Ground & Neutral in Subpanel
#1
03-31-03, 05:48 AM
Ground & Neutral in Subpanel
Last summer installed a 200 amp 40 breaker Square D Homeline panel box. After I wiring my renovated house, I was coming very close to using all 40 breakers. Tried to use a few tandem breakers, but discovered the Homeline box won't accept tandem breakers. Therefore, decided to add a subpanel. I installed another 200 amp 40 breaker Square D Homeline panel. I know I don't need another 40 breakers, but I figured that if I decide to go up to 400 amps in the future (a pool and spa are in the not too distant future), I would be able to just sever the subpanel cable and be ready to go. I installed a 240 volt 50 amp double pole breaker from the main to the subpanel and ran the line to another 240 volt 50 amp double pole breaker in the in the sub. I have three questions.
First: My understanding is that a subpanel needs to have a separate ground and neutral, so I have all of my grounds running to one busbar and all of the neutrals to the other. The problem is that I can't figure out how to separate the bars at the top of the box. It appears to me that the bars are connected at the top where the line would come in if it was not a subpanel. There is a phillips head screw that connects the busbar to the top cross bar, but it is either torqued down so tight or fastened some way since I can't budge either one of them. What am I missing here?
Second: I live in Virigina. I am assuming that I need to ground the box buy installing the grounding screw in the subpanel as well.
Third: I thought it would be a good idea to run the line from the main to the sub using two single pole 50 amp breakers to draw from both sides of the main bus. Couldn't find any single pole 50 amp breakers at the local warehouse. Should I do as I planned or is using a double pole breaker OK?
First: My understanding is that a subpanel needs to have a separate ground and neutral, so I have all of my grounds running to one busbar and all of the neutrals to the other. The problem is that I can't figure out how to separate the bars at the top of the box. It appears to me that the bars are connected at the top where the line would come in if it was not a subpanel. There is a phillips head screw that connects the busbar to the top cross bar, but it is either torqued down so tight or fastened some way since I can't budge either one of them. What am I missing here?
Second: I live in Virigina. I am assuming that I need to ground the box buy installing the grounding screw in the subpanel as well.
Third: I thought it would be a good idea to run the line from the main to the sub using two single pole 50 amp breakers to draw from both sides of the main bus. Couldn't find any single pole 50 amp breakers at the local warehouse. Should I do as I planned or is using a double pole breaker OK?
#2
03-31-03, 06:36 AM
Member
1. Homeline panels have a green grounding screw. If you do not install the screw, your neutral will not be bonded to the box. Use your ohmmeter to check to be sure. Don't base your decision on appearances.
2. The grounding wire from the main panel to the subpanel is the only grounding that the subpanel needs. Attach it to your grounding bar, which is in turn attached to the box.
3. Bad, very bad, very very bad idea. It's not safe, and it won't work anyway. Just install a normal double-pole breaker. This breaker already draws from both legs of the power. "Side of the panel" is completely meaningless -- that's not how it works.
2. The grounding wire from the main panel to the subpanel is the only grounding that the subpanel needs. Attach it to your grounding bar, which is in turn attached to the box.
3. Bad, very bad, very very bad idea. It's not safe, and it won't work anyway. Just install a normal double-pole breaker. This breaker already draws from both legs of the power. "Side of the panel" is completely meaningless -- that's not how it works.
#3
03-31-03, 06:55 AM
Double pole 50 will connect across both phases. Look at the configuration of the bus bars and you will see.
The two bars connected across the top is the neutral bar. It is to be bonded with the green screw and all the neutrals and grounds are to be connected to it ONLY if the panel is to be used as a Main Service Panel. You are using it as a subpanel and therefore should not use the green bonding screw and should buy a ground bar (for your brand / style of panel) which will mount directly to the "can". Your neutral bar will not be in contact with the ground bar and the neutrals and grounds need to be kept separate. You will need (4) conductors between your Main and subpanel (Separate neutral and ground). The neutral and ground will both terminate on the neutral bar in the Main panel.
Does your new 200A panel have a main breaker? You will need it if you ever decide to go to a 400A service.
If your main lugs are rated for #6 AWG (50 Amp wire), then you can run your 50A feeder directly into them and avoid an additional 50A double pole breaker.
The two bars connected across the top is the neutral bar. It is to be bonded with the green screw and all the neutrals and grounds are to be connected to it ONLY if the panel is to be used as a Main Service Panel. You are using it as a subpanel and therefore should not use the green bonding screw and should buy a ground bar (for your brand / style of panel) which will mount directly to the "can". Your neutral bar will not be in contact with the ground bar and the neutrals and grounds need to be kept separate. You will need (4) conductors between your Main and subpanel (Separate neutral and ground). The neutral and ground will both terminate on the neutral bar in the Main panel.
Does your new 200A panel have a main breaker? You will need it if you ever decide to go to a 400A service.
If your main lugs are rated for #6 AWG (50 Amp wire), then you can run your 50A feeder directly into them and avoid an additional 50A double pole breaker.
