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Old 07-25-2012, 05:47 PM   #1
moutard2
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30amps + 20amps = Disaster or Solution?

So what am I getting when I wheel up to a post with a 30amp and a 20 amp circuit and plug my "Y" shaped gizmo in? One part of the "Y" is 30 amp so I naturally plug it into the 30 amp circuit and then I plug in the other side of the "Y" which is a 20 amp plug. The bottom of this "Y" connector thingy terminates in a 50 amp plug into which I put the monster cable from the trailer. Am I getting 50 amps or something else or am I risking a massive catastrophe with fireworks? I did buy this thing at an RV dealer so assumed (silly me?) that it was safe to use.
 
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Old 07-25-2012, 07:20 PM   #2
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Not always. There's no guarantee that the power pedestal is wired to provide the full 30 amps AND not OR 20 amps. Same thing with a 50, and a 20 or 30.

There might be a way to measure and test to ensure this but I'm not familiar with it.

Not sure fireworks might occur, but I'd be more concerned with brownouts (not enough amps, but enough for some appliances to attempt to run). Brownouts are death to things with a motor like an A/C because they do not do well when they run at too low of a voltage. This causes the amps to rise to make up for it and then this could fry a motor.
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Old 07-25-2012, 10:49 PM   #3
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Quote:
quote:Originally posted by Art-n-Marge

Not always. There's no guarantee that the power pedestal is wired to provide the full 30 amps AND not OR 20 amps. Same thing with a 50, and a 20 or 30.

There might be a way to measure and test to ensure this but I'm not familiar with it.

Not sure fireworks might occur, but I'd be more concerned with brownouts (not enough amps, but enough for some appliances to attempt to run). Brownouts are death to things with a motor like an A/C because they do not do well when they run at too low of a voltage. This causes the amps to rise to make up for it and then this could fry a motor.
Art, I'm having trouble following your post. Wouldn't the uncertainty of the pedestal power be just as suspect without the Y cable? Why would the Y cable increase brownouts? Jim
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Old 07-26-2012, 12:43 AM   #4
NCFischers
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What you are getting with the "y shaped gizmo" is 30 amps on one leg and 20 amps on the other. It is designed to safely provide a little more power than just the 30 amp outlet. You will need to watch your usage since you don't have two 50 amp legs.
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Old 07-26-2012, 12:50 AM   #5
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Some campgrounds do not allow them to be used.
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Old 07-26-2012, 02:05 AM   #6
H. John Kohl
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Quote:
quote:Originally posted by NCFischers

What you are getting with the "y shaped gizmo" is 30 amps on one leg and 20 amps on the other. It is designed to safely provide a little more power than just the 30 amp outlet. You will need to watch your usage since you don't have two 50 amp legs.
Following on Jim's post
20 amp and 30 amp service have three wires. One Hot, one common and one ground.
50 amp service has two hot, one common and one ground.

First, the 30 amp to 50 amp dog bone or adapter you would normally us when only having 30 amp service takes that one hot and feeds it to both hot legs "A" and "B" of the 50 amp interface.

Your Y gizmo has the 30 amp hot going to one of the 50 amp hot "A" and then the 20 amp hot going to the other 50 amp hot "B" wire.
So if the pedestal is wired correctly it should do as Jim says provide a little extra.

Trailer usage:
50 amp service means there are two hot 50 amp feeds to the trailer. Your circuit breakers are set up that hot "A" goes to one breaker and hot "B" goes to then next breaker alternating down the line.
One deviation to this as with mine is that hot "A" goes to the first two breakers and hot "B" goes to the second two breakers. This means that every other pair of breakers are feed by the alternate feed.

When you use the 30 amp adapter only that means a total of 30 amps is provided to your trailer and both "A" and "B" leg share it.

The most critical thing is to know how your circuit breakers are wired and manage the power draws accordingly. I found both of my Air Conditioning units were wired to the "A" leg in the circuit breaker panel. Jim helped me move one AC over to the "B" leg so there was better distribution even on 50 amp service.

I hope this is not too confusing and has helped.



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Old 07-26-2012, 02:38 AM   #7
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When we owned our Keystone Sprinter trailer, (a 30 amp unit) I wired in a 20 amp outlet for the kitchen, we would have the 30 amp cord plugged in, and would plug the coffee maker, microwave and waffle maker, or whatever into that 20 amp circuit (and balanced what we used on it)
On the back of the trailer, I had a coiled 20 amp cord and the 30 amp trailer cord. Worked super.
Good answers from Jim and John on your question.
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Old 07-26-2012, 03:13 AM   #8
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I didn't buy one of those because the manufacturer of the one I was looking at said it wouldn't work with GFI 20amp outlets and I have yet to find a campground around here where the 20 amp isn't GFI.
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Old 07-26-2012, 03:33 AM   #9
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I have used mine at a few campgrounds, but like DQick said most campgrounds have GFI 20 amp plugs and they won't work. I have also used a 30 amp adapter on the 20 amp side and plugged into two 30 amp plugs. That seems to work every time! I don't use it very often, but wouldn't want to be without one.
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Old 07-26-2012, 04:56 AM   #10
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Quote:
quote:Originally posted by H. John Kohl

Quote:
quote:Originally posted by NCFischers

What you are getting with the "y shaped gizmo" is 30 amps on one leg and 20 amps on the other. It is designed to safely provide a little more power than just the 30 amp outlet. You will need to watch your usage since you don't have two 50 amp legs.
Following on Jim's post



Trailer usage:


When you use the 30 amp adapter only that means a total of 30 amps is provided to your trailer and both "A" and "B" leg share it.

The most critical thing is to know how your circuit breakers are wired and manage the power draws accordingly. I found both of my Air Conditioning units were wired to the "A" leg in the circuit breaker panel. Jim helped me move one AC over to the "B" leg so there was better distribution even on 50 amp service.

I hope this is not too confusing and has helped.
If A and B share 30 amps, how is that enough to run an AC unit?

Was having both ACs on the same leg on an older trailer or newer? Is this something I should have checked on a new trailer?

Thanks!
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Old 07-26-2012, 05:31 AM   #11
bncinwv
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We ran both ac's on a cheater box at the Mid-Atlantic rally in NC last year. I will add that you cannot use a hair dryer at the same time!! That was the first opportunity that we have had to use the box in over five years due to the aforementioned gfci issues.
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Old 07-26-2012, 06:19 AM   #12
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Seahunter,
It depends on how they install the circuit breakers at the factory but it's an easy fix. Each full size circuit breaker or twin circuit breaker is about an inch wide. The first inch wide breaker on the left is on the "A" power leg, the next one is on the "B" alternating A and B from left to right. Identify the two breakers for your AC units and see if they are on both on the A or B leg. If so, one can be moved. If you do it yourself, UNPLUG the trailer first.
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Old 07-26-2012, 07:31 AM   #13
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Incredible timing-my brother called me yesterday from a campground in Holland, Michigan to report that his "RV cheater" was working as advertised. I have yet to be able to use mine as all the 20 amp plugs on the servive posts have been GFCI protected.interstingly enough, we just returned from Zion, Illinois where all I could run was one A/C unit and a coffee pot in the morning off of a "30amp" plug. (It was over 100 degrees the three days we were there.)At home when I plug in, I can run BOTH A/c units with no trouble at all. A DVOM is now going into my tool box on all trips. But then again, it's not like I'll get a discount if I complain about low amperage at the post. LOL.
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Old 07-26-2012, 08:44 AM   #14
H. John Kohl
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[quote]quote:Originally posted by seahunter

[quote]quote:Originally posted by H. John Kohl

Quote:
Originally posted by NCFischers
-snip

If A and B share 30 amps, how is that enough to run an AC unit?

Was having both ACs on the same leg on an older trailer or newer? Is this something I should have checked on a new trailer?

Thanks!
seahunter
The main AC run between 15 to 20 amps especially at/during starting so if it is the only main draw of current no problem. The water heater, microwave, converter, and coffee pot also draws a lot of current.
This gets into power management turning on top priority items first and then later others. If you pop the 30 amp breaker you know you tried to run too much/many items at once and need to shut one or more down.
The key is the 30 amp pedestal breaker is only going to pass about 30 amps to the whole trailer.
Balancing the two AC was in my 07. It just took some of the major load off one leg. The more current passing though a leg increases potential for damage or deterioration. Again mainly power management, sharing the load or balancing the loads.




Quote:
Originally posted by BethandKevin

Incredible timing-my brother called me yesterday from a campground in Holland, Michigan to report that his "RV cheater" was working as advertised. I have yet to be able to use mine as all the 20 amp plugs on the servive posts have been GFCI protected.interstingly enough, we just returned from Zion, Illinois where all I could run was one A/C unit and a coffee pot in the morning off of a "30amp" plug. (It was over 100 degrees the three days we were there.)At home when I plug in, I can run BOTH A/c units with no trouble at all. A DVOM is now going into my tool box on all trips. But then again, it's not like I'll get a discount if I complain about low amperage at the post. LOL.
Kevin, If you don't have a Surge guard which displays the current draw I recommend that instead of a DVOM. The DVOM only reads voltage and is not rugged enough to give you current draw. A lot of time the pedestal will read good voltage until you put a load on the line then it drops.
I feel the surge guard is GREAT Electrical damage insurance.
Good luck.

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Old 07-26-2012, 08:50 AM   #15
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X2 on an EMS system our is the other manufacturer, but when we were stuck in this heat with 30amps the EMS helped me sort out what could run together and what couldn't.
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Old 07-26-2012, 08:56 AM   #16
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Thanks Jim and John for the replies, appreciate it.

X3 on the EMS. One of the first things we had installed on the rig so we would be safe from problem pedestals.

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Old 07-26-2012, 11:35 AM   #17
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X4 on that, we bought the "portable" one from Camping World and I feel much more at ease using it now.
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Old 07-26-2012, 11:43 AM   #18
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We use Datel ACM 20 meters. We paid $65 each and wouldn't be without them our our SurgeGuard (older model).

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Old 07-29-2012, 01:13 AM   #19
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A few weeks ago, I took Michael's mod and ran with it. The meters are easy to install and provide alot of useful information as to volts and amps on each leg of your power cables. I found most of my high draw devices were on the same leg ... fixed that issue post haste. The leads need to be lengthened, but Michael had already called the manufacturer and basically phone wire was the remidy. Your microwave, electric hot water heater, toaster, hair dryer, and central vacuum all pull on average 10 - 15 amps each. Factor that in to the A/C (that's one A/C) already pulling 12 - 14 amps on a hot day and you get the picture not to mention 2-3 amps for other stuff also drawing power like lights, TV, converter. For an answer to why you can run more at home ... usually a campground has multiple users that drag down voltage especially as the weather gets hotter. Watching the meters ... amps go up ... voltage goes down. Low voltage makes things run harder. Several years back, I hard wired in a 50 amp Autoformer ... it keeps the voltage up at certain campgronds and keeps my high current draw things happy.
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