I
I was wondering? if your main panel has ground bonded to panel & neutral bus bonded to
panel. wouldn't you still have a unsafe condition? that is if a neutral came loose wouldn't you have a ground that would go back to grounded appliances & ground on receptacles? a chance of shock to customer?

You here so much about this in a grounded neutral in a sub panel, you would
think the same condition would exist in a main panel that is in house with neutral bonded to ground...

Thanks for you time GM !

 

The neutral-ground bond occurs in the "main" panel, where you also have very good earth grounding and a neutral path back to the utility company. There is a very low chance of a problem at the main panel or at the meter causing a shock, compared to the risk of a subpanel installed out in the building which might have appliances like cloths dryers or water heaters could create a shock hazard between energized conductors and grounded plumbing or concrete floors.

The bond in the main panel also provides a low resistance backup path to force the main breaker to trip in the event of a hot-ground contact out in the building's wiring system.

 

The electric does not attempt to go uphill back to the appliances. It wants to get back to the source.

 

I can think of only one scenario where a loose conductor would cause an unsafe condition. That is where a 3 wire 240/120 dryer or range has its neutral become disconnected, at the panel or appliance. I will exclude a service open neutral that may expose lights and other equipment to far above 120volts. Incandescent lamps could shatter, i suppose.

 

Dryers and ranges have been required to be 4-wire 120/240 volt circuits for 19 years. You shouldn't find a dryer or range 3-wire circuit in a home built since 1996 except in some cases where the 1996 NEC wasn't adopted right away.

 

Hi again!
thanks so much for the reply's...what I have been seeing in NW Ohio is the power
company AEP is upgrading to under ground service. there is a lot of the customers that now have a service with a service & breaker. they have left the panel inside as they were with bonded net & grounds (same building) the customers I spoke to said the reason is the have shared wires ground & net, on sane bus bar
They say that AEP just had them add a service disconnect & it would be ok as they are.
Seems to me that is not correct. old main panel should be now a sub panel....

Thanks again for the help.......

 

If a disconnect has been set between the meter and the old panel, the disconnect is now the service where the neutrals and grounds and grounding takes place. The old panel now need to have the grounds isolated from the neutrals and a 4 wire feeder installed.

 

I'll add this advice is per the NEC (national electric code), which is only a model code. Your state or local government, or power company may have modified the national code to make the exterior disconnect practice legal with a three wire feeder in your area. The safety of the situation is hard to measure, but the legality is probably much more straightforward.

 

Thanks again!
I don't know why the power co. claims they are ok......Everything I have been taught is the same as your reply!....thanks for all the help. I will contact customer......GC

 

Maybe it was just the wording, but this has bothered me since this thread was started. Your neutral bus should be directly grounded by the Grounding Electrode Conductor and the neutral bus is then bonded to the panel box usually by means of a bonding screw or sometimes with a bonding strap.