Amperage Draw On A/C

Noticed this weekend that when hot inside the salon the a/c draws about 24 amps, Coleman 16000 BTU roof top camper style, when inside cools down it draws about 16 amps. Is this normal for an a/c to draw more amps when hot inside?

When it is hot inside the compressor of your a/c will run to get the temperature down. When cool inside the compressor will not be running but the fan will continue to run, thus the difference in load. The condenser head pressure when first started will also be high and cause a high amp draw, as the condenser pressure starts to come down so will the draw. I don't think anything abnormal is happening with your a/c.

LaBomba said:

When it is hot inside the compressor of your a/c will run to get the temperature down. When cool inside the compressor will not be running but the fan will continue to run, thus the difference in load. The condenser head pressure when first started will also be high and cause a high amp draw, as the condenser pressure starts to come down so will the draw. I don't think anything abnormal is happening with your a/c.

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He's saying 24 amps till it gets cool then 16 amps. Are you saying 16 amps is normal when only the fan is running???

I just looked up a Coleman 15K RV AC and it is spec'd for 16Amps full load cooling.

Is it possible you have some other loads you're not taking into account?

I have never seen a normal 16K Btu A/C draw that much current even when it is hot outside. I suspect that you may have a dirty condenser coil. Take the top off of the outside unit and see if you can spray a hose through the condenser coil without getting any water inside. A spray of household cleaner will help get the dust and dirt off.

David

kchace said:

He's saying 24 amps till it gets cool then 16 amps. Are you saying 16 amps is normal when only the fan is running???

I just looked up a Coleman 15K RV AC and it is spec'd for 16Amps full load cooling.

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No, just that the load does reduce as the temperature comes down both by unloading or stopping the compressor, and the head pressure reducing as the compressor pumps down. 16 amps is certainly too much for just the fan. I did not have the specs on this unit, if it is drawing more than expected the OP may want to check the coils both on the rooftop and in the cabin for fowling. They may just need a good cleaning and this could reduce the draw. For what it's worth and what I have experienced in RVs.

higher heat load = Higher amp draw

Heat load in the space will cause an increase in amp draw. The more work (heat removal) the higher the amp load will be. Other factors such as outside air temp and airflow across the evaporator will change amp flow also.

My 25 year old 12K Mermaid draws under 10 amps when the compressor is running.
Ran some checks on a neighbors boat and his old Cruiseair 16K ran 16 amps running, his 12K ran 12 amps....Somewhat straining his 30 amp circuit (burned connectors). Cleaning up connectors and the boat side plug has helped some..

Amp draw should not change much depending on condenser and evaporator temps. And any change would actually be backward from that observed: If salon is hot, evap pressure will be higher than when it is cool. Compressor load is a function of pressure difference between condenser and evaporator. Cooler in the salon mean lower evap pressure, thus more delta p in comp, thus more load.

Can't see any reason for the thing to draw 24A right after startup. On my Mermaids, they actually draw less for a few minutes til refrigerant conditions get stable, then amps creep up. But only change a couple amps one way or the other.

According to the last log, my 16K BTU Cruisair pulled 14amp to start and 9.5 about a minute later with 95 degree interior and 85 degree outside. Raw water temp was 84.

What is the voltage when the A/C is running. If you have low voltage uour amperage draw will go up. 24 amps is way high for a 16000 btu A/C. Also id you have L5-30 connectors on your 30 amp power cords, you are approaching the safe limit on them. They are rated for 30 amps, but I would not load them over about 70% of the 30 amps due to the small contact area in the plugs. Have you checked for loose or corroded connections?

24amps is absurd. These things likely have start relay and capacitors. Maybe failing

sdowney717 said:

24amps is absurd. These things likely have start relay and capacitors. Maybe failing

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Or a measuring error.

Is this just a momentary start-up spike or does it last longer? Some motors draw significantly more current immediately at start-up, but then drop almost immediately to normal range.

You might consider using your lazer temp to check the terminals on the AC as well as the temps on where the wiring enters and is distributed.

IF the air cond is not eating hose amps , something could be getting really hot.

GRP fires are hard to put out.

If the compressor is going out it will draw more amps till it trips the onboard breaker. Then its done and time for a new unit. By the way my 2 ton household unit draws about 20 amps on start up and 9 running.

It may be worthwhile to check the capacitors. Failing ones can cause high amp draw and/or heating of windings. With the proper DMM it's an easy task, they're inexpensive to replace and easily sourced. Don't need to be OEM, you'll pay two prices. De-power, disconnect, and momentarily short the cap before testing.