Easier and safer if they already have dedicated circuits for window shakers (common in some older houses; I had one at the window in the hallway upstairs at my last house) is to just replace the 15 or 20A single breaker with a two pole, move the wiring to the new two pole breaker (white "neutral" is now a hot leg, put a ring of tape around each end) and replace the 120VAC recep with the appropriate 240VAC recep. done and done, easy, and like I said, safe (and to code.)
nate
The wiring and the receptacle. A 6-15 recep is not tested for or listed for loads higher than 15A (maybe 20A for a safety factor) 50A is definitely pushing it.
nate
Agreed on both points.
Yes... so we've identified the plug on the new heater (NEMA 6-30P) Or have we? What is the nameplate amp rating on the new heater? 6-15P looks similar to 6-30P but is physically smaller. 6-15P also similar in size and shape as 5-15 (standard household 3-wire plug/recep) or 5-20 (similar 20A plug/recep, with the neutral horizontal instead of vertical) except both current carrying blades are horizontal.
Question is now, what voltage is available at the existing recep, what gauge wire is feeding it, and what is the amp rating of the breaker protecting the circuit? Finding a 277VAC recep on a 240VAC circuit would not be proper, although I am slowly learning to expect things to not always be correct or code compliant.
nate
OK, so you've proven my point.
That's fine if it's the only outlet on the circuit. In fact that's how I wire my 240V power tools (12-2 with the white wire painted red). That's not a very common situation in existing wiring, though.
The greenhouse is 14' by 12', just a hobby greenhouse for my wife, nothing industrial or commercial. The line is 240v. Both heaters are rated at 30 amp.
Paul
I thought you said the new heater had a 6-30P plug on it? Heater should be rated at something less than 30A then (I think 24A max, as a heater would be considered a continuous load? Not sure if there are special rules for heaters.)
In any case, if you are certain that the line is 240V and not 277V, verify that the wire used is at least 10AWG, install a 6-30R receptacle for the heater, and change the breaker to a double pole 30A if necessary.
nate
No different than the 18ga zip cord from your table lamp to the 15A receptacle possibly on a 20A circuit - the breaker will never trip. The circuit breaker in the panel is sized to protect the circuit wiring,
*not* the appliance that may be plugged into the receptacle.
Right, but the 14/2 would be considered "circuit wiring" and in fact all wiring on a circuit must be the same size.
There's an odd exception for kitchen circuits but I don't know if it applies in this case.
nate
Wrong! Code doesn't cover your "18ga zip cord"; beyond its scope. The outlet is part of the "wiring". It *is* covered by the fire code.
If he put a 50A plug on the cordset to the A/C it would be fine.
The "Edison circuit" thing only relates to shared neutrals.
If I put a 50A plug on the cordset to my A/C and plug it into that 50A circuit it's entirely to code. The permanent wiring and receptacle are appropriately protected by their 50A breaker, and the cordset to my A/C is protected by it's internal circuit breaker. There is no code requirement that an appliance must utilize the full Ampacity of the circuit it's plugged into.
Appliances aren't fixtures. There is no code requirement that an appliance must utilize the full Ampacity of the circuit it's plugged into. An appliance that utilizes from 0-80% of the circuit's Ampacity is perfectly fine.
Don't confuse overload protection with overcurrent protection. A fault will trip a breaker with smaller wire than is safe for a load. This assumes you are dealing with a known load that has an acceptable ampacity on the wire
Fixture wires are regulated in the NEC article 402.5(2)
(2) Fixture Wire. Fixture wire shall be permitted to be tapped to the branch-circuit conductor of a branch circuit in accordance with the following: (1) 20-ampere circuits ? 18 AWG, up to 15 m (50 ft) of run length (2) 20-ampere circuits ? 16 AWG, up to 30 m (100 ft) of run length (3) 20-ampere circuits ? 14 AWG and larger (4) 30-ampere circuits ? 14 AWG and larger
Yes? 14ga wire for an A/C that draws less than 15A is perfectly acceptable, even if it's connected to a circuit capable of supplying more than 15A.
I guess I should have included 240.5(1) (2) expands on (1)
(1) Supply Cord of Listed Appliance or Luminaire. Where flexible cord or tinsel cord is approved for and used with a specific listed appliance or luminaire, it shall be considered to be protected when applied within the appliance or luminaire listing requirements. For the purposes of this section, a luminaire may be either portable or permanent.
Somehow, I find that totally believable. What happens when I plug a 100 watt lamp (18 gauge wire) into a 20 amp, 12 gauge wire socket?
Stirred not shaken. Wired, not plugged.
Bruises the vermouth.
Yeah but a 650 mA cell phone charger won't be protected by the 15 amp breaker either but no one says don't plug your charger into a 15 am outlet.
Easy experiment.
Greg
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