Help on 2-phase DRYER hook up (electrical panel side)

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Old 02-05-18, 04:51 PM
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Help on 2-phase DRYER hook up (electrical panel side)

I had my electrical panel open to replace a GFI.

I noticed that the Electrician who a week ago installed a DRYER (over/under type) left the WHITE wire HANGING with electrical tape on end, connected only black and red (the type run has no green). Some major "american label" brand dryer (though made over seas).

It's obviously a two phase hookup (30A, dryer): I've not done the panel for that before. But i assume it still needs ground, and only two wires are attached to panel anywhere.

It's a new Bosch 500 series for my old folks - not mine. It has a 3-prong plug. The "contractor" did install a box, however the box is loose to the touch (i cannot plug or unplug the unit without the box crumbling the drywall "work")

I'm wondering if this hanging wire is due to "some new kind of dryer hookup" not done with older dryers, or if this person was a scam artist not a real electrician. I also note the company promised to have an electrical inspector see the work: and re-neged on that part of the contract. There seems to be (a few) other code issues - lack of fasteners, and drilling 3 holes at a stiff 20 degrees through the main load bearing joistss (1 goes through, 2 go only 1/2 through and stop, as the installer "changed his mind" where to drill 2x), and going under joists instead of through (lays on HVAC metal duct no fasteners - i think it's suppsed to go through joists - but not %100 sure on that).

MAIN QUESTION is main panel 2-phase hookup. Does it require at least 3 wires be used (1 per phase and no transformer neutral, and one earth ground).

Thanks, Fairfax, VA
 
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Old 02-05-18, 05:07 PM
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There are no such a thing a 2 phase. It is 1 phase or 3 phase.
In the US, we have 1 phase. Split phase to be more accurate.

If you have European style dryer, you have 220V (which usually also work on 240V in the US) only dryer. Thus, no need for neutral (white wire that is not connected).
Do you have bare copper ground wire? If it is there, you are all good.

Does your dryer have

This type of plug? Then you have 240V 30A.

If you have following, you have 240V 20A
 

Last edited by ray2047; 02-05-18 at 06:05 PM. Reason: Changed "It is 1 phase or 2 phase to It is 1 phase or 3 phase
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Old 02-05-18, 05:09 PM
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This is 240v...... single phase.

Most new dryers require a four wire plug and receptacle. Not sure on your Bosch but it shows a 4 post wiring terminal block.

If he ran the 4 wire cable he should have installed a 4 wire receptacle and new dryer cord.
As it is.... when the dryer is wired for 3 wire connection.... it requires two hots and a ground. The neutral is not required and can be capped off for future use.
 
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Old 02-05-18, 06:39 PM
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thank you. but your only right about phase if you assume phase angle is not allowed to complete the joining 1/2 phase 120v for 240v. i'll keep in mind most people don't use the term that way, however, i think your right to say it's not used in USA
 
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Old 02-05-18, 06:41 PM
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Sounds like a half-.... installation. It doesn't sound wrong necessarily, but definitely not the way it should have been done.

The box should of course be solidly mounted. And I believe all new dryers require 4-wire connections. (can someone confirm?)
 
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Old 02-05-18, 06:47 PM
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https://www.thespruce.com/installing...reaker-1824649

I've done more reading. Your right that dryers "allow 4 wire hookups" however they do not "require" them (see local code). I know in my area I've never seen anything but a "3 prong" installed.

However! I DO have the problem feared. The wire is 10/3, R,B,W. R,B are connected to the new double throw 30A GFI and W is dangling with electrical tape on end (not attached to anything in panel). I assume there are no "un-grounded" dryers being made from what you all have said, and bosch user manual mentions not to run it un-grounded and to use 3 or 4 wire according to (local) requirements.

I do know that a 4th wire, if used, provides neutral or 0V to the "power/generator", while the required ground provides "earth ground" which connects to earth at the panel but also runs back to the street transformer (the two are roughtly 0v but used differently and not to be mixed).

thank you all very much for your sharing your know on it !
 
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Old 02-05-18, 06:55 PM
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Can you give me the exact model number or at least a picture of the cord or plug?

Looking up Bosch 500 series, it appears it uses regular American 120/240V plug. It looks like a condensing dryer, which doesn't require dryer vent.
If that is the case, the wire definitely is wrong.
Should have connected neutral and use 4 prong outlet and cord.
There is no reason not to when they already have used 10/3.

Your right that dryers "allow 4 wire hookups" however they do not "require" them (see local code). I know in my area I've never seen anything but a "3 prong" installed.
The NEC requires 4 prong with new installations and Fairfax county adapted it long ago (not sure of exact year).
3 prong is grandfathered if it was there before the code change.

In the Fairfax county and city there are plenty of 4 prong. 3 prong exists only in the old houses.
 
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Old 02-05-18, 07:04 PM
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The wire is 10/3, R,B,W. R,B are connected to the new double throw 30A GFI and W is dangling with electrical tape on end
Is it 10/3 Nm-b (romex) cable ?
If it is...... there will be a bare ground in it.
 
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Old 02-05-18, 07:08 PM
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good question. in some areas if you have a "3 prong, 3 wire" and continue to use it, this is fine ... but if you install a new outlet you may be required to use a 4-wire (so, if you install a new oven, you'd request a 4 prong plug with it). i'm looking for my area but not terribly concerned since the house is still using 3 prong elsewhere, and it's "already done".

Reason: i didn't order the work, the guy who did will _never_ complain of unfinished work. Thus it's just been magically "added to my work load" and I've already wasted time having to learn yet another thing about another profession to do more work and ... I already have way to much to do of my own with nearly a 0 budget. not happy.
 
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Old 02-05-18, 08:31 PM
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if you install a new outlet you may be required to use a 4-wire (so, if you install a new oven, you'd request a 4 prong plug with it).
There is no may be. It is required. If you are just replacing the appliance, you may continue to use 3 prong. If you relocate the appliance, (thus moving/extending wire) then you are required to replace it with 4 prong.

not terribly concerned since the house is still using 3 prong elsewhere
I wouldn't worry too much either, but if the wire is already pulled in 10/3, then there is no reason not to wire it correctly. Just replace outlet and cord and connect neutral.

3 prong is safe as long as nothing happens to the neutral connection. But, the consequences can be deadly. The reason why 3 prong is no longer allowed.
 
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Old 02-06-18, 02:02 AM
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The install currently has the neutral current on the ground conductor. They left the neutral unused which was incorrect.
 
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Old 02-06-18, 07:37 AM
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I noticed that the Electrician who a week ago installed a DRYER (over/under type) left the WHITE wire HANGING with electrical tape on end, connected only black and red (the type run has no green).

A real electrician wouldn't do a hack job like you have, This obviously was just a "Not-So-Handy" handyman and NOT a real electrician.
 
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