It's not just harmonics that come into play here.If the load on the two phases is not balanced the load on the neutral could concievably be the same as any two phases.I can gaurantee you that any electrical engineer or proffessional electrician doing a service on his own house would not use a derated or undersized neutral to save a few bucks. The only time I've seen a derated neutral used in a house is if there is an electric furnace where the bulk of the load on the main service is at 240 volts and the load is inherently balanced between the two phases.
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Electricians in the house?
- Thread starter Freestyle72
- Start date
The reason is the way the transformer is wired it is a 220 service, the neutral is a center tap from the middle of the winding giving you 110v between the neutral and either hot, or 220 between the 2 hot wires.
While I do not disagree that a full gauge neutral may have advantages (at least theoretical) the 2010 book (for Ontario) I had said that undersized neutrals were OK and went into length about it. Did the code change again to now not allow it?
The codes change all the time like the requirement for a fire/heat barrier (1/2" drywall/cement board) behind the panel, then no requirement etc...
I am working from the 2009 version... I thought it only came out ever 4 or 5 years....
Or does a smaller one with revisions come out every year?
Or does a smaller one with revisions come out every year?
They come out every X number of years, my book is the last one before the current one (which I think "expired" in 2010 but I would have to double check the date).
2009 is the "current" version. However, as stated previously, there are numerous bulletins that we receive which clarify or update certain codes.
The bulletin I have in front of me which is from 2009 when the new code changes were introduced, states :
SERVICE NEUTRAL :
-to avoid differences of opinion in determining unbalanced load required in Rule 4-022, the following neutral size will be accepted for single dwellings- 120/240 volt single phase services :
1) for 60 amp and 100amp services, the neutral will be the same size as the ungrounded conductors and may be bare or insulated.
2) for services rated 125-225 amps, the neutral will be at least #3 awg copper, or #0 awg AL, bare or insulated.
The code book states that #0 (60deg) AL is good for 100amps. Also states in the foot note, that #2 AL (95deg) which is rated at 95amps, when used as a 120/240 service, is good for 100amps.
These bulletins and code changes are approved by several electrical engineers from ESA, and from outside engineers. Changes of this nature are not taken lightly.
Just because people are used to the "old way", doesn't mean the new way is incorrect!
Bottom line...........if it makes you or anyone sleep better at night, then run full size neutral, and bigger ground. It will surely pass!
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The purpose of a neutral conductor is to carry unbalanced current.
Any 220v item such as pumps, AC, electric heaters, are equally balanced on their 220v loads, thus no neutral is required to return the power.
Its 220V stoves and dryers that require a neutral, as in addition to their 220v heating elements, they have timers, clocks, rotisseries, etc and other 120v items and need a neutral to complete their circuit. Also multiwire circuits where 2 powers and neutral are run to feed two separate circuits, a neutral is required so carry back the unbalanced load between the 2 circuits.
Electricity is fun, eh?
As for the reduced size of grounding in 200-400amp services......
It was explained to us at an ESA seminar back in 2009 when the new code changes were
introduced, that in studies, they found that when there was a fault to ground, the current flowed to the grounded conductor/neutral from the panel to the meterbase, back to the transformer, substation, etc.
It appears that these transformers, substations, etc are so well grounded, and electricity is lazy and takes the path of least resistance, that the fault current took that route rather than through the bare ground wire connected to a 3/4inch water pipe, or a small ground electrode plate buried in the dirt.
So yes, on all our residential electrical services....(up to 400amp, where we used to run a big fat 2ot ground wire). All we need is a puny #6.
Hey, it meets code now! and like I said, if it makes you sleep better at night, keep running the 2 ot bare.
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It was explained to us at an ESA seminar back in 2009 when the new code changes were
introduced, that in studies, they found that when there was a fault to ground, the current flowed to the grounded conductor/neutral from the panel to the meterbase, back to the transformer, substation, etc.
It appears that these transformers, substations, etc are so well grounded, and electricity is lazy and takes the path of least resistance, that the fault current took that route rather than through the bare ground wire connected to a 3/4inch water pipe, or a small ground electrode plate buried in the dirt.
So yes, on all our residential electrical services....(up to 400amp, where we used to run a big fat 2ot ground wire). All we need is a puny #6.
Hey, it meets code now! and like I said, if it makes you sleep better at night, keep running the 2 ot bare.
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interesting, why don't most of the clocks etc on the stove just run on 220v?
not sure why a dryer would require neutral, it's a motor, heater & timer, couldn't all those run off of 220?
Just got off the phone with my inspector and he said for the undersized neutral smallest I can go is 1/0 stating some rule like "In a 200amp service a neutral shall not be less than 1/0 aluminum or...blah blah copper"
THAT is an excellent question.. and I bet [my guess] there is a price / cost based on the available current to the device.. and might cause CSA issues.
for example.. the clock motor in a stove must meet locked rotor testing for 18days.. and not catch fire. this is done with impedance protection not fuse protection.
to cause high impedance you use longer conductor, smaller diameter conductor, lower voltage, etc.
if you increase the voltage, then more condutor is required in the winding.. and more cost to the manufacture.. whereas the lower voltage winding costs the mfgr nothing, only the installer must supply that one more wire... just a guess..
My stove has 110v plugs on it for kettle etc, since it has 220 feeding it and the neutral is for unbalanced load, if i use 110v appliances plugged into the stove does it draw more power (wasting on the neutral) than if i had the appliance plugged into a dedicated 110v outlet? or am i not understanding what the neutral does...? my regular 110 outlets have neutral too right? shouldn't i just need the hot and ground? I understand how dc works and i know ac has alternating polarity requiring adaptors to rectify the current (like on the regulator/rectifier i just replaced on my bike) to use devices like my computer... but then we also have devices that don't use a ground...
Your regular outlets have a neutral.
They require a neutral, but they dont require a ground to work. The ground wire is only for safety, dont include it when trying to understand how the circuit works.
With the 110 outlet on your stove, your not wasting anything.
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