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Thank you for the help. Please feel free to tell me how I’ll melt myself. But really I just want to use a low-power way to dry clothes while not using the stove.

Summary:

The dryer itself (heat pump) is low-amp (max < 3.5a @ 220v), and the stove that will share the outlet pulls ~17a with two burners set to max.

Details:

1 — Wall plug is 14-50

2 — Amps at the breaker = 40a, dedicated, handlebar-tied

3 — Amps typically used by the dryer @ 220v: 3.2-3.5 amps max (measured on two friends’ units).

4 — Stove amps / my max use: Two burners use 17-18a total.

• Given the 80% rule: recommended max draw is ~7,500 watts / 32a at a time. • The dryer running with two burners at max (won’t use at the same time anyway) = ~20a

My concerns: (1) If the dryer is made for a 30a service, would that pose an issue re: internal wiring somehow (despite the low 3 amp / 750w draw)?

(2) The outlet splitter is UL listed, made my a US company, manufactured in China (of course). Any bad ideas there?

I can’t change the wall service or upgrade at the box, as I’m renting. Fortunately, it was renovated a couple of years ago, is a big building, is in a major city.

14-50 splitter I’m considering — www.amazon.com/dp/B079JPWSZT/

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    Splitting 220/240 is iffy best of times. Doing it when renting is getting into illegal/lawsuit territory.
    – crip659
    Oct 18, 2022 at 20:17
  • What 80% rule? Neither of these are continuous loads.
    – KMJ
    Oct 18, 2022 at 21:05
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    That splitter cord doesn't appear to be UL listed. Parkworld also sells a bunch of sketchy adapters that are a Bad Idea, such as 14-50P to three 5-15 outlets.
    – KMJ
    Oct 18, 2022 at 21:07
  • Thank you all, for the honesty. I won’t do this if it’s unsafe. I suppose my question is now: due to the splitter being a point of failure itself, and that the 30a washer would be on a 40a circuit (not a good idea absent a way to stop current to the dryer if it starts to encroach 20+ amps), it’s an idea that could go wrong, and the wrong is big enough to be an issue. Oct 18, 2022 at 22:29
  • I can’t pay to have things rewired because I’m in a rental and won’t be able to get permission. Otherwise I would love to do it right regardless of the cost. Looks like I’ll spend $1500+ ($1k extra than the open-box 240v heat pump dryer) and get a 120v Miele model. Which is the only 120v I can find that’s available in the US. Thank you again for educating me. Though I had a bias, and wanted it to work, I knew I had to understand better. You have all helped. Oct 18, 2022 at 22:53

2 Answers 2

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You have to do Load Calculations the official way

No, you don't get to "make up" your own method of provisioning circuits. You have to follow the official methods documented in NEC.

  • The dryer is provisioned based on the data on the nameplate, which indicates its operating amps or VA. Heat pump dryers are entirely motor loads (but multiple motors) so NEC 230 applies. Hopefully the nameplate will state a minimum and maximum breaker size. I do not believe a 125% derate is applied to dryers.
  • The range also has a nameplate. You must run that through NEC 220.55 to compute the size of the circuit required, however if the documentation specifies min or max breakers that too must be respected.

We can help with these calculations if you post nameplate data.

It seems extremely unlikely that both accept the same circuit breaker size.

As such you will need a subpanel to give them independent power behind their own breakers. You're not allowed to under-fuse a range or dryer, but you are allowed to oversubscribe the subpanel.

Beware 3-wire connections

Note also that "classic" 3-prong connections for ranges and dryers are dangerous as all getout, because the 3rd wire *is not ground, it is neutral. They tie the machine chassis to neutral, so when the neutral wire has a problem, it energizes the chassis of the machine and kills people - usually children who squeeze behind the dryer to fetch a ball or something, their muscles twitch madly but it doesn't push them out of contact because of the confined space. What a way to die.

If you have 4-wire supply, by all means use it.

However if you are stuck with 3-wire connections, here's a trick. Heat pump dryers don't need neutral. Ranges don't need neutral. Ovens need neutral, but only for the oven light and sometimes electronic controls. So try NOT hooking up neutral to the oven. If it still works (sans oven light) then you don't need neutral. Convert the 3rd wire to ground only and don't connect neutral.

In that case, the subpanel can be wired 3-wire with no neutral. Leave the neutral bar empty. Buy an accessory ground bar, paint it green in an obvious way, and use that for grounds. Remove the neutral bond. That way if some half-wit fits a 120V circuit later, it won't work.

Don't buy electrical gear mail order

14-50 splitter I’m considering — (link)

Well, Mr. Rockefeller, if you can afford that pricey thing you can afford to do the job properly. Clearly, cost is no object.

The problem is, that item is certainly not UL listed, and is illegal to use in this case because it will put the 10-20A heat pump dryer on a 40/50A breaker.

But the universal problem with mail order electrical (aside from being wildly overpriced when it is legitimate) is that an awful lot of what is sold is dangerous junk straight from China. It's being sold direct mail because that bypasses our product-safety apparatus (UL, FTC, all that stuff). Amazon protests that things in the Amazon Fulfillment Centers might ship to Mexico or the Virgin Islands, and FTC/CPSC has no standing to enforce Mexican codes. Then they say "well, if we shipped one to USA that was a clerical error by the 3rd party seller, who should have clicked the box to disable US sales". The lawyers have every angle figured out. The consumer safety agencies have said flat out that they don't have the annual budget for a legal fight with Amazon. But eBay, Banggood, wish.com, Aliexpress, all that is the same garbage. And overpriced too, SMH, at least you'd think dangerous junk would be cheap.

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  • I love to learn, and not endanger myself or others. I really, really admire your restraint while detailing, with levity, why this would be a bad idea and how to do it correctly. I can’t pay to have things rewired because I’m in a rental and won’t be able to get permission. Otherwise I would love to do it right regardless of the cost. Looks like I’ll spend $1500 ($800 extra) and get a 120v Miele model. Which is the only 120v I can find that’s available in the US. Thank you again for educating me. Though I had a bias, and wanted it to work, I knew I had to understand better. Oct 18, 2022 at 22:50
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    @Eats Well, answers around here follow Code, and I certainly couldn't possibly tell you to build your own "octopus cord" using a 2-space subpanel as an enclosure and using a quadplex breaker therein. Nope, can't say that! Oct 18, 2022 at 23:01
  • I’m so glad that you would never do that, because I would never call-in a favor with an IEEE doctorate friend so he can teach me a few more useful things about this. I’m very, very glad that you’ve saved him from spending time with me, on this breakered, subpanel, safe octopus cord. (But really, thank you, I’ll likely just spend the extra $1k for the only 120v option available in north america). Oct 18, 2022 at 23:21
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The correct way to do this would be to install the appropriate circuits.

You didn't specify the brand or model of dryer, but I can guarantee that whatever it is, it's designed for use on a 30 amp or smaller circuit. You're putting it on a 40 amp circuit. If it has a fault, it could end up failing in unexpected ways such as catching fire, since the internals are all engineered to work with 30 amp over current protection.

This will probably 'work'. It is a risky choice, and you will be liable if it goes wrong.

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  • Thank you for the clarity and honesty. I won’t do this if it’s unsafe. I’m just wondering if there’s a way. And this is perhaps my biggest issue, seeing as how the breaker is meant to protect wires (and the LG 24” heat pump dryer is a 30a design). Is there a safe way to trip the circuit between the dryer and the splitter, if the amps pulled ever begin to exceed 20-30a? Oct 18, 2022 at 22:21
  • How about a 120v dryer instead? The Miele TXI680WP is a heat pump dryer that you can plug in to a normal outlet. It's not cheap but compared to other heat pump dryers it's also not that expensive. Installation needs a drain and a wall outlet, that's it. Or you could go with an all-in-one washer/dryer. LG makes a couple, maybe Samsung does as well. Those hook up to the usual washer connections, with no extra connections needed for the dryer function. You put in dirty clothes, clean dry clothes come out.
    – KMJ
    Oct 18, 2022 at 22:52
  • This is exactly what I’m thinking. It’s only a question because I had a line on an open-box LG, that’s $1k less than the Miele — which is the only 120v dryer sold in the US, far as I can find. The issue with the all-in one is the chorus of people who say that they constantly break down and don’t dry very well. But that really opens things up, if I can get over that aspect. Thanks again for your help — it’s not the answer I’d hoped for but I feel much better educated now. I can’t thank you all enough. Oct 18, 2022 at 23:17
  • Two of my friends own the all-in-ones and love them. You just have to be realistic about how they behave: it takes a long time to do a load of laundry, you can't pack them full, and they do have a lot more stuff to go wrong on them. If you do small loads a little more often, do the loads overnight, and do maintenance like cleaning the filters, they can work great. And it's tough to beat the convenience.
    – KMJ
    Oct 19, 2022 at 3:38

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