whats your thoughts

[Mr.MOD]

i was asked to trouble shoot a residental 100 amp panel seems there is no power at the panel only when a load is applied to either phase.
when i arrived onsite (this is a total diy ho rehab) the only conductors connected to the panel where the direct buried feeders from the 100a meter disc.
it tested good for 120v on each phase to net/grd and 240v between both phases i connected a temp rec to a 15a breaker and pluged in a 3 lt rec tester and it showed correct, i then connected a temp socket w/ 60w incadesent in line. if the load is applied to phase a the 120v goes to 0 and open hot shows on rec tester dido with phase b however 120/240v is always available at the load side of the disconect
i changed the disconect 100a breaker, dbl checked all connections/torques and got same effect
leads me to think there is an issue with the direct buried feeders, i can only estimate the feeders are from 5-8 yrs old.
any other ideas? as all are welcomed

 

[walkerj]

First, before anyone else says anything, you need to use a solenoid tester or "wiggy"

 

[Mr.MOD]

First, before anyone else says anything, you need to use a solenoid tester or "wiggy"

i use a fluke volt/con tester and a digi muiti for accuracy between 120-240

 

[Rewire]

You will probably find the problem lies in the underground feeder most likely the neutral is almost cut through and just making enough contact to get a reading but when load is applied you expierience voltage drop . A quick check would be turn off power and disconnect the neutral at both ends and run a #6 jumper in its place . We had this same issue and had to dig up the old line we found the neutral almost completly cut.

 

[LarryFine]

Mr. Mod, you did a lot of unnecessary work after an incomplete troubleshoot.

The only results that matter are those obtained with loads on both phases.

 

[PetrosA]

I'm going to agree that it sounds a lot like a neutral problem. I'm attaching instructions for one way to safely test it without the risk of sending 220V through stuff in the house (it sounds like that wasn't an issue here). If you can use the jumper method, you can also check the customer's side of the neutral by taking readings at the panel instead of shutting every other row of breakers. It's all about limiting the voltage to 120V max.

 

[growler]

i was asked to trouble shoot a residental 100 amp panel seems there is no power at the panel only when a load is applied to either phase.
when i arrived onsite (this is a total diy ho rehab) the only conductors connected to the panel where the direct buried feeders from the 100a meter disc.
it tested good for 120v on each phase to net/grd and 240v between both phases i connected a temp rec to a 15a breaker and pluged in a 3 lt rec tester and it showed correct, i then connected a temp socket w/ 60w incadesent in line. if the load is applied to phase a the 120v goes to 0 and open hot shows on rec tester dido with phase b however 120/240v is always available at the load side of the disconect
i changed the disconect 100a breaker, dbl checked all connections/torques and got same effect
leads me to think there is an issue with the direct buried feeders, i can only estimate the feeders are from 5-8 yrs old.
any other ideas? as all are welcomed

Dig that feeder cable up and replace it. If you are wrong then it will motivate you to become a better trouble-shooter. I have said it before and I'll say it again, " shovels are motivational in nature". :grin:

 

[Power Tech]

If the DB is aluminum, it turns to dust if there is a nick or pinhole. Get a call from a trailer park with DB/AL almost every time it rains real good.