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Old 08-09-2018, 12:25 PM   #1
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30 Amp and A/C's

Has anyone tried to use the A/C's on 30 amp? That is, will they rotate in use or do you use just one of them? Thanks This is in a 39FK
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Old 08-09-2018, 09:06 PM   #2
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My EMS will shut down A/C's as needed. I can set a priority unit with the EMS so the priority stays running while it shuts down the other ones, I have 3 A/C's.
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Old 08-09-2018, 09:17 PM   #3
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I see you have a Riverstone. You probably have 3 A/C's with the Power Management System (PMS). The PMS should sense and display 30 amp connection. It will sense the load on each leg going into the trailer from the power post and will control which A/C's are used to control amperage draw. I use mine on a 30 amp at home with no issues. I have a Cedar Creek with the PMS.
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Old 08-10-2018, 10:16 AM   #4
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If you have the same PMS we do then it'll switch automatically, but please don't ask me how it works
I try to upload the pdf manual.
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File Type: pdf 00-10050-000-Power-Control-System-Midi-Manual-B-1.pdf (466.0 KB, 45 views)
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Old 08-10-2018, 10:30 AM   #5
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Voltage is key, whether your running one or multiple AC units. An EMS is a great tool to have and it will look after you automatically and shut power off at 104 volts. Low voltage damages AC units and it may *seem* like they're running fine but damage is cumulative and cause premature failure. Voltage is a big problem in the heat of summer and older CGs can be much worse because of how they used to wire them. If you have an EMS that will only allow one at a time, great. But otherwise just turn one on at a time.

Running more than one AC unit on 30 amps is not a good idea. You at least want to be close to 120 volts. But you won't know how stable the voltage is under heavier loads and the momentary startup. An AC draws around 50-60 amps on startup and voltage can get very low and be hard on the compressor motor windings. When you read comments like "I do it all the time and it's fine" they don't know the damage they can be causing and how much it will cost for a new AC unit(s).

FWIW, a permanent LED voltmeter inside is also a good tool to have. It's good to keep an eye on voltage as it can fluctuate and/or be low when you first plug into a pedestal. An autoformer is another good "tool" to have. If the voltage is low it can keep you going.

I've read elsewhere that some CGs have been turning away customers with 50 amp RVs when they only have 30 amp pedestals available so you might want to confirm in advance. Have not run into this anywhere yet. Being able to "survive" on 30 amps if you have a 50 amp RV is a good plan because some CGs have very few 50 amp sites available.
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Old 08-10-2018, 10:41 AM   #6
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30amp service, itself, is not a limiting factor for running two Air Conditioners at once - it really depends more on their size/amp needs, and the other 'things' you wish to run at the same time.

For most of us, with 50amp(100amps total), we are accustomed to having everything at once, whenever we want.
When we 'adapt' down to a single line 30amp incoming power supply, we have to 'manage' what we want to use, so that we don't trip the outside Power Supply breaker.

Some EMS systems may allow you to override it's 'default' systems and run two AC units at the same time, while some may not, but it's certainly conceivable that you can run two, like we do - but we also don't have an EMS, so we decide ourselves what and how we want to do it.

Most AC Units are either 13.5k or 15k, and draw between 8amp and 15amps, with the higher draw at the initial compressor start up, but much lower while running. You can run both on 30amps by turning on one, allowing it to start the compressor, then start up the other. Once they are running together, they will most probably be below 30amps total, and then you can 'test' how much more room you have by adding other items, such as by plugging devices into the outlets. Once you trip a breaker, you'll have a good gauge as to what you can do on 30amps with both Air Conditioners in play.

If you have a residential fridge, which I imagine you do, keep it powered before you start the AC Units, as you'll want it always powered regardless.
Cut OFF the battery Charger, cut OFF the Electric water heater and other 'non essential' items, until you test and know what your 30amp supply can handle.
Some 30amp outlets are on overly sensitive breakers, and can trip before you might otherwise expect. That's not a limitation of your coach, but more of an 'old' 30amp outlet, or power supply. Good, newer, 30amp outlets probably won't readily trip just because you go over 30amp for a second or so, but are designed to trip only when the physical wire heats up past a certain point, sometimes even slightly more than 30amps.

btw... your coach really doesn't care about any differences between 50amp and 30amp, but your EMS system does, and is there to take the 'management' out of your hands and tries to handle the difference for you, moving power from one device to another, when the situation demands. If you want to use your microwave, it may shut down your air conditioner, or water heater, while the microwave is working, etc. It may also not allow you to use two Air Conditioners at the same time, even if you really expect it due to extreme heat, at least not without you intervening.

EMS are great systems, but in some situations you may want to 'handle' the management of your energy yourself!
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Old 08-10-2018, 11:04 AM   #7
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Originally Posted by myredracer View Post
Voltage is key, whether your running one or multiple AC units. An EMS is a great tool to have and it will look after you automatically and shut power off at 104 volts. ...

Running more than one AC unit on 30 amps is not a good idea. You at least want to be close to 120 volts.
While I understand your concern, Voltage is a condition of concern ALL the time, not 'just' because you might want to run two ac's while on 30amp service - the two conditions are not necessarily related.

If you are concerned about low voltage, you have to ALWAYS be concerned about it, regardless if your are on even on full 50amp service and only running one ac unit, or running two, or even running three. It would matter not.

The question of whether you 'can' run two ac units on 30amps is the typical question that most folks are concerned with because the normal
'but, somebody told me...' mindset reasons that you can't, you might 'break' something, or otherwise render your coach unusable thereafter.
All is bunk. 30amps is 30amps, regardless of 'what' you are wanting to use it for. Two ac units within that limit of amps knows no difference than if you were plugged into 100amps of service.


travel, use it, enjoy! : )
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Old 08-10-2018, 11:21 AM   #8
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My CC will run two ac units on 30 amp service.

You best turn everything else off. My ems said I was running 34 amps. The charger was also on. No fridge. I have a gas fridge.

If they both attempt to start together, no way.

50 amp is really 50 and 50 or 100 amps total. 3.3 times as much as 30 amps
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Old 08-10-2018, 11:30 AM   #9
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right, and it's a little confusing for most of us, at least at the start, about why '50amp RV service' is actually 100amps ... the simple quick answer is that the electrical industry refers to it that way because it is 240v service at 50amps. You'll notice that it has a 'double-pole' 50amp breaker at the Shore Power pole, which is TWO 50amp hot lines combined into a single output outlet, which is what we plug into.

Our breaker box, within our coach, though, uses both of these 50amp incoming hot lines separately - in otherwords, we have two 'sides' within our breaker panel. (some larger coaches may actually make use of the 240v service for a clothes dryer, but most of ours don't).

So, if you have two 50amp hot lines coming into your coach's breaker panel, you have access to 100amps of total power.


It's just better than having to use TWO shore power cables... : )
or a MUCH thicker one!
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Old 08-10-2018, 11:47 AM   #10
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Thanks to all that responded. I do have EMS on board. It should take care of things nicely. We will have to hook-up to 30 amp temporarily at our grand-daughters.
Thanks again
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Old 08-10-2018, 12:01 PM   #11
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that would be a good time to test your systems' handling of running two ac's while there... then you can rest assured that 30amp service at rv parks or campgrounds won't be as limiting as some may tell you.

we arrived last month at a beautiful mountain top campground below Franklin, NC... a nice 'niche' campground for only several coaches, and we were at the 'top' site... what beautiful views.

we arrived during a hot afternoon, climbing the road to the site, set up, plugged in, and ran both AC units to cool down the coach - it was probably mid 90's with good humidity, which makes it seem even hotter.

while I was outside hooking up the portable satellite for some tv viewing later, the owner stopped by on his atv. He apologized profusely as to our only having 30amp service, and wished he could have switched us to the site down the hill, where a fifth-wheel RV sat, that had only one AC unit.

I told him that there was no apology needed, as I was running both AC units just fine... He was SHOCKED! I even revealed that my fridge was running, several fans near the bed, the TV and receiver, and other things, all at the same time.
After I provided some quick explanation, he admitted that while he had a motorhome of his own, with two ACs, he had always been 'told' that he could never run both at the same time on 30amp service. He never 'tried' to, but just relied on what others said.


Everyone has a learning moment. Some sooner, some later. : )
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Old 08-10-2018, 12:41 PM   #12
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30amp service, itself, is not a limiting factor for running two Air Conditioners at once - it really depends more on their size/amp needs, and the other 'things' you wish to run at the same time.

Most AC Units are either 13.5k or 15k, and draw between 8amp and 15amps, with the higher draw at the initial compressor start up, but much lower while running. You can run both on 30amps by turning on one, allowing it to start the compressor, then start up the other. Once they are running together, they will most probably be below 30amps total, and then you can 'test' how much more room you have by adding other items, such as by plugging devices into the outlets. Once you trip a breaker, you'll have a good gauge as to what you can do on 30amps with both Air Conditioners in play.
Yes, low voltage is always a concern regardless but this post is about AC units on 30 amps. Not sure where you get 8 amps for a running current? The Coleman 13.5K AC unit draws 13.1 amps according to their specs here. https://www.airxcel.com/coleman-mach...le/mach-3-plus That current is at 120 volts too, and AC units draw more current as the voltage goes down. Startup inrush current is 50.5 amps. Two of these AC units would be drawing 26.2 amps (on high) and then you've got maybe another 5 amps or so for converter draw, fridge on elec., TV, etc. It's not a good idea to be running at or near 30 amps on a continuous basis as it risks the plug to pedestal connection overheating, especially since 30 amp pedestals are often well used and abused.

If you have one AC already drawing 13 amps, 5 amp of misc. and then 50 amps at startup, that's a momentary draw of 68 amps when starting a 2nd AC unit (for a 13.5K unit). There will be a momentary voltage dip and can be a little or a lot depending on the CG wiring. Running AC units under low voltage, running or startup, is hard on the motor windings and shortens motor life over time. As voltage drops, a motor generates less HP and draws more current as it tries to drive the compressor load and windings can heat up and damage the insulation. Older CGs can have small gauge wire to the pedestals. Have seen as small as #10 to pedestals. As I say, AC units can fail one day for no apparent reason and the cause can be low voltage.
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Old 08-10-2018, 05:20 PM   #13
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The RiverStone have 15k air conditioners, ours draw 13 - 14 Amp on startup and then drop down to 11 - 12 Amp when up and running, if you can trust the display.

And yes, Voltage is the number one concern as we found out last week. Low campground voltage is kind of the norm and it drops with increased draw and such. We stayed at a park in the Rockies with 30 Amp 122 Volt (on the meter) service but as soon as I turned on the rear AC the Voltage must have dropped below the 103 Volt? threshold of the SurgeGuard which immediately cut the shore power power and handed it over to the inverter. I only noticed this when I heard the low battery alarm beeping after an hour or so. The point I'm trying to make is that with inadequate campground wiring (to small of a wire) the voltage drop becomes sudden, unexpected problem. Also, a weak breaker on the pedestal can obviously trip long before it's rated current is reached.


Off topic: We drove 6 hours yesterday through 91F - 96F heat and when we set up in the late afternoon the inside of the trailer was still 76 F.
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Old 08-10-2018, 09:37 PM   #14
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Running anything from a 30-amp service can be a crap shoot based on the system that is supplying the power, the condition of the equipment plugged in, and the number of others in the vicinity using electricity. Running two air conditions on a thirty-amp circuit is not usually a problem. It might be for some folks whose ACs are not up to snuff. When dry camping we use our little 4K generator to run our AC and the kids AC in their travel trailer who do not have a generator. Both 13,500 BTU air conditioners run fine, each cycles their compressors and fans as controlled by each air conditioner. The little generator has no problem starting another air conditioner with one running and the 30-amp main breaker has never tripped.
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Old 08-11-2018, 05:31 AM   #15
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I have a related electrical question, though I do not wish to hijack this thread.

I have toyed with the idea of adding a portable AC to our Rockwood for especially hot times (parking in full sun at near 100 degrees). Either a second roof unit wired independently from the RV circuitry or a portable unit which would have it's own 110v. wire and plug to the power pedestal.

I would run a 110 v. line outside to the 20 amp AC house type outlet which most power pedestals offer.

I assume that outlet is a separate 20 amp circuit from the main 30 amp and would not deplete any power from my 30 amp service, yet should provide sufficient amperage to power the second unit.

Any thoughts?

Larry
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Old 08-11-2018, 08:13 AM   #16
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Some are confusing EMS vs PCS/PMS.

EMS - Electrical Management System Monitors power and voltage into the RV from the pedestal and protects the RV from voltage, frequency problems and surges. Typically connected at the campground power pedestal electrical service. Some are better than others protecting from more issues and some are simply surge protectors.

PMS/PCS - Power Management System or Power Control System. Monitors current on each leg and sheds (turns off) individual loads necessary to stay below maximum current for the RV and/or Current Connection. Typically controls A/Cs & water heater. System can detect current connected shore power (50a, 30a, 20/15a). Great for when a 50 amp RV is connected to 30a service. Units are permanently installed inside the RV with a user control panel.
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Old 08-13-2018, 10:40 AM   #17
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For me, by watching the Progressive Industries EMS (Electric Monitoring System), we are able to run 2 air conditioners on 30amp service. We manage what other loads are running (fridge and water heater are both on gas and we've been known to turn OFF the converter). But it makes a huge difference when we have to slum it on 30amp.
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Old 08-13-2018, 10:45 AM   #18
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Quote:
Originally Posted by myredracer View Post
Yes, low voltage is always a concern regardless but this post is about AC units on 30 amps. Not sure where you get 8 amps for a running current? The Coleman 13.5K AC unit draws 13.1 amps according to their specs here. https://www.airxcel.com/coleman-mach...le/mach-3-plus That current is at 120 volts too, and AC units draw more current as the voltage goes down. Startup inrush current is 50.5 amps. Two of these AC units would be drawing 26.2 amps (on high) and then you've got maybe another 5 amps or so for converter draw, fridge on elec., TV, etc. It's not a good idea to be running at or near 30 amps on a continuous basis as it risks the plug to pedestal connection overheating, especially since 30 amp pedestals are often well used and abused.

If you have one AC already drawing 13 amps, 5 amp of misc. and then 50 amps at startup, that's a momentary draw of 68 amps when starting a 2nd AC unit (for a 13.5K unit). There will be a momentary voltage dip and can be a little or a lot depending on the CG wiring. Running AC units under low voltage, running or startup, is hard on the motor windings and shortens motor life over time. As voltage drops, a motor generates less HP and draws more current as it tries to drive the compressor load and windings can heat up and damage the insulation. Older CGs can have small gauge wire to the pedestals. Have seen as small as #10 to pedestals. As I say, AC units can fail one day for no apparent reason and the cause can be low voltage.
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Old 08-13-2018, 10:49 AM   #19
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Startup inrush current is 50.5 amps.
I'm not arguing and seriously want to learn. But I can't wrap my head around the 50.5 amps start-up current. The A/C is on a 20amp breaker in the panel in the camper. A 30amp campsite is on a 30amp breaker at the pedastal.

How does 50.5amps get past both breakers?
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Old 08-13-2018, 10:50 AM   #20
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Originally Posted by Grapehound View Post
I have a related electrical question, though I do not wish to hijack this thread.

I have toyed with the idea of adding a portable AC to our Rockwood for especially hot times (parking in full sun at near 100 degrees). Either a second roof unit wired independently from the RV circuitry or a portable unit which would have it's own 110v. wire and plug to the power pedestal.

I would run a 110 v. line outside to the 20 amp AC house type outlet which most power pedestals offer.

I assume that outlet is a separate 20 amp circuit from the main 30 amp and would not deplete any power from my 30 amp service, yet should provide sufficient amperage to power the second unit.

Any thoughts?

Larry
Yes, this is done by lots of folks and is a very economical permanent fix. Easy to do. I would go with the second roof unit. Wiring can be run across the ceiling with wiremold to a closet and down thru the trailer floor.
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