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Old 11-20-2014, 10:33 AM   #15
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FWIW I would measure it in the MH anyway. The electrician already said the pedestal was good so it sounds like a bad connection at the socket for the cord or the cord or a stuck transfer switch or ... Easiest thing to do is start at the breaker box and see if you need to work backwards up the line. Just be careful!
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Old 11-20-2014, 11:13 AM   #16
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I have seen electricans measure L-1 and L-2 to neutral 120/120 it's good

But never measure L1 to L2 (if not double the first reading or rather the total of the first two, it's bad).

Technically what you have is a centertapped transformer

"Primary winding and it's many turns"
L-1 Secondary -Neutral- Secondary L-2

That is how you get 240 volts divided into two 120 volt feeds, 50 amps, is all you get, but you use those same amps ... Twice. (or rather can) .


To the person who said "Had that problem but it fixed it self"

Two possible answers... ONE loose connection,, Speed bump, pot hole, rail road tracks,, Re-seated teh connector when it bounced.

Two: It is a computer, you shut off 12 volts powering it down, when you restored 12 volts it rebooted,,, properly this time.
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Old 11-20-2014, 12:38 PM   #17
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wa8xym- What do you perceive the problem to be if they did just jumper the two legs out at the back of the 50 amp socket. I see two problems one of which will not bother a lot of people. If you do not have a dryer or some other device in your camper that needs 240 volts to work then it wont matter if they are the same phase or not. OR if the campground wiring is not heavy enough to carry 100 amps of current to your site that might cause the wiring to burn up and some problems from that. Other wise I do not see whether it is 120 volts L-L or 240 volts L-L as long as both legs are 120 volts to neutral. I actually think it is a bit safer for electronics if it is both the same phase. With the normal 240vLL combination if the white neutral wire opens up you could have a situation where your 120 volt electronics gets 240 volts through it. With the 120vLL combination that could never happen.
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Old 11-20-2014, 12:50 PM   #18
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wa8xym- What do you perceive the problem to be if they did just jumper the two legs out at the back of the 50 amp socket. I see two problems one of which will not bother a lot of people. If you do not have a dryer or some other device in your camper that needs 240 volts to work then it wont matter if they are the same phase or not. OR if the campground wiring is not heavy enough to carry 100 amps of current to your site that might cause the wiring to burn up and some problems from that. Other wise I do not see whether it is 120 volts L-L or 240 volts L-L as long as both legs are 120 volts to neutral. I actually think it is a bit safer for electronics if it is both the same phase. With the normal 240vLL combination if the white neutral wire opens up you could have a situation where your 120 volt electronics gets 240 volts through it. With the 120vLL combination that could never happen.

It does introduce the possibility of the coach neutral having to carry up between 50-100 amps under heavy electric usage. The neutral is not designed to carry that load. This overload of the neutral could occur from the coach load center through the transfer switch to the pedestal. It is true that an open or floating neutral can cause serious damage to electrical components.

A well designed EMS like the Progressive that has been discussed will monitor and shut down the connection if these conditions are present.


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Old 11-20-2014, 02:09 PM   #19
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Steve has hit the nail on the head. If the pedistle is not wired correctly the EMS will limit your amps to 30, and it can overload the neutral. Check the power between L1 and L2 it must be around 240 volts. Campground electrician probably checked between L1 and neutral or ground and L2 the same, and said it's good. A common mistake.
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Old 11-20-2014, 03:43 PM   #20
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as always thanks for all of the responses. yes, my coach is set up with a 50 amp plug, I have to use an adapter at any campgrd that only has 30 amps. I have checked everything in the coach, all breakers are on etc. The campground I was at before I arrived here was 50 amp and I had no issues so feel confident it is the campgrd plug. I would move, but I am an Amazon Work kamper and they provide the site. Yes, they now have other sites available in other campgrounds but the hassle of moving, etc hooking up my trailer to go 2 or 3 miles is not worth the hassle for what amounts to 4 more weeks as long as I am not hurting my coach.
Yes, I di have a surge protector at the pedestal and it shows both legs being ok.
Thanks for all of the help, if and when it gets a little warmer here and I have the day off I will check everything at the pedestal with my meter.
You stated you had to use an adapter because the pedestal only has 30 amps. This is why you can only use 30 amps. The adapter splits the single 30 amps to your 50 amp plug. The ems system sees this as 30 amps because the power on the 50 amp plug is on the same phase. To got 50 amps you must have two 120 volt circuits that are out of phase and produce 240 volts when you read across the two legs.
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Old 11-20-2014, 05:25 PM   #21
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It does introduce the possibility of the coach neutral having to carry up between 50-100 amps under heavy electric usage. The neutral is not designed to carry that load. This overload of the neutral could occur from the coach load center through the transfer switch to the pedestal. It is true that an open or floating neutral can cause serious damage to electrical components.

A well designed EMS like the Progressive that has been discussed will monitor and shut down the connection if these conditions are present.


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I have to think about this reason. I have thought about it before but have not done any deep thinking about it. The idea you are conveying is that even though the neutral is the same for both phases they are 180 degrees out of phase so the neutral if both phases had equal current would be out of phase and there is no current flow in the neutral. The only time there would be no current flow is when one phase has a higher or lower current than the other one and then the neutral carries the difference. I see that reasoning I just am not sure how valid it is. I have not thought about why but I dont see where L1 has exactly 42 amps and leg 2 has 43 amps so if I measure the current in the neutral I am going to see 1 amp of current flow. If you think about the current flow in the center tapped transformer the input current is equal to the sum of both currents in relation to the center tap current. So if I have a transformer with connection L1, L2 as the input leads. L3,L5 as the outputs with L4 being a center tap. If I put 100 amps in I am only going to be able to get 50 amps out of L3 L4, and 50 amps out of L4 L5 Now if I measure current at L3 is it going to be 50 amps or 100 amps. I honestly do not know but it will be an interesting topic of conversation with some of my friends.
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Old 11-20-2014, 05:38 PM   #22
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You stated you had to use an adapter because the pedestal only has 30 amps. This is why you can only use 30 amps. The adapter splits the single 30 amps to your 50 amp plug. The ems system sees this as 30 amps because the power on the 50 amp plug is on the same phase. To got 50 amps you must have two 120 volt circuits that are out of phase and produce 240 volts when you read across the two legs.
No, he said:

Originally Posted by Catcoach
I have to use an adapter at any campgrd that only has 30 amps.

He didn't say his current hookup was only 30 amps.

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Old 11-20-2014, 06:02 PM   #23
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FWIW - You are not putting 100 A in. Look at the transformer circuit and you will see you are putting out 50 A @ 240 VAC. The center tap splits the voltage resulting in 180 deg phase shift relative to the neutral. That way you can draw 50 A from each leg but that is still 50 A in the winding and 50 A in each branch.

FWIW 2 any semi competent electrician understands the need for the 240 VAC on the pedestal. If they did not just jack in a premade indicator like a lot of folks here recommend then they probably opened up the pedestal and measured at the socket terminals. That leaves the contacts as a problem as well as the rest of the chain into the breaker box in the unit. That is why I would still open up the breaker box and measure there first. Better yet start at the transfer switch and see what is coming into that then what is going out. Depending on what kind of inverter setup you have there may be a second transfer switch in the inverter.

FWIW 3 I would really be tempted to arrange to plug into the next site long enough to check the wiring. If that works you know it's the pedestal socket. If that does not work it is the MH. Case closed as far as the park is concerned.
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Old 11-20-2014, 06:41 PM   #24
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It does introduce the possibility of the coach neutral having to carry up between 50-100 amps under heavy electric usage. The neutral is not designed to carry that load. This overload of the neutral could occur from the coach load center through the transfer switch to the pedestal. It is true that an open or floating neutral can cause serious damage to electrical components.

A well designed EMS like the Progressive that has been discussed will monitor and shut down the connection if these conditions are present.


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This is correct. If L1 and L2 are the same leg then technically you can only use 6000 watts of power before you overload the neutral or 80% of that so say 4800 watts. A properly wired 50 amp pedestal should provide up to 12000 watts or 80% so say 9,600 watts.

L1 and L2 need to be separate legs for your energy management to see 50 amps. This is for good reason as Steve has said, you can overload the Neutral. There for the energy management has limited you to 30 amps.
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Old 11-20-2014, 08:08 PM   #25
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wa8xym- What do you perceive the problem to be if they did just jumper the two legs out at the back of the 50 amp socket.
I see 3 possible problems, The first, For Reasons STEVE pointed out is the posibility that the Fire Department will come calling. Due to the overload of the neurtal wire which is not rated for 100 amps.

The second is the PCS will sense it as 30 amp service, not 50, requiring an override

And the 3rd is some of the all-electric right might just need the full 240.

Oh, and a 4th (Forgot this cause I already pointed it out)

Recall I said the advantage of 240 volts divided is that the round trip voltage drop is halved due to the same amps being used twice?

Well now its increased

Lets say you are dropping 2.5 volts at 25 amps draw, Both lines are drawing 25 maps.. So your round trip loss is 5 volts, but your volt meters only see 2.5 since they only see one way.

But if you put one wire feeding both legs, now it's 2.5 out, and 2.5+2.5 back (Drop from both sides) so you have 7.5 volts total drop. ON BOTH LEGS.

This may sound confusing but think of this.

You have 3 water lines, each 1/2 inch in diamater

You are pusing water into one line, and sucking it from another,, the third line is connected to the far end of both of thse with a "T". no water flows in this line under this setup.

Now lets reverse the suction line, Now we are pushing water into both lines.. The "Neutral" Pipe, now has to carry the return from BOTH of the other lines,, Major increase in back pressure (Voltage loss).
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Old 11-20-2014, 09:59 PM   #26
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I see 3 possible problems, The first, For Reasons STEVE pointed out is the posibility that the Fire Department will come calling. Due to the overload of the neurtal wire which is not rated for 100 amps.

The second is the PCS will sense it as 30 amp service, not 50, requiring an override

And the 3rd is some of the all-electric right might just need the full 240.

Oh, and a 4th (Forgot this cause I already pointed it out)

Recall I said the advantage of 240 volts divided is that the round trip voltage drop is halved due to the same amps being used twice?

Well now its increased

Lets say you are dropping 2.5 volts at 25 amps draw, Both lines are drawing 25 maps.. So your round trip loss is 5 volts, but your volt meters only see 2.5 since they only see one way.

But if you put one wire feeding both legs, now it's 2.5 out, and 2.5+2.5 back (Drop from both sides) so you have 7.5 volts total drop. ON BOTH LEGS.

This may sound confusing but think of this.

You have 3 water lines, each 1/2 inch in diamater

You are pusing water into one line, and sucking it from another,, the third line is connected to the far end of both of thse with a "T". no water flows in this line under this setup.

Now lets reverse the suction line, Now we are pushing water into both lines.. The "Neutral" Pipe, now has to carry the return from BOTH of the other lines,, Major increase in back pressure (Voltage loss).
ok item #4 is not valid. If it is a 2.5 volt drop at that point it wll be the same in both sides of the 50 amp wire when it gets to the coach unless there is a marginal difference in the wires in the cable.

Like I said in my earlier post I think that what everyone is saying about the neutral makes sense i just have to think about why that is. There seems to be something wrong in thinking that if you have two 180 degree out of phase circuits the neutral could be carrying zero current if they load is exactly the same. I need to think about that for a while.

I also pointed out that if there was a load such as a dryer that needed 240 volts it would not work

I am not sure how a PCS works if you think they work by looking for 240 volts then I do not know enough to argue with that.
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Old 11-21-2014, 04:32 AM   #27
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Gemini,,, Your lack of understanding of electrical issues is clear.

#4 is valid, I explained it two ways, Alas, I know no other way to explain it

If the voltage drop ONE WAY is 2.5 volts, (At the current drawn) then if you have both L-1 and L-2 drawing the same current the voltage drop displayed on your meter, on either leg, will be 2.5 (the one way drop) since the neutral is not carying any current.

But if you put both legs on the same leg, it triples since you now have the voltage drop from Transformer to RV, (2.5 volts that does not change since the current drawn did not change) but the neutral is carrying double the current, thus it has double the voltage drop (5 volts) so you have 7.5 volts dropped total.

THIS IS WHY they use 240 volt divided, at 50 amps and not just a 100 amp line,,, They can use much smaller wire and still get good performance.

Voltage drop is a function of three or 4 things.
1: Current
2: Wire cross section
3: Wire length
4: Wire composition (Copper, Aluminum, Other) and connection quality.

Double the current you need to double the cross section. or you increase the voltage drop.

The neutral is the same as the two hot legs, so with double the current it will have double the voltage drop for the return trip.

If you wish you can take a course in electronics theory at any community college, this will explain it all to you.. And earn you a certificate..

IF
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Old 11-21-2014, 07:15 AM   #28
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FWIW I have never seen a rated conductor for premises wiring that could carry double it's rated current safely. You will get excessive line loss but you will not see the fire department if all the connections are tight.

FWIW2 what bites with electricity is loose connections. The resistance goes up so more heat it generated and in bad cases you get arcing. That is why they check line insulators with IR sensors or noise sensors. In a HV transmission line the problems stands out with the proper gear. For something like a MH where one can pull the plug a finger on the connector can tell one a lot. ;-)
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