Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
Gulf Stream Owners RV Forum
 


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 12-25-2006, 05:38 PM   #1
Raymond James
Junior Member
 
Join Date: Dec 2006
Location: Raleigh, NC
Posts: 4
Default 50-amp vs.30-amp.

Margaret and I have taken the giant leap and traded in our 25' Fleetwood Mallard travel trailer for a 2007 Prairie Schooner, which we will pick up on February 19th. That is our decision. That is the earliest we can get up to Martinsburg, PA to pick up our PS. We noticed that unlike the Mallard, the PS has 50-amp. We already know that lots of camp sites only offer 30-amp service. How will this affect us in our 50-amp PS? We read about a pigtail for plugging the 50-amp unit into a 30-amp outlet. Is this safe and will it damage our electrical system? We just began RVing this past year and next fall (after I retire) we will be full timing. We are very excited but we are novices and need all the feedback we can get.

Thanks,

Ray and Margaret
Raymond James is offline   Reply With Quote
Old 12-25-2006, 11:39 PM   #2
djqualls
Senior Member
 
Join Date: Aug 2006
Location: Tecumseh
Posts: 175
Default

Having a 50 amp service is a luxury compared to having only 30 amps available. With 50 you are able to run more accessories than with 30 (i.e. the A/C and Microwave while watching TV and doing laundry). While having only 30 amps you will need to be more power conscience limiting the things you can run concurrent.

I do understand that many parks only offer 30 amps and using a 50 to 30 adapter is safe because you can only use 30 amps thru the system which is sized with wiring to handle 50 amps. You won't be taxing your 50 amp system by stepping down to 30.

While I'm not familiar with Trailers and their appliances and power consumption, I do know that you will look for 50 amp service and enjoy the added convenience that it offers. 20 more amps go a long way in the summer when you don't want to shut down the a/c just to dry your hair and nuke some bacon........

Good Luck

Dave....
__________________
2006 TourMaster T-36 / Good Sams / FMCA 380624
djqualls is offline   Reply With Quote
Old 12-26-2006, 08:32 AM   #3
earljan34
Senior Member
 
Join Date: Jul 2006
Posts: 320
Default

Ray & Margaret, Congratulations on your new GS PS and may you enjoy it for many years to come! Dave gave you the right info on the adapter, I have used a 20amp to keep the batt charged all winter before I installed a 50amp in the back yard. Just don't try to run everything at once when on 30amp and you will be ok.

Earl & Jan
__________________
2005 sunvoyger, # 8368 , 2001 Jeep toad, 1-Wife, 1-Dog Tori the Maltese. FMCA 64574 Good Sam life member


www.IRV2.com, www.RvNET.com, www.thatscamping.com
earljan34 is offline   Reply With Quote
Old 12-27-2006, 08:31 AM   #4
TSoul
Senior Member
 
Join Date: Feb 2006
Location: Carlisle
Posts: 112
Send a message via Yahoo to TSoul
Default

You have gotten good information. However, I would like to clarify something about a 50amp service. 50amps service is actually two 120vac lines. What this means is that you can draw 50 amps on both lines and it will give you a total of 100 amps at 120vac. So instead of having an extra 20 amps from a 30amp plug in you actually get 70 amps more. This is very helpful when one has two ac units or wishes to use multiple electric heaters. Just don't plug those electric heaters into on 15amp or 20amp circuit in the trailer or you will trip the breaker.
I hope this makes sense I wanted to clear things up a little and I hope I did not add to your confusion. Happy Camping.

PS you will love Martinsburg RV they are a great bunch of people.
__________________
2005 GS Crescendo (8356) w/2003 Wrangler toad
TSoul is offline   Reply With Quote
Old 12-27-2006, 03:51 PM   #5
Timothy
Senior Member
 
Join Date: Jun 2005
Posts: 393
Default

Quote:
Originally Posted by TSoul
You have gotten good information. However, I would like to clarify something about a 50amp service. 50amps service is actually two 120vac lines. What this means is that you can draw 50 amps on both lines and it will give you a total of 100 amps at 120vac. So instead of having an extra 20 amps from a 30amp plug in you actually get 70 amps more. This is very helpful when one has two ac units or wishes to use multiple electric heaters. Just don't plug those electric heaters into on 15amp or 20amp circuit in the trailer or you will trip the breaker.
I hope this makes sense I wanted to clear things up a little and I hope I did not add to your confusion. Happy Camping.

PS you will love Martinsburg RV they are a great bunch of people.
You would have 50 Amps at 240 volts. The 50 amp breakers are tied together by code, exceeding 50 amps on either pole would cause the breaker to trip.
When you use an adapter the 2 120volt feeds are tied togethter in the adapter and you have only 120 volts on the mains in the panel where when using 50 amp feed you would have 240 volts across the mains.
Sorry, but 50 amps single phase = 50 amps.
__________________
Tim
Timothy is offline   Reply With Quote
Old 12-27-2006, 05:11 PM   #6
TSoul
Senior Member
 
Join Date: Feb 2006
Location: Carlisle
Posts: 112
Send a message via Yahoo to TSoul
Default

A house dryer is wired at 50 amps at 240 vac however nothing in a motorhome is 240vac and therefore it is wired differently. Each hot of the 50 amp service is on a seperate bar in the breaker box. It provides two lines of 50 amps at 120vac. So 50 amps on line 1 and 50 amps on line 2 equals 100 amps. At the sametime one must never plug into a house 240 line unless it is set up spacifically for an RV. If one would plug a 50amp motorhome in a 50amp dryer outlet one would effectively let all the smoke out of the electronics. And as we all should know the smoke must stay in the electronics in order for them to keep working.
__________________
2005 GS Crescendo (8356) w/2003 Wrangler toad
TSoul is offline   Reply With Quote
Old 12-27-2006, 08:21 PM   #7
Timothy
Senior Member
 
Join Date: Jun 2005
Posts: 393
Default

Quote:
Originally Posted by TSoul
A house dryer is wired at 50 amps at 240 vac however nothing in a motorhome is 240vac and therefore it is wired differently. Each hot of the 50 amp service is on a seperate bar in the breaker box. It provides two lines of 50 amps at 120vac. So 50 amps on line 1 and 50 amps on line 2 equals 100 amps. At the sametime one must never plug into a house 240 line unless it is set up spacifically for an RV. If one would plug a 50amp motorhome in a 50amp dryer outlet one would effectively let all the smoke out of the electronics. And as we all should know the smoke must stay in the electronics in order for them to keep working.
Actually a house dryer is wired at 30 Amps 240 volts, and a house range would be wired at 50 amps 240 volts.
Provided the plug would fit, you could plug your 50 amp RV power cord into the range receptacle and it would work.

Just like your home panel the 50 amp panel in your RV has 2 busses, you would read 240 volts across those 2 busses, and while you may not need 240 volts for any one appliance in a motor home there is indeed 240 volts (limited to 50 amps) at your panel. I am assuming there is a 50 Amp 2 pole main breaker in your panel, if not then the breaker at the power box would be the 2 pole current limiting breaker.

To understand this you have to go back to the transformer that is providing power for the campground or your homes use, most transformers have a 7200 volt primary side with a 240 volt secondary. The secondary winding is center tapped and grounded, thus your would read 120 volts in either direction to ground from the secondary.
The two secondary lines are what provides the 240 volt (hot) power to the main buss or meter socket or whatever and the grounded center tap becomes the neutral.
Looking at your 50 amp rv plug you have 4 conductors, 2 are the hot conductors, one is the neutral conductor and one is equipment ground.
In most homes the equipment ground and the neutral are on the same buss in the electrical panel, however codes require them to be seperated in an RV or mobile home. If you look in your RV panel you will see all the white neutral wires going to one ground bar and all the bare wires going to another that comes from the green wire on your cord. If you have an genset, there will be a transfer switch somewhere too.

Whew, this is getting long winded!! OK now when you get to a park that has only 30 amp service, you plug your 30 amp adaptor into your 50 amp cord. The adaptor takes the 2 hot wires (that you normally would read 240 volts across) and ties them together, so now the 2 busses in your panel box are as one however the ampacity is restricted to 30 amps by the breaker at the feed box. Your cord is plenty big because it can carry 50 amps, so no worries there.

When one side of your panel (one hot wire) is conducting, the other side is not (in a sense) until current changes direction and both are limited to one cycle per second (60hz) so basicly your limited to 50 amps during that cycle. Keep in mind that current flow changes direction once a second and this should make more sense......I hope, I know I'm not very good at explaining things.

I do agree though that if you let the smoke out of your electronics they're toast!!!!
__________________
Tim
Timothy is offline   Reply With Quote
Old 12-28-2006, 09:52 AM   #8
TSoul
Senior Member
 
Join Date: Feb 2006
Location: Carlisle
Posts: 112
Send a message via Yahoo to TSoul
Default

My mistake on the dryer outlet I forgot they were 30amps and not 50 amps. All that you say seems to be correct to me also.
I have a 50 amp service in my motor home that goes thru a surge gaurd that is hard wired ( I totally recomend this set up). Then it goes to a inverter/charger that is 50 amps and puts out 3000W. Now when I run both AC units, on one line each and I run say the microwave or other heavey loads (basically having everything on at once) I draw maybe 30 on one line and 30-40 on the other line and together they excede 50amps. I concluded that because a 30 amp breaker is a single pole breaker and a 50amp is a double breaker then I can pull more amps than just 50amps but not more than 50 amps on any one line. That is why I say there is a total of 100amps. Each breaker of the 50amp allows 50amps to flow thru.
Now I will ad my disclaimer. I am a electronics person not really a proper electician. My research has lead me to believe the above to be correct however, what I have learned maybe flawed. I am not the type to make a hard stand on anyone point and not admit when I am wrong. So please don't feel that I am taking that type of stance here. I will admidt when I am wrong but would like to have good information to learn from so that I know I am wrong. Thanks for your expinations. I hope the original poster got his answer and not more confusion. Sorry if I mucked things up.
__________________
2005 GS Crescendo (8356) w/2003 Wrangler toad
TSoul is offline   Reply With Quote
Old 12-28-2006, 11:11 AM   #9
Timothy
Senior Member
 
Join Date: Jun 2005
Posts: 393
Default

Quote:
Then it goes to a inverter/charger that is 50 amps and puts out 3000W. Now when I run both AC units, on one line each and I run say the microwave or other heavey loads (basically having everything on at once) I draw maybe 30 on one line and 30-40 on the other line and together they excede 50amps. Sorry if I mucked things up.
No no, not at all and there are a few more things in this equation that I didn't know about. I am a little confused about the inverter/charger and the ampacitys that you see when under full load, are you running off of the inverter or shoreline power? Do you have some type of power managment system that is giving you the amperage readings or are you taking actual readings? Hmmm, the other thing is what is the output of the charger/inverter, I think it's probably protected by a 50 amp breaker our fuse but it's true output can only be 25 amps right??? (P/E=I) or am I messing up on the output voltage of the invertor? I figured 120V.
And I messed up on one of my statements it should be that we AC changes direction (polarity) every 1/2 second not every 1 second. (E1=Epk*sinT) can show the two null points in a 1 second cycle (or the voltage at any given point using theta in degrees).
Ach - maybe we should put this subject to bed and go camping!!! Iv'e been in managment too long now and forgotton most of this stuff!!!!!
__________________
Tim
Timothy is offline   Reply With Quote
Old 12-29-2006, 08:50 AM   #10
TSoul
Senior Member
 
Join Date: Feb 2006
Location: Carlisle
Posts: 112
Send a message via Yahoo to TSoul
Default

lol I think maybe this baby needs to be put down for a nap myself.

The Surge Gaurd 50amp surge protector has a monitor panel that displays two incoming lines of amps. That is where I get my amp usage information. It also tracks incoming AC volts.

My RS3000 xantrex inverter also displays the information of amps on both lines. The RS3000 is 50amps and is on a 50 amp breaker. It is not wired to everything in the coach however. So sometimes there is different amps being drawn thru the inverter compared to the entire coach. But the surge guard does a good job of tracking that information anyway.

Now when I am pluged into shore power 50amps or when I run my Genny I get to see how many amps I am drawing on lines 1 and 2.

If I have both AC's running and the inverter/charger is pulling power to charge batteries and then the hot water heater is on electric and we run some tv's and hit the microwave then I often will see a combined amp usage of over 50 amps. No breaker gets thrown because each line is drawing less than 50amps each.

120vac at 60hertz will change polarity 1/sec the sinewave goes high then low in one second. One could also say that it changes directions once every half second. Its 6 of one or 1/2 a dozen of the other. It depends how you want to say it.

The reason a 30amp or even a 50amp rv can not be pluged into a 30amp dryer plug is because it is wired at 240vac and the rv is wired for 120vac and you would have a major melt down if one did that.

A stove outlet is 50amps and wired for 240vac however it has 2 legs that are 120vac and that should be able to work if one would plug there rv into it. Somehow that makes me uncomfortable and I personally would not do it. But I could because both the surge guard and the inverter have sencing capability and would not let electricity in if it was not wired correctly.

As far as your formula P/E=I, I thought it was P=IxE lol just kidding.

The inverter losses some P because of heat loss so the actual amps out would be less by 9% or so. I have 4 12vdc deep cycle batteries and have never tried to draw max power from them. Unless you want to count trying to drive the one overhead AC with them. That only worked for about 5 minutes and it was an experiment that failed. But thats another thread.

As far as a power management system goes. I don't really have one. My equipment will just shut things down if I draw to much. Most times its a breaker. So I am the power manager for the coach. But I do have some nice gagets to help me manage things better.

Thanks for all your responses I think we gave a lot more info than the original poster really wanted. lol Sorry for all the ravings everyone.

I hope everyone had a great Christmas and will have a safe and happy new years.

As soon as Frieghtliner gives me back my coach I will be ready to go camping again.
__________________
2005 GS Crescendo (8356) w/2003 Wrangler toad
TSoul is offline   Reply With Quote
Old 01-27-2007, 10:16 AM   #11
Timothy
Senior Member
 
Join Date: Jun 2005
Posts: 393
Default

I posted this (50 amp) question on all experts and this is the answer I recieved from Bob Thompson, Master electrician.

http://www.allexperts.com/user.cgi?m...34&qID=4606119

The link will probably only work for about 3 days, text is below.

Answered Question


Subject RV service
Question Hi Bob,
Some RV's have a 50 amp service at 220 volts. I have a friend who says that means he actually has 100 amps available - 50 amps on each leg. Is this correct, I argued that if he has a 50 amp breaker that's all he would get is 50 amps because you only have the current for one cycle. Which one of us is right?
Thanks for your help!!!
Tim

--------------------------------------------------------------------------------

Answer Tell your friend to pony up...you are right. That's why it's ALTERNATING current...when one phase is positive, the other is negative and vice versa. You'll only get 50 amps.

Bob Thompson
Master Electrician
Previous business owner.
__________________
Tim
Timothy is offline   Reply With Quote
Old 01-27-2007, 11:28 AM   #12
RJ82much
Senior Member
 
Join Date: May 2005
Posts: 572
Default

Sorry Timothy, but Bob Thompson, master electrician did not fully understand your application. You do have 100 amps total, available for use, at 120 volts, in your motor home.

The way to look at it is thru power analysis. For the techies in our group, I'm ignoring some details, like power factor, etc -go easy on me.

Bob Thompson is correct about the 50 amps at 240 volts. The power of that service is (240 volts) times (50 amps) = 12,000 watts. You have 12,000 watts available to use in any form you wish.

If you're only using it at 120 volt level, then you calculate
(12,000 watts) divided by (120volts) = 100 amps.


OR, suppose you have a really cheap welder. If you set it on a 12 volt AC tap, you will have
(12,000 watts) divided by (12 volts-ac) = 1000 amps-ac !

Please, think of everything in terms of POWER = volts x current which is the same as:
amps = POWER / volts
__________________
Bob

'05 Sun Voyager #8351
https://www.much2see.com/index.html
RJ82much is offline   Reply With Quote
Old 01-27-2007, 11:53 AM   #13
RJ82much
Senior Member
 
Join Date: May 2005
Posts: 572
Default

I need to do a follow up, but wanted it separated from the above. Bob Thompson's answer is just the reason you never want to have a house electricion to do major repairs on your motor home.

In short, in home wiring, at higher "loads", either 120volts (plug-in space heaters, microwaves, curling irons, etc) or 240volts (well pump, cook stove, etc), the higher the load, the LESS current is flowing in your neutral wire! In fact because of this, utility companies often reduce the size of the neutral wire. Electricians are allowed to do this as well. Bob Thompson would confirm that. You have to get into electric theory why, but not here!

In our coaches, when plugged into shore power, the same is true. Since the system is broken into 2 busses, the worst that happens is the neutral carries the same current as the line, till the neutrals combine either at the breaker box or the transfer switch, where it is reduced (subtracted).

The potential for problem occures when you use your generator. There are 2 independent windings in your generator. They are in phase, meaning that there isn't the cancellation that Bob Thompson alluded to. Under these conditions, your neutral will carry the sum of the individual currents where ever the wires are combined in a common run. That can happen at the transfer switch to breaker box under your bed, and it can occure between the generator junction box to the transfer switch. That neutral can see upwards to 100 amps. Don't mean to scare anyone, but a house electrician is liable to wire these segments with undersized neutral wire for these runs because they don't understand.

I realize this is "Blah blah blah" to most of you, but just remember to be careful when you turn your house electrician loose on your motor home wiring.
__________________
Bob

'05 Sun Voyager #8351
https://www.much2see.com/index.html
RJ82much is offline   Reply With Quote
Old 01-28-2007, 10:33 AM   #14
Timothy
Senior Member
 
Join Date: Jun 2005
Posts: 393
Default

Quote:
Originally Posted by RJ82much
Sorry Timothy, but Bob Thompson, master electrician did not fully understand your application. You do have 100 amps total, available for use, at 120 volts, in your motor home.

The way to look at it is thru power analysis. For the techies in our group, I'm ignoring some details, like power factor, etc -go easy on me.

Bob Thompson is correct about the 50 amps at 240 volts. The power of that service is (240 volts) times (50 amps) = 12,000 watts. You have 12,000 watts available to use in any form you wish.

If you're only using it at 120 volt level, then you calculate
(12,000 watts) divided by (120volts) = 100 amps.


OR, suppose you have a really cheap welder. If you set it on a 12 volt AC tap, you will have
(12,000 watts) divided by (12 volts-ac) = 1000 amps-ac !

Please, think of everything in terms of POWER = volts x current which is the same as:
amps = POWER / volts
Bobs response to this below.

Answer 50 amps at 240 volts is indeed 12,000 watts, and it's 12,000 watts spread equally (hopefully) across two legs (A & B) of a normal 240/120 volt single phase service. Each leg (A or B) will "see" half (again, if the loads are equally distributed) of the available power, or 6,000 watts. And 6,000 watts divided by 120 volts is indeed 50 amps, and if you add A & B, you'll get 100 amps, theorhetically, but two problems....one, your 50 amp service WIRE is not designed for 100 amps; and two, if for some reason you had all 120 volts loads, and placed them all on a single phase wire, you'd be overloading one of the service wires, generating a lot of heat, possibly start a fire and your service would fail. This is the practical world and why we "balance" services, but your friend is right in one respect....12000 watts is 12000 watts.

Bob Thompson
Master Electrician
Previous business owner.

And to sum this up, in a perfect situation the neutral would carry no current if the load is balanced, that is why you only need one neutral it only carries the unbalanced load.
This is the end of the argument for me, we are both right/wrong in a sense.
__________________
Tim
Timothy is offline   Reply With Quote
Old 01-28-2007, 11:53 AM   #15
RJ82much
Senior Member
 
Join Date: May 2005
Posts: 572
Default

Ha Ha Ha, I think Bob & Bob both said the same thing, just a different way.

Timothy, you are doing the right thing by questioning & not merely taking either Bob, or Bob's word as gospel.

My (Bob) only cause for wiring concern is if someone adds a generator, or upgrades to a much larger unit than originally installed. Or, if they need to replace their transfer switch & end up with rewiring.

Thanks for the opportunity to post my words as well as read other's.
__________________
Bob

'05 Sun Voyager #8351
https://www.much2see.com/index.html
RJ82much is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 10:50 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
×