how to check volts in plug

[Bryan]

hey guys,
I recently plugged in my bus for the first time, and some of the electronics inside didn't seem to be working properly. I was told the plug at the building was recently installed. We decided to disconnect and use generator because I certainly didn't want to under power and damage anything inside. I have a 50amp plug, and of course adapters to change it to a 30amp 3 pin plug. But how would i know if the building is supplying proper to me, and would my breaker box protect me from under power or damage? Thanks for your input!

I also find it kind of strange that my generator only has 3 wires coming off of it to power the bus, yet my campsite plug has 4 prongs.

[eagle19952]

The four wire at the pedestal in the rv park is 220v AC.
When you add the "adapter" to three wire...it becomes 110v at the 30 amps even if it is in the 4 wire hole.
if your gen is 3 wire it is 110v
the only way to tell what from waht is with a VOM.

[Bryan]

Thank you! So if my generator is 110v... then why do I have a 220v plug for the campground? Maybe I'm completely missing something, but it seems that if my 110 generator was sufficient to power the interior of the coach, why wouldn't I just have a 30amp 110v plug coming out for the campground? Thanks!

[eagle19952]

Thank you! So if my generator is 110v... then why do I have a 220v plug for the campground? Maybe I'm completely missing something, but it seems that if my 110 generator was sufficient to power the interior of the coach, why wouldn't I just have a 30amp 110v plug coming out for the campground? Thanks!

uhmmm...because you aren't the only rig that uses that spot...

is it your campground ??

it takes four wires to safely deliver 220v to an RV..

the adapter knows that and deals with it for you. ... simply put.

[Bryan]

okay, I understand about the campground side, because other RVs have 220 therefore would need to hook to the 220 on the campsite... I'm sorry I may have miscommunicated, I'm referring to the plug on my RV, not the plug at the campground. I think I'm coming to the conclusion that since campgrounds have 220 hookups, mine was converted from a 110 to a 220 plug. Thank you for your help! have a great day!

[luvrbus]

It was probably converted from 30 amp to 50 amps to run both AC at 1 time, the legs split in the box of your coach making 2- 110v legs I doubt you have anything that requires 220 volts, your generator is probably the same 2-110v legs  

[Sam 4106]

Hi Brian.

To make your questions more answerable,  it would be useful to know which of your buses you are asking about. Please include that information.

Thanks, Sam

[Bryan]

Hi Brian.

To make your questions more answerable,  it would be useful to know which of your buses you are asking about. Please include that information.

Thanks, Sam

I need to get in better habit of that!... 1996 Prevost XL

[wildbob24]

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[bobofthenorth]

Bryan here is some basic electrical information that may help you understand your system and the difference between 50 and 30 amp RV services:

As Clifford has already pointed out, it is very uncommon to encounter any appliances on an RV that actually require 220 volts.  Nonetheless, 50 amp services are 220 volts which tends to confuse a lot of people.  You can think of any 220 residential service as a 110 volt "high" leg and a 110 volt "low" leg, the difference between the two legs giving you a 220 volt service.  But more importantly it gives you two 110 volt services when compared to the neutral conductor.  So that's a 50 amp RV service - 2 legs of 110 volts with each leg running through a 50 amp breaker for a total potential power of (50 x 110) + (50 x 110) or roughly 10,000 watts.

A 30 amp RV service on the other hand consists of a single 30 amp leg at 110 volts or roughly 3000 watts.  Which should help understand why large coaches have 50 amp services - the 50 amp service actually delivers more than 3x the power of the 30 amp version.

[Bryan]

Bryan here is some basic electrical information that may help you understand your system and the difference between 50 and 30 amp RV services:

As Clifford has already pointed out, it is very uncommon to encounter any appliances on an RV that actually require 220 volts.  Nonetheless, 50 amp services are 220 volts which tends to confuse a lot of people.  You can think of any 220 residential service as a 110 volt "high" leg and a 110 volt "low" leg, the difference between the two legs giving you a 220 volt service.  But more importantly it gives you two 110 volt services when compared to the neutral conductor.  So that's a 50 amp RV service - 2 legs of 110 volts with each leg running through a 50 amp breaker for a total potential power of (50 x 110) + (50 x 110) or roughly 10,000 watts.

A 30 amp RV service on the other hand consists of a single 30 amp leg at 110 volts or roughly 3000 watts.  Which should help understand why large coaches have 50 amp services - the 50 amp service actually delivers more than 3x the power of the 30 amp version.

Thank you Bob,
It would probably be in my best interest to learn a little bit more about how electricity works. I understand volts, amps, watts... however I've never grasped 110 vs 220 with the legs, neutrals, and grounds. Common sense tells me that since a regular 110 outlet has 3 prongs (power, neutral, ground), that a 220 should have 6 prongs since it is double... but of course that is not the case, it only has 4 prongs, so I'm assuming both legs share the neutral and the ground?

[Oonrahnjay]

It was probably converted from 30 amp to 50 amps to run both AC at 1 time, the legs split in the box of your coach making 2- 110v legs I doubt you have anything that requires 220 volts, your generator is probably the same 2-110v legs  

     That's exactly how I have my bus wired.

...  Common sense tells me that since a regular 110 outlet has 3 prongs (power, neutral, ground), that a 220 should have 6 prongs since it is double... but of course that is not the case, it only has 4 prongs, so I'm assuming both legs share the neutral and the ground?

     Exactly.  They don't *have* to share a single prong and conductor wire but since they're going to be bonded together with all the other neutrals or grounds at a breaker or panel, you might as well.  Why pay for and have the size and weight of two wires and a more bulky plug and socket when one will do the job for you?  (Of course, the issue of "bonding" can be another can of worms.)

[bobofthenorth]

. but of course that is not the case, it only has 4 prongs, so I'm assuming both legs share the neutral and the ground?

That's correct.  The reason that works is because the two power legs effectively cancel each other out when they are loaded.  In a perfectly balanced 50 amp RV service which is fully loaded (ie. drawing 50 amps on both hot legs) there will be zero current flowing in the neutral conductor.  That's why the shore cable only needs one neutral conductor - because it can never carry more than 50 amps which would be the situation if one leg was loaded to 50 amps and the other leg had no load at all on it.

[Bryan]

Thanks guys!!! So the 3 wires coming off of my generator are probably (2) 100v legs and (1) neutral? Where is the ground? Thanks!

[Oonrahnjay]

Thanks guys!!! So the 3 wires coming off of my generator are probably (2) 100v legs and (1) neutral? Where is the ground? Thanks!

       Answer is "that depends".  The generator head may be set up so thatl you will have 120V from the generator.  The wires will likely be black, white, and green (or bare copper ground).  If it's wired to give 240V by using both legs (the individual legs may be split in the wiring or breaker box to give 120V), the wires may be black, red, and white with the ground made or run separately. 
       The only way to tell is to check with a meter.  If you check between any two wires and you have 240V, it is 2 50Amp legs for a total of 100Amp @ 240V.  If you find a hot wire and there's 120V between it and both others but no power between those other two, it is probably 30Amp @ 120V. 
       But here's an important thing, unless you KNOW that the person who installed the electrical equipment in your bus really knew what he was doing, you could have *anything* in there and some of those anything could be dangerous.  If you can't be sure the installer was competent, you need to find someone who is to check out your system and be sure it's set up right.

       One other thing, most electricians will call the thing that's on the end of a wire with the prongs sticking out of it the "plug".  It should be 100% dead when it is not attached to something else -- if it's not, you have a very dangerous condition.  That something else, usually a box attached to a wall with slots or holes in it for the prongs to go into, is called a "receptacle" or "socket".   When you're ready to hook up your shore power cord, you should have the plug end in your hand and the campground (or whereever) should have a socket.  The plug you have must match the socket.  (And we won't even get into the fact that some campgrounds mis-wire their sockets so you can't trust that you have a proper neutral or ground where you should have it -- this is probably another dangerous condition.)  There are testers that you can attach to campground sockets to be sure the voltage is correct and that the terminals are wired correctly and you have safe neutral and ground connections.  Everyone should have one of these testers and know how to use it (or know how to use a meter to accomplish the same thing) before you attach your bus to the pedestal.