NA electrician help

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
I am installing a device at work, and trying to see if the info I have so far tells me what size cabling to buy.

(Yes I will be doing this myself; no there are no reputable electricians in my area - if I hire one, likely I will have to instruct them on what to do or I will have to fix their work afterwards, just to get those concerns out of the way. Oh, and although there is no code enforcement where I am, I will be doing it to that standard or better)

I am awaiting the installation manual but notice in the brochure this info:

240V AC, 1Ø, 60Hz @ 70-100 Amps

There is 50' from the distribution panel to the device. The cable will run loose in the attic; a wooden structure. Or I could use conduit if necessary.

What gauge wire for each leg and ground?
 
No branching; dedicated circuit. Will PM you what I have so far, in case interested. Thank you.
 
I suggest you consider conduit. One of my clients is a wildlife control company, and their techs almost daily send me pictures of Romex that's been gnawed bare by mice, squirrels, and roof rats. We're talking fires waiting to happen.

Rich
 
Let'sgoflying! said:
240V AC, 1Ø, 60Hz @ 70-100 Amps
Click to expand...

This should do:

aIndoor_Extension_Cords.jpg


...I know...zero help...
 
Might help to know what it is, but you are talking about a big cable. You would have to size it for 100 amps min (probably bigger) according to the spec you gave and according to the calculator someone supplied you would need a #1 copper conductor for the hots and a #2 for the ground. If it is a big motor you may even need bigger. You should probably wait for the install manual or call the factory for advice. My advice is worth what you paid for it.
 
Really need the specs. Also Romex may be allowed, however so cord may not. Lots of variables. Also if in an attic you may need to adjust conductor size based on ambient temperature. Type of load (motor, continuous vs non continuous, etc.) may also come into play. That being said, if you upsize the conductors from the NEC chart, you will likely cover all of those issues.
 
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RJM62 said:
I suggest you consider conduit. One of my clients is a wildlife control company, and their techs almost daily send me pictures of Romex that's been gnawed bare by mice, squirrels, and roof rats. We're talking fires waiting to happen.

Rich
Click to expand...

There are a few tens of millions of homes around the nation wired with Romex. You'd think a hundred or so would burn down every day!

In this case though...I don't think they make 100A Romex. Dave will likely have to go with conduit and individual conductors.

Dave, also, find out for sure if it's 120/240 or 240 only (yeah, I know, your OP only says 240 but make sure). If it's 120/240 then you need three conductors plus a ground, if it's straight 240 then you only need two conductors and a ground.

Edit: by God they do make #2 Romex. Who woulda thunk it! It's only rated at 95 amps though.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM10
 
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timwinters said:
There are a few tens of millions of homes around the nation wired with Romex. You'd think a hundred or so would burn down every day!

In this case though...I don't think they make 100A Romex. Dave will likely have to go with conduit and individual conductors.

Dave, also, find out for sure if it's 120/240 or 240 only (yeah, I know, your OP only says 240 but make sure). If it's 120/240 then you need three conductors plus a ground, if it's straight 240 then you only need two conductors and a ground.

Edit: by God they do make #2 Romex. Who woulda thunk it! It's only rated at 95 amps though.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM10
Click to expand...

I'm actually surprised there aren't more fires.

My client's inspectors and technicians send me pictures like the attached almost every day. The inspectors have to document any animal damage that they find prior to starting the job anyway, so they send me the pictures in case I want to use them on the site. I have hundreds -- maybe thousands -- like this, many of which are far worse in terms of how much copper is showing. This one just happened to be handy because it was just sent.

Rich
 

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hey- I have always wondered why a breaker would not prevent such a fire.
 
It wouldn't need to when the exposed copper is the ground wire (at least it appears to be). That might be white insulation that's chewed through but it looks like ground wire wrapping paper to me.

Not that other chewed wires that Rich has seen aren't a problem but this one doesn't appear to be. The outer sheath of today's Romex is relatively worthless anyway. Really thin, crappy stuff. It really doesn't provide much, if any, safety and the ground wire is always "unsheathed" underneath...unless you count brown paper as sheathing! :)
 
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timwinters said:
It wouldn't need to when the exposed copper is the ground wire (at least it appears to be). That might be white insulation that's chewed through but it looks like ground wire wrapping paper to me.

Not that other chewed wires that Rich has seen aren't a problem but this one doesn't appear to be. The outer sheath of today's Romex is relatively worthless anyway. Really thin, crappy stuff. It really doesn't provide much, if any, safety and the ground wire is always "unsheathed" underneath...unless you count brown paper as sheathing! :)
Click to expand...

Personally, I'm a fan of BX cable or conduit.

Rich
 
looks like the minimum bid for the device is higher than planned, probably not installing. Anytime soon that is. Thanks for the help.
 
timwinters said:
There are a few tens of millions of homes around the nation wired with Romex. You'd think a hundred or so would burn down every day!
Click to expand...

Roughly 28,600 electrical fires per year, works out to about 78 per day, so you're not that far off, actually.
 
denverpilot said:
Roughly 28,600 electrical fires per year, works out to about 78 per day, so you're not that far off, actually.
Click to expand...

Not from Romex though. The data suggests that the worst months for electical fires are December and January...i.e. space heaters and Christmas trees. Also, Most others are caused by faulty electrical outlets and old, outdated appliances. Other fires are started by faults in appliance cords, receptacles and switches.

Chewed Romex isn't even on the radar screen.

Besides, if your house has large enough holes to allow varmints to come in and chew up your wiring then you have bigger issues than just electrical. Renovating with a substantial fire might be in order. :)

Seems like backasswards home mx to call pest control to eradicate varmints instead of a carpenter to fix the holes.
 
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timwinters said:
Seems like backasswards home mx to call pest control to eradicate varmints instead of a carpenter to fix the holes.
Click to expand...

We had three little bastard field mice get in and we have no holes. They probably came right in an open door on a summer day.

They were very dead, four days after I heard the first scratching one night in the basement ceiling. Figured out how they got in there, with some
help from the dogs, and found out that modern mouse bait is phenomenal at getting their attention... on to the trap that snapped their little annoying necks, that is.

Day two we held two mouse funerals and day four the last. The third one was apparently twice as smart as his friends. That meant he just died last in the great zombie mouse apocalypse of 2015.

There's plenty of barns around here that have hungry barn cats. They should have taken their chances in one of those. They stood no chance at all once they got in here.

I haven't figured out what to hang up to warn them that they won't survive if they step over the doorway threshold again. Otherwise I wouldn't be rude and I'd hang up a little "no mouse zone" warning sign for them.

Gotta be PC and all, these days.

Not knowing what their religious beliefs were, we gave all three of them a nice semi-spiritual but non-denominational chuck into the garage trash can with silent "meditation" provided, after wrapping them up in plastic to avoid any possible exposure to the Hanta virus.
 
timwinters said:
. . . .

Seems like backasswards home mx to call pest control to eradicate varmints instead of a carpenter to fix the holes.
Click to expand...

Not really, at least not once you've seen the difference between how carpenters and animal-control guys do the work.

Carpenters, by and large, have no idea how resourceful animals can be when they really want to get into a house, so they use materials and methods such as expandable foam that don't have a chance of being effective. The only thing expandable foam accomplishes is giving the rodents belly laughs right before they chew through it. Rodents can gnaw through mortar or galvanized sheet steel if they need to. Foam doesn't even slow them down.

Most carpenters and handymen also don't understand how small a gap most animals need to get into a house, how easily they can travel through the house inside the walls and ceilings, or the complexity of their pheromone communication (which allows them to mark the entryways and paths that they use).

Very few animal-exclusion jobs done by carpenters, homeowners, or handymen are successful. It's really a specialty in its own right.

Rich
 
You can not lay cable loose in an attic. It needs to be attached to and follow the surface. The only real exception for this is when it's fished into an enclosed space.

50' isn't typically a length you worry about voltage drops. Note the wire for 70A is going to be large. You're talking 4 gauge (for 70A typically) or larger (depending on what cable type you are using). If you're using cable, the ground will be sized already in the cable. If you are using individual conductors, the ground can be sized smaller (it depends on the breaker size and whether you're using copper or aluminum).
 
flyingron said:
You can not lay cable loose in an attic. It needs to be attached to and follow the surface.
Click to expand...

I have often wondered about that, Ron. (anyone know where the NEC discusses this?) I have seen several attics now where the romex was laid wiley niley on the joists without attachment and by electricians (not diy-ers) and it drives me nuts. I think cables should be attached, parallel where possible, large radius bends, overhead not on the path where traffic is expected - but have never seen specifics on how it should be done.
 
NEC 334.30 Securing and Supporting Nonmetallic-sheathed cable shall be supported and secured by staples, cable ties, straps, hangers, or similar fittings designed and installed so as not to damage the cable, at intervals not exceeding 1.4 m (4 1⁄2 ft) and within 300 mm (12 in.) of every outlet box. junction box, cabinet, or fitting. Flat cables shall not be stapled on edge. Sections of cable protected from physical damage by raceway shall not be required to be secured within the raceway.

(A) Horizontal Runs Through Holes and Notches. In other than vertical runs, cables installed in accordance with 300.4 shall be considered to be supported and secured where such support does not exceed 1.4-m (4 1⁄2-ft) intervals and the nonmetallic-sheathed cable is securely fastened in place by an approved means within 300 mm (12 in.) of each box, cabinet, conduit body, or other nonmetallicsheathed cable termination.

FPN: See 314.17(C) for support where nonmetallic boxes are used

(B) Unsupported Cables. Nonmetallic-sheathed cable shall be permitted to be unsupported where the cable:

(1) Is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable.

(2) Is not more than 1.4 m (4 1 ⁄2 ft) from the last point of cable support to the point of connection to a luminaire or other piece of electrical equipment and the cable and point of connection are within an accessible ceiling
 
living in a 'no code' area has its advantages.... and its major conflagration hazards!
("no code" meaning; no one checks out here)
 
It did not sell at minimum bid! So we are serious contenders again, pending an inspection.
And I am back to looking at providing service.

240V (no 120V)
1Ø
60hz
copper
100A (I am told this number has built-in excess capacity)
distance is closer to 75' including drops and required routing
am told it can accept 10% voltage drop but I want to shoot for 3%
it will run in conduit (is plastic ok?) in the ceiling/attic. I'd think our max temp up there is 130F
No motors

Glenn's site says 1 AWG (but no mention of ground size)

This site agrees; #1

But this one says #4

So does this one say #4.

But this 2002 NEC chart
http://www.usawire-cable.com/pdfs/nec ampacities.pdf
does not have any amp ratings near 100 for #4 wire so I think it must be #1.
 
My circa 1980 Square D Motor Data Calculator & Wire Sizer says:

#3 THW copper is good for 100 amps and needs 1.25" conduit for three wires.

Voltage drop / 100' is:

.048 volts / amp @ 95% pf
.045 volts / amp @ 80% pf

So, worst case scenario, for a 75' run, your voltage drop should be about 4.5v. Or 2%.

I always run full sized grounds but that's just me.
 
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The US Code rates ampacity by three things:
Wire Size
Aluminum or Copper
Insulation Temperature (30/60/90C).

Tables in the code tell you what.

The bigger issue is what is this "device." Welders have distinct requirements than most other things, for example.
 
Its a digital radiograph unit. Navigator 3500 Plus.
(does that info alter the "max100A" spec?)
 
No, and although x-ray tubes have cooling motors, their draw is small and they usually run continuously, heat is the tubes enemy. 100A listed, does figure in a safety factor. I found the model DR 3500C brochure to list: Breaker size - 100A
 
If it's a non-continuous 100A, you can size the conductors right at 100A. Again, the tables in the code give you the ampacity baed on the type of conductor (copper vs. aluminum and insulation rating). Here's table extracted from the code: http://www.cerrowire.com/ampacity-charts

If you want to use cable, you're likely at those ratings using Type SE cable (Type NM which is the normal housing "romex" doesn't typically come large enough) which would have to be 3g (copper) or 1g (aluminum). Of course, depending on your local code and just where you are installing this, there may be a requirement for conduit (most likely THHN or THWN conductors).

Note, that in most cases, you hare absolutely required to use an electrician to wire this stuff up. Exemption for DIY work is limited to owner-occupants of single family house.

Any electrician would know this off the top of his head.
 
Yeah, I had to tell an electrician that the door jam switch he just installed (which they had previously replaced because it burnt up) was only 12v rated.
 
Rule of thumbs math here.
Install #2's (copper)
Use conduit.
I'd recommend a disconnect near the gear.

Regardless if you think you live in a "no code" area or not...if there is a fire, your insurance company may want to see the permits for the installation...choose wisely.
 
Kelvin said:
Rule of thumbs math here.
Install #2's (copper)
Use conduit.
I'd recommend a disconnect near the gear.

Regardless if you think you live in a "no code" area or not...if there is a fire, your insurance company may want to see the permits for the installation...choose wisely.
Click to expand...

What he said.

Code requires a service disconnect for equipment servicing. It must be within sight and within 50 ft. In this case rated for 100A.

John
 
flyingron said:
If it's a non-continuous 100A, you can size the conductors right at 100A.
Click to expand...

The load is for a couple of miliseconds at a time ( or tens of seconds to recharge a capacitor bank). The rest of the time it's controls and cooling fans etc.
 
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flyingron said:
Note, that in most cases, you hare absolutely required to use an electrician to wire this stuff up. Exemption for DIY work is limited to owner-occupants of single family house.
Click to expand...

You've been living in the east far too long. Vast expanses of "fly over country" have no codes, even within the city limits of smaller communities.

Kelvin said:
Regardless if you think you live in a "no code" area or not...if there is a fire, your insurance company may want to see the permits for the installation...choose wisely.
Click to expand...

I've never seen that happen either. Not to say it won't...just never seen it.
 
There are places that don't have any enforcement, but most of the country does have codes. Even out in those big flat empty states in the middle.
 
Code. Covered in post #1.
Doing it to code or better, so that is not really a pertinent topic.

I'm doing my own study on it, then will probably hire a local sparky, correct his ideas and errors and watch him like a hawk to make sure it is done properly.
 
flyingron said:
There are places that don't have any enforcement, but most of the country does have codes. Even out in those big flat empty states in the middle.
Click to expand...

No, of the 50 or so O'Reilly stores I built when I was doing that, 8 of them had no building permit requirements whatsoever. All were towns of over 5k...O'Reilly doesn't build in a town much smaller than that. (Granted, a few were immediately outside of the city limits in the county).

Kelvin said:
Regardless if you think you live in a "no code" area or not...if there is a fire, your insurance company may want to see the permits for the installation...choose wisely.
Click to expand...

Another observation regarding this statement. How does an insurance company ask to see a permit if there is no "building regulations department" or permits to be had?
 
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