I installed a subpanel yesterday (see thread "Installed a subpanel!")
and am now having concerns. I attached EMT conduit to the panel and
subpanel using proper fittings. But the panel and subpanel are painted
with some sort of a grey paint. Does that paint conduct electricity? I
rely on my conduit to be the ground and, obviously, it needs to have
an excellent electrical bonding to the panel and subpanel.
The subpanel is on a 60A breaker.
My common sense suggests that the panel paint is probably conductive
and that since everything else is attached in the same way as my new
conduit, I should not worry. And yet, I would like a clarification.
Don't depend on the panel's paint to be conductive because that is not
likely to be the case. Take the tip of a large screw driver and scrape
away some of the paint before you tighten the locknut. Just back off
the locknut to the end of the threads and scape away the paint around
the knock out, then tighten the locknut. Put the tip of the screw
driver on one of the teeth of the locknut for the connector. Smack the
back end of the screw driver a good rap with the side of your lineman's
pliers or any similar tool. This will drive the locknut down tight and
cause it to bite through any remaining paint on the panel cabinet.
If you really want to make it bomb proof you can buy two bonding
bushings and apply one to the connector threads at either end of the
conduit run. The bonding bushings are fitted with a terminal lug for a
bonding wire that goes to the bonded buss bar in each of those cabinets.
In the sub panel's cabinet that should be the Equipment Grounding
Conductor (EGC) buss bar. In the service equipment cabinet it would be
the neutral buss bar. The use of bonding bushings is only required for
service raceways and raceways enclosing conductors with a voltage of
over 250 volts to ground. Best practice would be to pull a copper EGC
with the circuit conductors in the EMT and terminate it at the bonded
buss bar in each panel's cabinet.
Thanks. My trouble is that I do not see a grounding buss bar on the
subpanel (will check again). There is, obviously, a neutral bar, but
not the grounding one. I know that I cannot use the neutral bar as
grounding bar. Will look again tonight when I come home.
My panel is a HomeLine 6 outlet panel.
I have the same panel in my *detached* garage.
You need to add a "ground kit", and remove the bonding screw in the
neutral bar that shorts it to the metal box. You currently have the
grounds and neutrals on the same bus. This is OK for a service panel
(that's what I have), but not for a subpanel (what you have, but you
wired it like a service panel.)
You need to connect the white neutral wires to the neutral bus and the
bare/green ground wires to the ground bus.
It's is sold as a "Main lug load center suitible for service equipment".
It is up to you to install it correctly as a subpanel OR as a service panel.
Don't forget to remove that green screw from the neutral bar. It's
threaded into the metal back of the panel box. That's important. Tape
the screw inside the bottom of the box somewhere so you don't lose it.
That's a good question. If he ever takes out the subpanel to put in a
bigger one, he'll still have the screw in case he wants to use the old
panel as a service entrance for a new building someday?
In other words, it's probably not very important to keep the screw, but
I would keep it anyway because I'm a packrat. However, it is important
to remove the screw for this installation.
You have to buy and install the separate ground buss for the Square D
product lines. Unlike the GE line they don't have a readily dividable
neutral buss bar. With the GE line removing the main bonding jumper
leaves the buss bar on one side of the cabinet bonded to the cabinet and
the buss bar on the other side insulated from the cabinet so that every
cable has to have one conductor run to the other side of the cabinet. I
prefer the add on ground buss bars because I can have one on each side
of the panel and thus avoid having to run each circuit to the other side
of the panel from were it enters the cabinet.
Thanks, I will need to visit HD anyway, to buy outlets and to return
stuff, and I will look for grounding bar and ask for advice. I will
then use some sort of a clamp to safely connect the conduit with the
grounding bar, without relying on the quality of contact between the
conduit and subpanel body.
I thought that you had originally planned to pull an equipment grounding
conductor along with your two hot wires and neutral? Using the conduit as
a ground conductor is acceptable, but it is also the minimum standard.
To be honest, I forgot about it, did not have the bushings etc. Stupid
I will now go back to what I did, will unscrew the panel adaptors and
scratch the painted surface underneath, just to be safer.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.