re: OT Electrician advice needed: running 110v off of 220v line

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none of my house wiring has ever caused a fire. So far.

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You're hired!

With all due respect, you can't afford me!

But I do, on occasion, work for beer and boudin (after the job is done of course).

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OT Electrician advice needed: running 110v off of 220v line


Yeah, don't do it.

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I built a brewery control box that has 50amps in and controls a 23 amp 240v heating element and a 15 amp 120v outlet.

It can be done.

Custom made control box with what I assume are properly sized conductors and circuit protection =/= jury rigged wiring behind a wall.

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Disclosure - not an electrician, just an EE. But I have lot of hands-on experience and none of my house wiring has ever caused a fire. So far.

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It is always amusing to look at appliances, and see that adherence to the electrical code ends where the power cord enters the appliance, and standard engineering design takes over. For example a clothes dryer or electric range will have 4x #6 power cord externally, but transition to #14 wire internally going to the heating elements. The engineer has determined that for the needed internal wire length #14 is sufficient for the I*2R loss, but outside the unit the electrical code has to be complied with. I recently got a home standby generator, the electrician ran #2 wire the 18” from the meter base to the transfer switch as required by electrical code wire tables. I told the guy that from a engineering point of view # 10 wire would work perfectly fine, he assumed I was nuts.

The correct way would be to run a new 120V circuit to where you need the new outlet, or to tie into an existing 120V circuit near where the outlet needs to go. An electrician will be able to check if you can add the outlet to a nearby circuit or if you will need a new run.

The Oven circuit needs to be a dedicated circuit. The NEC will let you run a range and a oven on the same circuit, provided they do not exceed the circuit's rating. Not all municipalities will allow that though.

The sub panel thing won't fly bc it is very doubtful that the existing wiring has the capacity to remain compliant in running both the oven and the new branch circuit.

If you just want to blow money, they could probably put in a sufficiently sized run / sub panel.

I asked an electrician friend, he said to see 210.19, so I did, his explanation made more sense than the shite below:


210.19 Conductors — Minimum Ampacity and Size.
(A) Branch Circuits Not More Than 600 Volts.
Informational Note No. 1: See 310.15 for ampacity ratings of
conductors.
Informational Note No. 2: See Part II of Article 430 for mini-
mum rating of motor branch-circuit conductors.
Informational Note No. 3: See 310.15(A)(3) for temperature
limitation of conductors.
Informational Note No. 4: Conductors for branch circuits as
defined in Article 100, sized to prevent a voltage drop exceeding
3 percent at the farthest outlet of power, heating, and lighting
loads, or combinations of such loads, and where the maximum
total voltage drop on both feeders and branch circuits to the
farthest outlet does not exceed 5 percent, provide reasonable
efficiency of operation. See Informational Note No. 2 of
215.2(A)(1) for voltage drop on feeder conductors.
(1) General. Branch-circuit conductors shall have an ampacity
not less than the maximum load to be served. Conductors shall
•
N210.19 ARTICLE 210 — BRANCH CIRCUITS
70 –62 NATIONAL ELECTRICAL CODE 2017 Edition
be sized to carry not less than the larger of 210.19(A)(1)(a)
or (b).
(a) Where a branch circuit supplies continuous loads or
any combination of continuous and noncontinuous loads, the
minimum branch-circuit conductor size shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load.
(b) The minimum branch-circuit conductor size shall
have an allowable ampacity not less than the maximum load to
be served after the application of any adjustment or correction
factors.
Exception: If the assembly, including the overcurrent devices protecting
the branch circuit(s), is listed for operation at 100 percent of its rating,
the allowable ampacity of the branch-circuit conductors shall be permit-
ted to be not less than the sum of the continuous load plus the noncon-
tinuous load.
(2) Branch Circuits with More than One Receptacle. Conduc-
tors of branch circuits supplying more than one receptacle for
cord-and-plug-connected portable loads shall have an ampacity
of not less than the rating of the branch circuit.
(3) Household Ranges and Cooking Appliances. Branchcircuit conductors supplying household ranges, wall-mounted
ovens, counter-mounted cooking units, and other household
cooking appliances shall have an ampacity not less than the
rating of the branch circuit and not less than the maximum
load to be served. For ranges of 83
/4 kW or more rating, the
minimum branch-circuit rating shall be 40 amperes.
Exception No. 1: Conductors tapped from a 50-ampere branch circuit
supplying electric ranges, wall-mounted electric ovens, and countermounted electric cooking units shall have an ampacity of not less than
20 amperes and shall be suf?cient for the load to be served. These tap
conductors include any conductors that are a part of the leads supplied
with the appliance that are smaller than the branch-circuit conductors.
The taps shall not be longer than necessary for servicing the appliance.
Exception No. 2: The neutral conductor of a 3-wire branch circuit
supplying a household electric range, a wall-mounted oven, or a
counter-mounted cooking unit shall be permitted to be smaller than the
ungrounded conductors where the maximum demand of a range of
8
3
/4-kW or more rating has been calculated according to Column C of
Table 220.55, but such conductor shall have an ampacity of not less
than 70 percent of the branch-circuit rating and shall not be smaller
than 10 AWG.
(4) Other Loads. Branch-circuit conductors that supply loads
other than those specified in 210.3 and other than cooking
appliances as covered in 210.19(A)(3) shall have an ampacity
sufficient for the loads served and shall not be smaller than
14 AWG.
Exception No. 1: Tap conductors shall have an ampacity suf?cient for
the load served. In addition, they shall have an ampacity of not less
than 15 for circuits rated less than 40 amperes and not less than 20 for
circuits rated at 40 or 50 amperes and only where these tap conductors
supply any of the following loads:
(a) Individual lampholders or luminaires with taps extending
not longer than 450 mm (18 in.) beyond any portion of the lampholder
or luminaire
(b) A luminaire having tap conductors as provided in 410.117
(c) Individual outlets, other than receptacle outlets, with taps
not over 450 mm (18 in.) long
(d) Infrared lamp industrial heating appliances
(e) Nonheating leads of deicing and snow-melting cables and
mats
Exception No. 2: Fixture wires and ?exible cords shall be permitted to be
smaller than 14 AWG as permitted by 240.5.

220 is just 2 110 lines

I don’t think you can meet code either way. Using the 220 volt circuit to feed a distribution panel, from which you feed both the 110 volt receptacle and the 220 volt oven is a good idea, but I doubt you would be able to get the access to that panel required by code.

The other way you suggested is surely against code, though I could not cite why.

I think you should run another 110 volt circuit from your existing panel or from a nearby circuit.

ETA: Unobtainium is correct when he says

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If this is an older home then the original oven circuit only has two 'hots' and a ground conductor and no neutral. Using a ground wire as a normal current-carrying conductor is a big no-no.

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BTW, I’m an EE as well.

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couldn't I just change the single gang receptacle to a dual-gang, then use an adapter like this? It has a 15a fuse built-in:

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I doubt it. Wouldn’t that be hidden by the oven? Surely that would not meet code requirements for a circuit interrupter. Even if it’s accessible it is probably not listed as suitable for that service.

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I think you should run another 110 volt circuit from your existing panel or from a nearby circuit

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Correct answer.

I've been a master electrician for 30 years.