Hi there!

I had a scary moment today when I moved the aluminium dryer duct (hot air vent) which is connected to the wall vent right above our electrical breaker panel. When the duct touched the breaker box housing in the process, blue arcs started to spark pretty heavily. In the past the dryer duct had already touched the breaker box and this never happened before. What could be the reason for this?

Thanks!

 

Welcome to the forums!

Do you know if the dryer is grounded? Do you have an electrical meter handy?

 

Hi! Thanks for your quick reply. I actually forgot to mention: the duct was not connected to the dryer at the moment I moved it...

 

Please post a couple of pictures of the area so we can better understand. http://www.doityourself.com/forum/li...rt-images.html

 

It would also be wise to turn off the main breaker and remove the duct to see into the area.

It would appear that the duct is connecting your grounded (hopefully) panel to a live wire.

 

Hi,

here's a picture of the area:



The red circled area is where the duct touched the panel. It did this (the arcs) twice in a row, since then however, it didn't do it again when the duct touched the box afterwards... The panel is a grounded 200 Amp panel that has been newly installed when we moved into the House 6 years ago. The cabel that you see behind the duct is a 240V cabel for said dryer. It is grounded and there are no bare wires or anything. There are a couple of old electrical 120V circuits that are not grounded however, which I intend to have replaced soon. I'm in the process of renovating our basement, and I created some new outlets and lights, which I actually connected to those ungrounded circuits, properly connected with cable connectors inside metal connection boxes. I still connected and attached the new 14/2 ground wires to the outlet/light boxes as required, so that everything will be grounded once those old base wires from the panel are replaced. So I'm not sure if that can be part of the problem, although I doubt it... I verified the ground on those other circuits from the panel, that are grounded, with a voltage tester just to be sure, and there definitely is ground in those.

 

Hi again,

I'm actually wondering: there is an old outlet on the same wooden panel than the breaker box:



This outlet is not grounded. I used it just prior to the incident with a wet dry vac. Could it be that somehow the panel got charged while running the vac since there is no ground? At the same time the breaker panel itself is grounded, so I don't know...

 

No reason that would happen. Panels don't become "charged". It appears to have been the low voltage terminals on the door bell transformer.

 

Oh, now that's interesting... So the transformer sitting on the breaker box would charge the housing with low voltage, resulting in those arks...? I mean, the duct didn't touch the transformer, only the corner of the breaker box. Buy still, wouldn't the charge then go through the breaker boxes own ground connection? And why did this only happen twice and not anymore the next time? In any case, I would guess it would be safe to replace that transformer with a new one, right?

 

As said before there is no such thing as charging the breaker box. If the duct didn't short the transformer I'm out of ideas.

 

I never assume a panel is grounded without checking it first. I've seen many residential services where the neutral bonding screw or strap was never installed.

 

Do my eyes deceive me or is that panelboard sitting on the floor? I'm too lazy to look it up but isn't there an NEC requirement that the lowest CB must be a certain distance above the finished floor?

 

The original pictures showed the panel mounted Canadian style, sideways. I turned them but I just just noticed he is in Canada so maybe it is sideways. Maks, did I screw up. Is the panel mounted sideways?

 

From Post #1

I'd say the panel is mounted sideways for sure.