4-wire

Status
Not open for further replies.
The simple answer is most anything requiring a neutral (dryer, range, etc.). Unbalanced load not allowed to be carried on a bare conductor.
 
The four wires would (normally) be Phase A, Phase B, Phase C, and Neutral (grounded). Most water heaters are single phase, and thus would only need two wires. A range might need both single phase 240 volts and single phase 120 volts, and that would require three wires. Generally, only a three phase load would need four wires. Please note that the Equipment Grounding Conductor (green or bare copper) would be in addition to the number of wires described above.
 
Do you know whether most 240v air compressors require 4 wires counting the equip. ground? How about most arc welders?
 
charlie b said:
The four wires would (normally) be Phase A, Phase B, Phase C, and Neutral (grounded). Most water heaters are single phase, and thus would only need two wires. A range might need both single phase 240 volts and single phase 120 volts, and that would require three wires. Generally, only a three phase load would need four wires. Please note that the Equipment Grounding Conductor (green or bare copper) would be in addition to the number of wires described above.
Click to expand...

Charlie thanks for claryfing this. I agree. 3 wire wg, 4 wire wg, etc. wg (with ground) is the key and not inclusive with nominal trade wire count.
 
A better way to look at this is when does the connected load require a grounded neutral conductor. If there are no loads to neutral than obviously its not required, rangers and dryers have timers and motors that need 120v.
And you can always tell from the nameplate or instructions.
 
dryer hookup...

dryer hookup...

My house has a 3 wire dryer hookup. Is the third wire a nuetral (and thus ok to return the small amt of 120v) but with no ground; or is it a ground (not ok for the 120v, but good for the obvious reasons)?
David
 
daddyray said:
My house has a 3 wire dryer hookup. Is the third wire a neutral (and thus OK to return the small amt of 120v) but with no ground; or is it a ground (not OK for the 120v, but good for the obvious reasons)?
David
Click to expand...

David the NEC has allowed the neutral to be used as the grounding means for electric ranges and dryers.

The frame of the range or dryer is electrically bonded to the neutral at the units connection point.

This is now not allowed for new installations, now any new installation must get a 4 wire feed.
 
GENERALLY,

welders, water heaters, A/c units, elec heater = 3 wire

ranges, dryers and most (some) cooktops = 4 wire.


The appliances (range, dryer) seem to sometimes use 120V for low heat and control wiring thus requiring the neutral wire.
 
daddyray said:
My house has a 3 wire dryer hookup. Is the third wire a nuetral (and thus ok to return the small amt of 120v) but with no ground; or is it a ground (not ok for the 120v, but good for the obvious reasons)?
David
Click to expand...

Read 250.140

Roger
 
iwire said:
David the NEC has allowed the neutral to be used as the grounding means for electric ranges and dryers.

The frame of the range or dryer is electrically bonded to the neutral at the units connection point.
Click to expand...
Correct, but under certain conditions as per 250.140. Notice the exception states that ALL the conditions must be met.

BTW, if anyone knows the reasoning behind exception #3 and why it specifies the use of SE type cable instead of say 10/2 or 8/2 RX I'd be interested in knowing what it is. If you don't want to take up the space here and divert from the OP please send me a PM.

Thanks,

Phil
 
Status
Not open for further replies.
Top