4 wire dryer 3 wire plug subpanel... risks


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Old 02-18-24, 01:19 PM
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4 wire dryer 3 wire plug subpanel... risks

ok so the interior of my house is going under construction. currently have a newer 4 wire dryer with neutral/ground jumper and 3 wire cord to a 3 wire receptacle. carport has a subpanel fed with 4 wires and neutral/ground is not bonded as required. want to put the dryer in the carport temporarily but obviously its a no-no. the bonding thing is so that the metal structures of appliances and such cant have the returning current meant to be on neutral go through the grounds/metal structure itself correct? if the only other things in the carport are a water heater (240v no 120v neutral), lighting circuit with plastic box/switch, receptacles with plastic boxes/receptacles, and a ufb going underground out to the barn which is also just plastic boxes/receptacles/switches there are no risks of shocks on anything else, correct? or still possibly the water heater because even though it has no neutral it has a ground thats now shared with the neutral or other things? it's on its own dedicated circuit though from the subpanel separate from the dryer... also what confuses me is on the main panel the ground and neutral is bonded in the panel and at the dryer, so the dryer itself has the same shock risk in the house as in the carport? I can't imagine so but in my mind can't see why not, since the ground is theoretically a neutral return path in the house too, correct?
 
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Old 02-18-24, 01:38 PM
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and yeah I guess I could buy a 4 wire plug and 4 wire receptacle and some 10/3 but its only gonna be out there while my bathroom and laundry room are being remodeled (flooring, shower, and fixtures and stuff, not changing wiring. and both are kinda the same room). and I already have a 3 wire rec. and plenty of spare 10/2 for a temp solution.
 
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Old 02-18-24, 02:00 PM
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Since it is only for temporary use I would not bother changing the cord on the machine or running a 4 wire circuit.
 
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Old 02-18-24, 03:45 PM
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When you connect a 120/240 device to three wires.... you are jumpering the neutral to ground.
240v devices like a water heater don't require a neutral.

The reason connecting the neutral to ground is now against code is because if the ground opens... so does the neutral. In the case of a dryer.... if the ground wire got disconnected... the frame of the appliance would now be hot. Definitely not an ideal situation.
 
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Old 02-20-24, 12:04 PM
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I don't think 10/2 was ever allowed, To use the 3 wire method the white also had to be insulated?
 
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Old 02-21-24, 03:48 PM
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I don't think 10/2 was ever allowed
True! 10-2 was never approved to wire a 120/240 volt dryer using a 3-wire receptacle although I have seen it done a few times. The reason is that when using 10-2 the bare ground wire becomes a current carrying neutral. Even if it is for a temporary connection, buy 10-3 and do it right.
 
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Old 02-21-24, 04:16 PM
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Years ago the dryers ran strictly on 240v.
The drum motor, control board and heating element were all 240v.
That's the reason for the widespread use of 10/2 w/ground.

The appliance manufacturers figured how to make the appliances cheaper by converting
everything but the heating element to 120v.

The appliance companies were the ones to promote or "approve" of using a four wire
appliances on three wires. It was never code approved.
 
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Old 02-21-24, 04:25 PM
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Years ago the dryers ran strictly on 240v.
That must have been before my time. I remember seeing 10-2 used for a dryer circuit in the late 1970s and dryers at that time definitely were 120/240 volt and needed 10-3. I know of a younger couple that just bought an existing home in 2017 and it also has 10-2 for the dryer circuit. That house was built somewhere in very early 2000s.
 
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Old 02-21-24, 04:49 PM
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10/2 was definitely used a lot longer than it should have been.
 
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Old 02-23-24, 04:39 PM
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SE cable with bare neutral was allowed in the old days (only from main panel though).

Most appliances sold in N. America require a neutral. They could easily make them 240V only like the rest of the world but it saves a few pennies.
 
 

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