Is it safe to split a NEMA 10-50 receptacle to a range to add a pair of 5-15 GFCI receptacles?

Unfortunately, I am currently renting, and the homeowner refuses to allow any work to be done. I have lots of experience in wiring things the right away, but I am not a licensed electrician. I really don't want to do this, but I don't really see much of a choice. I'm wondering if it can be done safely.

The main floor of my house only has two circuits to run four window air conditioners, 2 desktop computers, heat lamps for 2 reptiles, ceiling fans, microwave, air fryer, Keurig, fridge, etc. We trip a breaker several times a day. The biggest problem is the computers losing all unsaved work. I've thought about getting a UPS for them, but it charging its battery after every outage could just make things worse. We were tripping breakers several times a week even before we started using the air conditioners.

We only trip breakers when someone is using the microwave, air fryer, or Keurig. If I could add a circuit or two to the kitchen, we'd be all set. The Frigidaire fef389cfsk range uses a NEMA 10-50 on a dedicated 50a breaker. I'd like to move the 120v kitchen appliances to that 120/240 circuit. We don't use the oven in the summer anyway, but we do still use one of the burners.

Since the 10-50 does not have a grounding conductor, I'm thinking I should use a pair of 15a GFCI receptacles, since GFCIs are rated to run safely without a ground. I would take a standard 10-50 range cord, run it to a 10-50 receptacle for the range to connect to, then to a pair of 15a circuit breakers, and finally into a pair of GFCI receptacles (one for each ungrounded conductor) mounted in a metal box. So this would be a custom-built plug-in adapter. I would not be making any changes to the range or the existing wiring.

My biggest concern is the metal frame of the oven. If the oven was wired correctly, it will be bonded to the grounded conductor. The same conductor that just 6' away the microwave would now be using as a current-carrying conductor. I'm assuming the range already uses the grounded conductor as a current-carrying conductor for its lights, clock, timer, etc., but those are all minor loads. The reason ranges are being switched to four-wire cords, instead of three, is so the frame is not bonded to the grounded conductor, but only to a separate grounding conductor. I just don't have enough experience jury-rigging something like this to know if that is a real problem or a theoretical one, or if there is another problem I'm missing.

Better ideas are always welcome.

Thank you.

  • How old is the house in question? Is moving some things off these two circuits an option at all? (say to a second floor room, or to the basement?) – ThreePhaseEel Jun 1 at 2:19
  • 1917. No second floor. I can't figure out a way to get an extension cord to the basement without drilling a hole. Basement steps are out back. – Pascal Jun 1 at 2:55
  • I take it there are no outlets in the basement? – ThreePhaseEel Jun 1 at 3:04
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    Is the landlord forbidding you to DIY electrical? Or is he forbidding you to hire a competent electrician to do the electrical? – Harper - Reinstate Monica Jun 1 at 13:05
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    Put those computers on a UPS if you value your data! Also, they'll help smooth out the power dips that must be happening any time you use power anywhere else in the house. I'm not certain, but I really don't see the charging cycle using all that much power, but even if it does, having slightly dimmer lights while charging would be better than losing data or blowing components. – FreeMan Jun 1 at 14:15

The grounding/GFCI scheme sounds plausible. However, you still have a big problem that the 15A receptacles will be on a 50A breaker. They must be on 15A or 20A breakers. Anything larger and you risk a problem of an appliance fault that doesn't cause a ground fault but results in 2X overcurrent (i.e., 30A or possibly more) never tripping a breaker and instead causing a fire from overheated wiring.

In addition, there are code issues with removing and/or piggybacking on the range circuit. But ignoring that (e.g., if you simply unplugged the range and heated everything in the microwave) you still have the true safety issue of 15A/20A receptacles on a 50A circuit breaker.

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  • I've used UPS PDUs before with built-in 15a breakers. No idea where I'd get any though. – Pascal Jun 1 at 2:50
  • That works (not necessarily to code, but "works") if you hardwire your UPS into the circuit. But you aren't talking about hardwiring, you are talking about receptacles. But a dual receptacle might have the server on top and the bottom open for the toaster, mixer, Keurig, etc. Any of which can have a fault and burn the house down because the 50A breaker didn't trip. – manassehkatz-Moving 2 Codidact Jun 1 at 3:09
  • I was thinking more along the lines of taking the same type of 15a inline circuit breaker that I've seen in UPS PDUs before (the type where the UPS has a 30a outlet and the PDU only has 15a outlets) and wiring those inside my adapter between the 10-50 receptacle and the 5-15 GFCI receptacles. – Pascal Jun 1 at 3:17
  • APC MXA101 is the kind of PDU I was thinking of. It has a 30a input and five 15a inline breakers for its 15a receptacles. No idea where I can get those breakers though. I guess that PDU is what I'm planning to build, just with 50a passthrough instead of the 30a it offers. – Pascal Jun 1 at 3:21
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    No, just no. You're coming up with a kludgy solution to a very real problem. If anything went wrong, you could cause serious damage to yourself or the building. This is the kind of stuff that would be perfectly acceptable building in a lab as an experiment. But not in the kitchen of a rented house. – manassehkatz-Moving 2 Codidact Jun 1 at 4:02

Part 1: Know your loads

Unfortunately, I am currently renting, and the homeowner refuses to allow any work to be done.

I feel you. Same situation here, except my service is 120V/30A split to two 20A circuits for the whole house.

We trip a breaker several times a day.

STOP. DOING. THAT. Right now!

When a breaker trips, reset it ONCE. If it trips again, leave it be for an hour. Why? So the wires inside the walls can cool down.

We had the same problem with kitchen appliances, heater-fans to warm the bathroom and office, all stacked on top of one another. I sat my sweetie down and I said "Let's talk amps." I showed how to find the nameplate on a toaster or heater-fan, to look for "amps" in the 1-13 range or "watts" in the 10-1500 range (and divide by 120). The toaster is 8-ish amps, the heater-fans are 12.5 (unless on low, then 6). The last trip (and some intentional shut-the-breaker-off testing) told us which outlets and lights are on which circuits. Now it's straightforward. Crunch the numbers. Toaster + heaterfan = set heaterfan on low to allow some headroom (limiting pull to 14A).

We do the dance. Haven't had a trip in gosh, when was that, I wanna say 2016?

I have lots of experience in wiring things the right away, but I am not a licensed electrician. I really don't want to do this, but I don't really see much of a choice. I'm wondering if it can be done safely.

The main floor of my house only has two circuits to run four window air conditioners, 2 desktop computers, heat lamps for 2 reptiles, ceiling fans, microwave, air fryer, Keurig, fridge, etc.

Do the dance. If necessary put stickers on every appliance indicating its amperage draw (either derived from nameplate or from a Kill-a-Watt power meter). You'll quickly discover the reptile lamps, ceiling fans and fridge are basically rounding error, and you'll identify certain specific appliances which are piggies. (generally, things which make heat).

As for the PCs you'll need to get a Kill-a-Watt and measure actual load in different states of operation. Idling or word processing will be quite different from running CS:GO at 120FPS and 4K or whatever.

In the kitchen it's pretty straightforward. You just rolled down a list of heat appliances. The default draw is 1500W (12.5 amps), and the microwave may go as high as 1800W (15A). Because that's the UL hard limit for plug-in appliances. In our house the kitchen is super easy, only use one at a time. And in your case make sure the other stuff on that circuit is below 3A and you're golden.

Breakers have a fairly forgiving trip curve. They're designed to allow short term overloads since wires take time to overheat. So when you are tripping, you're way overlimit.

You don't have a prayer until you get conscious of your loads. Then it's just a numbers game. Make sure there's room on the circuit for what you're about to run. Walk the house, pause 2 air conditioners, do the kitchen stuff, turn em back on. I bet the PC is rounding error if you're not gaming.

For us, knowing our loads solved the problem.

I'm glad your onboard with avoiding hokey-dokey

Like this thing here you mentioned, there are 2 sources for those suicide cords. That one is from Cooter down in Fool's Hollow, who knocks them together on order. Cooter doesn't have any assets, so when that rig kills your wife, you have no recourse. The other source is China, good luck suing them. Of course, eBay, Amazon Marketplace, Banggood, DealExtreme, AliExpress and other direct mail sources are full of toxic dangerous junk. Avoid all of it.

The zoro.com item is an electronic component, and you can't use those directly as mains wiring equipment. It's either more cheap Cheese or it's RU Recognized, meaning if you were getting equipment UL-Listed, UL would ignore that component since it's preapproved.

Grounding is the biggest issue. That's what prevents you from just grabbing any random PC-grade PDU (that is UL-Listed).

One alternative to grounding is to fit a 2-pole GFCI breaker, change the socket to grounded (NEMA 14-50) and label it "GFCI Protected/No Equipment Ground". Then a 50A PDU would plug right in.

Part 2: the hard way

Honestly, if it were me, and I could not solve the problem with load management, here is what I would do. All of this is a big fat code violation - let's be clear on that.

As it happens I've been looking at very compact panels. Square D makes a "QO" 8-space barely bigger than a sheet of paper. I'd start with a piece of plywood and bolt that panel to it. I'll leave the layout to you. Then I'd come off it with 1/2" EMT conduit or just conduit nipples, out to 4-11/16" (120mm) square boxes, as many as 4 of them.* Power can pass through boxes, so feel free to put a 2x2 array of them on one side of the panel. Don't mount boxes flush to each other or you won't be able to get the cover plates on lol. Many nipples give you 1/4" or 1/2". Screw everything firmly into the plywood; use short screws.

I would get 2-gang mud rings* or Decora domed covers* for those. The mud rings can be pretty flat. These metal big deep boxes are specifically for the space two GFCI+receps take up. (you don't wanna know the price of a GFCI breaker in QO).

The GFCI receps will ground through their mounting ears. No need to wire a ground.

Through the conduit, I'd run black white brown gray. The electrical supply house will probably sell you the gray by-the-foot. Gray is the "alt" color for neutral. So black+white is circuit 1, brown+gray is circuit 2. If you need circuit 3+4, those are red+white-tagged-red, and blue+gray-tagged-blue.

This rig can support up to 8 circuits, so with 15A circuits that'd be (nameplate) 60A per leg which is overkill because we provision circuits on the assumption that only some are used at a time. Even eight 20A circuits (nameplate 80A per leg) is totally fine on a 240V/50A feed.

You don't need any grounds because the receps ground through their yokes and EMT carries the ground, but here's the important thing: Do Not, DO NOT connect neutral to ground ANYWHERE. The steel boxes are not GFCI protected, so we want the "grounding ha ha" in this system of metal totally isolated from the neutral coming from the NEMA 10-50. Because that neutral can be dangerous! That's why NEMA 10-50s are banned. That means remove the ground strap/screw from the neutral bar. If leakage happens between hot or neutral and the chassis of this thing, you're up the creek pretty much, because it's on the wrong side of the GFCIs to save you. So I would look for a way to independently ground this chassis.

To bring power into the thing, I'd use a standard NEMA 10-50 range cord and land the wires on the hot and neutral lugs. Take the range cord to the electrical supply and have them sell you an appropriate strain relief to enter a knockout.

That's about the best I can see to do. It's bad, it's Code-violating, but at least we're doing our best not to kill you.

* Get these at the electrical supply, they're twice as much at big-box.

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