โJan-03-2014 07:56 PM
โJan-09-2014 08:16 AM
BurbMan wrote:This is the reason you find a double pole c/b on the pedestal and in your trailers load center for 50 amp service. Been that way for decades.
Interesting stuff! It never occurred to me that a faulty neutral could create voltage fluctuations in a split phase set up like a home or RV but makes perfect sense the way it's explained.
Interested to see if OP can locate the problem, and if so whether it was in the RV or on the supply side.
Previous S&B house in NY had a 12/3 running from the main panel to the 2FL where it split into two 15A bedroom circuits with a shared neutral. Was AL wire to boot!
Found this from a Square D tech bulletin, note second bullet:
There are several significant disadvantages to be found in the practice of
sharing neutrals:
โข On two-pole common-trip circuit breakers, both circuits are interrupted
during any type of fault. If a shared neutral circuit feeds many rooms,
then all rooms lose power if a fault occurs in any one room. If a shared
neutral circuit feeds receptacles and lights, both will lose power with a
fault on either one.
โข If the homerun neutral is lost, the connected loads are subject to
voltages varying from 0 V to 240 V (line-to-line). The likely result
from this is severe damage to any connected devices due to extreme
under- and over-voltage conditions.
โข On two-pole independent-trip circuit breakers, one may find hot wires
in a junction box that was presumed dead. One cannot overemphasize
how dangerous this would be. If one of the shared neutral circuits were to
trip due to a short-circuit or overload, the other circuit would remain hot.
Anyone servicing any device in that junction box may be exposed to
live conductors.
The NEC still allows shared neutral circuits, but I believe it now requires them to be on a common-trip double breaker to avoid the hazard identified in the 3rd bullet above.
โJan-09-2014 07:56 AM
SDrummer wrote:
So I went ahead and unplugged everything from the outlets and turned off all the lights. I measured the voltage with nothing on and it was 117V.
I then turned on the AC and measured the voltage again at the same outlet and it increased to 118.5V.
I checked all the outlets and on the ones I could get a reading it was the same around 118.5V.
However on two of the GFI plugs, the one in the bedroom and kitchen, The voltage readings kept fluctuating between 0V & 5V. I then turned off the AC and measured the voltage however the voltage did not change and was still fluctuating between 0 & 5V.
My girlfriend had been using the plug in the bedroom for her curling iron just fine thirty minutes prior to me checking the voltage.
โJan-09-2014 07:06 AM
โJan-09-2014 06:19 AM
โJan-09-2014 06:12 AM
wa8yxm wrote:
If both hots were on the same leg.. Then he'd not have this problem with imbalance, and if he had an open neutral he'd be seeing LOW voltages all around.
NO, that's it not the problem. Please consider what you are typing before misdirecting.
That said: What you typed is 100% correct and true.. Just not the problem in this thread.
โJan-09-2014 06:11 AM
CA Traveler wrote:wnjj wrote:Both of these posts are incorrect.JimM68 wrote:
ok, read the first half of the first page. Rig is a 50 amps with an open neutral.
OP is not qualified to fix this.
Things will continue to blow up. Recommend an electrician. unfortunately, most electronic / computer types just have no clue about a/c power, particularly 2 phase stuff. (and yes, generally 50 amp rv power is 2 phase, even though it doesn't need to be and is not specified to be.
If 50 amp RV power uses a 4-pin plug, it had better be 2-phase. If both hots are on the same phase the neutral wire needs to handle twice the current which it likely isn't capable of. The only safe way to use such a system with a neutral wire sized for 50 amps is to use a double pole 25 amp breaker.
50A RV power is in fact single phase. 240/120V power comes from a SINGLE center tapped winding on a transformer with the center tap being the neutral. As such current in the winding and hence both hot legs flows in one direction or the other and can only be single phase.
The neutral does in fact handle only the difference of the two hot leg currents which with the dual 50A CB restricts the neutral current to 50A in this SINGLE PHASE system.
50A RV power is not multiple phase power like you might find with a Y or Delta configuration.
50A RV power is also the same at the typical household power except that the typical home has a bigger panel like 200A. Otherwise both are single phase.
It's very common but incorrect to refer to 50A RV power as 2 phase. Split phase is a good description of 50A power.
โJan-09-2014 05:51 AM
wnjj wrote:Both of these posts are incorrect.JimM68 wrote:
ok, read the first half of the first page. Rig is a 50 amps with an open neutral.
OP is not qualified to fix this.
Things will continue to blow up. Recommend an electrician. unfortunately, most electronic / computer types just have no clue about a/c power, particularly 2 phase stuff. (and yes, generally 50 amp rv power is 2 phase, even though it doesn't need to be and is not specified to be.
If 50 amp RV power uses a 4-pin plug, it had better be 2-phase. If both hots are on the same phase the neutral wire needs to handle twice the current which it likely isn't capable of. The only safe way to use such a system with a neutral wire sized for 50 amps is to use a double pole 25 amp breaker.
โJan-09-2014 05:43 AM
โJan-08-2014 07:52 PM
JimM68 wrote:
ok, read the first half of the first page. Rig is a 50 amps with an open neutral.
OP is not qualified to fix this.
Things will continue to blow up. Recommend an electrician. unfortunately, most electronic / computer types just have no clue about a/c power, particularly 2 phase stuff. (and yes, generally 50 amp rv power is 2 phase, even though it doesn't need to be and is not specified to be.
โJan-07-2014 03:19 PM
โJan-07-2014 02:24 PM
โJan-07-2014 12:47 PM
Wayne Dohnal wrote:But thats redundant... ๐generally 50 amp rv power is 2 phase,Wow, you're likely to get a few pages of flogging for saying this. Been there, done that. It's even worse than saying "hot water heater"!
โJan-07-2014 12:19 PM
โJan-07-2014 12:07 PM
generally 50 amp rv power is 2 phase,Wow, you're likely to get a few pages of flogging for saying this. Been there, done that. It's even worse than saying "hot water heater"!
โJan-07-2014 11:18 AM