I agree the NEC calls for 12 gauge, that is clearly specified.  However, doing an actual voltage drop calculation shows a difference of 0.7% vs. 1% (10 foot run, 20 amps, 12 vs. 14 gauge).  I wouldn't go to the trouble of pulling new Romex to save 0.3% when both calculated figures are well below the 5% rule.  You could even argue those numbers are lower since a 20 amp circuit is only supposed to run 16 amps continuous.  The startup surge doesn't count since it is allowed to be much higher than the continuous rating.

 

I have about 12 ft of wire in the 179 from the breaker panel to the air cond.

 

So 12 ft of 14 has 2.2% voltage drop and 12 ft of 12 has 1.4% at 40 amps.  A difference of .8 %.

Yes nowhere near the 5% target- but then that figure doesn't take into account generators that can barely supply enough to start the air conditioner as is.

 

Am I going to rip the ceiling out to rewire it?  NO!

 

But- if the undersized wire can be fished out while pulling a new wire in without a bunch of trouble then YES I will, heck may even go 10 gauge as long as I'm doing it 

 

Point is Dometic specs 12 gauge, I presume they have their reasons, and the NEC specs 12 gauge, but FR didn't do it, proper wiring would be a very minimal expense.

 

My only disagreement is that in this case changing to 12 gauge wire is going to give you any appreciable advantage during startup.  I'm talking physics and not NEC.  The home run is too short.  If this were a 20 amp kitchen countertop circuit and the home run was 75 feet back to the panel, then yes that 12 gauge would be necessary, due to physics and NEC.

 

Headcold - 2000 watts is marginal.  You may find it will start it when it is 75 degrees outside and you are at sea level.  85 at sea level maybe ok, but 95 is too much.  85 at 5000 feet may be too much.  Higher altitude and/or temperature lowers the output rating of a generator (any engine).  Higher temperature increases the internal pressure in the A/C which requires more watts to get it started.  The watts needed goes too high and/or the watts available from the generator is too low and the A/C will stall and the generator will trip its overload protection.

 

furpod - yes, the calculations are within limits.

Wow! That's really interesting. Could you please tell me the exact time and place you were. That's quite a meteorological anomaly as far as I know. I'm pretty sure the average temperature difference between sea level and 5000 feet is about 20 degrees. At 8000 feet it's probably pretty close to 30 degrees, meaning the sea level temperature where you were was well over 115 degrees for a week. I'm not familiar with that kind of incident in Colorado, but I'm sure you will set me straight with time and place so I can verify.

Thanks!

fred

I'm sorry, I'll rephrase. Please tell me where and when so I can verify. Does that help? I really would like to know where it ever got that warm at 8000 ft. for a week.

Thanks!

fred

 

Nope, I used to camp in the high Sierra for weeks at a time usually 7400 and up.. as I said, where I camped, no need. Rockies must be different. Don't intend to find out.

Not sure why you would suggest that, but thanks for the data. June 2012 was, for sure, a weather anomaly. I do think AC @ 8000 feet would be an extremely rare need.

Thanks for the data and please have a wonderful evening.

fred

If it is easy to do it, great, I was just trying to save you from doing the work.  You will get a gain, just very small.

No ethanol is good long-term for the carb, too, so it is a good strategy.  I add Stabil to mine, too, but don't believe them when they say it can preserve your gas for a year.  Last year my Yamaha worked fine with new gas and started on the first pull.  Next tank I put in year-old gas and it took 10 pulls to start it each time I tried.  It ran fine but I have to wonder how much less power it would produce if I pushed it to the limits.  Next tank, back to fresh gas and it started with 1 pull again.  Now I rotate my gas supply (about 25 gallons) every 6 months, still using Stabil.

Shorter cord will help a little, too.

Surprised me as we were dealing with 4wd trails still snow blocked literally 2 miles away.

We were at USFS Haviland Lake CG.   Very unusual to me for the USFS as it had electric and water hookups at most sites-  I almost never see that in the southeast,  if I ever have! 

Very dry and dusty though, not helped by some of the "hosts" zooming around in golf carts far exceeding the posted speed limit and stirring up huge dust clouds

 

Haven't had a chance to pull on the wire yet, have to dig out a gigantic silicone glob where they sealed it coming into the A/C opening to connect it to the control box.  Also have to look under the shower area to see if that is where the wire ran leaving the convertor/breaker box.   Probably won't get back on that project for awhile as we head out for almost a week..