I just bought a new TT and it has a 15K BTU Dometic air conditioner. The Jayco I traded in had a 13.5K BTU Coleman (Airxcel) unit.According to the manufacturer's specs the 15K Dometic draws less (13.2A) at full load than the 13.5K Coleman/Mack/Airxcel (15.2A) at full load. That seems backwards. Does Dometic just use a more efficient compressor or are they being tricky with the numbers?Also, does air conditioner current draw vary with outside temp?

My 15000 draws 19amps at 119 volts. I have seen it as high as 30 when voltage is low. Running for long periods itself shouldn't draw more current but having all your neighbors running theirs at the same time may drop voltage resulting in a higher draw.

Voltage drop in an RV park could be an issue. However, I'm more concerned with running it on my Honda eu3000i. Right now the outside temp is in the high 90's and I've been running the Dometic 15K a/c at 70 degrees for the last 2 hours on the Honda with no issues at all. I've been running the fan on high. According to my Fluke meter it's been drawing 14.6-15 amps @123VAC every time I look at it. I think I'm going to let it run another hour or so with the fan set on auto and then declare the test a success.

OK folks, I just made some interesting observations.I went out and set the thermostat up to 75 and put the fan in the auto position so it would cycle off and on with the a/c. I watched several cycles.Every time the fan would come on (2.1A) and run for about 10 seconds. Then the compressor would kick on and only draw about 9A. It would gradually (over 4-5 seconds) taper up to around 15A and then stay there. It never indicated any kind of "start surge" like I was expecting. Maybe Dometic has added some logic in the a/c or in the thermostat that prevents the high current surge that normally accompanies compressor start up. At any rate, the Honda is not having any problem running this 15K BTU unit.

My 13.5 Coleman Mach usually runs about 13 amps.

The "head pressure" is dependent on ambient air temps along with "run cycle" so depending on what outside temp was and how long you monitored it (ie. number of cycles), you may not have reached its highest "demand". The "starting capacitor" is used to limited the high current draw during startup.

Air Conditioner Current Draw | Good Sam Community

campigloo
Explorer
Aug 02, 2015
My 15000 draws 19amps at 119 volts. I have seen it as high as 30 when voltage is low. Running for long periods itself shouldn't draw more current but having all your neighbors running theirs at the same time may drop voltage resulting in a higher draw.
hohenwald48
Explorer
Aug 02, 2015
Voltage drop in an RV park could be an issue. However, I'm more concerned with running it on my Honda eu3000i. Right now the outside temp is in the high 90's and I've been running the Dometic 15K a/c at 70 degrees for the last 2 hours on the Honda with no issues at all. I've been running the fan on high. According to my Fluke meter it's been drawing 14.6-15 amps @123VAC every time I look at it. I think I'm going to let it run another hour or so with the fan set on auto and then declare the test a success.
hohenwald48
Explorer
Aug 02, 2015
OK folks, I just made some interesting observations.

I went out and set the thermostat up to 75 and put the fan in the auto position so it would cycle off and on with the a/c. I watched several cycles.

Every time the fan would come on (2.1A) and run for about 10 seconds. Then the compressor would kick on and only draw about 9A. It would gradually (over 4-5 seconds) taper up to around 15A and then stay there. It never indicated any kind of "start surge" like I was expecting. Maybe Dometic has added some logic in the a/c or in the thermostat that prevents the high current surge that normally accompanies compressor start up. At any rate, the Honda is not having any problem running this 15K BTU unit.
lbrjet
Explorer
Aug 02, 2015
My 13.5 Coleman Mach usually runs about 13 amps.
budwich
Explorer
Aug 02, 2015
The "head pressure" is dependent on ambient air temps along with "run cycle" so depending on what outside temp was and how long you monitored it (ie. number of cycles), you may not have reached its highest "demand". The "starting capacitor" is used to limited the high current draw during startup.
Huntindog
Explorer
Aug 02, 2015
budwich wrote:
The "head pressure" is dependent on ambient air temps along with "run cycle" so depending on what outside temp was and how long you monitored it (ie. number of cycles), you may not have reached its highest "demand". The "starting capacitor" is used to limited the high current draw during startup.
X2.
It's a double edged sword. The hotter it gets, the higher the head pressure, so more amps needed... At the same time, the generator power goes down as it gets hotter.

This why I don't think much of driveway tests. A success in the driveway doesn't always make for success when camped.
chr_
Explorer
Aug 02, 2015
It's amazing a 1 ton unit in an rv can draw 13A and the 3.5 Ton units on my house draw only 11...
time2roll
Nomad
Aug 02, 2015
chr$ wrote:
It's amazing a 1 ton unit in an rv can draw 13A and the 3.5 Ton units on my house draw only 11...
Home unit is 240 volts cutting amps in half and system is more efficient as not nearly constrained by physical size and weight.
I believe 1 ton is 12,000 BTU
time2roll
Nomad
Aug 02, 2015
hohenwald48 wrote:
According to the manufacturer's specs the 15K Dometic draws less (13.2A) at full load than the 13.5K Coleman/Mack/Airxcel (15.2A) at full load. That seems backwards. Does Dometic just use a more efficient compressor or are they being tricky with the numbers?
Probably uses a newer scrolling compressor.
hohenwald48
Explorer
Aug 02, 2015
budwich wrote:
The "head pressure" is dependent on ambient air temps along with "run cycle" so depending on what outside temp was and how long you monitored it (ie. number of cycles), you may not have reached its highest "demand". The "starting capacitor" is used to limited the high current draw during startup.

I probably looked a 20 or so cycles. I let it run with fan in "always on" mode for 2 hours and then in "fan cycle" mode for another hour. Like I said, outside temp was in high 90's and inside thermostat setting at 70. Generator and TT were in full sun. Probably not worst case but pretty near what you'd expect on a 98 degree summer day in a WalMart parking lot.

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