120v present but no power?

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OK. apprentice question here. helping out one of my best friends with what i thought was a simple problem.

the problem: a guest house in the back portion of his house has an overhead service drop to the SUB PANEL at the cottage. the 60amp sub is fed from the main panel. eventually we are going to trench and put the cottage on its own meter... NO POWER AT COTTAGE!!! i checked all connections to the sub panel. I get 120v at each leg and 240v between them. Everything used to work in the cottage and one minute nothing.

Possible lost neutral? The main panel is new. New breakers all around. New romex at cottage. The only suspect could be the aluminum overhead service wire acting as neutral.

Tomorrow I'm going to splice in a heavy duty extension cord and see if it eliminates the problem. this should be an easy fix but its gotten frustrating!!

ideas?
 

ericsherman37

Senior Member
Location
Oregon Coast
Well if you've got power leaving your main panel and no (or partial) power arriving at your sub panel, then logically there's something going on with the wiring between those two points.

Did this start when the new main panel was installed?

Is the sub's main breaker(s) on?
 
I test 120v/240v all the way down the line. at the main panel lugs, at the 2pole 60a OCPD feeding the sub. at the lugs on sub panel. at the 4 individual 20a breakers feeding the cottage.

the conductors feeding the cottage run in rigid pipe from main panel to back of the house, then spliced with kerneys and above ground to cottage where they are spliced and then run in rigid again to sub at cottage.

DMM says 120v//240v. but when i plug anything in no power? has to be a loose neutral but where? the splices look ok. but the neutral above ground is bare aluminum twisted. has to be it. right?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
If you have 120V from neutral to hot on both legs and 240 across and nothing works then I would guess there is no voltage, or next to none, when there is a load present. Check the voltage with the loads turned on. Sounds like a bad neutral connection that is allow you to read voltage but does not have enough connection to run loads. You should however have 240V loads or those connections are also poor.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired) DINOSAUR
What is your reference for your 120v reading, the neutral or ground ?
(if they are separate)
 
reference is 120v hot to neutral. the sub at cottage has groundbar isolated from neutral. at main they are bonded together. the ovhd conductors have been moving around in the wind and i'm sure its the stupid neutral.

the urgency is that my friend starts radiation treatment next week and he needs to stay in the cottage away from his family (new baby) for a couple of days. we are eventually going to trench and do proper service to cottage.

in the meantime...i'll discard the ovhd conductors and splice in a heavy duty extension cord and see what happens. he only needs lights to work back there while he deals with his treatment.
 
2 insulated one bare. the conductors are exactly as you'd see from POCO.

also i didn't check voltage when under load..cause nothing works...so there really is no load.
 

480sparky

Senior Member
Location
Iowegia
..............DMM says 120v//240v. but when i plug anything in no power?..........


What do you mean by 'no power'? Voltage goes to zero under load? If so, you've got such a poor connection that voltage will show up without a load, but disappears under load. Test with a wiggy and see what happens.
 

480sparky

Senior Member
Location
Iowegia
reference is 120v hot to neutral. the sub at cottage has groundbar isolated from neutral. at main they are bonded together. .........

If you only have three wires coming in, how do you have your neutral & grounds separated in the panel? Either the neutral or the ground isn't hooked to anything.
 
right. no actual ground from main panel. ground is water pipe at cottage. this will be fixed when we do proper service install.

i'll check to see what voltage drops to when i plug in a drill or something. if i have 120v with no load, then plug in a a saw and it drops to zero that means bad neutral? or poor connection of a phase? connections are solid in main panel. suspect is the kerneys...
 

480sparky

Senior Member
Location
Iowegia
right. no actual ground from main panel. ground is water pipe at cottage. this will be fixed when we do proper service install.

i'll check to see what voltage drops to when i plug in a drill or something. if i have 120v with no load, then plug in a a saw and it drops to zero that means bad neutral? or poor connection of a phase? connections are solid in main panel. suspect is the kerneys...


Poor connection in both phases. I'd visually inspect every termination and splice. My guess is there's some aluminum that's corroded.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
reference is 120v hot to neutral. the sub at cottage has groundbar isolated from neutral. at main they are bonded together. the ovhd conductors have been moving around in the wind and i'm sure its the stupid neutral.

the urgency is that my friend starts radiation treatment next week and he needs to stay in the cottage away from his family (new baby) for a couple of days. we are eventually going to trench and do proper service to cottage.

in the meantime...i'll discard the ovhd conductors and splice in a heavy duty extension cord and see what happens. he only needs lights to work back there while he deals with his treatment.
You have have no equip ground to this building if you only have a three wire overhead. Are you sure the neutral and eg bars are isolated? They could be bonded at the cottage in the past but any changes you make may require a 4 wire feeder. Sick people do not tolerate shocks as well as healthy. Be careful with what you are doing.
 
sub @ cottage is bonded to water pipe. we are going to do the trench and feeder underground properly next month. he only needs to stay there for a couple of days until he isn't radioactive anymore. ill re-splice each connection and ditch aluminum conductors.

thanks for the help guys.
 

480sparky

Senior Member
Location
Iowegia
Water pipe is not a ground terminal. It's a grounding electrode, and nothing more. A dead short to ground will NOT trip any breakers.
 

A.D

Member
Location
N.Y.C
you should try using a pigtail and light bulb to test the voltage for 120v....Then use two pigtails in series for 220v. Sometimes dmm give you inaccurate readings
 
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