Additional ground bar

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Jack Hass

Member
Location
NY
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I would like to add an additional ground bar to the panel. The panel is a Murray LC3040B1150. On the panel door it says to use the LX series ground bar and mount it on the right side under the neutral bus. I went and got the LX ground bar from the supply house. Problem is, none of the existing holes line up with the mounting holes on the ground bar. So I drilled and tapped one hole, and used an existing hole for the other screw mount. On the hole I drilled and tapped, I cannot get the screw to the proper tourqe of 24-30 in-lbs. Is there anything wrong with putting a locknut on the back of the box? Or should i just try a larger self tapping screw? Note, the black screws are not what came with the ground bar, they are the same screw size though, just longer. Had them in my parts box. Thoughts?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Well, aside from the obvious issue that if you no longer have access to the box once installed you will never be able to either remove or retighten the screw, there is one other question:
If one or both screws will be providing the electrical bond between bar and enclosure, will it meet the technical requirements for number of threads engaged?
An existing hole for that purpose might well be formed to provide additional metal depth. (Actually you can see this in the second photo.) Your drilled hole will not.
You are correct to use a self-tapping (thread forming) screw instead of a sheet metal screw.
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Any idea what to use to tighen the drilled hole?
Not really. A tee-nut inserted from the back would not let you mount the bar flush.
My inclination would be, as long as you are using one existing hole with sufficient thread depth, to put in an oversize screw and leave it at that. But make sure that you use fine threads. You still may not be able to get to the required torque on that screw, but as long as the other one is OK I would say no big deal.
An inspector might want to see you using a green screw for the existing hole although the NEC does not, AFAIK, care.
 

kwired

Electron manager
Location
NE Nebraska
If you are adding an additional bar - that should mean the box is already bonded by what is existing. Why not just run a bonding jumper to this new bar from an existing one, move a conductor or two to the new bar if needed to make room for bonding jumper on existing, and not worry so much about how it is attached to the cabinet?
 

Jack Hass

Member
Location
NY
If you are adding an additional bar - that should mean the box is already bonded by what is existing. Why not just run a bonding jumper to this new bar from an existing one, move a conductor or two to the new bar if needed to make room for bonding jumper on existing, and not worry so much about how it is attached to the cabinet?



This is what I was leaning towards doing. I just don't feel comfortable with not getting the proper torque on the screw.
 

ADub

Senior Member
Location
Midwest
Occupation
Estimator/Project Manager
This is what I was leaning towards doing. I just don't feel comfortable with not getting the proper torque on the screw.

Is the new bar on there solid or is it loose yet?


Sent from my iPhone using Tapatalk
 

jap

Senior Member
Occupation
Electrician
If you are adding an additional bar - that should mean the box is already bonded by what is existing. Why not just run a bonding jumper to this new bar from an existing one, move a conductor or two to the new bar if needed to make room for bonding jumper on existing, and not worry so much about how it is attached to the cabinet?

My thoughts exactly,,,,,,


JAP>
 

jap

Senior Member
Occupation
Electrician
Dont tell anybody, but, if I've already installed an appropriate size bonding jumper to the new bar,,,,,I've been known to remove one of the terminal screws in the middle of the bar, drill a hole through it, and install 1 more fastener in the middle of the bar to the panel can, just out of spite sometimes....:eek:hmy:


JAP>
 

Cavie

Senior Member
Location
SW Florida
This is what I was leaning towards doing. I just don't feel comfortable with not getting the proper torque on the screw.

I would be interested in seeing the results of a poll on how many electricians use a torque screwdriver. In 45 years I've never seen one much less used one.
 

jap

Senior Member
Occupation
Electrician
I would be interested in seeing the results of a poll on how many electricians use a torque screwdriver. In 45 years I've never seen one much less used one.

I often find if I actually go back and put a torque wrench on somthing I've tightened by hand I've overtightened every time.

JAP>
 

kwired

Electron manager
Location
NE Nebraska
I often find if I actually go back and put a torque wrench on somthing I've tightened by hand I've overtightened every time.

JAP>
Same here - when using a wrench.

Torque screwdrivers though you about twist your wrist off if you use recommended torque level on some equipment. In particular I have noticed this on several circuit breakers and NEMA contactors.
 

jap

Senior Member
Occupation
Electrician
Same here - when using a wrench.

Torque screwdrivers though you about twist your wrist off if you use recommended torque level on some equipment. In particular I have noticed this on several circuit breakers and NEMA contactors.

And by that time it usually slips out and jabs you in the eye.

JAP>
 
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