Wiring a 30A Disconnect
garlicjim
14 years ago
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Comments (19)
petey_racer
14 years agogarlicjim
14 years agoRelated Discussions
240V, 30A heater on a 240V, 50A circuit?
Comments (9)"I thought that for continuous loads / single appliance circuits, the breaker sometimes WAS also protecting the equipment." The OCD is for the permanent wiring only. "Or is that just for AC hermetic compressors - the MAX FUSE specification on the unit, etc." Even for a motor load or hermetic compressor the OCD is for the permanent wiring. Larger motors and hermetic compressors contain their own overload protection. The overload protection is designed to breal the circuit if excessive power is drawn. The OCD in the panel os short circuit protection for the permanent wiring. It needs to be limited to make sure the built in protection can interrupt the circuit under overlaod conditions. A motor that pulls 20 amps running may have overload protection at around 30 amps (with a time delay 'built in' by the thermal mass). The contacts are designed to work with no more than about 30 amps. A direct short in the motor may pull 10,000 amps. The contancts are not rated to interrupt this kind of current. The OCD in the panel is designed for this and WILL provide the protection to the permanent wiring under short crcuit condions to preven overheating of the branch circuit conductors. Using equipment on an oversized branch circuit may result in the wiring in the equipment failing before the OCD can be tripped. The equipment wiring then becomes the fuse. Never a good idea and not allowed under the NEC. Even in vehicles it takes special wire and insulation to create a 'fusible link' in the wiring harness. In vehicles even the length of the wire matters for fusible link applications. Install a smaller breaker and change the receptacle to the correct style....See MoreReplace 50A outlet with a 30A?
Comments (7)Thanks bus_driver! The guy at the electrical supply house said the same thing, including changing out the breaker. he said the L6-30 didn't use the neutral so I should clip it back to the insulation, cap it and leave it in the junction box. I'm thinking I might call an electrician to do this just to be safe tho!...See More2000W 120 V Water Heater - 30A Circuit Required?
Comments (12)OK, so based on the OP's facts, and using this morning's undiscounted Home Depot prices in my area (Virginia), the 240V solution would be $23.89 or 68% more expensive (see calculations below). If the question were restricted to the materials cost of wiring alone, the single-pole HWH heater would set a DIYer back an additional ten bucks. Big deal. And, true, #14 is easier to work with, but we're talking about a 20' run with two connections. Again, big whoop. It seems to me that the determining factor is whether or not the smaller 15-gallon unit is fully adequate to do the job. I have no informed opinion about that, but on first glance it sounds as though it is. (Plus the OP likes the space-saving aspect as well.) Missing from the analysis are the recurring costs. It stands to reason that it takes more power to keep 20 gallons warm than 15 gallons. Depending on how long the unit is kept in service, any small difference in wiring costs would likely be eclipsed by energy costs over time. I know that, to some people, bigger is always better, but the greener I get, the less often I buy into that proposition. But perhaps that's religion or politics, eh? FWIW (very little, I'm sure), I'm not seeing any significant advantage to the 20-gallon 240V model unless the 15-gallon unit is inadequate to do the job reliably and efficiently. - Tom *** 120V *** 30A single pole breaker: $5.21 25' 10-2 NM wire @ 1.19: 29.75 HWH price differential: 0.00 (baseline) Materials total: $34.96 *** 240V *** 15A double-pole breaker: $11.30 25' 14-2 NM wire @ .57: 14.25 HWH price differential: +33.00 Materials total: $58.85 Breaker prices above are averages of three common types: 30A/SP: BR=3.27, QO=7.12, GE=5.25, Average=$5.21 20A/DP: BR=7.47, QO=15.47, GE=10.97, Average=$11.30...See MoreQuestions about disconnected wires and low voltage in a switch.
Comments (5)When the switch is "on" the voltage should be pretty close to zero. When the switch is off, you might read something closer to 120V. Odd small voltages probably indicate that you're reading phantom induced voltages. You meter has a very high input impedance. Twisting the wires together and taping them is ***NOT*** a legal way to connect things. If there's not a proper fastener under all that tape, yes put a wire nut on it. MAKE SURE YOU TURN OFF THE BREAKER FIRST. As for the two cut off wires, they probably were connected to something that has been removed. Hopefully, they don't have voltage on them because even though they're not stripped, it's still possible that the tips could touch or arc against the metal box or other conductive stuff in the box. I'd cap them off with a wire nut or something just to avoid problems. This whole thing reeks of some previous harry homeowner doing some DIY work. You may want to have someone with a clue take a look at things just to make sure it is right. It's not possible to tell by looking at a photograph....See Morepetey_racer
14 years agohendricus
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garlicjimOriginal Author