39

Why bury a cable when you can be future-proof? The primary issue with direct buried cables is that you have to dig them up in order to upgrade them, a costly proposition. Hence, it's a far better choice to spend the money to lay a couple of fat PVC conduits now and then pull wires through them, than to have to dig things up 5 years down the road because ...


33

Some brands of GFCI’s trip on power loss. I first found this when putting them in on a bathroom sink outlet that was switched. Every time the light switch was turned off the GFCI tripped when the switch was turned back on. I switched brands and the problem went away. I think this was an early safety that today some new GFCI’s make you press test then reset ...


26

Oh dear. This is a foogly mess. First, you did the right thing by punching that main panel breaker down onto a single. The problem is with the subpanel; it is very badly misconfigured by a guy who cut a lot of shortcuts. First, it is illegal to double-tap neutral bar screws like that, unless the panel's labeling or instructions say they are intended ...


25

I'm going to be a bit contrarian and say 10/3 UF. It's pricier and overkill for your existing setup, but here's why it could be worth doing it now. A single 12/2 means you only get 20 amps at your shed. Period. Next year, you buy some power tools and you start taxing your 20 amp. If the breaker pops, you get to walk back to your main panel. Pop it multiple ...


21

When determining feeder conductor size, you'll want to consider the "lowest temperature rating of any connected termination, conductor, or device" as per National Electrical Code (NEC) Article 110.14(C). While the cable/wire may be rated at 90°C, you'll likely find that the terminals are rated at 75°C, or not labeled at all. 110.14(C)(1)(a) tells ...


18

Whoever wired this panel simply was not paying attention The installer who wired this panel did not pay attention to the schematic on the label, assuming that removing the bonding strap was enough here. However, the split ground design of these Murray panels means that the left-hand bar is factory bonded to the case, with the right-hand bar being the only ...


16

Bonded ground/neutral If you have the neutral and ground bonded at a subpanel, then you'll get neutral return current through the ground wire back to the main panel (since there are now multiple paths). Even worse, as @Tester101 points out, if the neutral ever has a fault, everything will continue to work but you'll have all the current on the ground, which ...


15

Just wire it up. There is no problem using a sub panel that can take more current than you will ever feed it. Points to note: The cable to your hot tub will be rated for 50A (not 100A); therefore you must not upgrade the breaker in your main panel to 100A. It would be sensible to add a note near the main panel that the cable is only rated for 50A, so not ...


13

My answer is almost always the same when talking about garage subpanels. 60 ampere double pole breaker in the main panel. 6 AWG copper wire (x4) for a run less than 75ft., 4 AWG copper wire (x4) for runs less than 150ft. 60 ampere panel with 60 ampere main breaker. Unless you're running a whole bunch of stuff at once, a 60 amp panel should serve you well. ...


13

The 100A breaker is overcrowding the other slots for a reason: to enforce stab limits. Even a stopped clock is right twice a day, and FPE got that right. If you did what you wanted to, you would have 130A on those two stabs. That's over stab limits for a lot of modern panels! If you've ever seen panels where the main breaker is in the upper left corner ...


13

Ed's advice is correct. For a time, some builders of GFCI devices considered this behavior to be a "feature". Undocumented, of course. This is largely gone from the market, so I would cautiously buy one of a particular make/model, and see if it works as you like. If it does, buy more. Too bad, it would make a nice feature for some applications, like a ...


12

The common solution is to attach a piece of plywood larger than the panel to the studs, and then attach the panel to the plywood. This also provides a good place for attaching cables, so you can get a nice organized installation. Additionally, this technique provides the benefit of being able to insulate behind the panel.


12

Let me try and answer some of your questions. First the panels you are looking at that are rated 100A simply means you can use them for any application up to 100A. You can for example add a 60A breaker to your existing panel and protect the new subpanel with a 100A rating. It is not so much what the panel is rated as what the protection is rated. You can ...


12

Generically I'd knee-jerk to conduit and 30A 240V service with a sub-panel, but if your needs are going to be adequately met by 20A 120V power and the loading is sufficiently low that the voltage drop from 200 ft of 12Ga wire won't be a huge issue, yes, you can do that. Given the relative expense of digging a ditch once, and never having to dig it again if ...


11

It's all about Volt Amperes. NEC 2008 gives us an easy way to do things in residential. 220.82 Dwelling Unit. (A) Feeder and Service Load. This section applies to a dwelling unit having the total connected load served by a single 120/240-volt or 208Y/120-volt set of 3-wire service or feeder conductors with an ampacity of 100 or greater. It shall be ...


11

If your panel is full, you'll likely want to have the service evaluated, to determine if it's still large enough to meet your needs. It's possible that you may want to upgrade to a larger service, which will likely require new service conductors and a new service panel. If this is the case, you'll simply have a larger panel installed. If you don't have/...


11

I can tell you right now that that liquidtight is too small for what you want to do The AC installer likely ran either 1/2 or 3/4" for the LFMC, depending on the size of the circuit. That's going to be no good for the fat wires you're running, which require 1" for sure if not 1.25" or larger. Never fear, aluminum's here! For wires this size, furthermore, ...


10

The neutral and ground MUST NOT be bonded at a sub-panel. They should only be bonded at the main service panel. If you bond them anywhere other than the main service, the neutral return current now has multiple paths, including though your ground wire. You should be able to buy a second bar for the sub-panel if it really is meant to be used as a sub-...


10

Yes, you can. The systematic computer programmer in me even thinks it's a good idea, allowing a "star" topology for electrical distribution. You will need 4 wires, as others have mentioned. Keep the ground and neutral separate in the subpanels. The only place they should be bonded is in the main panel. You will need ground rods at the new location. Yes, it'...


10

I've labeled your image, to help you understand what's going on. Off to the left, the grounding electrode conductor enters the box and terminates at the grounding bar. The feeder coming in the top of the disconnect has three wires, two ungrounded (hot) conductors, and a grounded (neutral) conductor. The two ungrounded (hot) conductors terminate at the ...


10

Edit: I wrote this answer before the photo was added. I will defer to Harper’s answer that goes into much detail about the problems. You have a 240 volt sub panel which was fed from a 240 volt breaker. Now you’re feeding only half of the sub panel with a 120 volt breaker. Sorry, what did you think would happen? Maybe you don’t understand how dual-leg 240 ...


10

I've built several such sheds, and a #12 UF-B (moisture and UV light resistant) cable (usually gray) is appropriate on a 20A breaker (or smaller). Depending on where you are it may need to be buried to a particular depth. Conduit is a good idea and may reduce the depth requirement. Otherwise, use your best judgement to prevent damage in the future. Because ...


10

It's a rating. Like tires. Go shopping for tires. Almost any tire these days is rated 112 mph. *You're allowed to drive 65 on those, it is saying don't exceed 112 mph*. It's the same with subpanels: The "100A" is a maximum rating. Do not exceed 100A. However, you certainly should exceed your feed-breaker size of 50A. Even if 50A panels existed, ...


10

In the USA you get to play fast and loose with this. If you simply extend with 12 AWG, you'll have 0.6% voltage drop per amp that you draw... so a 1/4 amp battery charger won't give any drop at all, but a 14 amp lawnmower will give you about 8% drop - not good. For permanently installed wiring, I like to keep voltage drop under about 5-6%. So you're pretty ...


9

This is not an answer related to code but simply doing the layman's math. First off the Freezer should be on a dedicated circuit. Not because of any excessive amperage draw, but because if you fire up the table saw and the dust collector at the same time and it pops the breaker, you don't want the freezer being shut off for potentially an undetermined ...


9

Pull 4 conductors (2 ungrounded (hot), 1 grounded (neutral), 1 grounding) (250.32(B)(1)). Grounded (neutral) and grounding bus must be separate at sub-panel (250.32(B)(1)). No need for a GFCI breaker in the main panel, unless your local code requires it. A grounding electrode system is required at the second structure (250.32(A)).


9

This is a "walk in the park" with enough knowledge, but what you've said reveals some gaps. Also an EE degree can do more harm than good, because it encourages you to overthink or "outsmart" the NFPA. Don't go there: instead be paranoiac about not being "that guy". (by the way, hiring an electrician is no cure-all; with the building boom, you may get a ...


8

If you're in an area that has adopted National Electrical Code, you'll have to run a 4 wire feeder. You'll also still need the ground rods at the shed, which you'll bond the grounding bar in the panel to. If it's an existing 3 wire feeder, and there are no other conductive paths between the buildings. Then yes, you'd bond the grounded (neutral) bar. However, ...


8

Go out the bottom, otherwise the hole or any flaw in the conduit will bring water, rust and failure into your box. Use two conduit bodies to make your 180 degree turn. You can do this pretty tight to the box surface if you really want to. Do not strap the conduit to the box, strap it to the wall. Use THWN-2 wire in the cable. This is rated for outdoor ...


8

Watch your stab limits Sure, you can fit as many 100A breakers as you please. What you cannot do is place them opposite one another so they clip onto the same bus stabs. Those little bars of metal, which are typically shared by breakers across from each other, have "stab limits" limiting the max current you can put on any one of them. The stab limit ...


Only top voted, non community-wiki answers of a minimum length are eligible