voltage drop in hot weather

Hi,

I was at a private home, not a campground. I'm no longer there so I can't get a "reading" at the outdoor 15 amp wall circuit. I can say that at 5:30 a.m. voltage inside the RV with no load (other than a kill-a-watt meter) was 124.4 volts.

Connection to shore power was a 15 foot #12, a 15 to 30 amp "dog bone" and 25 feet of #10.

I moved to the generator from shore power at 2:30 p.m. local time and wattage dropped down to 1630 from over 1900 on shore power. Voltage from the Yamaha 3000 iSEB in eco mode was 121.9 with the air conditioner running.

I turned off the air and genny as I was not going to be in the RV for some hours.

At 6:45 p.m., I started the genny in full power mode, waiting 3 minutes, turned the air conditioner on, and then moved to eco mode. There was no question of the air conditioner cycling as the inside of the RV at that point in time was 37 C. Out of doors the temperature was 41 C.

We went out for supper.

Two hours later the interior of the RV was at 24 C.

I moved back to shore power. Voltage while running the air conditioner was 113 and wattage was around about 1330.

My plans this summer include abandoning the #12 cords and making up 50, 75, and 100 foot #10 extensions, to get away from the "daisy chain" I use now.

A standard 15k AC will pull about 14.5 amps(hi fan) at 95 degrees. It will pull 1 amp MORE for every 10 degrees above 95. That means IF he has an AC (15k) pulling 14.5 and now at 15.5(105 degrees), he has already overloaded his supply(15 amp). Subtract about 1.5 amps if he has a 13.5k AC. STILL over his 15 amp supply. Remember, the AC is NOT the only 120 appliance drawing power. You have the Power Converter and anything else(refer, unless on LP). Doug

MEXICOWANDERER wrote:
More data por favor. What was the voltage as measured at the FEEDER wires at the pedestal? Obtainable at an unused 120vac receptacle.

x2 ... only way to rule out if the problem is on your end, or the campground's end.

wa8yxm is thinking the same way I do.

Under-voltage and alternating current motors starting under load.

I have seen windings go from 30C to 200C in seven seconds flat. You don't want to know what that does to wire insulation or varnish.

An unloader would be the way to go. Jaja fat chance.

pianotuna wrote:
I was running the air conditioner on a 15 amp shore power connection.

That's all they had? I'll bet your plugs/sockets were getting pretty hot.

Several things... First: The voltage of 107 was most likely with the A/C compressor running and likely running for a while.. The danger is not in running it at 105, it is in STARTING it at 105, Unit draws way more power when starting than it does one second later. Then as the coils heat up (The Evaporator) it draws more and more.. here are some facts.

I have two A/Cs recently the front one, a Carrier Air V, begain tripping on me (Tripping the circuit breaker that is, 20 amp) Finally I wrapped a clamp on ammeter around the proper wire and observed.

Fan only, just a few amps, then the compressor kicked in and there was a spike too fast for the meter to respond to and display, then it settled down to the proper 13 to 14 amps (the meter does not do tenths, I have another meter that does but did not wish to dig it out) Then after a few mintues of run time, as temps rose, the current clmibed to 21 amps and then CLICK to zero.

Finally I went topside (next AM) with screwdriver brush and air hose and jet.

Removed covers.. Removed a lot of "Stuff" (Fibrous stuff that builds up on condenser coils) using brush and compressed air, Re-covered save for 7 screws I replaced this AM (6 were missing, I put one in my pocket so I could buy the right size) Breaker has not tripped since.

Your readings, at the RV end, I would not worry about 107 running,,,, I might about less than 110 with the compressor IDLE.

I do not see a problem, run the A/C. I have run mine at 100 volts all day long.

More data por favor. What was the voltage as measured at the FEEDER wires at the pedestal? Obtainable at an unused 120vac receptacle.

Hi,

I don't mind running my A/C at 105 volts input. It will draw more amperage, but that is still OK. THe higher wattage was due to higher discharge pressure in the 105F heat. The compressor needs to get the Freon up to about 300 PSI where it will convert back to a liquid at about 130F. Then it will drop to about 80 PSI inside at 45F.

On a cooler day, normal high side pressure is about 200 - 225 PSI with low side pressure at 70 PSI (40F). This is only a 130 PSI differential, so easy on the compressor. On a hot day, it can be 220 PSI differential, and that is when you are drawing 1900 watts!

For kicks and giggles, here is my low voltage story. I was in the pits at a drag race in Bowling Green KY, over Father's day in 2006. I have a voltage booster with a pair of 12 volt coils in it, so I can boost 12 or 24 volts.

The plug is a pair of 15 amp receptacles with #10 wire coming down the pole from some overhead #2 wires, fused at who knows how many amps - probably 100 - 150? I plugged in my 50' long #14 gauge cord, then a #12 gauge 25' cord, then the 25' #10 cord, then the voltage booster, finally my 30' cord from my RV. It then goes through a 25' long #10 wire to the inverter and back, to the fuse panel, then 10' or so to the A/C unit. I was reading about 128 volts while only the TV was on. My inverter/charger was off. I was at 12 volts boost, so input must have been around 115.

When the A/C was running, I was getting down near 105 volts, so I changed to the +24 boost, and kept it on! This gave me about 115 inside. And probably about 95 volts before the booster?

Anyway that is the extreme use of #14 wire to run a A/C unit, and can only be done with a voltage booster! If I had been drawing 1900 watts (just using your example) then I would have had about 19 amps going through the #14 gauge wire, and it would explain why the 15 to 30 amp adapter melted to the 25' extension cord. . . .

Fred.

The whole system probably dropped a little too. LOTS of AC's running all over at that temp.