1

I have an old 225 Amp 30 space commercial flush mount sub-panel in my home with bolt on breakers that has worked for years. Now, there's 120v on one bus and 0 volts on the other bus.

When I remove the leads from the bus, I get 120v on each lead, so there isn't an issue with he wire. It seems I have to replace the panelboard, as when I attach one the lead to the bus the voltage drops from 120v to 0v (the other lead is fine).

I can't seem to find a replacement panelboard for an I-T-E NLA30-3L.

Does anyone know where I might be able to find a replacement?

Are the panel boards repairable?

Is there a replacement panelboard perhaps from Siemens or any other company that will accept the same I-T-E bolt-on breakers so I don't have to replace all of the breakers?

  • 2
    Why not have someone that knows what they are doing check it out first? From your description it does not sound to me like the issue is with the panel. – Speedy Petey Apr 30 '16 at 23:51
  • It sounds like a bad hammer in the main breaker to me. Turn off all the breakers and flip the main on and off 10 times. If it works it won't last long and is time for a new main breaker almost impossible to find or a new panel. Bolt to buss breakers are usually commercial grade so you may be able to find a replacement main. I wold not change out parts from other vendors because it won't be a listed product. – Ed Beal May 1 '16 at 0:32
  • Are you saying the voltage on the incoming feeder leg in question drops from 120V to 0V when you connect it to the main breaker? Also, does this fault stay on the same leg or switch legs if you switch which hot wire goes to which terminal on the main breaker? – ThreePhaseEel May 1 '16 at 0:44
  • How are you measuring the voltage (where are you putting the probes)? – Tester101 May 1 '16 at 1:27
  • I had a friend that is an electrician troubleshoot it after I did, and he came up with the he same results. – Bruce May 1 '16 at 13:46
2

This sounds like a bad connection upstream of the panel. No load, you get voltage - apply a load, voltage goes away.

Try turning off all the breakers on the affected bus, with it connected. Does voltage return?

Try (since you seem comfortable handling the feed wires - right, you do say sub-panel) marking the feeds and see if the problem follows the wire, or stays with the bus. If it follows the wire, the problem is not with the panel.

  • I turned off all of the breakers and voltage at the feed on the problem leg goes to 120v. I thought this might indicate a bad breaker or short on a specific circuit, but it doesn't seem to be the issue, When I turn on any breaker connected to that bus, the voltage drops. When I turn on the breakers one by one, some breakers knock voltage to 0, some to 70, some to 90, two breakers don't create any voltage drop, and one breaker fluctuates to various voltages between 20 and 40. – Bruce May 1 '16 at 14:21
  • Thank you for your answers and suggestions. I appreciate your help! – Bruce May 1 '16 at 14:24
  • Look at the sub-panel feed's connection to the breaker at the upstream/main panel. If that's fine, go looking for junction boxes. – Ecnerwal May 1 '16 at 15:01
  • There is a junction box. Didn't mention it as power in and out of the Polaris taps in the box is 120v on each feed. – Bruce May 3 '16 at 3:41
  • Perhaps this indicates something.... The voltage on every other pair of breakers fluctuates between 0 and 30v even though each feed is 120v. If I remove the load wire from one of these breakers, and turn the breaker on, the voltage on that breaker varies from 108v to 119v. Although not 120v, the voltage increases significantly if there is no load on the breaker. – Bruce May 3 '16 at 3:44

Not the answer you're looking for? Browse other questions tagged or ask your own question.