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I have an electric dryer (Samsung DV42H5000EW) and it is connected to a 30A (I believe it dual 30A as there are 2 arms that are connected to each other both saying 30A) 240V breaker. The wall socket is a 10-30R connection at the dryer. I believe 10-30R sockets require 240V if I am not mistaken. The house was built maybe 10/15 years ago. I am guessing the wiring is still good and nothing wrong (that i have seen so far)

I am running some bitcoin/altcoin mining equipment from this wall socket when the dryer is not in use. The equipment came with China GB2099 to C19 power cords. They use 2100w. I am in the USA so these cords will not work for me.

What I ended up doing is getting a 10-30P to L6-30R converter, and purchasing a L6-30P to C19 so that I can connect it to the mining equipment.

This works perfectly. I can run one of the machines off of this all day with no issues.

I figured since it's 30A 240V I can technically run 2 of the 2100w machines on the same power outlet as I am below the 5760w (80% continuous load threshold). I purchased a C20 to x2 C19 splitter so I could connect both machines. I ran it for 2 or 3 days with both of them running without any circuits popping or issues with the machines themselves.

My wife asked me to turn off the equipment so she could use the dryer. When I did I noticed the plastic receptacle (10-30P) was warm to the touch as was the first 6 inches of the wire. But both of the hot (Left/right) prongs on the 10-30P were HOT. I could only touch them for a few seconds without having to take my fingers off. The top/bottom prongs were just warm. I checked the rest of the cables and nothing was hot/warm anywhere else. Just on the 10-30P and first 6 inches of wire.

Once my wife was done with Laundry, I checked the 10-30P (for the laundry machine) and it was not warm at all. I reconnected the mining equipment and ran both of the machines again for a few hours and checked the 10-30P. Same thing. Receptacle was warm but the hot prongs were HOT.

I let it cool down and connected it once again but only one of the machines this time for a few hours and the 10-30P was not warm and the prongs were barely warm. I know the circuit can handle the load as I am well below the 80% threshold.

Do you think the wall socket (10-30R) needs to be replaced. The 10-30P to L6-30 connection? Should I not be running this load on this socket/circuit? Did I put myself in danger by running them both on the same circuit?

I am a little confused as to why it's getting so hot if it is rated to handle that load. I figured I would try to get some help here before I call and pay an electrician.

Thanks in advance.

-- Edit

Thank y'all for the help. I instead opted to setup a co-location contract with a local data center that will provide the power/cooling/facilities at almost the same cost it was for me to run it in my garage. Safer and much more of a legitimate location for the equipment. I am having an electrician come out to replace that plug with the 14-30 like suggested. i did not know it was outdated.

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    Are you putting yourself at risk with Chinese electrical cords on a 30 amp outlet with multiple adapters ? We can start counting code violations if you would like. The answer is yes , you have 14 awg cords on a 30 amp circuit to start with (those cords are only rated at 15 amps), by swapping that plug in and out it will get looser, as it heats up this will affect the force holding the prongs and they will start arcing , now when that happens and your bitcoin mining platform goes up in smoke from the spikes generated by arcs, it’s hot= BAD install the correct circuits before it is two late. – Ed Beal Jan 20 at 18:42
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    The heat is a warning! Something isn't right. Your total wattage is 4,200 continuous. While a clothes dryer typically is rated between 3,500 and 5,000 watts, it's doesn't draw that continuously, the element cycles on and off to maintain the desired temp. This is especially true if using a "delicate" or "warm" setting. Also, being almost an entirely resistive load, the power factor is going to be very near 1 (one), your BTC miners might have power factor low enough to cause problems. Also, your receptacle might be compromised at this point due to the heat, the jaws may have metal fatigue. – George Anderson Jan 20 at 18:45
  • Yeah, I've seen a dryer plug + receptacle burn up before, likely due to either a badly torqued screw or failed spring tension in the receptacle contact itself. – ThreePhaseEel Jan 21 at 0:22
  • Can you turn the dryer breaker off and post a photo of the inside of the receptacle box please? Replacing the receptacle "like for like" may not be your wisest move here, given the recency of the house... – ThreePhaseEel Jan 21 at 0:23
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    I just discovered your "2100W" number is apocryphal (made of myth and legend). You got it from the volts and amps on the DC buses. It has nothing to do with the AC requirement in amps or VA, which is what matters to provisioning. One of those will be on the AC power supply nameplate, and the supply I spotted online said 15A. Now you derate 80% (125%) of that, giving 18.75A you must provision. It might not actually draw 15A, and if you measure the supply's performance in worst-case conditions and it is lower in amps or VA, then you can provision for that instead. – Harper - Reinstate Monica Jan 21 at 1:57
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The reason that certain sized wire must be used for a given amperage is because the wire gets hot when electricity is pulled through it. That said, some equipment from China isn't known for complying to all the regulations we have, and the conductors in the adapters could be undersized.

Many conductors and connectors are rated for 75C, which is 167F, and certainly hot enough to burn you. However I don't think anything that you can easily touch should get that hot while in use, so I would assume that something is wrong. I would suspect the adapter first, but you should also measure the amount of current the equipment is using. It could be pulling a lot more than you think (closer to 7000W) which would overheat an adapter that was probably meant for closer to 4000W.

If you wanted to tinker with the wall outlet, you can make sure the wire clamping screws are tight, and they have a good, solid connection. The dryer works, and the computers work, so I don't think anything is "wrong" with the wiring itself.

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Don't bother calling an electrician. You'll pay $200 for a lecture.

You've been putting yourself and your wife in danger for quite some time.

You're really playing with fire with that dryer socket

The NEMA 10 is an obsolete, dangerous and illegal (for work since 1989?) dryer socket. It is widely understood that it is fragile, and is not intended for frequent interchange of plugs.

It does not have a ground wire. Worse, the appliance industry lobbied NFPA to allow an "exception to code" in which the wire can be "pseudo-grounded" by attaching it to the neutral wire. The rationale for this outright bootlegging is The recep is rarely disturbed, since the plug is never touched except when people upgrade dryers.

Good thing too -- because in this kind of bootlegging, when the neutral wire fails, the chassis of the dryer is energized with line voltage. Further, there's a washer sitting right next to it that is properly grounded. Nothing has GFCI, so this is a recipe for murder.

What's the price of a human life? In BTC?

The art of bitcoin mining is containing costs

Let's tally up the costs so far, shall we?

$50 -- 10-30P dryer plug to L6-30 twist-lock (shady Amazon seller, as it's illegal)
$22 -- L6-30P to NEMA C19 (shady seller off Amazon, also illegal)
$25 -- C20 to dual C-19 splitter from showmecables.com
$97 total just in hokey dokey adapters

As opposed to

$10 -- #10 ground wire to retrofit ground to dryer recep location $8 -- the modern Leviton 30A NEMA 14-30R recep
$11 -- Eastman 6-ft 10/4 4-wire dryer cord
$20 -- 240V/20A breaker x 2
$25 -- 50' of 12/2 cable
$1 -- 2-gang steel junction box
$1 -- blank cover plate for steel box
$8 -- 2 strain reliefs for supplied cords
$84 total to run 2 new circuits properly and fix the dangerous dryer socket too

In this case you simply cut the useless Chinese plug ends, send them through the strain reliefs, and mount them in knockouts on the box. Save cost of NEMA 6-20 sockets and 6-20 plugs, which are about $10 a pop.

Why

A 30A breaker cannot protect a 9 amp miner. It just can't. If that miner has a problem, the 30A breaker will go get marshmallows and graham crackers and make Smores. It will not trip. This 9A load must be plugged into a 15A circuit (or 20A due to an exception).

You need ground and the NEMA 10 dryer plug doesn't have it. The dryer has neutral, and you're bootlegging ground from neutral. Sockets that have ground are NEMA 6 or NEMA 14.

Those hokey adapter cords are junk-ola. They cannot get a UL listing (read: UL won't list them, because hooking a NEMA 10-30 to a NEMA 6-30 involves bootlegging ground; they're fine with 6-30R to 14-30P). As such, builders don't even try to build a quality product, and hork-a-dork them together as they please. I bet the builder is some random handyman who doesn't even own a torque screwdriver. (hence the overheating).

The dryer pulls just as much current as the miners, so the socket heating is clearly due to the hokey-dokey adapter. This is why I never buy illegal adapters off eBay, I make 'em myself! J/K, I do the job properly because as you can see, the proper job is cheaper than the fairly expensive connector shells, especially in the NEMA L family. The fool selling you the $50 adapter isn't buying a yacht off the proceeds, since there's probably $30 in materials in that, plus all the BS of dealing with Amazon shipping, plus the civil liability when one of those adapters kills someone.)

The US has a socket type that is comparable to EU/Asia sockets; it is the NEMA 6-15 and it breakers at 15A. In our tradition of having a 20A circuit/socket that is backwards compatible with the 15A socket, we also have a NEMA 6-20, which breakers at 20A, and delivers a blistering 4800VA of power. Take that, Europe! (2 of your beasts is a wee bit more than 4800VA after the 125% derate (you call it an 80% derate, same thing), so a duplex 6-20 won't quite do.)

Since those receps are expensive, I got rid of them entirely and have you hardwire the supplied cord straight into the circuit.

Speaking of that, big problem. I went and looked up your "2100W" power supply. 2100W is the output of the power supply on the DC-bus side. I should've had a hint when it was quoted in "W" instead of "VA". You can't provision 125% of the output load! (125% = your 80%). The 125% isn't for internal efficiency/power factor! You have to look at the AC-side nameplate specification. "2100W" power supplies actually have a 15 amp spec, and that's about right given the poor efficiency and power factor of these things. Now you multiply by 125% and get 18.75 amps. So clearly, one of these per 20A circuit. VA is "watts" that takes takes into account power factor. Power factor is "You have to generate/deliver the entire sinewave, but I'm only gonna use parts of it".

Wacky illegal stuff is the nope

I recognize that you have to buy the bitcoin mining units themselves from China. But as far as everything else you procure that relates to mains power:

  • Alibaba/AliExpress/Chinatown variety store: NEVER
  • eBay: NEVER
  • Amazon Marketplace (Sold by and ships from XXX): NEVER
  • Amazon Marketplace+Prime: (Sold by XXX and Fulfilled by Amazon): NEVER
  • Amazon proper (Sold by and ships from Amazon.com): source of last resort (contaminated by counterfeits; wildly overpriced), then see Home Depot
  • Local Electrical Supply house: YES, YES, YES: Best selection, best price on anything out of the mainstream; will not give bad advice.
  • Home Depot / Lowes / Menards: YES if the item is UL, CSA or ETL listed with a file number
  • HWI / ACE / local hardware store / Target / Kmart: see Home Depot
  • Walmart retail: See Home Depot
  • Walmart online: See Amazon. Literally. It's Amazon.
  • Local PC shop: power cords only
  • Mouser / Digi-Key: NO (RU listed not UL)
  • Grainger / McMaster-Carr / GALCO: Probably yes
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    sorry @manassehkatz for the cross edit, I just realized the "2100W" number is completely bogus. – Harper - Reinstate Monica Jan 21 at 1:52
  • Lets make this more simple. He needs to buy an digital meter with an "amp clamp" to see how much power his BTC miners are actually drawing. He may have to split up a cable to get the amp clamp around one conductor, but it's worth destroying a cheap cable to get an accurate amp reading. I also think some comments are not realizing the servers are running at 240, not 120. 2,100 watts at 240 is only 8.75 amps. . So for 2 that would be only 17.5 amps. No way that could heat up the plug like that. So I do agree something weird is going on here that he needs to get sorted out. – George Anderson Jan 21 at 6:44
  • @GeorgeAnderson The clamp meter would be helpful. However, 2100 watts isn't at 240V, it's at 5V. That is the power supply's output spec. The power supply has to convert it. If it had 100% efficiency and 100% power factor, yes, it would be 8.75A, however the power supply has neither - by a long shot. The one I googled had an AC-side nameplate of 15A or 1800W. That's about right for cheapies given inefficiency and crud power factor. – Harper - Reinstate Monica Jan 21 at 9:49

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