we all know better

[LKHA]

Ok we all know better to combine the ground and neutral in any electrical project but in a conversation how do the manufacturers get away with it. the dryers and stoves are dual voltage units with 3 wire cords. No way am I saying to do it but how do they?

 

[lincoln]

on a 220 3 prong outlet there is no safety ground, two hots and a neutral, of a 4 wire it is 2 hots, 1 neutral and one ground. most places in the US require the neutral be bonded to ground and the main panel.

this can cause problems, in my old apartment something was feeding back on the neutral so it was a good 30 vac above ground and water pipes. you would get s buzz if you were touching metal parts of the stove and running the water

 

[LKHA]

this is what we know but dryers and stoves are three wire cords how do they get away with it

 

[mattmcl]

I seem to remember that three phase appliances don't need a safety ground, but I can't remember why.

 

[LKHA]

my house is sigle phase no three phase available in the sticks

 

[lincoln]

this is what we know but dryers and stoves are three wire cords how do they get away with it

its to code and i can't see it from my house, have you ever lived in a house with only 2 wire outlets? i would set a short stack on it is a hold over form that + expect to use a bonding lug.

re 3 phase
much stickier issue, most shops i have worked in cord mounted three phase 480 did have a ground but no neutral, 208 on a 4 wire plug <edit>had a nutral<edit> there is a 5 wire twist lock/ pin and sleeve plug. big stuff was direct wired to a disconnect and is bonded. nasa types they would require one safety ground per hot conductor.

 

[leboeuf]

I'm not arguing code here or anything, just talking theory....
In a 240V appliance the potential is developed by referencing two 120vac 60hz signals that are out of phase. So all of the current that flows to the device comes from these two 120v signals. The neutral line is therefore unused from a voltage reference standpoint and is actually a direct connection to your electric panel's ground....

So if you have one outlet per circuit breaker, you should be ok.... I might be concerned if the one plug was being used for both 240vac and 120vac stuff though... I wonder if your 3 wire 240vac appliance has any 120vac stuff running on it?

 

[sketerbuck]

I have been an Electrician for over 20 years. Most 240 volt appliances don't have a neutral. The current is the same on both hot wires so there is no current to return to ground. If you have a 120volt light in the appliance then it would need a neutral and the nameplate would tell you that. The ground wire is just to bond any metal parts so if electricity comes in contact with them then the breaker will trip. Three phase equipment is also a balanced load and usually doesn't need a neutral , however I have only seen three phase panels in commercial applications.

 

[lincoln]

The neutral line is therefore unused from a voltage reference standpoint

correct additionally it will take what ever the mismatch with 120v loads on different phases.

I might be concerned if the one plug was being used for both 240vac and 120vac stuff though... I wonder if your 3 wire 240vac appliance has any 120vac stuff running on it?

different plugs are required, i have seen it done but it is not to code and not safe. most of my 220 v at the house dose not. the way they usually do it is the low voltage uses a transformer that has two primary winding. in series for 220 or parallel for 120. switching mode power supplies just get line voltage and will figure it out on there own. my cheapy laptop power supply is rated from 100 to 240 vac

 

[leboeuf]

the low voltage uses a transformer that has two primary winding. in series for 220 or parallel for 120. switching mode power supplies just get line voltage and will figure it out on there own. my cheapy laptop power supply is rated from 100 to 240 vac

Ahh ok, I suppose that all is safe then

Actually the digital switching circuitry isn't all that simple inside that cheapy laptop power supply.......

 

[lincoln]

ya, the 110 vs 220 is for older liner, switching = pwm

 

[Mista_Sparkle]

The 3 wire 220 connectors are actually Hot, Hot, Ground aren't they? there isn't a need for a netural because the current is balanced between the 2 hots correct? I believe the 4 wire 220 are Hot, Hot, Neutral, Ground and 4 wire 3 phase are hot, hot, hot, ground and 5 wire hot, hot, hot, neutral, ground.

 

[Dwain]

In my area, the new electric stove outlets (not sure about dryers) require 4 wires. Isn't the 4th wire for a ground?

 

[Mista_Sparkle]

iirc, the 4th wire is actually a neutral brought about by companies using the ground pin as a neutral for some applications because there wasn't a neutral in the older style outlets.

 

[Hermit]

New appliances do not come with cords from the manufacturer. There are too many different codes. All come with the capability of being hooked up to 3 or 4 wire receptacles.

 

[Hermit]

I have been an Electrician for over 20 years. Most 240 volt appliances don't have a neutral. The current is the same on both hot wires so there is no current to return to ground. If you have a 120volt light in the appliance then it would need a neutral and the nameplate would tell you that. The ground wire is just to bond any metal parts so if electricity comes in contact with them then the breaker will trip. Three phase equipment is also a balanced load and usually doesn't need a neutral , however I have only seen three phase panels in commercial applications.

What do you consider an appliance? Over 30 years of appliance repair have taught me that most do. Some air conditioners and of course hot water tanks are the exception.

 

[bendavanza]

My new range came without a cord. I wondered why. This makes sense.