Conduit sizing question

[DerStig]

I need opinions (ideally from people who have experience with this wire size). I am looking at two potential scenarios for a sub panel:

- 45 ft
- Indoors/open ceiling/unfinished basement
- 3x 90 degree turns, 2x45 degree turns, some of these 90 degrees will be “pull boxes” so I wont come close to 360 degree limit
- Either #1 CU CCC x 3 with # 6 GND OR #2 CU CCC X 3 and # 8 GND

Given the above, I would like to find out what conduit size I should be using. Before you point me to NEC Conduit fill tables, I am aware of them, I read them and I know as per NEC i can use 1 1/2” for the #1 cu scenario and 1 1/4” for the #2 scenario.

That being said, I dont know if those sizes are difficult or if I should go with 2” instead. The 2” conduit is huge but I am happy to invest into it if its worth the hassle.

One other question I have is, is there an advantage of using a big conduit in terms of sharing that conduit with something else in the future such as running additional other smaller wires? But is that a big no, in which case this conduit has to be exclusive to the original wires I put in it?

 

[pattenp]

If run is inside why are you wanting to use conduit?

 

[DerStig]

If run is inside why are you wanting to use conduit?

That is not my question

I want to use conduit because it looks cleaner. I dont like romex (hate it infact) because it never lays flat and straight and drives me crazy.

I would also have to drill a fairly big 1-1/2" hole on over 20 joists, some are double sister joists. Not to mention, I would still need some form of conduit because part of the run involves basement brick wall and I cant run the cable naked there.

I understand as per NEC, this cable can be stapled/mounted bottom of joists. But I would not do that - I dont think it's safe.

 

[u2slow]

I would probably try to use equivalent ampacity alum cable. The cost savings over copper and conduit are significant.

Also, 1-1/2" and larger EMT you need hydraulic bending equipment - unless you can make do with only pre-bent and straight pieces. 2" is only worth it if you're already planning on upgrading again. No conduit expense at all when you go with cable.

EDIT: An armoured type cable can be exposed where needed.

 

[DerStig]

I would probably try to use equivalent ampacity alum cable. The cost savings over copper and conduit are significant.

Also, 1-1/2" and larger EMT you need hydraulic bending equipment - unless you can make do with only pre-bent and straight pieces. 2" is only worth it if you're already planning on upgrading again. No conduit expense at all when you go with cable.

EDIT: An armoured type cable can be exposed where needed.

What does armoured mean here? Do you consider the SER cable on gray plastic cover armoured? Or is there some form of metal jacketed MC type SER cable that I am not aware of?

As I said, this is a personal choice but I dont want to have an exposed 125A cable on my ceiling. And I dont want to drill lots of big holes next to already existing many holes weakening the joists.

To answer your question on bending, I can make it work with pre-bend connections. I honestly didnt even know big PVC can be bent.

 

[MattT]

I wouldn't upsize conduit for a run that short. Pull boxes will probably give you more trouble than the pulls between them. Looking at your bends it's 360* total so I'd rather do the entire run with bends if that's possible.

 

[u2slow]

What does armoured mean here? Do you consider the SER cable on gray plastic cover armoured? Or is there some form of metal jacketed MC type SER cable that I am not aware of?

As I said, this is a personal choice but I dont want to have an exposed 125A cable on my ceiling. And I dont want to drill lots of big holes next to already existing many holes weakening the joists.

To answer your question on bending, I can make it work with pre-bend connections. I honestly didnt even know big PVC can be bent.

Yes, like MC or AC. Most common here is ACWU, which adds a layer of soft PVC on top (makes it Wet or Underground rated also.) Cable can be painted, or hidden behind a crown molding or build a small chase. It will be skinnier than a finished 2x4.

PVC conduit? Ok... we use metallic conduit inside.

 

[DerStig]

Yes, like MC or AC. Most common here is ACWU, which adds a layer of soft PVC on top (makes it Wet or Underground rated also.) Cable can be painted, or hidden behind a crown molding or build a small chase. It will be skinnier than a finished 2x4.

PVC conduit? Ok... we use metallic conduit inside.

I am looking at ACWU right now. Its interesting but I'm not sure if this is stocked anywhere locally here.

 

[Norcal]

PVC indoors is a more European thing, either SER cable, MC, or EMT in my thinking, last time I used PVC inside was for 400 hz power for a test stand & had the choice of PVC or non ferrous metallic conduit.

 

[DerStig]

PVC indoors is a more European thing, either SER cable, MC, or EMT in my thinking, last time I used PVC inside was for 400 hz power for a test stand & had the choice of PVC or non ferrous metallic conduit.

How would one use EMT in this case?

 

[exranger06]

One other question I have is, is there an advantage of using a big conduit in terms of sharing that conduit with something else in the future such as running additional other smaller wires? But is that a big no, in which case this conduit has to be exclusive to the original wires I put in it?

You can put other wires in the conduit too, but you have to derate the conductors when you have more than 3 current carrying conductors in the same conduit (310.15(C)(1)).

 

[Innovate1]

Aluminum is more flexible and thus an easier pull even with a bigger size I think. Don't have nearly the experience with this that some others here do...

If you have room some longer sweeps will help but your runs aren't real long so may not be worth it. You can bend PVC by heating it. I like to use steam through a larger pipe because it heats evenly and allows an even bend. Several minutes of steam is enough.

You don't want to go with NEC minimum size. Go up at least one size - it will make things a LOT easier.

 

[DerStig]

Aluminum is more flexible and thus an easier pull even with a bigger size I think. Don't have nearly the experience with this that some others here do...

If you have room some longer sweeps will help but your runs aren't real long so may not be worth it. You can bend PVC by heating it. I like to use steam through a larger pipe because it heats evenly and allows an even bend. Several minutes of steam is enough.

You don't want to go with NEC minimum size. Go up at least one size - it will make things a LOT easier.

Looking at PVC conduit fill table : http://www.elliottelectric.com/Stat.../ElectricalTables/Conduit_Fill_Table_PVC.aspx

- Minimum size to fit 3 conductors #1 is 1 1/4". A size higher is 1 1/2" which fits 3 conductors (plus I will need #6 EGC).

Is that big enough for 1-1-1-6 for a comfortable run? Is it worth dealing with 2"? I have no problem paying extra for 2" PVC. The only issue with 2" PVC is the parts of the run where pull boxes are required OR where I need to drill through the basement brick wall becomes more difficult.

 

[u2slow]

'Comfortable' is about the lengths and bends involved. If they are only short stops between pull boxes and you're not forseeably upgrading to larger wire, then oversize conduit is academic.

If you go metallic, the conduit becomes the EGC.

 

[DerStig]

'Comfortable' is about the lengths and bends involved. If they are only short stops between pull boxes and you're not forseeably upgrading to larger wire, then oversize conduit is academic.

If you go metallic, the conduit becomes the EGC.

Anything larger than 125A is 150A which calls for 1/0. With the "upsize" guidance given here, that should still fit in 1 1/2". The next step up, 200A is probably the only scenario where 3/0 will need 2" PVC conduit - or so I think.

Its unlikely that I will need a 200A sub panel - ever. But you never know. If 10 years from today, the situation with the electric cars change so much so that you need a 400A service because now 100A chargers are standards, then maybe its a possibility.

 

[TRWham]

... If 10 years from today, the situation with the electric cars change so much so that you need a 400A service because now 100A chargers are standards, then maybe its a possibility.

If that becomes the situation then the tail is wagging the dog and EVs will have created as big a problem as they might have solved.

 

[u2slow]

Anything larger than 125A is 150A which calls for 1/0. With the "upsize" guidance given here, that should still fit in 1 1/2". The next step up, 200A is probably the only scenario where 3/0 will need 2" PVC conduit - or so I think.

Its unlikely that I will need a 200A sub panel - ever. But you never know...

The 'you never know' game can be costly and long-winded. In some cases causing massive delays while you over-plan and run out of $$$.

I'm at the other end of the spectrum. I only ran a 'comfortable' amount of power to my shop (#2 alum, 90amp) the cheapest way possible (bury cable). I ran the shop on #12 and #8 cords previously. If I need even more later on... I'll also be able to afford it better, so I'll deal with it then.

2 ways to look at it.

 

[Jim greengo]

2" is a lot easier to pull wires through if you have the room.

 

[7635tools]

I would probably try to use equivalent ampacity alum cable. The cost savings over copper and conduit are significant.

Also, 1-1/2" and larger EMT you need hydraulic bending equipment - unless you can make do with only pre-bent and straight pieces. 2" is only worth it if you're already planning on upgrading again. No conduit expense at all when you go with cable.

EDIT: An armoured type cable can be exposed where needed.

Not true. My greenlee 555 bender will do up to 2” rigid and it’s not hydraulic.


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[DerStig]

2" is a lot easier to pull wires through if you have the room.

And I’m sure 3” is even easier but the reason I am here is to ask people who has experience with #1 in PVC to see if 2” provides enough benefit over 1 1/2” that is worth dealing with it. The bend radius of 2” vs 1 1/2” is pretty large not to mention pull boxes are huge.

I like overengineering and I dont cut corners. I spent 2 months carefully planning and rewiring my entire basement into EMT and was able to get rid of couple of hundred pounds worth of romex. So imagine 9 different (incorrectly) runs of romex and now imagine just 2 runs of 3/4” EMT with junction boxes distributing in strategic locations.

Its my house and I am an engineer (by trade) so no problem doing extra work. That being said, I dont want to do so much extra work that it becomes wasteful and ugly looking.

 

[sparky 1971]

The #2's in 1-1/4" will be just fine. It may take a little bit of lube to make things easier because pvc is sometimes a *****. Don't worry about oversizing for the future. You probably won't be able to get anything in after the fact.

 

[DerStig]

The #2's in 1-1/4" will be just fine. It may take a little bit of lube to make things easier because pvc is sometimes a *****. Don't worry about oversizing for the future. You probably won't be able to get anything in after the fact.

What about 1-1-1-6 CU in 1 1/2”? Or 2”?

 

[sparky 1971]

What about 1-1-1-6 CU in 1 1/2”? Or 2”?

I have never ever used 1-1/2" for anything, ever and I have been doing this for 26 years. I just punched it into my pipe fill calculator. 24.91%. It should go screaming through no problem. 2" would be a waste of time, real estate, and a little bit of money.

If it's just a 100 amp subpanel, #1 copper is way overkill, but you probably already know that.

 

[sparky 1971]

I would probably try to use equivalent ampacity alum cable. The cost savings over copper and conduit are significant.

Also, 1-1/2" and larger EMT you need hydraulic bending equipment - unless you can make do with only pre-bent and straight pieces. 2" is only worth it if you're already planning on upgrading again. No conduit expense at all when you go with cable.

EDIT: An armoured type cable can be exposed where needed.

I have a Greenlee 1818. It is a manual Chicago type bender that can bend up to 2" EMT and 1-/2" rigid. There is also a shoe for 2" rigid aluminum, but I don't have one.

 

[DerStig]

I have never ever used 1-1/2" for anything, ever and I have been doing this for 26 years. I just punched it into my pipe fill calculator. 24.91%. It should go screaming through no problem. 2" would be a waste of time, real estate, and a little bit of money.

If it's just a 100 amp subpanel, #1 copper is way overkill, but you probably already know that.

It is a 125A subpanel. Because in the not so distant future, I have plans to build a detached garage which will have its own subpanel that is a subpanel to this 125A subpanel. That 3rd subpanel probably needs 60A as it will operate car lifts, 5hp compressor, and 8 hp car dryer.

I appreciate your help. I will go with 1 1/2” taking your advice.

 

[Innovate1]

I used 1.5" for Aluminum 1-1-2-4 XHHW and it went pretty easily - easier than I expected. Need someone on each end and used a little lube. Two 90s and 240 feet. If you only have a couple bends on each run I think that should be fine. You are right - 2" looks a lot larger.

 

[u2slow]

Not true. My greenlee 555 bender will do up to 2” rigid and it’s not hydraulic.

ooo... electric! We didn't have those....

I meant 1-1/4" is the largest hand-bender. If they make them for larger sizes, I'm not big enough to use.

 

[DerStig]

I am having second thoughts about the conduit. Are there any issues going with a 2/0 SER AL for 125A? Maybe I should just go with this.

Cost of conduit and THHN is around $400 vs $150 for the SER cable. But its the amount of work more so than the cost that I dont know if I should deal with.

Its about 44 ft of run. All inside unfinished basement. Portion of the run has to exit through brick basement wall into the attached/finished garage which will need to be in conduit even with SER but thats less than 2 ft or so.

 

[Jim greengo]

And I’m sure 3” is even easier but the reason I am here is to ask people who has experience with #1 in PVC to see if 2” provides enough benefit over 1 1/2” that is worth dealing with it. The bend radius of 2” vs 1 1/2” is pretty large not to mention pull boxes are huge.

I like overengineering and I dont cut corners. I spent 2 months carefully planning and rewiring my entire basement into EMT and was able to get rid of couple of hundred pounds worth of romex. So imagine 9 different (incorrectly) runs of romex and now imagine just 2 runs of 3/4” EMT with junction boxes distributing in strategic locations.

Its my house and I am an engineer (by trade) so no problem doing extra work. That being said, I dont want to do so much extra work that it becomes wasteful and ugly looking.

And that would be why I said if you have room.
Pulling wire through a 2" fitting beats pulling it through an 1 1/2" fitting ,especially with that many bends.
But you're an engineer,I'm just a lowly licensed electrical contractor .
Have it your way burger king.

 

[sparky 1971]

SER wouldn't be too bad. I think the most important thing would be to make sure that the holes in the joists are lined up. I have only used 2/0 SER one time. I didn't want to fight the joist cavity's with the duct work and plumbing, so I used two hole pvc straps to secure it to the bottom of the joists. Then I screwed 2X4's next to the SER, then took rips of plywood and screwed them to the 2X4's so that they overhung the SER

 

[DerStig]

SER wouldn't be too bad. I think the most important thing would be to make sure that the holes in the joists are lined up. I have only used 2/0 SER one time. I didn't want to fight the joist cavity's with the duct work and plumbing, so I used two hole pvc straps to secure it to the bottom of the joists. Then I screwed 2X4's next to the SER, then took rips of plywood and screwed them to the 2X4's so that they overhung the SER

I would staple SER (or use screw straps) under joists. I would not use any runner boards.

Then I would bring it inside a 2” pvc from ceiling cavity to transition through the basement wall.

Any more work than this then its not worth not doing full conduit.

 

[TRWham]

I am having second thoughts about the conduit. Are there any issues going with a 2/0 SER AL for 125A? Maybe I should just go with this.

Cost of conduit and THHN is around $400 vs $150 for the SER cable. But its the amount of work more so than the cost that I dont know if I should deal with.

Its about 44 ft of run. All inside unfinished basement. Portion of the run has to exit through brick basement wall into the attached/finished garage which will need to be in conduit even with SER but thats less than 2 ft or so.

Now you are thinking like an engineer. Cost and ease of installation are valid design criteria, and there is nothing wrong or unsafe about running SER in a code compliant manner. SER can even be exposed outdoors as long as it's not buried.

 

[DerStig]

Now you are thinking like an engineer. Cost and ease of installation are valid design criteria, and there is nothing wrong or unsafe about running SER in a code compliant manner. SER can even be exposed outdoors as long as it's not buried.

- Is there an advantage of using CU ser (1-1-1-3)?
- Can I attach SER to the bottoms of joists?
- Can SER be bent on its thinner side (but respect the 5X bend radius)?

Also I’m guessing 2/0 SER AL is much bigger than #1 CU and harder to struggle?

 

[sparky 1971]

I would staple SER (or use screw straps) under joists. I would not use any runner boards.

Then I would bring it inside a 2” pvc from ceiling cavity to transition through the basement wall.

Any more work than this then its not worth not doing full conduit.

I didn't use runner boards. I covered the SER with the plywood to satisfy the "protect from physical damage" rule.

If it was my own house with no permit pulled, it would probably just be screwed to the bottom of the joist. Then, when I sold the house and the home inspector called it out I would cover it.

 

[DerStig]

I didn't use runner boards. I covered the SER with the plywood to satisfy the "protect from physical damage" rule.

If it was my own house with no permit pulled, it would probably just be screwed to the bottom of the joist. Then, when I sold the house and the home inspector called it out I would cover it.

So the “protect from damage” is a problem when its running perpendicular to bottom of the joists?

 

[sparky 1971]

Yeah. People have a tendency to want to hang stuff from it. We all get punished for the stupidity of the rest of the world.

 

[TRWham]

So the “protect from damage” is a problem when its running perpendicular to bottom of the joists?

In an unfinished basement I doubt any inspector would consider it subject to damage, which is the standard. Just use listed straps to the bottom of the joists and drive on down the road. There is a reason 2224 Al SER at 90 A is the go to answer for sub-panels around here- it is sufficient and cost effective.

 

[TRWham]

So the “protect from damage” is a problem when its running perpendicular to bottom of the joists?

No, it is not a problem. To emphasize- the standard is that it not be "subject to physical damage." This does not mean it needs to be protected from all conceivable methods of mayhem.

 

[TRWham]

...Then, when I sold the house and the home inspector called it out I would cover it.

The next home inspector I meet who knows anything about electrical beyond checking GFCIs and grounds will be the first one.

 

[sparky 1971]

No, it is not a problem. To emphasize- the standard is that it not be "subject to physical damage." This does not mean it needs to be protected from all conceivable methods of mayhem.

Depends on where you are. Protected is up to the interpretation of the AHJ. Around here, we can't even run through drilled holes in an unfinished basement unless it's within a foot of a wall or beam. They figure that's too close to use for a coat hanger.