3 Phase Electrical

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To4raiden

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I'm a little new to electrical and am going to be working on and agricultural job that has a three-phase electrical control box with 300 amp lines of service for a 20hp pump for grape fields.

The customer wants to run power two double-wide trailers. They had already tapped into one of the lines with Polaris plugs and ran number to wire over to 125 amp sub panel but they were using to run small equipment but not any longer.

They are wanting me to use that sub panel to run power to the one trailer and then tap into another line of service with another sub panel to power the other trailer.

I know almost nothing about three phase systems. Is there any issue with topping into these. My recommendation to the customer was to have pg&e come out and run a new line of service for 200 amps and a sub panel to power the trailers.


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WAS HAVING TROUBLE UPLOADING PICS ON HERE

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Welcome to the forum. Without knowing more about the details of your install, I'm afraid I cant help much. What are the ratings of the subpanels? What are your expected loads? What size wire are the subpanels fed with?


I think I'd start by fixing problems in the existing panels before adding more onto them. The subpanels dont have neutrals and grounds separated, and need some serious shop vac'ing... are the deadfronts missing? Looks like Halloween in there. The brown-orange-brown phase tape and oversized conductor in pic #1 stick out too, as do all those double lugged and cut wires and neutrals grounded to the enclosure, even a black wire in pic #5. What a mess.
 
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First thing before even looking too far into the existing mess, what is the supply voltage?

Mobile homes are generally supposed to be connected to a 120/240 three wire (with ground) supply. If the existing is 208/120Y, though it very well may work, might not be code compliant. If it is 120/240 high leg delta, then you must make sure to not get tied on to the high leg, but otherwise will work assuming there is sufficient capacity.
 
kwired said:
First thing before even looking too far into the existing mess, what is the supply voltage?

Mobile homes are generally supposed to be connected to a 120/240 three wire (with ground) supply. If the existing is 208/120Y, though it very well may work, might not be code compliant. If it is 120/240 high leg delta, then you must make sure to not get tied on to the high leg, but otherwise will work assuming there is sufficient capacity.
Click to expand...

The color coding makes you do a double take and I've seen 250 v fuses used on 480. The transformer appears to be connected 240 and the coil does agree, so that leaves you concern, unless it is a corner ground.
 
ptonsparky said:
The color coding makes you do a double take and I've seen 250 v fuses used on 480. The transformer appears to be connected 240 and the coil does agree, so that leaves you concern, unless it is a corner ground.
Click to expand...
Yes, I did do a double take, but seems to be enough evidence that this is not a 480 volt system. If the loadcenters shown are on the same supply there must be 120 volts, but they are single phase load centers so we still don't know if the source is 208/120 or 240/120. A mobile home would certainly work on 208/120 in most cases, but probably is identified to operate on 120/240.
 
If in PG&E territory it is very doubtful that it's 208Y/120V for a AG service, they love 120/240V 3Ø and if a very old service, 240V 3Ø for AG pumps. The County I reside in did not require inspections for AG for years until the County Counsel informed the Board of Supervisors that that policy did not comply with State law, if you wanted to erect a agricultural structure, all that was required was a $75 permit fee, & no inspections, as long as the property was 5 acres or more. I have no idea if other Counties did the same.
 
norcal said:
If in PG&E territory it is very doubtful that it's 208Y/120V for a AG service, they love 120/240V 3Ø and if a very old service, 240V 3Ø for AG pumps. The County I reside in did not require inspections for AG for years until the County Counsel informed the Board of Supervisors that that policy did not comply with State law, if you wanted to erect a agricultural structure, all that was required was a $75 permit fee, & no inspections, as long as the property was 5 acres or more. I have no idea if other Counties did the same.
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Understandable, especially for limited load applications where they are supplying with an open delta transformer bank.
It is much the same here for AG related services, primarily high leg delta for most less then 250 volt applications. Even if a high power demand - it is mostly motor loads and why wouldn't you want 240 instead of 208 for those motors? If the majority of load is 120 volt loads then you would want to request a 208 volt system. As long as you are not isolated by too far from all three phases of primary distribution they will install 208/120 if you want it, otherwise open delta may be less cost to get to you if you can settle for that.

480 volt systems are mostly all wye systems here, with exception of limited loads or where open delta is more practical for the situation. Most old 480 volt full delta systems are simply remnants of what once was corner grounded systems. One POCO for certain (and the one I work around the most) has eliminated all corner ground services on their system for at least 25 years or so by now. If you have corner ground system within in their service area it is separately derived on the premises and not what they are supplying.
 
iwire said:
Do you have a code section in mind?
Click to expand...
This one, perhaps?...
550.4 General Requirements.

(A) Mobile Home Not Intended as a Dwelling Unit. A
mobile home not intended as a dwelling unit — for example,
those equipped for sleeping purposes only, contractor’s
on-site offices, construction job dormitories, mobile
studio dressing rooms, banks, clinics, mobile stores, or intended
for the display or demonstration of merchandise or
machinery — shall not be required to meet the provisions
of this article pertaining to the number or capacity of circuits
required. It shall, however, meet all other applicable
requirements of this article if provided with an electrical
installation intended to be energized from a 120-volt or
120/240-volt ac power supply system. Where different voltage
is required by either design or available power supply
system, adjustment shall be made in accordance with other
articles and sections for the voltage used.

(B) In Other Than Mobile Home Parks. Mobile homes
installed in other than mobile home parks shall comply
with the provisions of this article.

(C) Connection to Wiring System. The provisions of this
article shall apply to mobile homes intended for connection
to a wiring system rated 120/240 volts, nominal, 3-wire ac,
with a grounded neutral conductor.

(D) Listed or Labeled. All electrical materials, devices,
appliances, fittings, and other equipment shall be listed or
labeled by a qualified testing agency and shall be connected
in an approved manner when installed.
Click to expand...

Also see:
550.11(D)
550.30
550.31
550.32(C)
 
The first thing that concerns me here is that you have never done 3 phase, and someone gave you this project...

No offense, but a 300A 3 phase service run is NOT something that an inexperienced rookie should be doing, other than under the tutelage of a Master or at least an experienced Journeyman. Do you have a C-10 license? I seriously doubt it because in order to get one, you would have had at least SOME experience with 3 phase. So if not, nobody here should be helping you at all, because this is not the place to learn basics, plus that means you are working illegally in California.

I'm going to close this thread in accordance with the site rules, at least temporarily until we mods can discuss whether it's appropriate to let it continue.
 
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