Electricity: Friend or Silent Killer?

[Bierp]

Ok, this isn't quite technically a Montana question, but I have a lot of respect for the cumulative knowledge of this group and since this is for the shed I just bought that sits at my Montana home-base, I'm not stretching the rules too badly.

Here's what I'm trying to do: I have a new 10x12 wooden shed for our home-base location. Power at this location comes from a typical RV campground pedestal. I have outputs for 50amp (used by my Montana), 30amp (unused) and a 20amp (currently used by crappy, old shed that is going away in a few weeks.)

I want to take the 30amp power to my new shed, then break it off into two 15-amp circuits. This will allow a refrigerator and a freezer in there to have their own circuits as required in their manuals. (Also, non GFCI, which is oddly required.)

So today I purchased a 30-amp, 2 circuit sub-panel and two 15-amp breakers for it. I'm in the process of ordering a 50' 30-amp UL rated cord. (This is TT-30 to L5-30R.) I'm also going to order an L5-30 Inlet Box. My plan is to mount the inlet on the outside of our shed, connecting it through to the wall to the sub-panel. (Yes, I know this isn't ideal, but the requirements of our camping club here state that I cannot have underground wiring and sheds may not be hooked up to permanent power. This RV-power cable would qualify more as temporary power on an extension cord and will keep me out of trouble.)

So, I think all of that is sound, but here's my question. Do I need to ground the sub-panel in the shed?

If I do, that would probably require driving grounding stakes, right?

This is where it becomes clear that I don't really know much about electricity.

The only things that are going to run regularly are the two appliances and maybe a charger for the LED light bar we'll have there, but that will be rare.

Lightning is very, very rare in our area (outside of Seattle).

The distance from the power to the shed is roughly 35 feet, though I'll be running it through a 50 foot 10/3 cord.

Not sure which of these factoids are relevant, just throwing out thoughts.

I purchased a grounding bar for the sub-panel, but it's not going to do me any good without stakes, will it? (It's quite possible that sub-panel isn't the right term here. I'm connecting via an extension type cord to an RV pedestal, I'm not bringing in direct leads from a primary panel. Obviously this is where my lack of expertise becomes an issue.)

I watched one video where a guy has a true sub-panel and he referenced tying a bar back into the neutral, but I have no idea if that's valid or viable.

So please, electricians, put me on the right path here. (and also, please excuse any incorrect terminology I just used!)

Thanks,
Jeremy

[DQDick]

I try not to mess with electrical at all, but that said the first thing you need to do is see how the pedestal is wired. Frequently the assumption is made that you won't use the 50 and 30 at the same time so they are really one circuit and you really don't have both.

[rohrmann]

I did the similar thing with our 10 X 12 shed, installed a small sub panel, wired 30 amp Romex to an RV receptacle on the outside and use a 30 amp RV cord to the 30 amp outlet at the pedestal. No, you don’t need a ground rod at the sub panel, but you do need separate neutral and ground bars in that little box, with the neutral bar isolated from the box and the ground bar connected to the metal of the box. We never exceed 50 amps combined between the 50 and 30 amp services, so we have no problem.

[jcurtis934]

Your she'd is merely an outlet box on the end of the extension cord. No ground bar should be employed at the shed

[Bierp]

Originally Posted by DQDick

I try not to mess with electrical at all, but that said the first thing you need to do is see how the pedestal is wired. Frequently the assumption is made that you won't use the 50 and 30 at the same time so they are really one circuit and you really don't have both.

Hmm, that's an interesting point. Is there a way to test this? Some kind of circuit or continuity tester or similar?

We didn't have issues last summer with the 50 and 20 combo. (Our draw in summer is higher. Multiple AC's and such.) Not sure if that is relevant.

[rohrmann]

Originally Posted by jcurtis934

Your she'd is merely an outlet box on the end of the extension cord. No ground bar should be employed at the shed

In the box, you must provide continuity for all three conductors, the hot leg, the neutral, and the ground. All three must be isolated from each other, but the ground conductor must be attached to the box as a safety ground, so that is why the ground bar/terminal is solidly attached to the metal of the box, where the neutral has to be isolated, because it is a current carrying conductor, and of course the hotleg is connected to the hotleg buss bar which connects to the breakers. The ground bar is not a ground rod, but is just a terminal bar that has several screws into holes that the bare wires of the Romex are connected to.

[MARK A]

Hire a professional, unless you have a meter, and a main panel you don’t have 20-30-and 50A..

Mark

[PNW Fireguy]

The sub panel in the shed needs an equipment grounding conductor from the pedestal NOT a grounding electrode conductor from ground rods. Also in WA the WAC prohibits the use of extension cords for permanent wiring so you don’t want to use that analogy. My answer is brief and not all encompassing.

[steiny93]

couple things

I'm providing intel from my experience with my local electrical codes; your locals may be different.

For permanent structures extension cords don't qualify as 'approved' wiring sources. Use at your own discretion.

When using power within a residential source (house). Subpanels are not grounded separately from the main; they are grounded together. (the neutral in the subpanel isn't bonded to the panel) Dunno what the 'right' answer is for an rv hookup going to a shed but it'd be something to consider.


It sounds like you are trying to get a pair of circuits off a 30 amp for the sole reason to comply with the owners manual of a fridge / freezer saying they need different circuits. At the end of the day, if the two outlets are being powered by a 30 amp circuit, separating them after a subpanel or running them off a single cord with separate inline breakers is effectively the same thing. Except using a cord would meet code while having a panel hanging off a cord doesn't.

[Mark7]

In MN you would need to have a disconnect on the building. They will allow something as simple as a regular light switch for the disconnect provided it is rated for what you are feeding it with. If your sub does not have a mail breaker, you should consider a disconnect ahead of it. Thinking now... thats permanent wiring. Perhaps "pulling the plug" would suffice.

Second... I am sure GFI's are required in that out building. Some don't like them when refrigeration is involved, but newer GFI's are a lot more stable that early ones.

If I were doing this job, I would bond the neutral and ground in the sub panel for your outlet circuits. A 30 amp cord is only 3 wire anyway... I see no need for a ground rod any more than you would drive one every time you parked your RV.

Good luck!

[OzMonties]

Earlier (and even some modern) GFCI’s can have issues with fridge/freezer defrost heaters that for want of a better word, simulate a ground fault when the defrost cycle commences and the heaters energise.
Transient currents or electro magnetic interference from induction motors (fridge compressor) switching on and off can also cause GFCI trips.
The good news, you can purchase ground fault protection devices of reduced sensitivity which are tailored toward circuits that have these types of appliances running on them

[Tselby]

Anytime I've ever ran in extended service I always put a good ground in. in essence that's all you're doing is a extended service

[RichR]

I would be very careful of placing dissimilar grounds on an electrical system- you need to consult an electrician.

[DebNJim B]

"I want to take the 30amp power to my new shed, then break it off into two 15-amp circuits. This will allow a refrigerator and a freezer in there to have their own circuits as required in their manuals. (Also, non GFCI, which is oddly required.)"

Your problem isn't so much the grounding as it is the circuits. Since the 30A line is only 110volts you can't branch that to two separate circuits. The appliances will still be on one circuit. You can have two separate boxes but they will still be on the same circuit.

[rohrmann]

You have more than one breaker protected circuit in an RV with a 30 amp panel. This is no different. You bring the 30 amp power into a small breaker box, and you then have a couple of small breakers, 15 or 20 amp breakers, depending on the expected loads and size of wire connected to the loads, and you are good with multiple circuits.

[Creeker]

As a self employed electrical contractor of 25+ years with a Master license in three states; Read what rohrmann typed in both his posts!

I do not give out electrical advise over the WWW but I will tell you who you should be listening to.

[Bierp]

I definitely appreciate all the input, and yes, I value Rohrmann's input on all posts on this forum very, very much.

So, one little snag I just realized that might throw me a curve. The sub-panel I have doesn't have a buss bar so much as individual inputs for each of the two circuits. Since I'm bringing in 10/3 wire, there's only one hot wire. Can I use a jumper wire to bridge to the second circuit? (Similar to what is outlined in this image, though obviously my setup is different upstream.)

I would think this should be ok, but again I look to the group for advice.


Thanks,
J

[rohrmann]

That's exactly what I did and I also purchased a small ground bus bar to make the ground connections. You should have two connections for the hot legs, just jumper across the two to provide power to both sides for the breakers, just like in the picture.

[Bierp]

Excellent, thanks.

I have the ground bus bar installed already.

I'm bringing the 10/3 through the wall behind the input box. It'll climb the 2x4 inside roughly 4 feet to the panel. I wasn't planning to use any conduit. Is that a mistake?




I'll try to make the rest work tomorrow.

[Bierp]

Success!

Power to the shed has been achieved. Nothing appears to be on fire, so I'm calling that a win!

Appreciate all the assistance.