Your logic is not true in a campground pedestal. This single-pole miswiring condition can occur in campgrounds that originally had daisy-chained 30-amp pedestals which they upgraded to 50-amp pedestals without running new conductors for split-phase service. Thus the 2-pole pedestal itself can be wired with a single-pole 120-volt service capable of supplying 100-amps or more of current. The 50-amp pedestal breakers are downstream of this, so the 2-pole breaker can supply up to 50 amps for each leg. That becomes additive current up to 100 amps on the neutral, which causes a meltdown. I’ve discussed this at length with all the Surge Protector manufacturers who agree it’s a problem in older campgrounds.
All this time, I would just plug my Progressive Industries EMS-PT50X into the 50 amp pedestal and as long as it returned a code of E0, I thought I was good to go. I know better now.
However, this leads me to two questions. First, even if I judiciously watch the load, I assume using a dogbone to plug into a 30 amp pedestal can present the same issue for the 30 amp neutral? Second, if one continues this practice,, which EMS (50 or 30 amp) is appropriate? I've always used the 30 amp EMS plugged into the pedestal. However, I've read more than one forum response advising the original poster to just use their 50 amp EMS plugged into the dog bone. Thanks!
It should be noted that a 50 amp hookup wired with a single pole service consisting of only one hot conductor from the main service cannot overload the neutral because it will only allow a total of 50 amps of current before the 50 amp breaker would open. Only when two hot conductors are used, both originating at the service but both on the same leg can the neutral be overloaded. Personally I haven't seen this because if you run two conductors you have what you need for 240V but I can see it happening when installed by unqualified persons if the panel is a GE or a (gasp) FPE where 1" breakers can fit adjacent stabs on the same leg. Most modern panels configurations won't allow this and plugging on a two pole breaker would automatically give you 240 volts. Of course I realize you know this but wanted to put it out there for the benefit of some of your advanced readers.
Your logic is not true in a campground pedestal. This single-pole miswiring condition can occur in campgrounds that originally had daisy-chained 30-amp pedestals which they upgraded to 50-amp pedestals without running new conductors for split-phase service. Thus the 2-pole pedestal itself can be wired with a single-pole 120-volt service capable of supplying 100-amps or more of current. The 50-amp pedestal breakers are downstream of this, so the 2-pole breaker can supply up to 50 amps for each leg. That becomes additive current up to 100 amps on the neutral, which causes a meltdown. I’ve discussed this at length with all the Surge Protector manufacturers who agree it’s a problem in older campgrounds.
Great info, Mike!
All this time, I would just plug my Progressive Industries EMS-PT50X into the 50 amp pedestal and as long as it returned a code of E0, I thought I was good to go. I know better now.
However, this leads me to two questions. First, even if I judiciously watch the load, I assume using a dogbone to plug into a 30 amp pedestal can present the same issue for the 30 amp neutral? Second, if one continues this practice,, which EMS (50 or 30 amp) is appropriate? I've always used the 30 amp EMS plugged into the pedestal. However, I've read more than one forum response advising the original poster to just use their 50 amp EMS plugged into the dog bone. Thanks!
Mike,
It should be noted that a 50 amp hookup wired with a single pole service consisting of only one hot conductor from the main service cannot overload the neutral because it will only allow a total of 50 amps of current before the 50 amp breaker would open. Only when two hot conductors are used, both originating at the service but both on the same leg can the neutral be overloaded. Personally I haven't seen this because if you run two conductors you have what you need for 240V but I can see it happening when installed by unqualified persons if the panel is a GE or a (gasp) FPE where 1" breakers can fit adjacent stabs on the same leg. Most modern panels configurations won't allow this and plugging on a two pole breaker would automatically give you 240 volts. Of course I realize you know this but wanted to put it out there for the benefit of some of your advanced readers.
Thanks, Brian
Actually, most RVs have the disconnect on the plus terminal, while race cars have it on the negative terminal.