3 phase camp site wiring

rls7201 said:

With all those qualification you should already understand that the only 3 phase that will work in a camp ground is 4 wire 208/120 3 phase.  Energy management systems in 50 amp coaches may not respond well to 208. In an case, make sure and balance the load on the 3 legs. You may want to consult a more qualified electrician, as camp grounds do not use 3 phase for RV hook up sites.

Richard

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EMS systems monitor each leg for for 120 volts only, at my home base where we store the trailer I installed a 50 amp rec that only has one 20 amp 120 line to it and jumped the two lines together and the EMS can care less, same goes when when I use a 50 to 30 adapter.

Denny

Please, let's not give Kevin a tough time. He asked a question in good faith and got jumped on.

TonyDtorch said:

I could be wrong... but I don't think the 50 amp EMS systems ever looks at the two 120 phases as a 220 volt service, (or 208 in this case).

  Instead I think it sees them as two 50 amp 120 volt circuits,  as nothing in a motorhome is 220 vt.... so they can even be the same phase.

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Tony, you are NOT wrong.  The EMS is looking for 120V to neutral and out of phase hot legs, which of course is what a 3 Phase, 4 wire system would provide. 

w5kgt.......I've never wired a campground with 3 phase going to the pedestals....in fact, I've never wired a campground period, but I've been an Electrician for more years than I care to think about.  I'm guessing (because I've never done one), but it seems to me that the obvious way to distribute the loads (thus achieving some possibility of balanced loads) would be phase A and B to pedestal #1 (along with the neutral of course.  Phase B and C to pedestal #2 (again with the neutral), and then Phase A and C to the #3 pedestal (along with the neutral).  Pedestal #4 would then be the A to b, Pedestal #5 would be the B and C, and pedestal #6 would be the A and C.......and so on.  This would give you the best chance of balancing the distribution points.  Of course if there was let's say a camper in slot 1,4,7, and10 with no one in any of the others, all of the load would of course be on the A and B phases of the system....but that is pretty unlikely and unless the campground manager knew exactly how to stack the trailers so that some load equalization was taking place.  But even then, different camper are going to have different power requirements for their rig.

It's really not much different than wiring a 208, 3phase distribution panel in a light commercial setting.....you try to distribute the receptacle and lights equally across all three phases to neutral. 

xrated said:

w5kgt.......I've never wired a campground with 3 phase going to the pedestals....in fact, I've never wired a campground period, but I've been an Electrician for more years than I care to think about.  I'm guessing (because I've never done one), but it seems to me that the obvious way to distribute the loads (thus achieving some possibility of balanced loads) would be phase A and B to pedestal #1 (along with the neutral of course.  Phase B and C to pedestal #2 (again with the neutral), and then Phase A and C to the #3 pedestal (along with the neutral).  Pedestal #4 would then be the A to b, Pedestal #5 would be the B and C, and pedestal #6 would be the A and C.......and so on.  This would give you the best chance of balancing the distribution points.  Of course if there was let's say a camper in slot 1,4,7, and10 with no one in any of the others, all of the load would of course be on the A and B phases of the system....but that is pretty unlikely and unless the campground manager knew exactly how to stack the trailers so that some load equalization was taking place.  But even then, different camper are going to have different power requirements for their rig.

It's really not much different than wiring a 208, 3phase distribution panel in a light commercial setting.....you try to distribute the receptacle and lights equally across all three phases to neutral.

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You are on the right track but i would wire multiple pedestals to each combination with a full size neutral (required by code to handle unbalanced loads) and a ground wire also required by code.

Denny

As far as I know for grounding,  every sub panel is also required to be bonded to it's own ground rod.

TonyDtorch said:

As far as I know for grounding,  every sub panel is also required to be bonded to it's own ground rod.

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Every subpanel is required to have a ground wire back to the man service panel bonded to the neutral that's bonded to a ground rod at that point only.

Denny

rvpuller said:

You are on the right track but i would wire multiple pedestals to each combination with a full size neutral (required by code to handle unbalanced loads) and a ground wire also required by code.

Denny

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If I'm not mistaken, that's what I just said......other than mentioning the ground wire.....which is a given.

There are two entierly different 3-phase systems. and you have not identifierd which is used.

Beyond that I would also suggest professional help... Professional help should know which sytem (Delta or Y are I THINK the names of the two systems) and how to wire them.  I do not.  Well perhaps I do know Y but I do not know if you have that.

Unless someone screwed up big time when they brought the 3 phase in, it's not going to be a Delta system.  With Delta there are no provisions for supplying 120 volt to neutral from all three phases.  In fact, in a normal Delta configuration there is no neutral wire coming from the transformer feed.  With a Wye configuration there are three phases and a neutral.  Voltage values are also different between the two systems.  Phase to phase on a Delta (in this application) would be 240 volts.  Phase to phase on a Wye system would be 208 volts.

Well, it should be evident by now that w5kgt (Kevin) has more than sufficient skills to do the job.  Probably more than many of those who answered.  Sorry for the earlier confusion!

I'm still unclear on just what is being changed or added in this park, since it already has at least some 50A sites. Is it that existing 50A only pedestals are being replaced with 50/30/20 style? Or are more 50A being added?  If simply replacing the existing 50A pedestals, there is already a 4-wire supply to the site and no change in the max load.  But if replacing a existing 30A [only] with a 50/30/20, than the service to the site has to increase from 10 gauge to 6 gauge and 4 wires vs 3, and the max load increases from 3600 watts (120c x 30A) to 12,000 watts (240v x 50A).  But you know that already...

I'm also sure you are aware that you have to have a neutral to each site pedestal, so a 3-phase, 3-2ire source would need to gain a neutral somewhere along the line and become 4-wire.

I've worked at several campgrounds and did extensive wiring repairs & upgrades at two of them that were older and/or improperly wired to begin with. The two that I worked on that had 3-phase power to the park handled the power distribution in  the same manner: The main source supplied multiple 200A load centers and each 200A panel supplied 5 sites with 50A service. The 30A & 20A outlets in that 50A site pedestal are tapped off one of the 50A legs, so do not add to the total load. Supplying 5 x 50A outlets from 1 x 200A panel is the standard 80% load assumption permitted in the NEC, i.e. each outlet is assumed to average only 80% of its rated capacity.

Deleted since there were several posts while I was typing.

He can't type now... he's probably got wire soap all over his hands from pulling four lines of 4 or 6 gauge wire through some 3" schedule 80 PVC.

( I had a J card from IBEW local 11 )

This is a good discussion of RV parks, 208 volts and NEC 551

http://forums.mikeholt.com/showthread.php?t=155244

So, here is a question that is "back on topic" to some extent.  I have a T.H. and it is like most of the trailers/T.H./motorcoaches out there that use the traditional 120/240 volt feed from the campground pedestals.  So my question is this.....Are there a good number of higher end coaches or ?? that actually use 240 volts instead of the typical 50A 120 volt type system?  Or, do the manufacturers of these high end coaches that put 240 stuff in there caution or warn against using them on a 208 type campground feed?

I can't imagine that it is a huge problem nationwide, but then again, I don't have anything in my T.H. that uses 240 volts for proper operation.

Most stuff that uses 240 volts uses it to produce heat, and the only thing that will happen when using a heating element at a lower voltage is it will put out less heat.  A 240 volt clothes dryer will take a little longer to dry your clothes on 208 volts, an electric range with a step type control (low-medium-high heat) will run a little cooler at each setting.  Most likely the differences will be barely noticeable, if at all.  An electric stove with a continuous thermostatic control won't be affected except it will put out a little less heat at absolute high.

The only thing to be careful about is a 240 volt air conditioner, but even here there isn't enough difference between the voltages to worry about.

We lived in Japan for a number of years. The power on base was 120 but it was 50 cycle instead of 60 cycle. The microwave worked but made an awful BONG! noise. And the electric clocks lost 10 minutes every hour.

[quote author=Oldgator73]The microwave worked but made an awful BONG! noise. And the electric clocks lost 10 minutes every hour.[/quote]

LOL we lived in the UK for 32 years; "Mains" power there is 240V, 50 cps (Hz). It used to be fun to have folks relocate from California and vice versa and want to take their favorite electronics with them. In those days, folks' music came from 'turntables' that needed a change of pulley/gear wheel to get the music to play at the right speed.

Lou Schneider said:

Most stuff that uses 240 volts uses it to produce heat, and the only thing that will happen when using a heating element at a lower voltage is it will put out less heat.  A 240 volt clothes dryer will take a little longer to dry your clothes on 208 volts, an electric range with a step type control (low-medium-high heat) will run a little cooler at each setting.  Most likely the differences will be barely noticeable, if at all.  An electric stove with a continuous thermostatic control won't be affected except it will put out a little less heat at absolute high.

The only thing to be careful about is a 240 volt air conditioner, but even here there isn't enough difference between the voltages to worry about.

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Thanks for clearing that up for me Lou.  Like I said, I've never had anything RV related that used 240 volts and was wondering how the RV's that do use it managed to make it work in the 208 volt, 3 phase wired parks.  It makes perfect sense that the only things that need it would be heat producing items.

xrated said:

Thanks for clearing that up for me Lou.  Like I said, I've never had anything RV related that used 240 volts and was wondering how the RV's that do use it managed to make it work in the 208 volt, 3 phase wired parks.  It makes perfect sense that the only things that need it would be heat producing items.

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There are very few RV's that use 240 for anything as built. Some high end all electric coaches do, as well as a few after market conversions, particularly those with residential clothes dryers, but that's about it. There's even a couple of high end RV's that need two 50 amp connections to support all their gadgets...