High Leg Dryer

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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Wire_nutz said:
This is an existing installation. The panel board is full except for some of the High-Leg spaces are open.

This is a main lug panel board and left to right respectively, the far right lug is the High-Leg.
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This is very common in my area, especially where linemen moonlight as electricians, they know the high leg goes to "C" phase in the meter for it's proper operation, but do not know its code to flip it to "B" in the disconnect or panel. And then there are those that see all of the "spare" slots, and connect 120 volt loads there!
 
W

Wire_nutz

Member
We all know high-leg distribution is not common. My question is, was this ever code compliant to use a High-Leg on a dryer receptacle? If so is it compliant to today?s standards?

And if this is not code compliant to today?s standards, does one continue this method when adding or replacing equipment to this existing panel board?

If it is acceptable to have a high-leg on the receptacle, I will have to look at the dryer schematic and install the high-leg on the dryer terminal block that will not affect the 120 volt loads on the dryer.
 
N

norcal

Senior Member
Is the breaker a slash rated 120/240V or a 240V? That is another issue in addition to what has been said.
 
J

jetlag

Senior Member
Location
Eatonton, Georgia
Wire_nutz said:
I have a new single phase 240 volt electric dryer to replace an existing dryer. The existing dryer receptacle and supply cord is 3-wire without ground. The supply power is 240/120 volt 3-Phase 4-wire High-Leg. This is an existing outlet with with all 3 voltages present, 240/120/208. When the cord was installed on the old existing dryer, the high leg (208volt lead) had to be installed on the terminal block of the dryer that is not connected to the internal electrical parts that operate on 120 volts.

NEC Rules Only,

Question #1: Is it acceptable to hook up the new dryer this way also?

Question #2: Does the new cord and receptacle have to be replaced with 4-wire devices.
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I would never run the high leg to a single phase 240 v that has some 120 circuits inside, why would you want to have to worry about where to connect the high leg are you sure the old dryer was not 3 phase? The dryer requires 4 wire cord and outlet if a new circuit, I would be marking that high leg white and use it for neutral in the panel and connect to it and the other two hots and egc.
 
kwired

kwired

Electron manager
Location
NE Nebraska
mxslick said:
One thing to keep in mind:

How will you KNOW which leg a new dryer's 120v equipment is connected to? I don't think there is an industry standard that all manufacturers follow, so there is a 50% chance you can connect a dryer on the wrong leg and let the smoke out of the motor/timer/drum light (the most common 120v dryer loads).

I second the idea of moving the dryer's breaker so it is off of the high leg..and do it before something gets fried.
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Even if there was a standard to which leg gets the 120 volt loads all the cord installer has to do (especially with 3 wire flat cord) is turn the cord over and the 120 volt load is now on the other leg of the supply receptacle.
 
H

hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
I agree with the others as the high leg should have never been brought to this equipment, this is trouble just waiting to happen, and that there are some manufactures which will have 120 volt loads on both hots, lights and electronics on one, and the motor on the other leg, in which you would be out of luck, without changing the breaker space, if these panels will accept tandem breakers, then you could have an out, but if not, not sure which way to go, if you keep the high leg I would label it to death.

but you might have a 110.3 listing volation because of the 125/250 volt rating of the receptacle and cord, since you will have 208 to ground on one leg not 120, and kind of a 406.3(F) violation.
 
Chamuit

Chamuit

Grumpy Old Man
Location
Texas
Occupation
Electrician
Whether you can justify this install with Code references, or not, I think that the probability of someone who is not qualified or experienced enough to get ahold of this and make a bad situation out of it is too high.
 
W

Wire_nutz

Member
This is an existing installation. The panel board is full except for some open spaces for the High-Legs. Other dryer receptacles are wired with a High-Leg. The dryers connected to this panel and outlets are standard 1-Phase 120/240.

With the panel board being full and all the spaces being used. I would have to rearrange and rewire the whole panel board to eliminate all of the other High-Legs that are present the other dryer receptacles.

Since the panel board is full, and if I removed all the High-Legs from the other dryer receptacles and replaced them. This would affect all the other 1-Phase 120 volt branch circuits.
 
W

Wire_nutz

Member
With the responses most of us agree this is a troublesome existing situation and would have wired the dryer receptacles without the High-Leg.

The existing panel board is full except for a few High-Leg openings. If I remove the High-Leg wires from the other dryer receptacles and replace them; this would create a shortage of (Normal Nominal Voltage)
120 volt breakers that are presently feeding other branch circuits.

Before I can address this installation I need some supporting evidence this is not compliant.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
The panel (service) is 240/120 3PH 4W (high-leg).
The circuit is 240/120 1PH 3W (with a high-leg)
The device is 120/240 1PH 3W.
The breaker feeding this circuit is already existing (while it needs to be a 'straight 240V' breaker it is not really part of the discussion for a replacement load).

Article 250.140 is not applicable as this is not a range or clothes dryer.
422.40 simply requires the plug to be polarized or a grounding type.
It appears the most relevant code are 406.2(A), 406.3(D)(3), and 406.7 none of which address the issue of having a high-leg on a plug/receptacle.

So, what does the manufacturer of the plug/receptacle say about this installation? If they are a NEMA style 11 (rated 240V 3PH3W) I would think there is no problem. If they are a NEMA 10 (rated 120/250 1PH3W), I would want to hear from the manufacturer.

Do the instructions of the new dryer, address this issue like the old dryer's did?

The issue that someday someone may connect things wrong is a design, not a NEC, issue.
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
My input:

As an existing installation, the 3-wire circuit may remain, as long as the dryer's bonding jumper is used.

While it works with the high leg, as long as you connect the high leg to the heater-only line conductor, it's too easy for that to get flipped, sending 208v to 120v components.

In other words, I would never connect any 1ph load with line-to-neutral components to the high leg; I save that for line-to-line-only loads.

If you need to, add a 1ph panel for the dryers, removing the possibility of sending 208v to them on either line conductor.
 
J

jap

Senior Member
Occupation
Electrician
As long as the Dryer is using the feeder circuit neutral as the neutral for the interior 120v Lighting circuits and control power , there is no way to fool proof this installation.

If the dryer had an internal 240/120v Transformer for the lights and the control power it would be a different story. Then it wouldnt matter if the Wild Leg was used on the primary side of the transformer, but that is not the case.

Any time the wild leg is being used on a 240v circuit where 120v is being derived from the circuit neutral, there will always be that chance of it being accidcently swapped or moved and in turn burning things up.
 
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