Sub-Panel Power Present…But It Won’t Work

[Davey4000]

I just completed a sub-panel installation in my new detached garage. I have a problem I cannot figure out. The sub-panel has power, but I cannot get any items to work off of it. I’ve tried a drill and lamp to no avail (both work in the house). Voltage at the sub-panel measures (with VOM) 121V from 1st hot to neutral, 2nd hot to neutral, circuit breakers to neutral, busses to neutral and 240V from hot to hot. Very consistent and expected.

I even wired one receptacle straight off of a breaker to see if I had a problem with my receptacle wiring. I measure 121V by sticking the probes of the VOM into the slots of the receptacle, but it still will not light up a lamp when plugged in. It will, however, light a receptacle tester. By the way it indicates it is wired correctly.

Here is a summary of my installation:

- 200A main panel in house
- Added 100A double pole CB to power garage
- Ran three #2 CU THWN with one #8 ground to a 100A disconnect on outside of garage
- Ran three #2 CU THWN with one #8 ground from the disconnect to the sub-panel in the garage
- Total conductor length = 45’

It just seems odd to me that you can measure the proper voltage at the proper places, but fixtures will not work. This is very perplexing. Has anyone ever heard of a similar situation or have any ideas?

 

[GTS225]

Try checking voltage level at the panel, with a load plugged into an outlet. I've seen instances where the voltage level reads fine, until a load is placed on it and the voltage drops off. This is usually an indication of a bad connection somewhere upstream. (Not that I'm suggesting you missed something.)

Roger

 

[wilbilt]

Check your bus bars where the breakers attach in all the panels. You may have an arced spot that is causing high resistance. Also check the breakers (especially the mains) for arcing on the clips that connect to the bus.

 

[Davey4000]

Try checking voltage level at the panel, with a load plugged into an outlet. I've seen instances where the voltage level reads fine, until a load is placed on it and the voltage drops off. This is usually an indication of a bad connection somewhere upstream. (Not that I'm suggesting you missed something.)

Roger

Thanks for the suggestion Roger. L1=120V, L2=120V with no load connected. L1=240, L2=0V with a lamp plugged into an outlet fed by the L1 buss. What could cause this?

David

 

[rockwithjason]

You have a bad neutral connection somewhere. In a detached garage you should have an independent ground rod or ufer ground bonded to the panel can. You should not have the panel ground bonded to neutral with the green screw provided by the manufacturer. The neutral should come from the main panel and attach to the neutral buss in the sub panel

 

[69Cat]

No neutral return sounds right. Probably have the neutral in the garage actually connected to ground either in the garage or house instead of having the neutral return to the house neutral and so there is no current flow. The readings you are getting are therefore in essence a line to ground reading which reads the same. Its important to make sure the neutrals and grounds are properly connected - not to just make it work, but to make it safe.

 

[Davey4000]

Thanks RockwithJason and 69CAT. My neutral connection in the disconnect panel was loose. I tightened it and the problem was fixed. This forum is a life saver!

 

[rockwithjason]

loose neutrals create havoc on multi wire systems. Happens to the best of us.