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Old 07-09-2017, 12:51 AM   #1
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Running A/C on 20amp Outlet?

I've heard some people have some success running their A/C on standard outlets. I have a 20amp hookup at my home.

How do I go about ensuring all my peripherals are off such that there's no other draws other than the A/C?

I know how to turn the fridge off.

How do I go about turning off the converter/charger?

Anything else I should be aware of to turn off?
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Old 07-09-2017, 03:08 AM   #2
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Your A/C is going to draw more than 20 amps on compressor start, but depending on your breaker, it may not trip. It will certainly run below 20 amps. You cannot turn off your charger/converter as you need 12 vdc for control power for the thermostat. I have never investigated to see if that is provided through the A/C unit in the A/C mode, though I doubt it.
It is never wise to knowingly put a load on a breaker that you know exceeds its rating so the only way I know to assure you stay below 20 amps is to buy and install the Micro-Air 364. You will see a few threads on that. Except for the refrigerator and the water heater, the other AC loads in your trailer are minimal.
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Old 07-09-2017, 06:40 AM   #3
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If it's a newer trailer you can prevent the converter charger from charging the batteries by putting the use/store switch in store mode. Fridge on gas. Hot water heater off. That should be all your big draws.
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Old 07-09-2017, 07:02 AM   #4
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On mine, if you put it in STORE mode, you kill DC to the thermostat. Does that change for newer trailers?

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Old 07-09-2017, 10:46 AM   #5
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I have been following the Easy Start threads and intent to get one. Even in those instances on running on a single Honda 2000i generator, it seems important to minimize the loads.

Which is why I'm trying to find out more about how to keep loads down, especially the charger/converter.

I did play with the breakers a bit and it seems that if I were to cut the charger/converter, that the A/C powers down. Is it due to the controller running on the 12V circuit? I haven't played with the store switch to see how I can help this.
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Old 07-09-2017, 11:42 AM   #6
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Hi

Here's the hidden gotcha:

The compressor pulls a *lot* of current when in start mode. It is a very normal AC motor in that respect. When that current runs through a high resistance (like a long extension cord or long wires in general) the voltage drops. That's just the way it works. When the voltage drops, you get less power. The motor stays in "start" mode longer. That heats up the start winding more. That heat can lead to cumulative damage on the motor. Net result, sure it works fine for a month .... poof .... now you need a new AC.

This issue is not unique to AC setups in any way. It also applies to a whole variety of stationary power tools (radial arm saws, table saws ...) run off long extension cords. They don't die immediately, but they do die an early death.

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Old 07-09-2017, 11:43 AM   #7
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I plug my 2012 25fb into my 20amp home outlet every time were getting ready to go camping to run the a/c and get the fridge cold. I let it run for 2 days straight with no issues with a/c set a 70 degrees.
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Old 07-09-2017, 02:04 PM   #8
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20 amp service for a/c

Hi:
Just an added note. I have two Penguin 13500 units on my rig. When I put the second unit on I had an additional power line run to the new unit. That unit has been functioning with a 20 amp service for over ten years. The original unit is operated off the normal 30 amp service. (Most RV parks have a 20 amp outlet on the post with the thirty amp service.)
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Old 07-09-2017, 02:14 PM   #9
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I plug my 40' diesel pusher into a 20 amp circuit and can run one a/c and the inverter.
I suggest trying it and while at it put a tester to check your voltage.
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Old 07-09-2017, 02:48 PM   #10
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I can run my AC on an outlet. I do so at my garage and one camping spot I use. I have a voltage monitor at the outlet and use a digital gauge in the trailer to see what my voltage is. I have never tripped a breaker nor had the monitor cut power to the trailer due to low voltage.
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Old 07-10-2017, 05:25 AM   #11
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Quote:
Originally Posted by lsbrodsky View Post
On mine, if you put it in STORE mode, you kill DC to the thermostat. Does that change for newer trailers?

Larry
Seems so. I keep mine in store 90% of the time I'm plugged in and the a.c. works (and heat).
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Old 07-10-2017, 05:50 AM   #12
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Once you are plugged in, the converter is supplying DC to the DC loads, independent of the STORE switch position. In that situation the battery is not being charged from the charger, but is still connected to solar, if you have it.
AS made this fairly confusing. They have apparently done something different for 2018.

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Old 07-10-2017, 07:14 AM   #13
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Running a 13.5 or 15,000 BTU AC on a 20 amp circuit will eventually damage the AC unit. It may very well run for awhile (how long is anyone's guess) but make no mistake you are damaging the compressor whiule doing this.

There are ways to do this safely with hybrid inverters and large battery capacities, but these technologies are generally beyond the budget of most Airstreamers. To be more specific, the cost of the parts to do this, i.e., a hybrid inverter and upgraded batteries, would be in the range of $5,000 to $10,000 plus installation.
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Old 07-10-2017, 03:09 PM   #14
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Great responses and gives me confidence this is a reasonable option.

I think another takeaway is to make sure the power conduit (infrastructure and power cable) is not too long to prevent voltage drops. My 20amp circuit in only 10ft from the breaker box. I am using my 30amp cord from there, with a outlet adapter.

A breaker is a current limiting device. If it's not being tripped, the circuit current demand is obviously within it's capacity. Funny enough is that a long extension actually reduces the current demand as it's high in resistance.

That said, one still needs to be aware of the power path as a whole, which is the resistance issue that is being expressed. This is more of an issue in the 20amp circuit (vs 30) for longer runs. Sounds like this can cause damage to the compressor if the voltage drop is too high. So worthwhile to test with a voltmeter.
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Old 07-10-2017, 07:43 PM   #15
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Quote:
Originally Posted by pteck View Post
I've heard some people have some success running their A/C on standard outlets. I have a 20amp hookup at my home.

How do I go about ensuring all my peripherals are off such that there's no other draws other than the A/C?

I know how to turn the fridge off.

How do I go about turning off the converter/charger?

Anything else I should be aware of to turn off?
You can turn off the breaker for the converter in the panel. It will also turn off some of you receptacles, the legend for the breaker should indicate which ones. Also check the voltage at a plug in the trailer while the a/c is cooling the trailer. If below ~108 volts do not use the A/c as this will burn out the motor.

With good fully charged batteries all other 120v loads off, the A/C and converter should be okay on a 20 A circuit.

John
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Old 07-10-2017, 09:08 PM   #16
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If you are that close to your electrical panel why not just add a new 30 amp circuit?-- Frank
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Old 07-10-2017, 10:08 PM   #17
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If you are that close to your electrical panel why not just add a new 30 amp circuit?-- Frank
That is certainly part of the plan. To have a nice 30amp RV outlet right next to where we store the AS alongside the house.

Just wanted to know in the meantime, whether the 20amp outlet from the garage would work. And when we're on the road or visit in family that won't have a dedicated hookup.
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Old 07-11-2017, 11:15 AM   #18
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....

A breaker is a current limiting device. If it's not being tripped, the circuit current demand is obviously within it's capacity. Funny enough is that a long extension actually reduces the current demand as it's high in resistance.

....
Hi

A breaker is a protection device. It's purpose is to prevent the wiring from overheating and causing a fire. It has a "time to trip" profile that depends on the current being pulled. At very high currents (say 1,000A) it trips fairly quickly. At lower currents it does not trip as fast. Some curves arbitrarily found by Mr Google are at:

http://static.schneider-electric.us/...0600DB0105.pdf

Your breaker likely has a different set of curves. The curves shown on page 2 would let you run 180A through a 20A breaker for one second.

The compressor when it starts up pulls a lot of current (maybe 45A) for a brief time (maybe < 1 second). That may or may not trip this or that breaker. A normal voltmeter will not show a voltage drop in a short time period. For that you need something like an oscilloscope.

The curves on the breaker were done based on typical use / typical fault assumptions. They are by no means perfect. You can (and many do) damage things and not trip a breaker. They are very simple devices and don't protect everything always.

Bob
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Old 07-11-2017, 09:09 PM   #19
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Hi

A breaker is a protection device. It's purpose is to prevent the wiring from overheating and causing a fire. It has a "time to trip" profile that depends on the current being pulled. At very high currents (say 1,000A) it trips fairly quickly. At lower currents it does not trip as fast. Some curves arbitrarily found by Mr Google are at:

http://static.schneider-electric.us/...0600DB0105.pdf

Your breaker likely has a different set of curves. The curves shown on page 2 would let you run 180A through a 20A breaker for one second.

The compressor when it starts up pulls a lot of current (maybe 45A) for a brief time (maybe < 1 second). That may or may not trip this or that breaker. A normal voltmeter will not show a voltage drop in a short time period. For that you need something like an oscilloscope.

The curves on the breaker were done based on typical use / typical fault assumptions. They are by no means perfect. You can (and many do) damage things and not trip a breaker. They are very simple devices and don't protect everything always.

Bob
That's good information and is useful to know that the wiring is protected from over-drawing current. It surely includes margin for the wiring itself such that the breaker will trip before any damage to the wiring.

The 30amp service to trailers is not size for only the A/C, but rather the trailer system as a whole, including converter, water heater, fridge, and any peripheral accessories plugged in.

With that in mind, as long as one comprehends and respects the limits, I believe powering the A/C only, while on 20amp is very possible. Anecdotal evidence supports that this is true. I also intend to install an easystart such that initial draws are more reasonable and allow powering off a single Honda 2000i generator.
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Old 07-12-2017, 11:37 AM   #20
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That's good information and is useful to know that the wiring is protected from over-drawing current. It surely includes margin for the wiring itself such that the breaker will trip before any damage to the wiring.

The 30amp service to trailers is not size for only the A/C, but rather the trailer system as a whole, including converter, water heater, fridge, and any peripheral accessories plugged in.

With that in mind, as long as one comprehends and respects the limits, I believe powering the A/C only, while on 20amp is very possible. Anecdotal evidence supports that this is true. I also intend to install an easystart such that initial draws are more reasonable and allow powering off a single Honda 2000i generator.
Hi

Many things that are possible and that people get away with on a regular basis are not good ideas. I see people running red lights on a pretty often around here. They rarely get in trouble for it.

How well it works for you depends a *lot* on exactly how everything is wired up and hooked up. If you have a ten gauge copper extension cord that's 25' long that's very different than a 100' number 14 gauge that just happens to be made from aluminum. Both will plug into a 20A socket. There are lots of variables and things you need to look into. The point is that you can't *depend* on the breaker to tell you when you've goofed up.

Bob
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