30 Amp vs. 50 Amp

[irvsiegel]

  I've been told (by a salesman who was trying to sell me a coach with 50 Amp service) that a coach with only 30 Amp service would not be able to run both air conditioners at the same time.  Is this true?  Also, what are the real advantages/disadvantages of 30 vs. 50 Amps.  Thanks in advance!

 

[Ned]

Generally, you can not run two air conditioners at the same time on 30A service.  Some RVs will have a special controller that will allow you to run the 2 A/C units alternately on 30A, but it does that by only allowing one compressor to run at a time.

The biggest advantage of 50A service is you really have 100A service, 2 legs of 50A each, and you can run just about everything electric at the same time.  With 30A service, you have to do some energy management, either manually or with a controller to decide what loads can be allowed at any given time.

 

[2006F350]

I would have serious doubts that 30A service would power 2 A/C's, even hi efficiency units. All units I've seen that have 2 A/C's or 1 A/C and wired for a second or can be wired for a second all have 50A Service.

Ned: I had forgotten about the 2 A/C controller thingy until I read your post. Thanx for the reminder as I do on ocassion attempt to stay current with what's happening. 

As Ned said, there is a big advantage of 50A service, and the only disadvantage I've seen is that you are usually charged more for site rentals for 50A. I only specifically request 50A during the summer months when I know that I'll need the AC otherwise I'm happy with 30A.

Larry

 

[John From Detroit]

I've managed 2 AC's on a 30 amp circuit however

1: It was not all that hot and
2: I think the breaker was being "Generous" and
3: The park was mostly empty

As the park filled up and voltages dropped a bit both AC's at once tripped the breakers

There is a box, sells for 89.95 and I don't have the URL (Or don't care to look it up) that gives you a break out for one AC, this box consists of a power inlet,  breaker and extension pigtail.  Put it in a bay unhook the wire for one AC from your breaker panel and put into a junction box, wires from the junction box to the inlet's breaker and from the original breaker to the extension pigtail.

Normal operation you plug the pigtail into the inlet and it works

Abnormal operation you pull the pigtail out and plug the outlet end of a 12ga extension cord into the inlet, the other end goes to the 20 amp outlet on the post  This means the AC likley won't bother the post GFCI

 

[JIGGS]

I have a 30 amp service in my HM. Do i need 50 amps ? no.  You see I camp at some older campgrounds and they only have 30 amp service. What I can't do is run the washer/dryer and the microwave at the same time. I can run both air conditioners at the same time. I have what john was talking about and it works great. You can see this at www.psrv.net  I am in no means an electrician but had no problem hooking it up. This being said my HM is an 89 and doesn't have all the bells and whistles the newer ones have. So i say do you need 50 amp service  no.

 

[Gary RV_Wizard]

The "need" for 50A depends on you and your energy consumption habits.  A surprising [to me] number of people are large energy users by habit and just can't seem to grasp the notion of having a limit on the available power.  We work in campgrounds during the summer months and continually meet people who trip 30A breakers and can't understand why, even when it is explained to them. And among those who understand conceptually there are still many for whom keeping track of amps or watts is simply too much effort or perhaps just "too technical".  If you [or your mate] fit into any of those categories, you "need" 50A because RVing life will be a continual hassle without it. Be aware, though, that many older campgrounds don't offer 50A service and most campgrounds charge extra for it, typically $3-4 per day.

30A isn't a lot of power - only about 3600 watts (each amp @ 120V yields 120 watts of power).  Each a/c unit will draw about 1200-1400 watts in run mode and considerably more each time the compressor cycles on.  Coffee makers draw 1000-1100, microwaves need 1200-1500, hair dryers also about 1200, and so on. Plus there is always a background consumption by things like the refrigerator, battery charger/converter, water heater, etc, and those will vary according to what else is happening at the time. For example, if somebody is taking a shower, the water heater will be drawing around 8 amps, but if no hot water is being used it is probably idle most of the time and draws no power. It is sometimes difficult to maintain an awareness of just how much power is being consumed at any instant.

 

[John From Detroit]

I have what john was talking about and it works great. You can see this at www.psrv.net  I am in no means an electrician but had no problem hooking it up.

Thanks Jiggs.  I know about the device but had forgotten the link since I decided 90 bucks was about 70 more than it's worth to me

(Plus I can build one for less)  (And am going to do that once I get to better weather,,, bit chilly here now)

 

[Karl]

Be VERY careful when using one of those devices! Many parks have 50, 30, and 20 amp outlets on the same pole, and there's no way you can tell if the 20 and 30 amp outlets are wired to the same 120 volt leg of the 240 volt circuit without actually measuring with a voltmeter. If they are, o.k.; if not, you'll end up with one big spark because you'll be shorting both 120 volt legs together 180 degrees out of phase! And, if it feeds the main power panel, you're still limited by the 30 amp main breaker unless you replace it with a 50 - NOT a good idea! Too little info on the website, and very over-priced.

 

[John From Detroit]

If the Device Jiggs has is the one I"m thinking about this device isolates one air conditioner from the coach, completely and runs JUST that AC off the 20 amp main, both hot and neutral are isolated, only the safety even the safety ground is isolated though if the AC is mounted to a metal part of the coach it may be connected internally

Electrically it is as though you removed all the power wires from the AC and hooked up an extension cord JUST to that unit.

In fact, that is more or less exactly how you install it (Only you work at the breaker end of the wire instead of the AC end)

 

[Karl]

John,

The installation instructions say that you hook it up at the generator distribution box; not the breaker panel. Don't see how any isolation can be done there.

 

[John From Detroit]

Oh... That mis-print.  In looking for the manual for my transfer switch I find that a lot of rigs are wired so one air conditioner runs through the generator all the time,  Do not ask me why they do this but on these rigs the generator will have two different size breakers, One feeds most everything, the other feeds just that one AC unit. (and is 20 amp)  The folks who wrote the installation manual clearly have this type of a setup.  Which, by the way, makes absolutely NO sense to me  I mean, why would I want one of my AC breakers OUTSIDE the coach.  But it appears that's how they wire them..  Let me see if I can find a url for what I'm talking about

Try this link



The link is to a 30 amp intelltec transfer switch

The instalation instructions for that overpriced box are simply wrong.. I do agree the average user would never figure it out.

But a professional should be able to do it.. Oh well... I've done enough figuring for one week (There is a story here, posted elsewhere)

 

[GaryB]

if somebody is taking a shower, the water heater will be drawing around 8 amps, but if no hot water is being used it is probably idle most of the time and draws no power.

Gary

Does the water heater draw 8 amps only when in the "electric" mode, or also when in the "propane" mode?  I thought I read somewhere that it also draws current for some functions even when in propane mode.

Thanks
Gary

 

[Ned]

When running on propane, the water heater draws only a small amount of 12VDC for the controller.  It doesn't use any 120VAC in that mode.  And when in 120VAC mode, it only draws power when actually heating the water.  There is still a small 12VDC current draw, even in AC mode.

 

[Karl]

In addition to the controller board, there are one or two gas solenoids (redundancy) that use 12V also when heating water, even when on 120 Volts ac.

 

[Gary RV_Wizard]

Does the water heater draw 8 amps only when in the "electric" mode, or also when in the "propane" mode?

GaryB
Ned has already answered, so I won't repeat.

 

[GaryB]

Thanks all for the info!  That cleared up my question.

GaryB

 

[Snake Doctor]

? ?I've been told (by a salesman who was trying to sell me a coach with 50 Amp service) that a coach with only 30 Amp service would not be able to run both air conditioners at the same time.? Is this true?? Also, what are the real advantages/disadvantages of 30 vs. 50 Amps.? Thanks in advance!

We (DW and I) have a 04 Bounder with a 30 Amp service, we are able to run both AC units at the same time, with the fridge on AC the TV going and the sat reciver on, the power managment board with shut down the 2nd units compressor till the amprage is back under aceptable amps, if it gets over 30amps it will shut down the 2nd AC all together then the fridge to gas, and then the TV, I know a few will disagree but that is how mine works, motor safe?

 

[Ned]

That's exactly how an intelligent controller should work for a 30A wired RV.  Shut down the loads in increasing importance.  Of course, the TV is the most important item, so the last to be shut down

 

[Karl]

Welcome fellow Wisconsinite (or should that be Wisconsinonian :-\)

I know a few will disagree but that is how mine works,

Why would someone disagree, If that's how yours works? I have a '96 Bounder gasser, but my intelligent controller only shuts down the 2nd a/c; nothing else. Guess they weren't quite as intelligent back then.