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ok here is my first subpanel i've installed, please let me know what you think. let me know if you see any code violations or things i could have done better/correct.
see attached pic.
see attached pic.
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Why the main breaker? A sub panel usually gets its feed from the "main panel" that should have the breaker for the sub. Next time use a main lug panel for the sub panel. Other than that I see no problems. Is the neutral bus isolated from ground? I mean there is no bonding screw or jumper installed, right? -
I can't see in the picture: where is the grounding bus attached to a grounding connection? It's not connected to the neutral bus is it?Comment
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It was cheaper to buy a main breaker panel than a MLO panel. the Main breaker panel came with all the breakers plus the main breaker.
yup the bonding jumper was removed.
quote:Originally posted by HayZee518
Why the main breaker? A sub panel usually gets its feed from the "main panel" that should have the breaker for the sub. Next time use a main lug panel for the sub panel. Other than that I see no problems. Is the neutral bus isolated from ground? I mean there is no bonding screw or jumper installed, right?Comment
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nope the bonding jumper was removed and the gounding bus is attached to the sub panel case. this sub panel case is then connected to the main panel 6 inches away via conduit so the sub panel case gets it ground via the conduit.
Is this correct? should i have another ground cable from the main panel over to the sub panel? keep in mind the two are right next to each other, 6 inches away.
quote:Originally posted by SSN596
I can't see in the picture: where is the grounding bus attached to a grounding connection? It's not connected to the neutral bus is it?Comment
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You did a nice neat job routing all the wires to the buss bars, but you have lots of problems with your installation.
I have to agree with the others. I do not see a separate ground conductor entering this subpanel routed from the main panel. You need a #4 ground cable routed into this panel and attached to the ground bar. You will need to install a larger piece of conduit than what you have for the power cables/neutral cable and ground cable to have room. It should be a 1" min diameter and preferably 1 1/2" piece of conduit.
Is this sub panel in the same building as your main panel? If it is in a separate building you also need to install a ground rod at the building.
It also looks like there are straps connecting both the ground bar and the neutral bar to the panel frame. The neutral buss bar MUST be isolated from the ground bar and from the panel frame in a sub panel. It must float. So, the bonding screw or the strap needs to be removed from the neutral buss bar to accomplish this. Then using your meter make sure there is no continuity between the two buss bars.
I also see at least 14 NM cables routed into the top of this panel through one piece of conduit. This is a big no-no. First off NM cable should not be installed in conduit, there is a heat factor that prohibits this type of installation. And secondly there should be no more than 3 NM cables ran together through ANY hole or clamp. You run into derating problems with more than this and it could cause you problems.
You want to install NM cable clamps through the knock out holes in the top of the sub panel and install these NM cables through these clamps instead of routing them all into the panel through the piece of conduit. No more than 2 cables should be installed in any one clamp.
Sorry about the bad news, but you asked and that means you are concerned that it to be done safe and proper. So, you have alot of rewiring to do before you can say that. Please ask back with any questions and be sure to show us a picture of all your rework.
Here is a link that provides the installation instructions for a sub panel. This may help you with a few details.
Hazy, it's really cheaper to buy a panel that has a built in main breaker when going with a larger subpanel installation. The sub is still fed from a breaker in the main panel. But the subpanel is cheaper than one that is main lug. Check it out next time you're at Home Depot. A 100 amp Square D homline panel with a main breaker can be had for under $50.00.Comment
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If that's metal conduit connecting the two panels then that is fine and no separte ground cable is needed. But please verify using a meter that NO continuity exist between the neutral buss bar and the panel. And that you DO have continuity between the ground buss bar and the panel.Comment
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Yikes, ok now i am concerned because my main panel (which is right next to the subpanel) has all the NM cables in a 3” piece of conduit also.
I mirrored the subpanel wire routing the same as the main panel, in through the top via conduit This is in a 1 year old house and so I can only guess this is code in my area to do this. I know the city checked it for code because the proper stickers are on the main panel door
What am I missing here?
quote:Originally posted by kactuskid
You did a nice neat job routing all the wires to the buss bars, but you have lots of problems with your installation.
I have to agree with the others. I do not see a separate ground conductor entering this subpanel routed from the main panel. You need a #4 ground cable routed into this panel and attached to the ground bar. You will need to install a larger piece of conduit than what you have for the power cables/neutral cable and ground cable to have room. It should be a 1" min diameter and preferably 1 1/2" piece of conduit.
Is this sub panel in the same building as your main panel? If it is in a separate building you also need to install a ground rod at the building.
It also looks like there are straps connecting both the ground bar and the neutral bar to the panel frame. The neutral buss bar MUST be isolated from the ground bar and from the panel frame in a sub panel. It must float. So, the bonding screw or the strap needs to be removed from the neutral buss bar to accomplish this. Then using your meter make sure there is no continuity between the two buss bars.
I also see at least 14 NM cables routed into the top of this panel through one piece of conduit. This is a big no-no. First off NM cable should not be installed in conduit, there is a heat factor that prohibits this type of installation. And secondly there should be no more than 3 NM cables ran together through ANY hole or clamp. You run into derating problems with more than this and it could cause you problems.
You want to install NM cable clamps through the knock out holes in the top of the sub panel and install these NM cables through these clamps instead of routing them all into the panel through the piece of conduit. No more than 2 cables should be installed in any one clamp.
Sorry about the bad news, but you asked and that means you are concerned that it to be done safe and proper. So, you have alot of rewiring to do before you can say that. Please ask back with any questions and be sure to show us a picture of all your rework.
Here is a link that provides the installation instructions for a sub panel. This may help you with a few details.
Hazy, it's really cheaper to buy a panel that has a built in main breaker when going with a larger subpanel installation. The sub is still fed from a breaker in the main panel. But the subpanel is cheaper than one that is main lug. Check it out next time you're at Home Depot. A 100 amp Square D homline panel with a main breaker can be had for under $50.00.Comment
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Kactus - I do all my buying through reputable jobbers. I get 60% off ALL service equipment - Loews or Home Depot couldn't even come close to what I buy panels for!Comment
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The real question here is for what distance are these cables run in this conduit and bundled up like they are? Is it for greater than 24 inches?
If it is greater than 24 inches then I don't know what your city goes by, but I can tell you that per the NEC you are not within code. And the NEC is the minimum protection, most local codes will be the same or strickter, but never less.
"When you run multiple wires through a raceway (aka conduit), the combined heating from the adjacent wires can overheat the wires. Wires and cables are designed to allow a certain amp flow under specific ambient temperatures with a specific number of adjacent current carrying conductors. If the local temperature is over 85F, or you have more than 3 conductors in a raceway then you must reduce the ampacity of the wire. Oh, and if the conduit or bundling is less than 24" long, then you don't have to apply the multiple conductor derating rules."
The following is a quote from the link I'll post below:
"Section 334.80 [NEC 2002], Ampacity, allows the 90-degree column in the ampacity table to be used for derating, and the 60-degree column for maximum ampacity. It also refers to 310.15(B)(2), Adjustment Factor, that states where multiconductor cables are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a).
Therefore, if there are ten – No. 12 NM cables pulled through 1½ in. holes in joists without maintained spacing, the ampacity would have to be derated using Table 310.15(B)(2)(a). Ten MN cables would have twenty current-carrying conductors and be required to be derated to 50 percent of the ampacity. Table 310.16 allows 30 amps in the 90-degree column with a derating of 50 percent, equaling fifteen amps allowed on these cables and fifteen amps of overcurrent protection.
If there were six No. 12 NM cables pulled through studs, the same would apply. There would be twelve current-carrying conductors. Section 310.15(B)(2)(a) would require derating 50 percent of 30, equaling fifteen amps allowable, and fifteen amps off center.
If there were only four No. 12 NM cables, there would be eight current-carrying conductors with a derating of 70 percent of 30 amps, equaling 21 amps. Twenty-amp overcurrent protection is allowed per 240.4(D).
Additional derating may be required for high ambient temperatures in attic spaces and other high temperature areas. "
So, you have a problem and a dangerous one if your cables are run bundled together for greater than 24". This is whether they're in conduit or just all run together outside of conduit. And the derating factor is extended even further if any of these wires are exposed to high ambient temperatures, such as run through exterior walls, attics or conduit that is in direct sunlight. The breakers that are protecting the types of circuits you have here are too large for the derated factor of the wires. If I were you I would hire an electrician, a licensed one with lots of experiance to come in and take a look at what you have.
Hazy, it would be helpful if you'd throw in your 2 cents on this as I know you know the code pretty good.
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Nope, the conduit is less than 24 inches so i should be ok...
quote:Originally posted by kactuskid
The real question here is for what distance are these cables run in this conduit and bundled up like they are? Is it for greater than 24 inches?
If it is greater than 24 inches then I don't know what your city goes by, but I can tell you that per the NEC you are not within code. And the NEC is the minimum protection, most local codes will be the same or strickter, but never less.
"When you run multiple wires through a raceway (aka conduit), the combined heating from the adjacent wires can overheat the wires. Wires and cables are designed to allow a certain amp flow under specific ambient temperatures with a specific number of adjacent current carrying conductors. If the local temperature is over 85F, or you have more than 3 conductors in a raceway then you must reduce the ampacity of the wire. Oh, and if the conduit or bundling is less than 24" long, then you don't have to apply the multiple conductor derating rules."
The following is a quote from the link I'll post below:
"Section 334.80 [NEC 2002], Ampacity, allows the 90-degree column in the ampacity table to be used for derating, and the 60-degree column for maximum ampacity. It also refers to 310.15(B)(2), Adjustment Factor, that states where multiconductor cables are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a).
Therefore, if there are ten – No. 12 NM cables pulled through 1½ in. holes in joists without maintained spacing, the ampacity would have to be derated using Table 310.15(B)(2)(a). Ten MN cables would have twenty current-carrying conductors and be required to be derated to 50 percent of the ampacity. Table 310.16 allows 30 amps in the 90-degree column with a derating of 50 percent, equaling fifteen amps allowed on these cables and fifteen amps of overcurrent protection.
If there were six No. 12 NM cables pulled through studs, the same would apply. There would be twelve current-carrying conductors. Section 310.15(B)(2)(a) would require derating 50 percent of 30, equaling fifteen amps allowable, and fifteen amps off center.
If there were only four No. 12 NM cables, there would be eight current-carrying conductors with a derating of 70 percent of 30 amps, equaling 21 amps. Twenty-amp overcurrent protection is allowed per 240.4(D).
Additional derating may be required for high ambient temperatures in attic spaces and other high temperature areas. "
So, you have a problem and a dangerous one if your cables are run bundled together for greater than 24". This is whether they're in conduit or just all run together outside of conduit. And the derating factor is extended even further if any of these wires are exposed to high ambient temperatures, such as run through exterior walls, attics or conduit that is in direct sunlight. The breakers that are protecting the types of circuits you have here are too large for the derated factor of the wires. If I were you I would hire an electrician, a licensed one with lots of experiance to come in and take a look at what you have.
Hazy, it would be helpful if you'd throw in your 2 cents on this as I know you know the code pretty good.
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Panelbox bonding - equipment grounds.
Metal conduit with locknuts and bushings are ok in some instances
Better are metal nipples, locknuts, bonding bushings etc
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