Splitting generator output question

[Steve Fish]

Hi guys I’m trying to get power into the laundry room in preparation of whenever our next storm will hit. What I would like to do is bring the 240/30amp side output through a wall (10”concrete) and then split it into 2 15amp circuits. This will all be independent of the house wiring so no need for the backfeed discussion. I just want to make sure what I’m doing is as safe as possible. I will post some pics of the parts I have on hand. I don’t mind constructive criticism so please fire away. Thanks!
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[Jim Becker]

You need to use the four wire side of the 240v output to provide two 120v circuits because you need the neutral for those circuits. So you will need an appropriate matching 240/120 four wire male plug, a hunk of appropriate cable that has two hots, a neutral and a ground and a quad box with two dual 120v receptacles and appropriate cable clamp for the cable coming from the generator. Assuming that the box is metal, your ground must connect to both the receptacles and the box. The 'borg should have rubber coated cable that's great for this kind of thing and they sell it by the foot. You could also cannibalize a four wire generator supply cable and replace the female end with the box, et al, that I've already described.

[Rollie Meyers]

You cannot put 15A receptacles on a 30A circuit, it is just wrong from a safety & code prospective, a better is to get a small loadcenter, and put in 15 or 20A circuit breakers in it with GFCI receptacles, or GFCI circuit breakers, there are more details to do it right.

[Steve Fish]

You need to use the four wire side of the 240v output to provide two 120v circuits because you need the neutral for those circuits. So you will need an appropriate matching 240/120 four wire male plug, a hunk of appropriate cable that has two hots, a neutral and a ground and a quad box with two dual 120v receptacles and appropriate cable clamp for the cable coming from the generator. Assuming that the box is metal, your ground must connect to both the receptacles and the box. The 'borg should have rubber coated cable that's great for this kind of thing and they sell it by the foot. You could also cannibalize a four wire generator supply cable and replace the female end with the box, et al, that I've already described.

this is basically what I’ve done using the output shown on the right in the pic above. I have #12 wire but was wondering if I needed #10 for the neutral because it would be shared between the two circuits. My other concern is that I have plastic boxes and conduit so I’m not sure about grounding the generator itself? The reason I wanted plastic is everything metal goes to rust down here even galvanized stuff.

Rollie, I’ Leaving the left (3 prong 30 amp) outlet as is to feed the dryer which I was going to address next if this discussion got any traction. If that was the only outlet I would have used a sub- panel and breakers as you suggest

Thanks for your input guys

[Scott Brader]

I haven't used this product, but have seen it several times and would probably at least consider it for an application like yours.

https://www.amazon.com/Reliance-Control-Corporation-WKPBN30-EMW3790037/dp/B0743BQDT4

Scott

[Mike Henderson]

this is basically what I’ve done using the output shown on the right in the pic above. I have #12 wire but was wondering if I needed #10 for the neutral because it would be shared between the two circuits.

If I understand what you're doing - that is you have a 240 volt circuit with a neutral and you want to tap 120 volts off of each side (hot to neutral) - then your neutral is fine with #12 wire. The two hots are out of phase so the currents subtract on the neutral.

For example: If you have a 10 amp load on one side and nothing on the other, you have 10 amps on the neutral.

If you have a 10 amp load on both sides, you have zero current in the neutral - not 20 amps.

Mike

[Frank Pratt]

Like Rollie said, you can't put a 15A or 20A receptacle on that 30A circuit and expect to stay safe. Doesn't matter if you use #10 wire, the receptacle is still good for only 15A. If you proceed with this, you may well have a burned down hours to add to your power outage worries.

You can get a cheap, small 4 circuit panel, fill it with 15A breakers, & connect it to 4 receptacles. The other 30A circuit can't be used for the dryer because it has no neutral. Most dryers need 120V for the motor & controls.

[Steve Fish]

I spoke with Caterpillar customer service. They are very helpful and on call 24/7 which is good to know. I pretty much got the green light for what I need to accomplish. I just need to keep loads balanced across both sides. Here’s their cord that splits the 240........
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[Jim Becker]

If you can get a pre-made cable like that, jump on it. Much safer than rolling your own, IMHO. But yes, pay attention to balancing between the two sides and keep in mind this is absolutely for short-term, emergency use.

[Steve Fish]

Yeah for sure Jim. Eventually I will have the service panel replaced and I will probably go with a little bit bigger generator and an interlock system. Unfortunately I have to gut half the kitchen to get access to where the proper generator feed needs to go. Our walls are all concrete and block down here so it’s not easy. Thanks for the input everybody especially you guys that wouldn’t let me burn the house down. I do appreciate the heads-up

[Jerome Stanek]

Doesn't your generator have two 120 out lets mine has one from each side of the 240

[Jim Becker]

Doesn't your generator have two 120 out lets mine has one from each side of the 240

Some generators only have 240v output.

[Steve Fish]

Doesn't your generator have two 120 out lets mine has one from each side of the 240
Yes it does, currently those are already feeding into the main level. I’m just trying to avoid running outside in the middle of a storm to switch wires and extension cords around at the generator. All outlets are “hot “ all the time, no selector switching. So I’m only planning on drawing power from one source (120,240 etc) at a time to avoid overloading

[Mike Cutler]

. My other concern is that I have plastic boxes and conduit so I’m not sure about grounding the generator itself? The reason I wanted plastic is everything metal goes to rust down here even galvanized stuff.

Thanks for your input guys

Steve
What type of generator do you have? Is it a "Bonded Neutral to Frame", or unbonded. Regardless of plastic box or not, the ground still has to be carried through your "system". When using plastic boxes the ground wire is attached, electrically, to the yoke of the duplex receptacle, or switch. In a metal box, it is attached to both.
You run a significant risk of encountering a differential ground potential with what you are describing.
Most generators made after 2012 have to meet the OSHA requirements for a "Bonded to Frame Neutral". What this means is that the neutral return, the ground, wire(s) and the frame of the generator, are all at the same electrical potential. Some generators have a switchable neutral, most do not. In a "bonded to frame" generator the frame of the generator itself, is now "the reference". It's an odds on bet that your generator manual will tell you to drive a ground rod at the generator and attach a ground cable between the frame of the generator and the driven rod.
If you are going to be bringing power from an independent source into your house, everything better be at the same ground potential.
The extension cord, power inlet box, and stand alone breakout panel, are available through Generators Direct.
If you will have the ability to touch the metal part of any appliance plugged into your temp power system, and the bare metal of any appliance in your house not powered by your temporary power, but still electrically referenced to your main service panel ground, you will probably get a shock due to the difference in ground potential.
You really need to sort out the grounding requirements though.

[Jim Becker]

Yes it does, currently those are already feeding into the main level. I’m just trying to avoid running outside in the middle of a storm to switch wires and extension cords around at the generator. All outlets are “hot “ all the time, no selector switching.

That's interesting...the portable generator I had prior to getting my whole house unit would only permit "either" 120v or 240v, but not both simultaneously.

[Mike Cutler]

Jim
My "portable" generator has multiple outlets, of differing voltages, and amperage ratings. I have a Generac GP-17.5KW, generator.
I have a 240/50amp, 240/30 amp. 120/20 amps, both GFCI protected, and not, at the generator, and 12vdc.

A person running a portable generator, whether back feeding, or not, really needs to understand the grounding. Probably, at most, there will be problems with GFCI protected circuits, but,,,,
Lots of "newish" NEC codes, and OSHA requirements, have happened in the last decade. If you're going to run a portable generator, be damn careful, or break down and hire an electrician to install all the correct electrical equipment. Or, do as you have done, and install a permanent standby unit.

Off the soap box for now.

[Steve Fish]

Yes Mike, it’s ground neutral bonded to the frame. I’ve done a little more digging on the ole interwebs since I started this thread. Driving a ground rod in is in the game plan. The schematic can be found here.

https://s7d2.scene7.com/is/content/Caterpillar/CM20160617-56278-10847

[Bruce Wrenn]

I've just finished doing you want to do. At the entry point, I have a disconnect box from an AC unit that has two 20 amp breakers, which the 30 amp 220 feeds. From the generator to house, i use a #10, 4 wire cable with NEMA L14-30 ends on it. The disconnect box has a built in male NEMA L14-30 plug. From the breakers to recpt., I'm using #12 wire. Because I'm feeding a outlet box with two 20 amp recpt. in one box, which means two circuits, the breaker has tie bar connecting both sides together. This way if one side trips, so does the other. I also am building a generator shed, and have added electric start to generator. I own more generators than I have fingers on one hand, plus I bought another today. If it wasn't so late and seller so far away, I would have bought another in the last hour

[Jeff Body]

When hurricane Irma came through I was so unprepared it was scary. And I might add I had a wife that was 8 months pregnant at the time. I ended up going alittle overboard.
I purchased a Generac 7500W generator, Built a small lean to shed on the side of the house, and wired up a breaker panel interlock kit.
The hurricane that almost came through last week I felt so much more prepared.
With this generator I can power everything in the house except the central AC. BUT if I really want to run the AC I can make a few adjustments , like turning off the water heater, and any other unneeded rooms, to the breakers I can run the central AC.
I use alittle trick I picked up from some AC techs I know. I'll mostly only use that when we go to bed.

And I just realized I don't have any pictures of the shed finished.


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[Rollie Meyers]

I spoke with Caterpillar customer service. They are very helpful and on call 24/7 which is good to know. I pretty much got the green light for what I need to accomplish. I just need to keep loads balanced across both sides. Here’s their cord that splits the 240........
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The locking plug looks like a 20A, if it is a 30A then there is a problem with the 20A connectors.

[Frank Pratt]

The locking plug looks like a 20A, if it is a 30A then there is a problem with the 20A connectors.

That's an important point that at least one other poster and myself brought up, but it's being completely ignored by the OP.

[Mike Henderson]

The locking plug looks like a 20A, if it is a 30A then there is a problem with the 20A connectors.

I know a lot of this stuff is code, but why would there be a safety issue if the male plug is 30 amps? When we run a multidrop convenience outlet circuit we put 15 amp outlets on a 20 amp circuit breaker.

If the wire in this extension cord is rated for 30 amps, you could plug multiple loads into the 20 amp female plugs, as long as the total does not exceed 30 amps - and any individual load does not exceed 20 amps. I'm being general here and not taking into account any derating that might be required for a continuous load. I note that the circuit breakers on the generator are labeled as 28 amps.

Mike

[Jeff Body]

The locking plug looks like a 20A, if it is a 30A then there is a problem with the 20A connectors.

Nope.... That's a 220V 30A L14-30 locking plug. 20A plug has the key prong going outward and the 30A has it going inward.
When I was looking at generators some of them came with this cord and it plugged into the 30A outlet.