I just moved into a new home. The 240 volt outlet in the laundry room is four-pronged and my dryer is three-pronged. So I went Lowes’s and bought a four-pronged cord and installed it. That was the easy part. Now for the embarrassing part—I can’t figure out where the ground wire goes. I feel as if I should be immediately stripped of my Man Card™ and bitch-slapped with it, as this is a seemingly simple question to which the answer should be immediately obvious. Here’s the set-up after I wired it in. Being the idiot that I so often am, I neglected to take a ‘before’ picture, only an ‘after’ picture. Dryer is working fine, so at least I got something right. But where does that pesky ground wire go—where that white wire is screwed into the chassis of the dryer? And what does the red wire do? Black is hot and white is cold, but what is the red one for?
Your link doesn’t work.
Generally, Black is Phase 1, Red is Phase 2, and White is Neutral.
Green is Ground, and should connect to the chassis, usually with a green or metallic (unpainted) screw.
A dryer uses 240v (Black-Red) for the heater, and 120v (Black-White or Red-White) for the timer.
I can’t see the photo (try uploading it to imgur instead.)
But generally:
- The white wire should be removed from the chassis and connected to the neutral (white) wire in the cable.
- The ground (green) wire should be connected to the chassis.
- Both red and black are hot. North America uses the 240v split-phase system, so you should measure 240v between red and black, and 120v between red/white and black/white. The white wire is connected to the center-tap on the transformer feeding your house, and the red and black wires are connected to either end. The usual 120v circuits in your house are connected between one of those legs and the neutral.
Unless what you actually have is two legs of a three-phase system, in which case you should get something like 216 volts.
Unless dryer is really old, there should be a metal grounding strap between the terminals you attach the power cord to and the dryer’s frame or case.
For a four-wire cord, remove the strap and connect the cord’s green ground wire where the strap was screwed to the dryer’s frame, and the white neutral wire goes to the (usually) middle screw terminal where the other end of the strap was connected.
Here’s a picshowing a general idea of what you should end up with.
Yeah, but you generally only have that in large apartment buildings, usually of an older vintage. You’ll get somewhere around 208v in that case.
Thanks for the tip.Try this. Sorry about the other link; it works for me, so I assumed it would work for everybody else too.
Perfect. Disconnect the white wire that is currently screwed to the chassis and connect that to the middle screw with the white wire from the cord.
Connect the green wire to the green chassis screw that you removed the white wire from.
yep, this. I moved recently and had to change my dryer from a three-prong plug to a four prong.
So just to be sure that I understand you correctly, BOTH of the white wires (the one that is already on the machine and is still screwed to the chassis—I never touched it, AND the white wire from the new cord will both be screwed to that post?
And then connect the ground, of course.
Righto.
Great, thanks. I really appreciate the help.
The point of a ground is to stop the metalwork on the appliance from becoming live and giving you a potentially lethal shock. This could happen if some internal live wire got frayed and touched the metal chassis. If the chassis is properly connected to the ground circuit, the breaker will trip (or fuse will blow) and cut off the power.
You were ‘Man’ enough to ask for help. Put your card back in your pocket.
Just for the record, Bonehead Electrical would be a lousy name for a business, even if Bonehead was your last name.
What does connecting the white wire that was previously connected to the ground screw to the white terminal do? It seems the dryer was working without that.
I understand about the voltages and ground and stuff, just not sure about the extra white wire.
In MA you can’t have a company name different than your own name with a journeyman’s license. Poor Mr Bonehead is going to have to get his masters.
White wires or neutrals are ‘grounded conductors’. They provide a path to ground to serve as half an AC circuit.
Green wires are ‘grounding conductors.’ They provide a straight path to ground as a safety measure should a live wire come in contact with something it shouldn’t.
Both are going to the same place.
240v uses two hot conductors. It doesn’t require a neutral. In older 240v appliances they simply used the appliance frame as the ground for 120v applications like the time clock, amp draw on a clock was so low manufacturers viewed it as no risk. Older appliance plugs are only 3 wire. two hots and a grounding conductor. The grounding conductor is connected to the body of the appliance.
Newer code doesn’t want people using grounding as any part of a circuit. Even the for the lowest amperage applications. So a standard 240v appliance is 4 wires so things like the time clock don’t use the body of the machine as a neutral.
As a lot of homes are still only wired for 3 wire plugs the compromise is they can be wired 3 wire or 4 wire still. Eventually that will go away. New construction has no exception.
A company named “Service Ninja” was to do some network wiring.
The guy looked at a punch down panel and asked, “What is that thing?”
“Service Bonehead” would be more appropriate.
So previously, the 120V neutral was just connected to the body, that’s what that extra white wire is?
Because the two hot legs are (normally) 180-degrees out of phase with respect to each other, the neutral in a 240v circuit carries almost zero current. (The return from each hot basically cancels the other one out.)
For that reason, it was considered, in ye olden tymes, safe to use the white wire as both the return path (neutral) and the safety ground.
This is no longer considered safe for two reasons. The first is that the 120v electronics in newer appliances draw more power than before, and this power does NOT get cancelled out when returned via the neutral. So now the neutrals in 240v appliances with fancy electronics are carrying a nonzero amount of current all the time (when they’re on.) For that reason you don’t want the neutral connected to the metal chassis.
The second reason is for redundancy. Even if the neutral were carrying zero current, it’s still not a good idea to use that as an equipment ground. If the neutral should become disconnected and a hot wire comes in contact with the chassis, there is now no return path for that current (except, perhaps, through your body.) Modern code requires all appliances to have a completely separate grounding conductor for that reason (or they must have a double-insulated chassis, which generally means they’re made out of plastic. Not likely for a dryer.)
ETA: To be clear, the neutral is only required if the appliance has both 240v and 120v parts. Some don’t; for example many electric water heaters are wired hot-hot-ground. They have no 120v electronics, just a 240v heating element, so no neutral is required.