Generator and AC

[Padgett]

Now have finally gotten the solar in place and working and new GC2 batteries up to snuff I can turn to the issue of the AC and the generator.

Just to reiterate, I chose the Pred because it was physically the largest gen that could fit in my rear compartment. Also felt that 2500/2200 should be "enough" since a Honda EU2000i at 2000/1650 was not quite.

First I changed the oil for synthetic and made sure the carb and linkages was working properly.

Then hooking a load meter to the output and connecting a LG portable 7,000 btu AC and a 1500 heat gun as loads for testing. With load at 17.1A (tad over 2000W) the Pred had no trouble coping. Response was very quick when heat gun was cycled and AC start up peaked at 28A momentarily without incident (about 3300 watts).

Outside and with air temp at 85F and partly coudy (solar still charging) I first connected to a 100 ft 10ga extension cord on a 20A circuit and AC started immediately & DVM showed no real change in voltage. Camp ammeter set on peak hold recorded 52A on startup and 13.3A running.

Connected the generator. 120vac. Turned to HI fan and was pulling 3.3A/119vac. Turned to LO cool and voltage dropped to 51-54vac and peak current recorded was 52A. Never recovered or started in three trys five minutes apart. Reverted to HI fan after 3-4 seconds and voltage immediately recovered.

Now the LRA spec for the Coleman is 54A so numbers seem close. Evidently I need "more". How much is the question but must be close since did get it to start several times in Lakeland.

Next step is adding a "hard start" capacitor and see what happens.

I will find a way but starting with cheap (HS capacitor) and if not enought then will go a bit further out.

Two moderate ones
1) install a cutout relay on the fan motor to reduce load when compressor is starting (was trying by switching from a HI fan at full speed to LO cool. Didn't help )
2) Change to a dedicated circuit for AC with no other drains.

And two expensive ones
1) Replace the 125cc Pred engine with a 147cc from a 3000W gen. The footprint is what I need to preserve.
2) replace the '06 Coleman head unit with something more modern/efficient. Given the rate of cool down at 90F (TM is well insulated and I just reduced the roof sun load) I supect 11 or 12,000 btu would be "enough" and a high SEER reduces the startup load. Perhaps an 11,000 BTU Coleman Mach I PS to replace the Mach III.

Opinions ?

[rickst29]

Originally Posted by Padgett

Connected the generator. 120vac. Turned to HI fan and was pulling 3.3A/119vac. Turned to LO cool and voltage dropped to 51-54vac and peak current recorded was 52A. Never recovered or started in three tries five minutes apart. Reverted to HI fan after 3-4 seconds and voltage immediately recovered.

Now the LRA spec for the Coleman is 54A so numbers seem close. Evidently I need "more". How much is the question but must be close since did get it to start several times in Lakeland.

Next step is adding a "hard start" capacitor and see what happens....I will find a way but starting with cheap (HS capacitor) and if not enough then will go a bit further out.
Opinions ?

52A is the requirement with any 'itty-bitty' starting capacitor which the OEM product might have included. When starting the compressor, the instantaneous load is probably around 5000 watts - even on your 10 gauge extension cord, voltage probably dropped to 90-100V while starting the motor (100 feet of "30A" wire is going to cause a significant drop when pushed to 50A.)

The Predator can't budge the Compressor, and so it faces the 5000 watt "startup" requirement as a continuous load.

There are sometimes two sets of caps in a single phase motor, a Start cap and in some designs, a Run cap. Start caps can be +-10% of whatever was selected, they are not in the circuit very long. In fact, some motors, like refrigeration motors, sometimes have options tor "hard starting caps" that exceed that +10% value to take care of the need for higher torque because of having to start against a closed head. The trade off is added motor heat, but in refrigeration compressors, moving heat around is what they do! But doing that on everyday motors can cause premature failure, so stick to the +- 10%.

Running caps MUST be the correct size, otherwise you can kill the motor windings by over or under exciting them continuously. Over exciting causes increased heat with no increase in work, which eventually cooks the insulation; under exciting causes a loss of torque at the square of the decrease in relative voltage, so the motor under performs and overloads.

If you have a motor with no nameplate data and bad capacitors with no makings, you have a boat anchor. Sorry.

In the Mach-III, one cylindrical "can" actually contains TWO capacitors. (Both the "run" capacitor AND the "start" Capacitor; it has 3 terminals (not just two). The insufficiency of the OEM Capacitor has been well-researched, and there's a great product for this requirement:
http://www.amazon.com/Supco-SPP6E-Se.../dp/B002JP3MEK Buy that one - not the $10 capacitor alone, because the kit includes redundant timer circuitry to prevent frying the motor coils. And first, verify that the existing Capacitors (in the single cylinder) aren't blown - resistance should be infinity when they've been discharged. The SPP6E is an add-on kit, not a total replacement.

[davlin]

Plugging into "shore power" seems to work pretty well with my AC.

[TrailManorMan]

Same here........

[Padgett]

OK maybe I put too much in one post.
1) TM 30A wire connected to a 20A circuit in my garage with a 100ft 10GA extension the AC starts every time NP. Recorded 52A peak current with clamp on meter.

2) With 2500W (peak) generator it starts "occasionally" saw peak current when no start of 32A.

3) Also starts occasionally with EU2000i Honda

4) Suspect a 30A 120VAC isolation transformer could build enough of a field to smooth the transition (ELI the ICE man). Blem wit that is a 30A iso. trans. is within spitting distance of $600 & do not have one in the garage.

5) Have a SPP6 but just ordered an SPP6E as suggested. Not sure what will find when I pull the cover but think I remember seeing a spec for a hard start cap for TM but cannot find now.

Will wait to do more testing until cap gets here.

BTW just found this: "If you are adding a hardstart to your RV A/C unit, use the SPP6 [no E]. The SPP6E is not designed for 120VAC applications, The "E" series is also an instant restart unit, this does not allow the generator sufficient time to rampup to full power. The SPP6 has the preferred PTC relay and allows a longer ramp up time. The SPP6 is rated for 120VAC usage."

So which do I want ? The SPP6 or SPP6E ?

If dual, can tell from wire colors which is run and which is start.

Menwhile have a number of options to try as mentioned. May pull circuit at junction box under TM and wire straight from gen to AC so only have AC on circuit. Also may put fan on 3 second time delay so no other load when compressor starts.

[Padgett]

Meter arrived today and matches what I calculated: SPP6 is about 140uf suspect the original is about 1/2 that but willneed to measure. (run cap is 40Mfd aka 40uf, fan cap is 7.5 uf, might be dual, won't know until I pull the shroud probably on Saturday morning.

Guess I am having trouble with how the start capacitor, being unpowered until turned on, reduces the start current requirement. Perhaps just magic. Don't care if it will allow the Pred to reliably start the AC.

TM is currently open. Is there any reason to close it before working on the AC or is another 200 lbs up there OK as long as distributed ? (Have a 3'x3' piece of 1/8" plastic can set where I'll be).

Am still uncertain whether to use 6 or 6E but will have both.

[TrailManorMan]

You can go on the roof while open, distribute as you indicated and you should have no problems.

[hillbillyhotel]

I been on mine open,
and not seen 200 lb since high school , that was pre , star wars

[Padgett]

Thanks. Been working under to add an isolation switch and genny plug to the box where the ac lead changes from solid to stranded wire to go up the leg. Now just need to make a male-male lead to backfil when switch is off.

6E should be here on Saturday. Where I have TM open in back yard is in shade until noonish. Grotto is shaded all day & will have tarp on then.

[Padgett]

Friday morning. The SPP6E arrived and is clearly for 170V - 277V. Apparently there is another unit, the SPP4E which is designed for 90-130VAC. Since one of the elements in the unit is "voltage sensing" I'd be concerned about the 6E for a TM.

However like many things I have a lot of theoretical knowlege and little practical. Has anyone here used either/both ?

More testing. Now have yet another 120vac outlet on the curb side where the junction was once. Is switched so I could isolate the AirCon from everything else. Made little difference. Only extra load is the fan (3.3A on LO).

Just under 80F but Pred still could not quite kick off the AC. Had a clamp meter on the output & saw a peak output of ~35A. Would pull down to 50vac and never come back. Several trials 5 minutes apart. Did better when I first bought it.

Just for S&G I brought out the Honda EU2000i which is rated at 2000W peak. ECON off. First try grunted down to 50vac but peaked at 40A, 14% higher than Pred and double the rated peak. Second try grunted to 50VAC then recovered to 120VAC in seconds and Air Con started. Recorded a 33A peak that time.

So sounds like the Pred can provide 18A continuous where the Honda is rated at 13.5Abut the Honda can provide a higher momentary surge than the Pred.

Next thing will be to put a 3 second time delay on the fan motor when AC starts. Once I run a baseline there will add a Hard Start cap so need to know if the SPP6E is usable or do I need a SPP4E ?