trying to install an outlet in the HVAC closet next to an existing switch. The switch has 2 black wires, 2 red wires and a ground wire connected to it. There is also a lose white wire in the back, which i would assume is neutral, but when measuring voltage between Neutral and Ground there is none. Any ideas if and how i could power an outlet from this?

  • How fat are the wires (i.e. what gauge are they)? What does this switch control, for that matter? – ThreePhaseEel Mar 7 '20 at 22:13
  • It's possible that if the white is from the source cable that since it wasn't needed then it isn't terminated in the source panel. – NoSparksPlease Mar 7 '20 at 22:21
  • Switch controls AC, and it would seem as though it also controls the water heater. The cables are 10awg. I uploaded pics of the box to my google drive in case that helps drive.google.com/open?id=1zawFcIqhvm1NPZPVzuUmOdQs1vC4Gdcx – Frefro Mar 7 '20 at 22:47
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    That,s not a transformer then; it's a switching power supply; it matters here. What kind of plug does it have? Is it a wall-wart, a lump with prongs coming out of it? (They're 120V oriented, right?) – Harper - Reinstate Monica Mar 7 '20 at 23:56
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    "There is also a lose white wire in the back, which i would assume is neutral, but when measuring voltage between Neutral and Ground there is none" - That's the way it is supposed to be. – manassehkatz-Moving 2 Codidact Mar 8 '20 at 0:45

Can't put a receptacle here

Receptacles are not allowed on a circuit if more than half its capacity is provisioned to hardwired loads. A built-in air conditioner circuit will be 22A or so.

Can't put 15/20A receptacles on a 30A circuit

The circuit is breakered for 30A. That means you can't have a 15A or 20A recep on it, in any case.

The wall-wart doesn't lend itself to hardwiring... Unless it does

All the Dyson power supplies I turned up in a search were "hang off a socket" type wall-warts, and had a built-in plug matched to local power. Presumably yours is NEMA 1-15 or 5-15. If instead of a plug there were a pair of wires, we could make a case for "hard-wiring" the load, dodging the "no receptacles" and "no 15/20A receptacles" rules. However, I don't see a way to attach wires to that which I could defend to the inspector with a straight face.

There's also a question of whether the power supply is a factor in the battery charging. Batteries - especially the popular lithium batteries - absolutely require circuitry to prevent overcharging. If the vacuum simply wants a generic DC voltage such as 12 volts, and has that charge-controller circuitry onboard, then we can substitute any generic DC power supply of the coarsely correct voltage, and that can include supplies that lend themselves to hard-wiring. However, if the "keep the lithium battery from exploding" charge control circuitry is in the Dyson wall-wart, then we ned a Dyson branded supply involved somehow.

See if Dyson makes a car charger (cigarette lighter) for it. If they do, then any 12 volt DC power supply will do that supports hardwiring. It can be brought out to a cigarette lighter socket if it doesn't have one built-in. Then, use the Dyson car charger.

Don't trust that neutral

It's probably not even connected in the panel. By the way, the way you test it is measuring 120V between each hot and neutral. Regardless, I would just wire up the load 240V, as that dodges multi-wire branch circuit complications. Do not under any circumstance put a NEMA 5 socket on 240V.

  • We don’t know enough about the system to state a value for the AC system. If there is a inside air handler and outside compressor circuit it is common for them to be on different circuits. – Ed Beal Mar 8 '20 at 18:50

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