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Old 03-28-2019, 06:15 PM   #1
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Default Another Rooftop AC Question

Does anyone have a rooftop A/C unit that can be run when your rig is plugged into a 15 amp regular household outlet ?

See, the one thing about RV A/C units I don’t get is this....for about $125 you can buy a home window A/C unit that would aptly cool a small Class B or small B+, plugged into a regular household outlet.

But all three of our last, small rigs have required 30 amp service to run the much pricier rooftop A/C. So when we’re visiting friends or family and camped in their driveways, we can’t use our RV A/C as you’re not supposed to run it on a regular household circuit.

This situation...the power supply requirement difference between the RV rooftop and the household window A/C units makes no sense to me (and in fact seems a stupid way for manufacturers to ignore the real world use of their products).

There obviously seems to be a market for rooftop RV AC units for smaller rigs that would run on household power (these are used in some small camp trailers) so who’s making these?

Anybody?

Thx
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Old 03-28-2019, 06:27 PM   #2
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So, to follow up on this topic a bit further...

I went out to our rig and saw in the coach’s circuit box that there’s a 20 amp breaker for the rooftop A/C.

As you know, the warnings are if you plug your rig into regular household outlet and try run your A/C unit, it will damage the A/C unit’s electronics.

I haven’t figured out how to install a cheap, household window box A/C to my roof yet without it leaking in the rain so I’d love to find a rooftop unit designed for RV’s that would run on 15amp service.
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Old 03-28-2019, 06:30 PM   #3
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Lots of info on this in the archives. As a start get a 30 amp to 15 amp adapter and try it on your home outlet. What unit (brand, model, BTU) are you trying to run and we will suggest how to do it. A 10,000 BTU Dometic draws 11 amps, 13500 a bit more.

Use a short and heavy extension cord, preferably your 30 amp power cord. If you have trouble it will be with the compressor surge current at start and there are ways to deal with that.

You could get a Dometic Penguin II and talk to these guys: https://www.microair.net/products/ea...nt=30176048267

This will be an easy problem to solve for a Sportsmobile.
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Old 03-28-2019, 06:36 PM   #4
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Hmm. Don't know that much about it except for the fact that I run my old one (1997) on household circuit. So a question: If your current AC has a 20A breaker it shouldn't be hurt by running on a 20A circuit, should it? Is there a difference between supply and draw? IOW: your AC would require 30A to operate but trip a breaker if the unit itself draws more than 20. Hopefully someone with more e-knowledge than me can answer this.
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Old 03-28-2019, 07:03 PM   #5
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My previous travel trailer had a 15000btu it pulled right at 14 amps. I installed a microair easy start 364.
I could run that unit on a standard 15amp service (but nothing else).
https://www.microair.net/products/ea...nt=30176048267

My new class b has 13.5btu which pulls around 12amps no issues with it on 15amp services.

Note: always use a 12 gauge cord and keep cords short as possible.
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Old 03-28-2019, 08:41 PM   #6
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Default My A/C unit

Thx for responses guys.

My unit (it’s not a SMB) has an “Airxcel” brand, 9,600 btu rated, rooftop A/C.

Re:” So a question: If your current AC has a 20A breaker it shouldn't be hurt by running on a 20A circuit, should it? “
...but my older home (and many others) have 15 amp breakers, so maybe that’s still a problem?

Maybe I’m making too much of this.

It’s just that, with my previous rig....a Forest River Lexington B210...I was strongly warned NOT to run the A/C on household current, regardless of using a 30 to 15 amp adapter plug.

With this current rig, as described above, maybe that’s not a problem.

But I’m being cautious because if I make the wrong decision and wind up damaging the circuitry, the repair costs will pretty much equal the cost of a new unit (and my wife will kill me for being stupid!).
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Old 03-28-2019, 09:17 PM   #7
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Get an adapter and plug it in. You could get an AC voltmeter that plugs into a coach AC receptacle. When it reads 104 instead of 115, turn off the AC.

Yep, you are making too much of this.
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Old 03-28-2019, 10:46 PM   #8
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Quote:
Originally Posted by hbn7hj View Post
Get an adapter and plug it in. You could get an AC voltmeter that plugs into a coach AC receptacle. When it reads 104 instead of 115, turn off the AC.

Yep, you are making too much of this.
^^^This! The circuit breakers protect against overcurrent of the circuit. If the breaker of your 15A house circtuit pops, you will know the load is too high for the circuit. If it doesn't pop the breaker, you're good..

The reason to check for voltage level - IN THE VAN, or at the AC Compressor terminals, WITH THE AC RUNNNIG! - , is that a too low voltage can - over time - damage the compressor.

That's why it is important to use the shortest possible, or thickest AC extension cord between house and van as possible. The shorter the cable, and the thicker the wire, the lower the resistance of the cable and the lower the voltage drop.

That's it.. don't overthink it
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Old 03-29-2019, 12:35 AM   #9
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Keep in mind they have a 30A input for more than just the AC. You may have a microwave, lights TV all running at the same time. At that time you will defiantly blow a 15A circuit and possibly a 20A. While there is a lot more to it the best thing is measure the amp draw and voltage while it is starting up and also running. My own personal opinion I wouldn't run it on a 15A circuit with 14 gauge wires.
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Old 03-29-2019, 12:47 AM   #10
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Quote:
Originally Posted by GBail View Post
Thx for responses guys.

My unit (it’s not a SMB) has an “Airxcel” brand, 9,600 btu rated, rooftop A/C.

Re:” So a question: If your current AC has a 20A breaker it shouldn't be hurt by running on a 20A circuit, should it? “
...but my older home (and many others) have 15 amp breakers, so maybe that’s still a problem?

Maybe I’m making too much of this.

It’s just that, with my previous rig....a Forest River Lexington B210...I was strongly warned NOT to run the A/C on household current, regardless of using a 30 to 15 amp adapter plug.

With this current rig, as described above, maybe that’s not a problem.

But I’m being cautious because if I make the wrong decision and wind up damaging the circuitry, the repair costs will pretty much equal the cost of a new unit (and my wife will kill me for being stupid!).
What is the power draw? I'm thinking a 9600 btu unit will run just fine on a 15 amp circuit, just don't fire up the microwave or toaster oven. There should be enough headroom to have the fridge on 120 and run the converter, unless the battery is quite low. Maybe to be safe or if the breaker in the house kicks off, put the fridge on LP, assuming an absorption fridge. A compressor fridge should be fine.
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Old 03-29-2019, 02:01 PM   #11
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The converter draws a significant current. I have a surge protector in my Roadtrek, which monitors and displays voltage, amperage and frequency. Even after driving all day, charging the batteries from the alternator, the amp gage spikes to 10 amps when first plugged into shore power. The only thing on at this point is the converter. Your AC not only has a constant running current, it also spikes when it first starts. That's why it has a 20A breaker.
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Old 03-29-2019, 06:20 PM   #12
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Something else to think about besides using a short heavy (10 ga) extension cord;

If the 15 or 20 Amp receptacle is on the opposite side of the house from the main electrical panel you may have 100 feet of 14 or 12ga wire between the main panel and the receptacle; that effectively puts your air conditioner on the end of light weight 100ft extension cord;

Even with a 30A source you need some of monitoring the voltage.

I beleive the Eass Start referred to earlier monitors voltage among other parameters.
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Old 03-29-2019, 08:53 PM   #13
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Quote:
Originally Posted by GBail View Post
Does anyone have a rooftop A/C unit that can be run when your rig is plugged into a 15 amp regular household outlet ?

See, the one thing about RV A/C units I don’t get is this....for about $125 you can buy a home window A/C unit that would aptly cool a small Class B or small B+, plugged into a regular household outlet.

But all three of our last, small rigs have required 30 amp service to run the much pricier rooftop A/C. So when we’re visiting friends or family and camped in their driveways, we can’t use our RV A/C as you’re not supposed to run it on a regular household circuit.

This situation...the power supply requirement difference between the RV rooftop and the household window A/C units makes no sense to me (and in fact seems a stupid way for manufacturers to ignore the real world use of their products).

There obviously seems to be a market for rooftop RV AC units for smaller rigs that would run on household power (these are used in some small camp trailers) so who’s making these?

Anybody?

Thx
5250 BTU removable AC
https://safaricondoacc.com/boutique/...itioning-p112/
Here is an idea if you ever travel to Quebec, if you have a rear window to install the AC
Price quote is in Canadian dollars and one must pick up in Quebec ,that would cost $600. USD plus you would need to pay taxes of 14.975%
Or take this idea and app,y to your need.
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Old 04-04-2019, 07:09 PM   #14
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Default Thx for all the advice

Thank you for all the helpful advice.
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Old 04-04-2019, 07:20 PM   #15
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You have some good answers already. You might also want to consider the fact that your trying to cool a metal box versus at least some minimally insulated building's room with a wall or window AC unit. Most homes and business today also benefit from energy efficient windows. Less work to air condition these rooms with smaller AC units.

I have a friend with a 5th wheel RV that his AC unit never seems to do anything behind sticking your face directly in front of the rooftop AC's vent. The rest of his seemingly non or badly-insulated fiberglass 5th wheel trailer stays annoyingly HOT during some season trips. Our Class B's are either all or mostly all steel surfaced so while we have a smaller area than some RV's, they still take some work to cool and keep cooled. Of course the better the insulation job and type of windows, the better the results. And most Class B's have the big slider door that may open to the external environment, perhaps often on some days. In some cases a room in a house might just have a doorway into the rest of the interior. If so, that makes that room even easier to keep cool than if it had a glass slider access to the outside with or without direct sun beating on it. So it depends on a case by case basis but typically a house or business room is still easier to cool (or heat) than a potentially totally sun exposed metal box, often equipped with single pane glass windows all around on wheels for additional rising hot air to cook all sides.

I think it is likely that a 15 amp, 14 gauge wired 120 volt line running even a smaller window unit that might be hung on a house would heat up those wires more than you want. Especially since that 15 amp branch circuit will have some extended length cord adding to the resistive path.

I strongly recommend you look into adding a 30 amp breaker, properly sized and type of wire and receptacle for the distance required at least from the receptacle to the main or sub panel. To that distance you will also be adding the length of the RV's power cable but that should already have a slightly oversized wire than necessary for just it's length.

All of this combined will allow the compressor motor to easily start. Running current is less. And then you can also run some lighting and most if not all of the other devices in the RV at the same time without issue.

Operating a few well chosen items on 20 ampere wiring and breaker within a reasonable distance of the entire circuit wiring size from the breaker location is certainly do-able. You are not going to for example, run a 1,000-ish watt microwave (at least 8 amperes) at the same time as the roof top AC unit that required a 20 amp circuit. That implies that something north of 15 amps is drawn by the AC and thus was not put in a 15 amp circuit or that breaker would be popping before the (proper sized branch circuit wiring et al) decides to flame on you. It's all a matter of doing the right thing.
Maybe I just told you things you know electrically. My oops then.

The crux of the problem here is getting what it takes to optimze the environment in the metal box on wheels better than most RV manufactures are doing. The materials to do this can be quite expensive. And if you include the floor, that has to be done before the interior is built out. Walls, ceiling, doors and windows too but some of these areas can at least be partially improved if the coach interior is already built out. Starting this with a bare to the bones van would be ideal. If you can really tweak the environment to the max advantage, then an AC unit with less BTU output would be required and therefore much less current draw is possible!

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