Installing an electrical subpanel

[Slickdonkey]

Hi all, I posted this on another board but thought you guys might find it interesting here...

Ok, first off let me say this post is about electrical installations, and doesn't really talk about anything reef-related at all, so if this kind of thing doesn't interest you, be forewarned!

I estimate with all my equipment running I could draw close to 27 amps mid-day with all the lights on. Wow, that's quite a bit of juice. So my latest step in setting up this monster tank involves the installation of new electrical outlets. In fact, I figured on adding three 15-amp circuits. I chose this because it gives me some wiggle room as well as capacity for new equipment and overhead for motors startups on the pumps and chillers. I'll probably use one circuit for the chiller and heaters, one for the lights, and the other for the pumps and other miscellaneous equipment.

I know 20-amp outlets are common, but I chose three 15's instead of say two 20's for two reasons:
- I figure it's better to have more circuits of a smaller capacity rather than fewer with larger capacity. In case the breaker trips for some reason, less equipment will be affected if it's spread out over more circuits.
- My electrical panel is pretty darn full of 20-amp circuits already (see pictures below), and using a 15-amp circuit makes me feel better about my rapidly rising total. I have 200 amp service to my home.

The plan is to route three wires (14/2, about 90 feet each) to the crawlspace under the floor where I'll have my equipment set up. Should be a matter of just running the wires, popping in some new circuit breakers and I'll be ready to go, right? Well, with this project nothing is ever so easy, as you should know by now. I popped open my electrical panel...

Uh oh... I don't see much real estate in here. Come to think of it, when I installed that air compressor circuit last year I remember thinking "man, this panel is so full, I'm glad I don't plan on adding any more circuits in the future!". Hmmm.

I figured the best bet is going to be to install a subpanel. This is more work, but it gives me the flexibility I'll need to add my new circuits, and will prevent this very problem from happening again in the future if I decide to get a monster hot tub for the back deck or something.

Now I'm not an electrician, but I have done some basic electrical work and I work with low-voltage electronics as part of my job, so how hard could it be? I thought I'd take a stab at it and save myself a few bucks. If I just remember to respect electricity, it will respect me. Keep my tongue and fingers off the hot buses and I should be fine. I also enjoy learning these sorts of things. The knowledge may be useful in the future, and besides, family and friends will think I'm smart. As long as I don't kill myself. Then they may have a different opinion.

In most locales you're supposed to get a permit for this. I am unincorporated so have to get it from the county. I thought of another option to save a few bucks and got mine on eBay:

 

[Slickdonkey]

A subpanel is pretty simple, in a nutshell all you have to do is install a breaker in the main panel and run the wire to the subpanel and you're good to go. Sounds easy, but this took a fair amount of work in my situation. I chose to use a double-pole breaker to run 240V to my subpanel. I won't need 240V for this project but I might in the future, and besides, the oven that I'm moving to the subpanel will need it. It isn't any more difficult.

First of all, if you take a look at the picture of my main panel above, there's no room for the aforementioned breaker. Something's going to have to be pulled out and moved to the subpanel to make room for the subfeed. I chose the electric oven, which is the 30 amp double-pole breaker on the top left. As an added bonus I can replace this 2" thick breaker with one of the newer 1" breakers and save some space in the subpanel.

By the way, notice my main panel is one of the older split bus panels (probably original from 1975) and the main breaker is the 70 amp, second down from the top left. I decided to leave the power on to the house while working on this project, because as you can see there really is no main cutoff from the utility inlet. So the busses are still going to be hot regardless. I *think* on the newer panels you can use the main breaker to cut the power to the busses, which is certainly a good idea. Oh, and also my wife was having a party inside so I don't think cutting the power would have gone over well. I just have to be extra careful not to poke my fingers in the wrong holes or it will scramble my brains and I won't be able to finish the project! I guess you're not really in suspense because as you can tell I didn't die.

So, the first thing I did is to turn off the breaker for the oven, pull it out, and hang the subpanel on the wall next to the main panel. As an alternative I could have put the subpanel down in the crawlspace, but that's inconvenient if I decide to ever add circuits for anything other than reef equipment. This also would mean a 90-foot run of some really expensive thick cable (more on that below).

Here's a picture of the main panel minus my oven breaker and the subpanel hanging next to the main.

You can see the 14/2 white wires next to it which I ran through my garage and into the crawlsapce. This involved some measuring, barely missing my cold water line while drilling a hole, and hitting my head on the floor supports a few times, but otherwise was not difficult. Good thing I missed the water line or you'd be reading about plumbing as well.

My main panel is a GE panel, so I bought a GE subpanel as well. You don't have to, but this gives me some extra flexibility if I ever want to move things back and forth between the panels. Panels by different companies use different sized breakers, of course. I always see GE breakers in the hardware stores, so I don't think I'll have any trouble finding them for future expansion. This can be a problem with some of the off-brands (i.e. some stores carry only certain brands, but I almost always see GE).

 

[Slickdonkey]

The subpanel I bought is rated for 125 amps, so I decided I was going to feed it as though it was fully loaded. I don't think this will ever happen, but I figured I should plan for it now and not have to do anything to it later. If I were to do it again I think I would be less conservative and just go 80 to 100 amps. For one, the 125-amp breaker is expensive. It cost $56, and the 100 amp breakers are only $22. There is an exponential curve on price as these things get bigger. The other reason is that the wires rated for 125 amps (at 6 feet) are expensive, HUGE, and difficult to work with. They're so stiff that it's hard to bend them into the shape you want.

Check it out, I tried to get a picture of my thumb for comparison. There are three conductors plus the ground. This is 1/3 aluminium service entrance wire. I had to go to a contractor supply store to get this, and it was $16 for 6 feet. I would have preferred to use copper wire, but this was even more difficult to find, and you have to use a thicker gauge. I'm not sure why this is, but that's what everyone was telling me.

I stripped the wire with my razor blade (I don't have any wire strippers big enough) and scrubbed it down with a wire brush. This gets rid of little pieces of insulation I might have missed and gives the wire a nice shine.

I read that aluminium wire was used for home wiring when there was a copper shortage in the 1960's and 70's. Over time it would oxidize, deteriorate, and turn into a fire hazard. To prevent this, you can coat the wire and terminals with an anti-oxidant compound.

So, I attached the wire to the subpanel. The black and black-red striped wires connect to the main lugs, the white-striped wire to the neutral bar, and... did you notice anything missing in the subpanel picture above? Yes, there is no ground bar (which is where the bare ground wire attaches to). I had to go purchase this extra and attach it to the panel (on the left). The neutral bar is on the right. In a subpanel, the neutral bar and ground bar must be isolated from eachother. This also means the neutral bar is not connected to the subpanel chassis (sometimes there is a screw you need to remove, and you can see the neutral bar is insulated by plastic standoffs). By code, the ground and neutral should only be bound together in the main panel. I can't remember why this is, but it's the correct way to do it. Someone explained it to me once, but I've since forgotten. In any case, this is important for safety.

 

[Slickdonkey]

Once this was done, I routed the huge cable through a 1-1/4" hole in the stud and into the main panel. This was by far the worst part of the job. As you can see, my main panel is a real rat's nest of wires and there wasn't much room to run this huge thick cable up through the wires to the top of the panel where the oven breaker used to be. Much swearing and cursing was involved. It's also a little nerve-wracking because it is necessary to stick your hand in there and move these wires out of the way to make room. And sticking my hand into a live electrical panel and shoving things around just screams for a Darwin-award nomination. Tiffany was standing by with her finger on 911.

In the end I got everything to fit. I didn't have any wire-cutters big enough to trim these conductors, so I used Tiffany's pruning shears when she wasn't looking. Then, just attach the wires to the new 125-amp breaker and put it in. It looks so easy. The neutral and ground wire are circled where they connect to the ground bar.

 

[Slickdonkey]

For my final trick, I routed the wires for the oven into the subpanel and attached them to the new 30 amp breaker. Note that the double-pole 240V breakers (my oven is 240V) need to be located such that the breaker spans both hot busses (the white metal pieces). House wiring basically has two 120V feeds, and you can add them together to get 240V. That's what's going on here.

After this was done I flipped the subpanel breaker on in the main panel and used my voltmeter to verify I was actually getting 240V across the busses. Then I flipped on the oven breaker. Looks like all was well, so I shut off the subpanel again and finished hooking up my three reef tank circuits like you would any other circuit. I left these off when I powered up the panel, because the wires are still dangling in the crawlspace until I figure out where exactly I want to put the outlets. I'll probably know for sure once the sump is in its final resting place.

Here's the completed work:

I hope this was interesting and maybe informative. As I mentioned I'm not an electrician, so if you spot any errors in my installation please drop me a note!

 

[Slickdonkey]

Hey, does anyone know why my images aren't showing up and I see hyperlinks instead? I have my options set to allow inline images... I don't get it.

 

[gvibes]

<a href=showthread.php?s=&postid=7053302#post7053302 target=_blank>Originally posted</a> by Slickdonkey
Hey, does anyone know why my images aren't showing up and I see hyperlinks instead? I have my options set to allow inline images... I don't get it.

I think you have to add a

 

[Slickdonkey]

Yeah, I did... oh well.

 

[Whispre]

congrats on a job well done! oh, and on convincing me to call an electrician when I need to do this

 

[BeanAnimal]

I would have preferred to use copper wire, but this was even more difficult to find, and you have to use a thicker gauge. I'm not sure why this is, but that's what everyone was telling me.

The opposite is true. With copper, the wire size is not as large as the aluminum. However aluminum is cheaper and more common for SE cable.

I read that aluminium wire was used for home wiring when there was a copper shortage in the 1960's and 70's. Over time it would oxidize, deteriorate, and turn into a fire hazard. To prevent this, you can coat the wire and terminals with an anti-oxidant compound.

This IS NOT AN OPTION. IT IS A MUST!!!! You need to use NO-LOX or another aproved anti-oxidant. A light switch with a bad connection is one thing, a main lug feed by 1/0 wire and a 125A breaker is another.

You must also ensure that the "lugs" you are using are approved for both Cu and Au. If they are not approved, the galvanic reaction can cause one or the other to oxidize and create a very dangerous situation.

 

[BeanAnimal]

slick... I did not take a close look at your photos, but I would add that it is good practice to route the wires as NEATLY as possible. This makes a difference if you ever go to sell the house or have somebody come work in the panel.

It is a good idea to get a code inspection when adding a panel. I am not a big believer in permits or inspections, however a sub panel is somethin you want to have sticker on. This makes it easier to sell your house and also REALLY helps if there is a fire or other problem. You don't want your insurance company blaming you. For branch circuits and other additons, I don't bother (I just rewired my entire house...EVERY circuit!) I only got an inspection for the 200A panel and the sub panels. The wiring is still going on, but will not need inspected (technically it falls under the inspection of the panel as long as I use the same wiring standards I started with. The inspector does not need to come back again, he was happy with what he saw the first time.

 

[Slickdonkey]

Thanks Bean, I hadn't considered the insurance aspect. I just looked into getting the permit and inspection and it's under $100 so not a big deal...

One reason I didn't look into it that seriously is that I was considering having an electrician replace the entire main panel and use one that I can pick and choose which circuits to run off the generator (as opposed to the few that are connected to my transfer switch).

 

[BeanAnimal]

I just put a 200A into the wall and do not have room for the "generac" prewired transfer switch. Instead of moving some circuits to a dedicated "generator" sub panel, I am going to put the transfer switch on the service entrance. Sad part is that the 200A transfer switch costs 50% of the 7KW generators stand alone cost.

Bean

 

[Slickdonkey]

So that's what, $400 or so for the transfer switch? That's probably a better option than paying someone to rewire my entire main panel.

 

[BeanAnimal]

No the genset is close to $1800 and the transfer switch $800. I am a generac dealer... but the Home Depot price is about what I pay wholesale (for anything under about 20kW). I think HD sells the genset for $1900 and the transfer switch would be special order (the genset comes with that "pre wired" transfer switch, that is useless in my situation).

Bean