Reduced Neutral

[lady sparks lover]

Re: Reduced Neutral

I almost never run a neutral to a 208V/1phase load, such as a oven, motor,etc. Meaning only a select few!

Why would you need a neutral with this connection?

[ July 16, 2004, 12:50 PM: Message edited by: lady sparks lover ]

 

[don_resqcapt19]

Re: Reduced Neutral

Lady,

I'm not surprised by a dispute from Don, once again. I seem to always be his target.

I don't "target" anyone, but if I don't agree, I always post my opinion on what the code rule says.
Don

 

[don_resqcapt19]

Re: Reduced Neutral

I don't think that the code rule is saying that the grounded conductor of a 3 wire system that is derived from a 3 phase 4 wire wye system has to be the same size as the phase conductors. It only has to be sized to handle the maximum unbalanced load. It is my opinion that wording that says

There shall be no reduction in the capacity of the grounded conductor of a 3-wire circuit consisting of two phase wires and the neutral of a 4-wire, 3-phase, wye-connected system.

only applies to the wording that says

a further demand factor of 70 percent shall be permitted for that portion of the unbalanced load in excess of 200 amperes

Don

 

[lady sparks lover]

Re: Reduced Neutral

Originally posted by don_resqcapt19:
Lady,

I'm not surprised by a dispute from Don, once again. I seem to always be his target.

I don't "target" anyone, but if I don't agree, I always post my opinion on what the code rule says.
Don

I've noticed it, and it seems that way to me. Every since I came here on this site.

oh well, one thing I do know is not everyone is going to like you or agree with you.

 

[iwire]

Re: Reduced Neutral

Lady Sparks can I add my two cents, Don will nail anyone that he does not agree with.

JMO, Bob

 

[jpmccleery]

Re: Reduced Neutral

The building has a total of 64 apartment units being served from (4) 600 Amp 120/208 Volt Meter Centers. The service to each unit is 120/208V., 1PH. The possibility of having the neutral conductor serving the individual dwelling unit carrying the full 100 amps is next to impossible.
The calculated load as stated before is 95 Amps. What is the min allowable neutral?

 

[ryan_618]

Re: Reduced Neutral

Originally posted by jpmccleery:
The possibility of having the neutral conductor serving the individual dwelling unit carrying the full 100 amps is next to impossible.

I don't see how you can circumvent the math...the formula just doesn't lie.

 

[lady sparks lover]

Re: Reduced Neutral

Originally posted by iwire:
Lady Sparks can I add my two cents, Don will nail anyone that he does not agree with.


Lady

 

[wirebender]

Re: Reduced Neutral

jpmccleery

The calculated load as stated before is 95 Amps. What is the min allowable neutral?

The 120v load plus 70% of the range and dryer load(Article 220.22). I have no experience in washer/dryer combos so I don't know how much of the 3928 watts is 208 if any. I also agree with Lady that you may not be figuring your 120v load correctly as you didn't list a 1500 va laundry circuit load which is (IMO) still required in addition to the circuit for the combo washer/dryer. This of course depends on not applying the last sentence of 220.22 to the service as a whole. This is all just my opinion and would like to know if my thinking is flawed.

[ July 16, 2004, 06:15 PM: Message edited by: wirebender ]

 

[gnu_mike]

Re: Reduced Neutral

QUOTE:
"Also, what value would you assign these receptacles? The 180VA provision is pretty specific when it says that it does not apply to dwelling units."
Well, it's specific when it says that no additional load calculation is required for outlets in complying with the general lighting load. But, I think that outlets other than the required small appliance branch circuits should be tallied at 180 VA and added to the lighting load to determine whether or not you've complied with or exceeded your general load requirements.
NO?

 

[rb]

Re: Reduced Neutral

JPMCCLEERY:

You can't use the 70% demand factor permitted by 220-22 for the neutral load in excess of 200 amps.

Many people confuse the "no reduction in the neutral conductor" clause as requiring the neutral to be the same size as the phase conductors. This is not true. The neutral is only required to be sized for the maximum imbalance of the load that can occur on the neutral conductor. Line connected loads are not required to be included in the neutral calculation of 208/120 single phase feeders derived from three-phase four-wire systems.

It is feasible to have No. 3/0 phase conductors with a No. 2 neutral. It depends on the total phase connected load.