Conduit Sizing

[TractorJeff]

An friend of mine told me his Electrician is going to run buried 1&1/4" conduit for the 90 amp service to his shop which is about 100 feet from his garage which has (60amp) and 160 feet from his 200amp panel in the house.
I haven't got figured out how he is going to run the wire through 1&1/4" conduit?
Or is he thinking 60amp?

 

[PoorOwner]

Fill table says you can have up to 5 2AWG wire in 1 1/4 PVC sch40.

not sure if I understand it sounds like you are sayig he is feeding a 90A from a 60A sub panel?

 

[Bert_]

Fill table says you can have up to 5 2AWG wire in 1 1/4 PVC sch40.

This^

Assuming he is running 2-2-4-6 XHHW or something similar the pull won't be to bad at all.

 

[Stuart in MN]

Without knowing what kind of wire he's planning on using it's impossible to say

 

[TractorJeff]

I'm thinking he was telling me he hasn't decided(money) whether to sub off the garage 60amp panel carry 60 amps out to the next building.
Or Pay the difference in wire length to go into the house panel for 75 or 90 amps?
All he has to put out there is a 50amp circuit for a welder, 30amp circuit for an A/C, 20amp for an Air Compressor plus some lights and outlets.
He has had the 60amp in the Garage that he has run on for years, I think he is planning on running the A/C which is why he is waffling on the sizing?
He is so cheap that he never runs 2 of anything at the same time!

 

[zmaxmotorsports]

I wouldn't bother burying anything smaller than 2" for a service myself anyway.

 

[TractorJeff]

It already goes through his concrete floor so I doubt he wants to have the Electrician tear it out to go larger.
Any more positive comments?

 

[ard]

It already goes through his concrete floor so I doubt he wants to have the Electrician tear it out to go larger.
Any more positive comments?

I must have missed the "its already installed" and the "its already going thought the poured concrete" in your first post....

Do keep in mind that 1.25" for the full 160 feet is different in terms of pull than 1.25" for the first 6 feet then 2" the rest....

 

[zmaxmotorsports]

If you don't want anymore positive comments give us all of the facts before hand.
Some of us have done this profesionally for a lot of years,pulling that size of wire that far through that small of a piece of pvc is going to ****.
But good luck with it.

 

[matt_i]

Its not great but its doable, I'd try a full spool of Cu THHN #2 or #3 to get the amp rating @ the distance, using Cu to get the minimum cross section needed to carry the amperage as a penalty for going cheap on the original conduit. Phase-tape the conductors for identification. The larger ground isn't needed but you'll save on buying a 500' spool and won't have a lot left over at the end plus have to buy an additional length of #6 for a ground. But, price it both ways to be sure, have to have exact measurements plus a small safety factor. Gallon size wire lube while you're acquiring materials.

 

[TractorJeff]

Thanks Guys for the insight!
ZMAX don't get bent as all the facts/spec's currently available are in the first and fifth posts.
It will be interesting to see how the Electrician handles this and how far it bends my neighbors Bank Book!

 

[rburke65]

Is he thinking 60 Amp?.......I have no idea what he is thinking.

 

[zmaxmotorsports]

Thanks Guys for the insight!
ZMAX don't get bent as all the facts/spec's currently available are in the first and fifth posts.
It will be interesting to see how the Electrician handles this and how far it bends my neighbors Bank Book!

Did you notice the part where it says is going to run?
Nothing in the 1st post says anything about pipe having been run through a slab already,big difference there.
You haven't seen bent.

 

[TractorJeff]

Sorry ZMAX, its for sure called out in Post 7.
I'll be talking to him this weekend hopefully if the "Honey-Do" list at home isn't too big!

 

[Bert_]

I have no idea why eveybody is so worried about this, it's literally no big deal...

Lots of people here want to use 2" to make it easier and that's fine. It's extremely overkill for a 100A feeder.

I just pulled a 100A feeder though about 80' of 1" a couple weeks ago, it was copper so only #3, but it was pretty easy.

 

[ard]

Sorry ZMAX, its for sure called out in Post 7.
I'll be talking to him this weekend hopefully if the "Honey-Do" list at home isn't too big!

Post 7 is AFTER zmax posted his comments?!?!

Instead of doubling down on dumb, just say "my bad, didnt mention it- I should have".

 

[TractorJeff]

ard- your right!
I read early in the morning, then back up to reread, often over sighting the fact as you stated!
No Worries, My Bad!

 

[Aceman]

Assuming he is running 2-2-4-6 XHHW or something similar the pull won't be to bad at all.

I'm with Bert.

1.25" conduit is SOP for 100 amp circuits for our shop. We do it all the time. 100' is nothing for length either. It's not an issue.

I bet conduit fill is somewhere between 20-30%, well below the NEC maximum of 40%. The wire should fly in, if it doesn't, then they're doing it wrong.

 

[TractorJeff]

I mentioned to an Electrical Engineer about the 2-2-4-6, he wondered why you would undersize the Neutral that much?
Any insight?

 

[Aceman]

I mentioned to an Electrical Engineer about the 2-2-4-6, he wondered why you would undersize the Neutral that much?
Any insight?

It's obvious the electrical engineer you talked to is out of his area of expertise.

It's very common to drop the neutral down because there is no reason for a fullsize neutral when the shop has minimal neutral load. So there is no added benefit to a fullsize neutral when it's not needed or required.

Ask yourself this. If all the equipment you mentioned going in your friends shop is mostly all 240v loads (ac, air compressor, welder, etc) that don't use a neutral, why wouldn't a person drop it down a couple sizes?

 

[Bert_]

I mentioned to an Electrical Engineer about the 2-2-4-6, he wondered why you would undersize the Neutral that much?
Any insight?

Cost savings, easier to work with, easier to pull in conduit, more common if your using an underground cable (URD/MHF) rather than individual conductors. Extremely unlikely to cause any problems now or if you add loads in the future.

Sizing the neutral 2 sizes smaller than the line is pretty commonly accepted for services and many feeders. You will have 240V loads that do not even use a neutral and many of the 120v loads will be on opposite phases and the difference in neutral currents cancel.

A smaller neutral yet can be permitted, as small as a #8 copper or #6 aluminum for a 100A feeder, but you would have to do some extra calculations to determine it was OK. This is a bit extreme unless you have almost exclusively 240v loads and no plans to change that.

From my limited experience many electrical engineers spec whatever sound good on paper and do not even consider cost as a factor. Most jobs get the same "boiler plate" set of spec's with minimal consideration to the situation at hand. Obviously cost is a concern to most on here and we try to cut them in many ways while still ending up with a safe, functional, and durable end result.

I'm sure many of them would spec this project with copper and maybe even an UPsized neutral.I won't claim to be an expert but even if you have problems with harmonics any reason for an upsized neutral is a big load of BS.