Circuits with disconnect box

[kool55]

I am going to run 3 disconnect switch boxes for my 3 machines with 1'' conduit. Can I run the second and third circuits thru the first and second disconnect boxes? The boxes would be part of the conduit for those circuits. Was going to use LB tee fittings to each but this would be more simple. This is a straight line accross the wall. Thanks

 

[sberry]

Sure, dont see why not.

 

[sberry]

Someone else may be able to help here as I am not familiar with multiple machine wiring to great extent but with disconnects some can be fed with a single circuit? Or if the panel is near the breaker is a suitable disc, the switch would be redundant? Just a thought. Probably what you are doing is the most simple though as long as you have panel spaces, etc.

 

[Aceman]

312.7 and 312.8 are your references.

That being said every electrician and inspector(they'd probably even call you on it) I know of frowns on running wiring through disconnects that don't pertain to that particular disconnect. We'd typically run the conduit above the disconnects and T into the top of each of them with a chase ******, etc. We use wireway instead of T's for larger disconnects.

 

[Stuart in MN]

There are rules about how many current carrying conductors you can run in the same conduit, so you may have to derate them somewhat (in other words, use a larger wire.)

 

[sberry]

You got the poop from someone that deals with inspectors, go for that. A question though. When it says adequate space does that mean dedicated listed raceway thru the box or just box with enough area so pass thru didn't crowd it?

 

[LoneGunman]

I'd run the conduit into a junction box at each maching, mount the disconnect under the junction box, continue out of the junction box to your next junction box and disconnect. I don't think it's a code violation if you run the wires through the disconnects but I do think it's a crappy way of doing things.

 

[kool55]

I just came back in . Its almost done.I will take some pics tomorrow. I guess I can change it if you guys think so after seeing it. I ran#10 stranded wire from the 3 phase box 74'' to the disconect that feeds the Bridgeport. In the same conduit I ran #8 strand thru disconnect#1 to disconnect#2 that feeds the band saw. [4 wires each]. In the future I will run #8 stranded [3wire] , again thru disconnect#1 and#2 to future disconnect#3. All told there will be11 wires in the first conduit[3 phase box to #1 disconnect]. 8 between #1 and#2 disconnect. 4 between #2 and#3

 

[kool55]

Just thinking. If you change the conduit entrance location in a box, what do you do about the open hole from the first one?

 

[sberry]

They make plugs.

 

[kool55]

Good. Well anyway I cranked up the RPC and the newly aquired Grob saw works good. I returned the Bridgeport wiring back to factory after removing the VFD.

 

[kool55]

Here are the pictures

This is the 3 phase box withe cartridge fuses

Disconnect box#1

Box#2.[ still needs cord clamp]

 

[sberry]

I got to go, but if it was my shop probably would have done it similar.

 

[Norcal]

The white conductor used as a "hot" is a no-no in conduit it is not allowed to reidentify them either, in a cable assembly it is permitted to reidentify them, also if those grounding conductors are fastened w/ a sheet metal screw in that disco, that is another thing not permitted...

Both look pretty EZ to fix though.

 

[kool55]

Norcal, I don't understand that sentence. The white wire is the wild leg.Change color to?You are correct The grounds are secured with a sheet metal screw. Change to a machine screw?

 

[Torque1st]

If the white wire is the manufactured phase it is marked with orange tape and is referenced as the "B" phase. The utility supplied phases are referenced as "A" and "C". The order of the "phases" on devices must be "A-B-C" left to right and "A-B-C" top to bottom. The manufactured phase always goes in the middle.

 

[kool55]

Ok, I think I understand. In a cable I could mark the white wire with red tape to ID it as hot. but not if it runs in conduit. Right?

 

[kool55]

Torque1st, I was typing to Norcal with that last one. So I need to replace the white with orange?

 

[Charles (in GA)]

11 conductors in a conduit is a significant amount of derating. And by my calculations, overfills the conduit. 1" sch 40 PVC has a 40% area of .333 inches squared (40% is max fill allowed with more than two conductors). 7 ea #8 THHN and 4 ea #10 THHN adds up to .3406 inches squared in area, which exceeds the 40% fill.

NEC 310.15(B)(2)(a) says that for 10 to 20 conductors in a conduit, you derate by 50% of the amp ratings in the tables in 310.16 thru 310.19 and if need be, derate for ambient temps above 86F.

Charles

 

[Aceman]

That j-box with the fuses in it doesn't appear to be grounded? Also, why are there two ground wires between the j-box and first disconnect?

 

[OccupantRJ]

Good. Well anyway I cranked up the RPC and the newly aquired Grob saw works good. I returned the Bridgeport wiring back to factory after removing the VFD.

Just curious, why did you remove the VFD from the Bridgeport? Was it because you had another method now to run it, or was there some issue with it's use on the mill?

 

[Norcal]

Torque1st, I was typing to Norcal with that last one. So I need to replace the white with orange?

In a conduit you cannot use a white for a "hot" it needs to be repulled & replaced w/ another color besides green,white or gray. The NEC in art. 455.6(B) does not specify a color for the manufactured phase but say it shall be a distinctive marking identified at all accessable locations & be consistant throughout the system & premises. They don't spec the color but the high leg of a 240V delta is req. to be orange & on the "B" phase & that would not hurt to follow the same, but it is not required.

One should NEVER use green for a current carrying conductor nor use white/gray for a hot conductor in a conduit or tubing system.

As for the grounds a machine screw is fine, I prefer a ground bar kit where there is more then 2 to terminate, one catalog # is a Siemens GB-5. (5 term. ground bar).

 

[kool55]

ACEMAN, I ran the saw circuit first[#2 box ]. Just cut the grd. wire at box#1 on its way to box #2. Looking back now , no reason to do that. The phase box is not grounded., just the board in it. I need to correct.
I removed the VFD so the RPC would handle it all. I know I lost the variable speed doing this.
I guess I have too many conductors in 1 conduit?

 

[kool55]

Nocal. I used white because that color was being used in the 3 ph. box. I just continued with that color

 

[kool55]

11 conductors in a conduit is a significant amount of derating. And by my calculations, overfills the conduit. 1" sch 40 PVC has a 40% area of .333 inches squared (40% is max fill allowed with more than two conductors). 7 ea #8 THHN and 4 ea #10 THHN adds up to .3406 inches squared in area, which exceeds the 40% fill.

NEC 310.15(B)(2)(a) says that for 10 to 20 conductors in a conduit, you derate by 50% of the amp ratings in the tables in 310.16 thru 310.19 and if need be, derate for ambient temps above 86F.

Charles

I guess i can forget about running 4 more to the future 3rd disconnect box.

 

[sberry]

I do see a green coming in from the main with it and didn't catch the white being used for current. Here I don't keep 1 inch in stock so would have likely used 2 3/4's and changed the box elevations to pipe to them using EMT. As for fills while not to the letter I doubt these machines all run at the same time.

 

[sberry]

Just out of curiosity, how much do the machines draw while running? And of the 11 wires do we count the greens? For fill I guess but for current no? Could remove one of the green too?

 

[kool55]

Bridgeport 4 amps ., Saw 12 amps[I think].

 

[sberry]

Seems like it would meet de-rating? I got a couple pipes one of my guys stuffed but I havnt lost much sleep over it as there is no significant load on it.

 

[kool55]

I don't understand the derating thing .... yet

 

[sberry]

They dont want a wad of wire packed in with heavy loads to heat up in the pipe. 4 amps on a 10 wire is nothing and 12 on the saw isnt a big deal either. Dont sweat it, we got a couple code guru's here that will get it straight. Changes would be minor.

 

[kool55]

I ran the conduit that is above the disconnects months ago. It really is in the way of how I wanted to run the 3ph. I settled with the disconnect boxes lower than I like.I could run EMT and lose some of the grd. wires? I will rethink this tomorrow.

 

[Charles (in GA)]

I understand you are dealing with relatively fixed loads, that will never heat up the conduit, and while I don't know the capacity of your 3 phase converter, It may not even be able to power all the equipment at once (and would not need to unless you are darn fast on your feet). I was quoting code as it is the "official" minimum safe specification, yet, sometimes you have to apply some common sense. If both grounds were #10, which is acceptable, I think you would just fall in at the 40% fill, and even with one being a #8, you are so marginally over that it really wouldn't matter.

Charles

 

[Norcal]

Nocal. I used white because that color was being used in the 3 ph. box. I just continued with that color

The phase converter is wrong too then, I had assumed that it was done to match the cord colors.

 

[Steve from Socal]

I have never heard that you could not tape the white wires to re-identify them. In other words; you MAY use orange tape on the visible segments of white wire to denote the wild leg.

Steve

 

[Norcal]

I have never heard that you could not tape the white wires to re-identify them. In other words; you MAY use orange tape on the visible segments of white wire to denote the wild leg.

Steve

W/ a cable such as romex or a flex cord that is correct but not in a conduit...

 

[JBurgess]

On your saw you should be sure that your control circuit is not powered by the manufactured phase this will prevent voltage variations on the manufactured phase from affecting it.

 

[kool55]

With all the helpful info you guys gave me here, this is what I think I need to do.
1- Run future circuit in a sep. conduit.
2-Replace White manuf. leg wire with orange.
3-Change sheet metal ground screws.
4-Figure out manuf. leg orientation.
With that being said, maybe I can drop a ground wire out of this and share 1 ground wire between these 2 machines.
By the way, this is a 7.5HP RTC and I am the only one in the shop. It looks like I hurt myself by running larger conductors than needed.That ran me over in conduit capacity? Also I need to call the RTC guy and find out why he used White instead of Orange for the manuf. leg.

 

[Torque1st]

With no dissenting responses it looks like you are good to go with your plan.

I would not call the RPC manufacturer. It would be pointless.

Convention uses orange for the "wild leg" and there are other conventions. Yellow wire is used for circuits that are powered from another source. Then the colors get even more interesting when AC and DC control circuits and power are present. More fun is added when foreign wiring colors enter the picture.

A good read is in the NEC article 455.
Take note of the following:
455.22 Power Interruption. Utilization equipment supplied
by a rotary-phase converter shall be controlled in such
a manner that power to the equipment will be disconnected
in the event of a power interruption.