highpowered
Member
- Location
- los angeles
I had a call on a overheating panel on this system. I have never seen this system in use before and dont know much about it. Has anyone worked with this before? Any suggestions on troubleshooting?
Delta corner ground system
- Thread starter highpowered
- Start date
- Status
As far as overheating is concerned I don't know of anything unique about the system that would cause a problem. The usual culprits of overloads and loose connections would be suspect just like any other system. Can you provide any specifics ?
highpowered
Member
- Location
- los angeles
Yes went there 12am. The voltage to ground on the system is 110/208/110 3 wire. Im not sure if this is a corner grounded system or a y there are no labels. phase to phase its 213v/244v. interesting thing There are 2 small 100 amp, year 1925 transformers connected to the 110 legs(1 for each leg). only thing I can make out is 100 amp ratio 20? I have no idea why they would put those on there? They are mounted in a 6x8 pull box and go up to the meter in #10awg wire. The system is 2/0 i believe its in rag wire hard to make out. They have them on 200amp breakers witch i think someone changed the amps. i proposed ripping it all out and puting a new meter/panel in. My concern is that those transformers burned up they bypasssed them then had this heat up problem. I have no idea why those transformers where in line my only theory is the old meters where not made for big gage wire so they installed the transformers to connect meter??? Also what the proper way to ground this system (2 ground rods continuos cold water bond?
Last edited:
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Your system is not a corner grounded delta.
You have a center tapped delta, often called a High leg or Wild leg system.
It would be called a 240/120V (3-phase, 4-wire), per ANSI standards, although many utilities call it 120/240 3-phase.
The nominal system is:
L-L = 240V,
A-N = 120V,
B-N = 208V,
C-N = 120V,
There are several different ways to get this system, the most common being (1) small transformer and (1) large center tapped transformer, although some utilities might have used (2) small transformers instead of the large one.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re-reading your OP it sounds like your are talking about (2) current transformers that may have been part of a metering circuit.
Are you saying these CTs failed, and then were bypassed? By who? How is the metering being done now?
Have you talked to the utility about this install?
There is no special consideration needed for grounding this type of service.
Are you saying these CTs failed, and then were bypassed? By who? How is the metering being done now?
Have you talked to the utility about this install?
There is no special consideration needed for grounding this type of service.
highpowered
Member
- Location
- los angeles
yes the CTs failed burned up completely. There are numerouse wiring problems with the subpanel that is connected to this meter.
1) using 3/0 in seperate 3/4 to 1" conduits per conductor.
2) since there is no nuetral on this 3 wire system they grabed a nuetral from the seperate single phase panel in the same building and ran it to the sub for the 3 phase 3 wire.
numerous bolt on clamps patching the wires.
3) the sub panel thats loading off the 3phase is operating at 150amps per leg 16hrs a day sometimes 24 hrs. at this rate the ampacity should be jumped up to at least 125%if not 300%. (I was thinking run parrallel 3/0 to fix this)
4) I dought that the conduits are bonded to said subpanel.
as far as the utility owner does not want permit so I cant upgrade the power to 400 amp or even 250 but I can replace failed parts with new ones without permit. The owners "electrician" did the work on this to bypass CTs. Looks like he ran sub-panel as well. By all means if I had alot of work right now id tell him to take a hike he is to cheap for me to fix this but I gotta pay the bills
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
If these were utility CTs why are they feeding a subpanel?
Do you have a Service Entrance panel that is 240/120V 3-phase 4-wire with a proper neutral (even if it is neutral only between two lines)?
Is your problem panel a 3-phase 3-wire branch circuit panel fed by the service panel?
Single conductors run in individual metallic conduits are likely to overheat.
highpowered
Member
- Location
- los angeles
this is the service entrance. The service conductors go into a 3 phase fused disconnect. from there they go into a 12x8x8 cable tray where the 110 lines go into the CTs and 208 line feeds thru to a 10 ft cable tray that has various splice points for abandoned disconnects. The meter taps into the first cable tray CTs before it goes into cable tray. There are only 3 wires coming in from the service attachment point which is why I thought it was a corner ground untill I read the voltage. The nuetral they took is from a seperate service drop in a seperate electrical system in the same structure single phase. yes the 3pase bcircuit panel is the problem it is the only load on the above service.
Sounds like a disaster in the making.
Keep in mind, IF you do work on it without permits/inspections and it eventually fails, which seems likely from what you say, the one thing the owner, his lawyer and your local enforcement will remember is that YOU "are their electrician".
The dollar you make today on this type job may cost your 10 X that in the future.
Keep in mind, IF you do work on it without permits/inspections and it eventually fails, which seems likely from what you say, the one thing the owner, his lawyer and your local enforcement will remember is that YOU "are their electrician".
The dollar you make today on this type job may cost your 10 X that in the future.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
If you do nothing else, you should get rid of this 'neutral'.
If the service was really only 3-wire, it is possible it could have been metered using only 2-CT's.
highpowered
Member
- Location
- los angeles
Sounds like a disaster in the making.
Keep in mind, IF you do work on it without permits/inspections and it eventually fails, which seems likely from what you say, the one thing the owner, his lawyer and your local enforcement will remember is that YOU "are their electrician".
The dollar you make today on this type job may cost your 10 X that in the future.
Well said I have pictures and emails of my concerns and his responses
iphones n email r my best friendshighpowered
Member
- Location
- los angeles
is this possible to just have the system ive descibed without a nuetral? the messanger wire from the pole is not hooked up should I run 1 from it???
ptonsparky
Tom
- Occupation
- EC - retired
Go fishing. This sounds like a mess.
highpowered
Member
- Location
- los angeles
Thanks everyone I will be paid a fee to advise him on this what he does with the advice is up to him. I will not be touching this physically at all. I'm advising he updates service feeders, adds meter load center and transformer to add nuetral. Add ground rods(2 rods are requiered by LGJ) cold water bond and new subpanel with proper pipe size and wiring.:thumbsup:
- Status