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Old 19-01-2014, 12:58   #1
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How many amps does my AC draw?

Hello!

I have a Marine Air Systems Passport II aboard my Hunter 306. I have two resulting questions:

1) I'm trying to find out how many amps it draws from shore power. The following are the specs, which confuse me a bit:

Set Point Range 60F to 85F [15.6 to -29.4 C]
Temperature Range Displayed OF to 150F [-17.8 to 65.6 C]
Sensor Accuracy 2F at 77F
Low Voltage Limit 115 volt units 75 VAC
Low Voltage Limit 220 volt units 175 VAC
Low Voltage Processor Reset 60VAC
Line Voltage 115 Through 240 VAC
Hertz 50 or 60 Hz
Fan Output 12 Amps at 220 VAC
Valve or Heater Output 6 Amps at 220 VAC
Compressor Output 20 Amps at 220 VAC
Minimum / Maximum Operating Temperature 0 F to 180 F
Power Consumption Less Than 5 Watts

On one hand, the 5W consumption on the last line makes me thing it draws 5/130=0.04 amps per hour, which seems rather low. On the other hand, if I took the compressor output of 20 amps at 220V, convert it to W and back to amps at 130V I get 20x220=4400W and 4400W/130 = 33.8 amps, which seems a bit high.

Could anyone have mercy on my brain and explain how much my AC draws in cooling mode?

2) The reason for this whole thing is that I'm thinking of docking the boat at a friends' place in the Patuxent for a few weeks this summer. He's got shower power, but of the standard 130V/15amp kind that requires a typical NEMA 1-15 plug. If my AC draws anywhere close to that then it's pretty much a non-starter. But if this is feasible, do you think I can simply get a converter pigtail like the following to use my existing shore power cable:

Marinco 30 Amp Shore Power Pigtail Adapter

All your thoughts (constructive ones) are very much appreciated.

Cheers!

Nico
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Old 19-01-2014, 15:16   #2
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Re: How many amps does my AC draw?

Nico:

It looks like you have a big boat A/C unit of maybe 60,000 btu/hr or about 5 tons of cooling. That is enough to cool a good size house. So first of all is that what we are talking about?

Secondly the specs text is a little weird. It reads like something translated from another language. For example it reads "compressor output 20 amps at 220 VAC". It should read compressor INPUT.

But in any case, I will give it a shot:

Forget the 5 W number. I suspect that is "idle" wattage. The three consumers of 12, 6 and 20 amps at 220V are what you should focus on. And I don't understand what the valve or heater is. But I suspect that these are worst case nameplate numbers and the real load could be 20% less. So assuming that factor and adding up the three gives .8 * (12+6+20) = 30 amps at 220 V.

You are not going to run that on a 15 amp 120 V receptical!!!! You need a 50 amp 220 V supply to run that big load.

David
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Old 19-01-2014, 15:20   #3
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Re: How many amps does my AC draw?

What size AC??? How many BTU??
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Old 19-01-2014, 15:42   #4
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Re: How many amps does my AC draw?

Yeah, that would help, right? 10,000 BTU.
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Old 19-01-2014, 15:52   #5
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Re: How many amps does my AC draw?

It looks as if you have electric heat (6 amps) in the system. If so, the the heater should not run at the same time as the compressor. The you would be looking at 32 amps when cooling and 18 when heating. Are you sure the fan draws 12 amps? That is a pretty big draw for an A/C fan.
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Old 19-01-2014, 15:55   #6
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Re: How many amps does my AC draw?

That's the problem. It just doesn't make sense. Maybe the PO left me the wrong specs. I'll double-check everything when going aboard this weekend.

Thanks, though.
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Old 19-01-2014, 16:23   #7
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Re: How many amps does my AC draw?

The amperage draw on an air conditioner with a cooling capacity of 10,000 BTU/h, at 120 V should be approximately 0 Amps; at 220 V about 5 Amps.
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Old 19-01-2014, 16:24   #8
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Re: How many amps does my AC draw?

You should be able to run a 10,000 BTU Ac on 15 amps, but not much of anything else. I can run my RV AC on a 15 amp ciruit, plus a few lights, the battery charger, and that's about it.
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Old 19-01-2014, 16:25   #9
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Re: How many amps does my AC draw?

Gord,
What, you mean 10 amps at 120V?
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Old 19-01-2014, 16:50   #10
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Re: How many amps does my AC draw?

The specs you posted (and got from the PO) are for the Passport II AC controller. The controller itself draws 5W, and has outputs for a fan, a heater or valve, and a compressor. The output contacts are rated 20A @ 220V for the compressor output, 6A @ 220V for the heater output, and 12A @ 220V for the fan output. What your air conditioner requires depends on what you have connected to that controller.

http://www.marinespecialists.com/mar...t_II/index.htm
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Old 19-01-2014, 19:00   #11
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Call dometic and they will tell.you.the correct amp.draw. the problem is at start.up you get a big spike. They make a hard start kit that will lower the start up by 40% . It will make a huge difference. I installl them.on all my new boats.
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Old 19-01-2014, 19:25   #12
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Re: How many amps does my AC draw?

Quote:
Originally Posted by Bohemian17 View Post
Call dometic and they will tell.you.the correct amp.draw. the problem is at start.up you get a big spike. They make a hard start kit that will lower the start up by 40% . It will make a huge difference. I installl them.on all my new boats.
Shorepower doesn't care about inrush, only inverters and generators.
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Old 20-01-2014, 05:07   #13
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Re: How many amps does my AC draw?

Quote:
Originally Posted by a64pilot View Post
Gord,
What, you mean 10 amps at 120V?
OOPS!
Yes, should have read 10A @ 120V.
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Old 20-01-2014, 05:40   #14
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Re: How many amps does my AC draw?

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Originally Posted by DotDun View Post
Shorepower doesn't care about inrush, only inverters and generators.

Yes it does exceed the 15 amps even for a few seconds and you'll trip the breaker and of course then have no power
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Old 20-01-2014, 05:53   #15
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Re: How many amps does my AC draw?

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Originally Posted by a64pilot View Post
Yes it does exceed the 15 amps even for a few seconds and you'll trip the breaker and of course then have no power
Inrush is not a few seconds, it's on the order of 10's of msec. Breakers are built to allow overages of short timeframes for exactly this issue.
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