Deriving 110V power from 220V three wire

[iwire]

You will not be able to change others mindset.


I recommend you and your wife purchase a generator to power her stand so that you do not get connected incorrectly to a power supply.

 

[mastersean]

generator recomendation

generator recomendation

We use a generator often, but some venues don't allow them due to noise, this is one of those.

Thanks

 

[Strife]

I'm very confused about a common practice here in Nevada, My wife runs a concession trailer and typically goes to municipal venues such as concerts, fairs, etc.. Typically she tells them the power requirements for the concession trailer as a 30A 2p 4 wire L14- 30R plug 220V. We have equipment on board that is 220V and others that are 110V thus the 4 wire requirement. At some events they tie us into their on site lighting distribution system which is 240V 3 wire system. To accomodate the vendors they rent distributon boxes for everyone to plug into. They use the ground as the neutral for the 110V breakdown and in my opinion eliminate the safety by eliminating the grounding safety net. I believe they also render the function of the required GFCI protection pert near useless. They also do not modify any of the service equipment at their main distribution panel, I'm sure somewhere along the line the neutral and ground are bonded but isn't this a little to old school for modern code requirements? My wife uses a trailer which has it's own equipment ground but what about the vendors who are plugging into receptacles and running equipment off the GFCI circuits provided assuming they have ground protection from surge and ground faults? What am I missing here and what specific NEC code is not being followed? I sure would appreciate any input this just doesn't smell right on many levels and I would like to help them correct this issue before someone gets killed.
Thanks

Isn't this the same as hundreds of millions of stoves and dryers with 3 wires instead of 4? Sure new code requires a neutral, but WHY DO YOU THINK they still sell cords and receptacles with 3 wires?
Or isn't it the same as billions of dimmer switches with only two wires and a ground? Sure, part of reason new code requires a neutral to switches.
As far as the GFCI.... I'm not sure what's the problem with that? A gfci compares what goes out with what comes back, if it's more than 5 MA difference it trips. Regardless if it's a grounding or grounded conductor.
Keep in mind you're talking a temporary situation. The EGC is mainly designed as a redundant fault carrier(the neutral would trip the fault just as well, but the EGC is used as a redundant measure, in case the neutral fails, which does happen)

 

[hurk27]

I'm very confused about a common practice here in Nevada, My wife runs a concession trailer and typically goes to municipal venues such as concerts, fairs, etc.. Typically she tells them the power requirements for the concession trailer as a 30A 2p 4 wire L14- 30R plug 220V. We have equipment on board that is 220V and others that are 110V thus the 4 wire requirement. At some events they tie us into their on site lighting distribution system which is 240V 3 wire system. To accomodate the vendors they rent distributon boxes for everyone to plug into. They use the ground as the neutral for the 110V breakdown and in my opinion eliminate the safety by eliminating the grounding safety net. I believe they also render the function of the required GFCI protection pert near useless. They also do not modify any of the service equipment at their main distribution panel, I'm sure somewhere along the line the neutral and ground are bonded but isn't this a little to old school for modern code requirements? My wife uses a trailer which has it's own equipment ground but what about the vendors who are plugging into receptacles and running equipment off the GFCI circuits provided assuming they have ground protection from surge and ground faults? What am I missing here and what specific NEC code is not being followed? I sure would appreciate any input this just doesn't smell right on many levels and I would like to help them correct this issue before someone gets killed.
Thanks

I really intended to state the following conditions they (the event) are distributing 240V power comprised of 2 - 120V legs "A" and "B" from the service which has a neutral "C" , so it's probably a 120/240V 4 wire delta single phase. At the distribution junction #5 pull box that they have connected in the vendor service distribution box,, there's only 2 - 120V legs and a ground that run back to the main. It is strictly intended to operate 240V load only no neutral is present or required for that purpose. However they went in my opinion a little " Old school" by being able to derive 120V branch circuits for the vendor connection by using the Ground , thereby energizing the ground back to the neutral / ground bond at the main panel. There's no seperate ground in the distribution, no ground rod, no transformer in the distribution box creating it's own neutral. I had to change my 4 wire L14-30P plug (30Amp 125/250V rated 3P 4 wire) out to a three wire L6-30P (30Amp 250V 3P 3 wire) eliminating the ground and connecting the neutral wire to the ground screw on the plug, essentially cheating my panel inside the trailer to think that it's getting 2 120V branch feeds, which it is but my contention and question is "IS THIS SAFE"? and if not how many specific NEC violations have just been committed? Please site specific code article to win the booby prize.
Thanks ,
sorry for the confusion on the first pass and for potentially the second

Isn't this the same as hundreds of millions of stoves and dryers with 3 wires instead of 4? Sure new code requires a neutral, but WHY DO YOU THINK they still sell cords and receptacles with 3 wires?
Or isn't it the same as billions of dimmer switches with only two wires and a ground? Sure, part of reason new code requires a neutral to switches.
As far as the GFCI.... I'm not sure what's the problem with that? A gfci compares what goes out with what comes back, if it's more than 5 MA difference it trips. Regardless if it's a grounding or grounded conductor.
Keep in mind you're talking a temporary situation. The EGC is mainly designed as a redundant fault carrier(the neutral would trip the fault just as well, but the EGC is used as a redundant measure, in case the neutral fails, which does happen)

Strife in his post 13 I copied above you will see in red that he has not connected the EGC from the trailer to anything and being that it has no bond to the neutral anywhere then there is no return path for fault current, while bonding the neutral and EGC together at the cord cap would be the lessor of the two evils I cant not tell him this in a public forum for liability reasons of the forum as it is also a violation of code to do so, but since a fault is more likely to happen then a loss of the neutral then as it is now if a fault was to happen it would liven up the entire trailer to earth which could cause someone to be hurt or killed, this is why I strongly suggested that something needs to be done to correct this dangerous situation, the EGC needs a fault return path, that is the most dangerous part, and if anything this needs to be addressed ASAP!!!

Yes 3-wire appliance were and are still allowed to continue, but they are depending on the neutral connection to carry the fault current, if there is any voltage drop in the run back to the panel and the home owner just happens to be toughing the washer and the dryer when it occurs they could be shocked, now through in a bad heart or a young child and you just might end up with a death, also remember a 3-wire connection was never allowed from a sub panel and if you understand electrical theory you will understand why most cases it means a longer run which means more voltage drop resistance that will increase the voltage between two separately grounded appliances.
we also have to realize that since all services are in reality a 3-wire the same danger exist if the neutral connection is weakened or loss-ed, as anything that is grounded to this neutral will have an elevated voltage to earth, I wish they would require even a 4 wire service from the transformer, but we know that will not happen because the utilities will fight it because their lack of understanding the danger or putting cost over safety.