Electricians in the house?

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Freestyle72 said:
Also just reading about the undersizing to make sure I understand correctly the 4/0 aluminum is only good for 185 in reality but due to some rule for residential it's allowed and outlined here:

For 3-wire:
120/240 V and 120/208 V service conductors for single dwellings, or for feeder conductors supplyingsingle dwelling units of row housing of apartment and similar buildings, and sized in accordance with Rules 8-200(1), 8-200(2), and 8-202(1), the allowable ampacity for sizes No. 6, No. 2, and No. 4/0 AWG shall be 60 A, 100 A, and 200 A, respectively. In this case, the 5% adjustment of Rule 8-106(1) cannot be applied.

Also I have no idea where to find the rule about dropping ot #6... however going to 4/0 aluminun for the feeds does that make the 2" conduit too small and need to be bigger? Because I think my mast is only 2.5" possibly 3 max, so I don't think I can really go much bigger with the conduit.
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Also I rent my basement so does it still classify as a single dwelling? I have the full codebook, what gets me about the book is their definitions of things like "dwelling" and "residential" that worry me when it comes to showing my work to the inspector.
 
Freestyle72 said:
Dude at the electrical supply place told me 3/0 is cheaper per m than 2/0 due to it's more common use. He said 3/0 was $12/m and 2/0 was $13.XX.
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If you are paying more for 2ot than 3 ot.....you are shopping at the wrong supplier.
 
Freestyle72 said:
Also just reading about the undersizing to make sure I understand correctly the 4/0 aluminum is only good for 185 in reality but due to some rule for residential it's allowed and outlined here:

For 3-wire:
120/240 V and 120/208 V service conductors for single dwellings, or for feeder conductors supplyingsingle dwelling units of row housing of apartment and similar buildings, and sized in accordance with Rules 8-200(1), 8-200(2), and 8-202(1), the allowable ampacity for sizes No. 6, No. 2, and No. 4/0 AWG shall be 60 A, 100 A, and 200 A, respectively. In this case, the 5% adjustment of Rule 8-106(1) cannot be applied.

Also I have no idea where to find the rule about dropping ot #6... however going to 4/0 aluminun for the feeds does that make the 2" conduit too small and need to be bigger? Because I think my mast is only 2.5" possibly 3 max, so I don't think I can really go much bigger with the conduit.

EDIT: Figured out the bit about the conduit. 53mm or 2" is good enough for 3 wires in 3/0 and 4/0 and 4 wires in 2/0

Sweet I am learning a ton.
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Listen.......

All you really need is 2 black - 4ot AL, and 1 white #2 AL.

It will fit, and it will pass. ;)

And you can use the smaller #6 ground wire to boot.
 
SunnY S said:
Listen.......

All you really need is 2 black - 4ot AL, and 1 white #2 AL.

It will fit, and it will pass. ;)

And you can use the smaller #6 ground wire to boot.
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Bwahaha thanks Sunny S.

I also like to take advice but I also like to understand where it's coming from... I do get it now though. You got a PM on the way.
 
Freestyle72 said:
Also just reading about the undersizing to make sure I understand correctly the 4/0 aluminum is only good for 185 in reality but due to some rule for residential it's allowed and outlined here:

For 3-wire:
120/240 V and 120/208 V service conductors for single dwellings, or for feeder conductors supplyingsingle dwelling units of row housing of apartment and similar buildings, and sized in accordance with Rules 8-200(1), 8-200(2), and 8-202(1), the allowable ampacity for sizes No. 6, No. 2, and No. 4/0 AWG shall be 60 A, 100 A, and 200 A, respectively. In this case, the 5% adjustment of Rule 8-106(1) cannot be applied.

Also I have no idea where to find the rule about dropping ot #6... however going to 4/0 aluminun for the feeds does that make the 2" conduit too small and need to be bigger? Because I think my mast is only 2.5" possibly 3 max, so I don't think I can really go much bigger with the conduit.

EDIT: Figured out the bit about the conduit. 53mm or 2" is good enough for 3 wires in 3/0 and 4/0 and 4 wires in 2/0

EDIT #2:
Table 16 talks about the minimum size of bonding conductors... and I see there #6 is good for 200 amp...

Booyakasha.

Sweet I am learning a ton.
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One thing to remember, to add to your knowledge base, is that if for some reason you use a wire rated for a higher amperage your ground needs to be good for the amperage rating of the wire and not what your actually using it for.
 
01cbr said:
One thing to remember, to add to your knowledge base, is that if for some reason you use a wire rated for a higher amperage your ground needs to be good for the amperage rating of the wire and not what your actually using it for.
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That got covered a page back with the 3/0 copper (good for 210a) requiring a #3 ground.
 
Just going through the code book again tonight and I was wondering where the rule that allows the the #2 Aluminum white to be run with the 4/0 Aluminum hot legs?

Looking at table 36A it shows#2 Aluminum to have an ampacity of 140amp in NS75 and 165amps in NS90... There is no note accompanying to tell me it's ok. I am not doubting what Sunny said btw... I am just highlighting all the rules applicable to me in the code book and it's the only thing I would be stumped at if the inspector asked me why I used that.

EDIT: I think I found the rule I was looking for in section 4-022(2)(b) "A demand factor of 70% shall be permitted to be applied to that portion of unbalanced load in excess of 200A"

200 X 0.7 = 140amps...
This is the part where a little bit of knowledge is a dangerous thing.
 
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If you check the code book.... the ampacity charts are found in tables 1, 2, 3 and 4.

Look up "aluminum conductor", and "no more than 3 conductors in a raceway or cable" and you will see that #2 al is rated for around 100amps. :)
 
SunnY S said:
If you check the code book.... the ampacity charts are found in tables 1, 2, 3 and 4.

Look up "aluminum conductor", and "no more than 3 conductors in a raceway or cable" and you will see that #2 al is rated for around 100amps. :)
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OK so my question is this though. What makes it ok to carry only 100amps.. instead of the full 200amps?

Also just checked the code book and it's 95amps for #2 if I am not mistaken. Or were you rounding for 100 amps?

EDIT:

Whoops I see that in the note afterwards it makes an exception to the rule to say that #2 is good for 100amp... but again I beg the question why does the neutral only have to be good enough for 50% of load?

Or is this just a case of it is what it is?
 
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Freestyle72 said:
... but again I beg the question why does the neutral only have to be good enough for 50% of load?
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This used to be common practice. The neutral conductor only has to carry the unbalanced load. If the loads in your house are evenly spread across both live legs then there will be no current on the neutral. But, things are never exactly equal, so there will be some unbalanced load. With 3 Phase systems this becomes even more pronounced as some loads have no neutral at all, meaning there is very little unbalanced load. Half size neutral was more than enough.

However, that was then, this is now. In the meantime we started using non-linear loads, harmonics producing loads. Caused all sorts of problems. The loads were out of phase and didn't balance on the neutral. Neutral conductors were burning up all over the place. It is now common for engineers to specify double size neutrals in suspected harmonics situations even though the unbalanced load could never exceed 175% of line load and that harmonics problems have largely been corrected. All of this is history, but it leads us to your situation.

The code no longer allows for half size neutrals, or even reduced sized neutrals in services under 200 Amps. (4-022)
You need to use a full size neutral.
 
VFR.CBR said:
This used to be common practice. The neutral conductor only has to carry the unbalanced load. If the loads in your house are evenly spread across both live legs then there will be no current on the neutral. But, things are never exactly equal, so there will be some unbalanced load. With 3 Phase systems this becomes even more pronounced as some loads have no neutral at all, meaning there is very little unbalanced load. Half size neutral was more than enough.

However, that was then, this is now. In the meantime we started using non-linear loads, harmonics producing loads. Caused all sorts of problems. The loads were out of phase and didn't balance on the neutral. Neutral conductors were burning up all over the place. It is now common for engineers to specify double size neutrals in suspected harmonics situations even though the unbalanced load could never exceed 175% of line load and that harmonics problems have largely been corrected. All of this is history, but it leads us to your situation.

The code no longer allows for half size neutrals, or even reduced sized neutrals in services under 200 Amps. (4-022)
You need to use a full size neutral.
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I actually read over this last night. That was the exact answer I was looking for. So it looks like I will have to use 4/0 aluminum.

For those wondering..
4-022 Size of neutral conductor
(1) The neutral conductor shall have sufficient ampacity to carry the unbalanced load.
(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
electric-discharge lighting; 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.
(3) The size of a service neutral shall be not smaller than the size of a neutral selected in accordance with
Subrule (1) and shall
(a) be not smaller than No. 10 AWG copper or No. 8 AWG aluminum; and
(b) be sized not smaller than a grounded conductor as required by Rule 10-204(2), except in service
entrance cable or where the service conductors are No. 10 AWG copper or No. 8 AWG aluminum.
(4) In determining the ampacity of an uninsulated neutral conductor run in a raceway, it shall be considered
to be insulated with insulation having a temperature rating not higher than that of the adjacent circuit
conductors.
 
There was a bulletin (which registered contractors get from ESA every so often).

They are constantly "tweaking" the code which will show up in revised code book which changes every 4 years.

The bulletin states that reduced neutral is permissible in residential 200amp services.

I've been using #2 AL for the last 2 years, and we do tons of residential services! New and retro.

http://www.esasafe.com/pdf/bulletin_index.pdf

If I remember and have time tomorrow, I will dig the details of this bulletin up as I keep all my bulletins in my office for future reference.

Having said that, there is nothing that stops you, except for extra cost :) from using a larger size neutral.


.
 
Freestyle72 said:
I actually read over this last night. That was the exact answer I was looking for. So it looks like I will have to use 4/0 aluminum.

For those wondering..
4-022 Size of neutral conductor
(1) The neutral conductor shall have sufficient ampacity to carry the unbalanced load.
(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
electric-discharge lighting; 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.
(3) The size of a service neutral shall be not smaller than the size of a neutral selected in accordance with
Subrule (1) and shall
(a) be not smaller than No. 10 AWG copper or No. 8 AWG aluminum; and
(b) be sized not smaller than a grounded conductor as required by Rule 10-204(2), except in service
entrance cable or where the service conductors are No. 10 AWG copper or No. 8 AWG aluminum.
(4) In determining the ampacity of an uninsulated neutral conductor run in a raceway, it shall be considered
to be insulated with insulation having a temperature rating not higher than that of the adjacent circuit
conductors.
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Is this saying you only need a 100 amp neutral? If you read it it is the load for one ungrounded conductor. 200A service is 2x100A or am I missing something?
 
LOL...

God damn.. there is no denying Sunny knows his ****... links and all. Thanks dude. If I call ESA do you think they would divulge such information to me?
 
Scuba Steve said:
Is this saying you only need a 100 amp neutral? If you read it it is the load for one ungrounded conductor. 200A service is 2x100A or am I missing something?
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No if you read (1) and (2) I understand as saying the neutral conductur must carry all the unbalanced load. The maximum of which is equivalent to what an ungrounded conductor (which would include one of the main feeds) can carry. Thus 200amps...
 
The neutral isn't used because the pump the pump runs on 220volts.You use the neutral if you require 120volts
CruisnGrrl said:
The pump from my well runs on ~220V, when I bought the wire for it I was told to get 12 gauge wire which is 2 conductors and ground. any explanation on why the neutral isn't used? I don't know much about electricity but I thought AC required a Hot and a Neutral?
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This is becoming way more complicated than it needss to be.I've done a million 200 amp services and I've always used a 2" conduit and three copper RW90 3 ot conductors and a #3 ground.There is not an inspector on the planet that will not pass that.You can actually use a #6 ground now but if it's a short run I just use #3. As for using a smaller neutral, that is something that just isn't done anymore.I've been doing this for almost 30 years and I can count on one hand the number of times I've derated the neutral.
 
Did the undersized neutral rule just change again?

Last I read it was allowed for residential service, but I last looked into it in 2010. What is the latest up-to-date info on this (not what someone has been doing for X years but what is the code/rule today)? While I agree with harmonics etc. the logic goes beyond this in that most large load devices in the home come off of the two "sides" of the panel and do not put much load on the neutral (stove, dryer, central air, electric heat, etc.).
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