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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems
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  #1  
Old 07-31-2009
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How do I determine electrical draw

I have a 12000 BTU Aqua Air Reverse cycle air conditioner. I would like to measure the watts it takes to start it up and then start the compressor. My control switch has a start position and a run position. On start it starts the motor and run starts the compressor. Where should I check the wattage, some where on the unit or at the batteries?
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I have a 12000 BTU Aqua Air Reverse cycle air conditioner. I would like to measure the watts it takes to start it up and then start the compressor. My control switch has a start position and a run position. On start it starts the motor and run starts the compressor. Where should I check the wattage, some where on the unit or at the batteries?
The unit should have a manual with start up and run amps. It may even be on a sticker attached to the unit. I think they have to have it permantally mounted.

I honestly do not know how to get an exact mesurement without putting in a shunt since it is ac. Maybe Hello could help?

- CD
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According to published specifications, the 12K BTU AquaAir S*R-16 models draw 10.4 amps @ 115VAC or 1051 watts. The water pump will draw an additional 1-2 amps, depending on model.

To get inrush current, you'd need a clamp-on ammeter with inrush capability. The min/max setting won't tell you true peak amperage (you'd need something more sophisticated for that), but would give you an idea.

Many modern rotary compressors have a fairly low in-rush current demand, dampened somewhat by start capacitors. For example, my 16,500BTU Flagship Marine A/C draws 14.1 amps at full load, and the starting current requirement is only 21 amps.

Your mileage may vary, however :-)

Bill

Last edited by btrayfors; 07-31-2009 at 01:02 PM.
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Old 08-01-2009
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call up your local commercial electric company and tell them what you want, and its for a boat and you just want a guy to come buy after work. one of the guys there will have the meter to read it, they wont look at it as a real job hopefully. or go to a local electric supply house and hang out for a while, might cost ya 20 bucks or a case of beer. in real life the inrush is so short on new equipment its only 125 % of the running load. home depot sells clamp on ac amp meters for around 80 bucks, wont be perfect but close enough.

CD was right if the equipment is UL approved it has to have a perminate label with the load info. read a AC unit label is tricky, it will give you a few numbers, one is min circuit size, another max breaker size. the min circuit is normally 125% of running load, the max breaker is normally 125 % of the inrush, you only need to size the wire going to the unit to the min circuit size, its weird electric code thing.

i am a master electrician just so you know
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Old 08-04-2009
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Originally Posted by btrayfors View Post
To get inrush current, you'd need a clamp-on ammeter with inrush capability. The min/max setting won't tell you true peak amperage (you'd need something more sophisticated for that), but would give you an idea.
Could use a hall effects sensor too, but it is non-trivial. If I were doing it I would probably wire a hall effects sensor into the circuit which would provide an analog output that could be hooked to a scope to graph current usage. This has the advantage of being electrically isolated from your test equipment.
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CD was right if the equipment is UL approved it has to have a perminate label with the load info. read a AC unit label is tricky, it will give you a few numbers, one is min circuit size, another max breaker size. the min circuit is normally 125% of running load, the max breaker is normally 125 % of the inrush, you only need to size the wire going to the unit to the min circuit size, its weird electric code thing.

i am a master electrician just so you know
Pfft. I am ALWAYS right!!!! And fyi, I am a Master Sailnetter (which means I know everything about every subject known and unknown to man!!!).

HEHE!

Brian
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Pfft. I am ALWAYS right!!!! And fyi, I am a Master Sailnetter (which means I know everything about every subject known and unknown to man!!!).

HEHE!

Brian
Now Y'all put me in spot. I don't know who to believe, a master electrician, a master "Sailnetter" or just some other master BS'er
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