# Reduced Neutral CEC



## corisu (Nov 22, 2012)

Question for you guys,
I'm feeding a new panel from an existing service entrance disconnect fused at 175A. I need to pull a neutral through the existing pipe as it was feeding a furnace. Off this new panel I have a 20kw boiler, assuming I am reading the CEC 4-024 properly I can reduce the neutral to carry my unbalanced load which will be roughly 91A left after the boiler is fed. Is this true? If not can someone point me in the right direction.


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## FastFokker (Sep 18, 2012)

corisu said:


> Question for you guys,
> I'm feeding a new panel from an existing service entrance disconnect fused at 175A. I need to pull a neutral through the existing pipe as it was feeding a furnace. Off this new panel I have a 20kw boiler, assuming I am reading the CEC 4-024 properly I can reduce the neutral to carry my unbalanced load which will be roughly 91A left after the boiler is fed. Is this true? If not can someone point me in the right direction.


I don't know about your numbers, but yeah, there's been other discussions on here about reduced neutrals and apparently you can, so long as you meet the requirements.. those items such as non-linear loads `n such.


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## jgpoirier (Nov 23, 2012)

From what I remember, if the unbalanced load is over 200A a reduction in size of the neutral conductor may be to 70% off the unbalanced load. This though is my knowledge from 2009 code book, unfortunately I havent looked at 2012 yet. In my opinion you can't due to your unbalance only being 91A, and at that size is it even really that cost effective to downsize?

Guy


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## FastFokker (Sep 18, 2012)

Cleared this up yesterday as to what CSA means:



> (2) The maximum unbalanced load shall be the maximum connected load between the neutral and any one ungrounded conductor as determined by Section 8 but subject to the following:
> (a) there shall be no reduction in the size of the neutral for that portion of the load that consists of
> (i) electric-discharge lighting; or
> (ii) non-linear loads supplied from a 3-phase, 4-wire system; and
> (b) except as required otherwise by Item (a), a demand factor of 70% shall be permitted to be applied to that portion of the unbalanced load in excess of 200 A.


So, all known balanced loads can have a reduced neutral (e.g.. motors, heaters), but you cannot reduce the neutral supply balanced loads that are non-linear. 

The bonus is you can apply a reduction of 30% on unbalanced loads, in excess of 200A. 

Now a motor or a heater is obviously going to be inherently balanced... but as in a residence, you can't assume all 240V circuits are balanced. You COULD need proof when derating items like a stove or dryer or less common loads. 

It's pretty confusing wording when you just read it quick.

So say you had a house with 400A service, and there was 100A of balanced heat, and 300A of various loads. So you have 100A left over the 200A, which can be applied at 70%. So 100A*70%+200A gives you a total calculated neutral demand of 270A.

If there's any questions, ask away.. I might even have made a mistake in my calculations as I'm barely into my first coffee of the day.


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