and determine if this idea would make the difference.
It would have been interesting to know the start up power draw from a utility company power source. It would appear the Honda was overloaded and could only produce 85 volts at start up. I think the surge current may have been even higher if 120 volts and 30 amps were available.
Great post. I had similar trouble with my Coleman 13,500 and I ordered the "Hard Start Kit" from CW. It consisted of an additional capacitor to wire in. Cost $18, time 10 minutes. Now the genny is much happier starting and running the a/c. Mind you I have the Honda 3000i but it wouldnt kick over. If you have the problem and additonal resource is to call CW with your make and model number of a/c and request the "Hard Start Kit", and you better get it now before the heats settles in for the summer.
John, Lisa & Tara
2001 2500LT Suburban 8.1L 4x4 Autoride K/N, AIR HORNS
Reese 12klb w/dual cam, Prodigy, 27x Wilderness BH Trojan 125's, Honda EU3000, Dish 500, Xantrax 1200, Wilson Cellular Ant & Amp, L.I.B.B.A. #1747, Wireless WiFi, Water Camper
Do the newer AC units need the hard starts? Are compressors engineered in such a way that the hard starts are not necessary? From the data that Kenneth provided, it surely justifies the hard starts on on his unit. I have a 2004 Jayco with a 13,500 BTU AC. Would it benefit from a hard start? Sorry, I do not remember the brand. Anyone have an opinion on this?
Lee, Wife, Daughter & 1 Basenjis & 1 Rat Terrier
2003 F250 PSD SC 4X4 FX4 (Found On the Road Dead one time too many)
Replaced w/ 2008 2500 GMC Serria CrewCab, Duramax, Line-X
2004 305BHS Jayco Eagle 5er
Hard start kit, it just help your compressor a little "kick" to start, it does not remain in the electrical circuit after your compressor is running. most newer ac system do not have start capacitor/p. relay = hard start kit because they use PSC motors and cap tube or piston metering device. If your ac (super efficiency unit) is metering by TXV device then your ac may have start capacitor/P. relay. PSC motors are very sensitive to line voltage, a 5 to 10% drop will cause starting difficulty and overheating. Due to PSC motor starting torque is low, if you start/stop (short cycle) your ac, when system's pressures are not balance, compressor will overheat(internal overload opened). if your compressor start getting hard to start, then you may put a hard start kit, this also a good indication of your compressor life is near to the end (weeks to years, God know how long).
Ken, is the SPP6E a 2 or 3 wire starter? I'm looking in my Johnstone Supply catalog and see a SPP6 that is 2 wire (JS pt.# B11-519, $13.78). I also see a Supco SK3W2 JS pt.#B14-339, $22.89 3 wire (real potential relay) for 1-2 hp w/88-108uF cap. I used a 2 wire kit a while back on an RV A/C and it worked great. The tiny OEM PTCR was conducting .8 amps continuously and the smoke got out of it. The PTC material is solid state and it stops conducting when it heats up, which is nearly instantaneous. I called a Tecumseh dealer to get a real 3 wire start kit and they don't make one for the little RV rotaries. They recommended using the 2 wire aftermarket kit. The OEM capacitor was only 10uF. The new 88-108 really started it QUICK. I went to a Harris welding equip. seminar at the Palo Verde Nuc plant a few months ago. It was put on by a Harris employee who is also co-inventer of the 5-2-1 start kits. Man, was that guy sharp on motor stuff! A hardstart kit adds a lot of electrical life to PSC compressor motors even if they are not short cycling. The 2 wire kits are BAD for 240v single phase units. A 3 wire kit w/pot. relay is really necessary. I don't think a 2 wire kit on 120v. units would hurt because of only one hot leg on 120v. I'd have to draw it on paper to see if they would cause the same problems as on 240v. BTW, I'm running my air compressor with a 3 phase motor - on 240 single phase. About 25 yrs. ago, after seeing different types of phase convertors on refrigeration compressors, I got to playing with capacitors and potential relays to start 3 phase motors. My garage looked like Frankensteins laboratory for a year. I got it to work quite well! Craig
03Dodge QC HO CTD Dually NV5600 4.10 Rear/WD A2K turbo, TST/PMCR, 4" exh, PRXB Pacbrake, Rancho 9000s, FS Airbags, Onboard air/in-cab controls, Custom hauler bed. 98 Sunnybrook 30RLFS 5er WHOEVER INVENTED WORK DIDN'T HAVE AN RV!