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Posted By: royta first real sub-panel job - 12/16/04 08:29 PM
Yeah, I know it sounds bad, but it's true. All of the sub-panels I've installed were supplied by my employer and I just did the work. Well, I'm just starting out as a self-employed electrician, and could use a little advice on my first real sub-panel job.

Main panel is located at house. Sub-panel will be 120/240 single phase and will be located at well. There will be 300 feet of conduit, with the first 100 feet in IMC, and the final 200 feet terminating at the sub-panel in PVC. The sweep transitioning from the horizontal conduit to vertical into the sub-panel will be rigid so I don't cut a groove in 90 while pulling in the wire.

Pump guy needs a single 2-pole 20A circuit for the main pump, and space for a second 2-pole 20A circuit for future use. The future circuit would be used for a second pump that would pump water from a possible future storage tank to the house. I'll also install a 1-pole 20A for a couple receps and a light. A 50A sub-panel feed should do it. The hots will be #6 and the ground will be #10, but I'm wondering if I can run #8 for the neutral. What code allows downsizing the neutral for a sub-panel?

Sub-panel questions:

IT only needs to be main lug only, as the disconnect is located at the main panel, correct?

I get great prices from this wholesaler who is a GE only shop. Using the fancy GE configuration tool , it appears the TLM612RCU should work well. The future pump might not ever happen, but I'd hate to make them use a quad if they ever did. If I knew it wasn't going to happen, I'd just use a 4/8, like the TL412RT1.

I know I'll need a ground bar at the panel, but will I also need an Equipment Ground Kit? Or is the ground kit only for landing a large quantities of ground wires?

If the first questions weren't bad enough, I really feel stupid amongst you long-timers asking this question. Since my ground between the main and sub panels is #10 stranded, can I also use #10 stranded between the ground rod and the sub-panel, or do I need to use solid, or even a different sized solid? Well casing is PVC, not steel, so there will be no bonding of the well casing.

Thank you for your patience and help.

[This message has been edited by royta (edited 12-16-2004).]
Posted By: electricman2 Re: first real sub-panel job - 12/16/04 09:27 PM
Your installation is not really a sub-panel. It is a separate structure and is covered in Article 225. Many of the requirements for services apply. The 8AWG neutral is OK if load calculations show it to be sufficient for the unbalanced load. If the main lug panel is serving as the disconnecting means (225.31) it must have no more than 6 breakers. I would suggest installing a main. The GEC should be No. 6 CU or No. 4 AL
Posted By: royta Re: first real sub-panel job - 12/16/04 10:31 PM
Thanks for the pointer on where to look. The TLM612RCU is a convertible panel, but with a 100A Main Breaker Kit installed, it is nothing more than a 4/8. In order to install a second pump, a quad breaker would need to be used. It appears a TLM812RCU is the same physical size, but has more available spaces. Even with a 100A Main Breaker Kit, I wouldn't need to install a quad. Geez, this just keeps getting more and more expensive. Maybe I should just stick with a 4/8 and let the pump guy install 1/2" breakers if he needs the extra 2-pole. Or perhaps use the 6/12 and install a non-fused disconnect before the panel.

Posted By: shortcircuit Re: first real sub-panel job - 12/17/04 02:28 AM
Run a #6 copper to the ground rod as required by 250.66(A)...aluminum is not allowed to terminate within 18" of the earth outside...250.64(A)

Also the non-fused disconnect must be listed for use as service equipment...225.36

Posted By: caselec Re: first real sub-panel job - 12/17/04 03:44 AM
It sounds like the maximum number of circuits you will have in this panel is 3 so I wouldn’t worry about a main disconnect. Even if additional spaces are provided it is not a problem until more than 6 breakers are installed.

Why are you using IMC for the first 100 feet? If it is going to be underground I would try to use PVC for the entire run. If trench depth is the issue use RMC or better yet Ocal. In my area IMC would be gone in a few years and even RMC doesn’t last very long.

If you use an RMC 90 continue with RMC all the way to the panel. If not your going to need a deep trench to provide the 18” cover required over an isolated metal elbow.

Posted By: electure Re: first real sub-panel job - 12/17/04 12:07 PM
"I'm just starting out as a self-employed electrician"
Best of luck to you. [Linked Image]

I hope you've also taken the required action of getting yourself a contractor's license first.
Posted By: royta Re: first real sub-panel job - 12/17/04 01:55 PM
caselec - The owner got a little crazy with the trencher at the well end of the conduit run, so the top of the 90 will have the bury. Yes, the first 100 feet is near the house and will only have about 8 inches of cover. I might install the convertible 8/16 panel, and leave a note in the panel AND on the invoice, that the main breaker kit (I'll even leave the part number needed) must be installed before installed if there are seven or more circuits installed.

electure - Yes, that's all been taken care of. License, liability, etc. I still haven't taken the leap of faith of quitting my day job though. I wasn't doing electrical for almost four years before I decided to get my license. I certainly wish I knew more than I did, but at least I know better than to do any work I am unsure of. If I'm in doubt, I found out the answers first. Some of the things I don't know probably seem so simple to the rest of you, but like I said, I was normally just handed materials and told to do the work. In CA, an apprenticeship program was not required, so that's most of the problem right there. Lack of code knowledge was my main concern before getting my license. I mentioned this to my dad (plumbing/firesprinkler contractor/business mentor) and his friend (electrical contractor/old boss), and they said that with my personality of overanalyzing everything so much, that they knew I'd find all the answers I needed before doing any shoddy work. I've even called the local city inspector before doing a job.

I really do appreciate the help.


Side note/question on the 6 disconnect limit. Does the 6 disconnect rule still apply if this panel were located in/on the same structure as the main panel? Or, can you just use the main panel disconnect, or sub-panel disconnect in the main panel, to remove power?

[This message has been edited by royta (edited 12-17-2004).]
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