Question on Disconnect Switches

[HMF]

So the electrical service is being upgraded in the house to 200Amp.
Three 20A 220V lines are being installed for my SB Heavy 10 lathe and 2 mills, Burke #4 and Van Norman #12. My tiny shop is right next to the main panel.

I agreed to provide the three disconnect switches. They need to be non-fusible.

I am looking at some Cutler Hammer 30A, 240V 2 pole boxes:

http://www.southlandelectrical.com/itemdesc.asp?ic=DG221UGB-NS
http://www.mrsupply.com/cutler-hammer-disconnect-switch-dg221ugb.html
http://www.drillspot.com/products/6...al_duty_safety_single-throw_disconnect_switch

Question- there are 2 pole, i.e, they break the two hot wires. What happens to the neutral? Does it go through the box? (unbroken). Should I get a 3-pole switch so that all 3 wires in the 220V cable are broken?

Thanks!


:tiphat:Nelson

 

[Rbeckett]

Get a list of exactly what your electrician says he needs. It will help eliminate the mad Sunday afternoon dash to the big box store or the local hardware shop. When I had 220 run to my shop. He wrote me a list, I buried the cable and encased it in pvc, per his specs. Then I left the items he said he needed on the work bench and got the heck out of his way. I was the go boy. Go get this or that and a cold adult beveridge. It only took 15 or 20 minutes for him to connect everything and test the circuits. That worked really well for me and it was safe and to code and it only cost me materials and a few cold beers. I also threw him 50 bucks but he didnt want to take it so I hid it in his ashtray. He doesnt smoke so he will find it sooner or later.
Bob

 

[Kennyd]

You only need the 2-pole switches, the neutral (actually its a ground on 220v lines as you don't need a neutral) stays connected.

To say it in a different way, you only need to break the two hot lines.

 

[Gary Max]

I ain't a pro but the boxes I am using the there is a ground lug for the box---not part of the switch. This grounds the box and keeps the whole system grounded. Dang shame you need three---I got just the thing but only one of them.

 

[Tony Wells]

Standard single phase 220-240 V non-fused disconnects are 2 pole, and you will see them commonly on AC condensing units. Since in theory the neutral is not a current carrying conductor, there should be no need to disconnect it. The neutral should not be bonded to ground any place except the service entrance, so the ground lug should be used for the grounding conductor only, which does ground the box and any conduit properly connected to it. I usually buy 3 pole disconnects (some fused, some non-fused), since I use three phase in the shop, but if I do use one on a single phase device, I use all poles, and break the neutral also. There is no huge difference in expense, and no question about the device being disconnected. You should be good either way.

If necessary, I can look up in the NEC to see if there is a specific prohibition on using a 3 pole, but I don't recall reading one.

 

[HMF]

Standard single phase 220-240 V non-fused disconnects are 2 pole, and you will see them commonly on AC condensing units. Since in theory the neutral is not a current carrying conductor, there should be no need to disconnect it. The neutral should not be bonded to ground any place except the service entrance, so the ground lug should be used for the grounding conductor only, which does ground the box and any conduit properly connected to it. I usually buy 3 pole disconnects (some fused, some non-fused), since I use three phase in the shop, but if I do use one on a single phase device, I use all poles, and break the neutral also. There is no huge difference in expense, and no question about the device being disconnected. You should be good either way.

If necessary, I can look up in the NEC to see if there is a specific prohibition on using a 3 pole, but I don't recall reading one.

Tony,

Thanks for confirming things for me. For anyone else needing to do this, I am listing my findings here. Home Depot doesn't carry the non-fusible ones, only Murray 30A fusible disconnects ($25). Lowes carries only a 60 Amp non-fusible, which is too big. (I think it is used for central air in homes). Electrical suppliers want $50 each for the non-fusible Cutler-Hammer DG221UGB 2 pole 30A, and McMaster gets $57 for the non-fusible 3 pole. I need 3. NYC does not allow fusible ones, because they are connected to a circuit breaker on the other end.

I would prefer to break all 3 as you did with the 3 pole, but I don't want to spend $57x3. So I went on Ebay, 2 suppliers there are selling surplus new Eaton Cutler-Hammer 30A 2 pole non-fusible disconnects for $25 each, and I bought the 3 I need from there. The only hitch is that they arrive on time for the electrician.

Whether 3 pole is ok here, I don't know. NYC has unbelievably ridiculous modifications to the electrical code- all designed to generate ECB fines (revenue). You now need 4x4 receptical boxes, for example, in residences if you have more than one cable (MC) going into a recepticle. MC or BX are required inside walls, 10 recepticle maximum per circuit. [I asked this on HSM and got 30 different conflicting answers, by the way- so don't trust what you might read there- ask your licensed electrician!]

I used a disconnect rather than a 240V outlet (one line), even though I can only use 1 machine at a time. Why? The electrician made it worth my while to do so. The machines are near the panel, very little wire needed. So he is giving me a good price for 3 hard-wired lines as long as I provide the disconnects. The disconnects can be locked with a padlock, so the kids can't play with my machines.

I did the rough wiring to the kids' rec room and my shop, except for the 220 lines. Two licensed electricians who came to the house for estimates said I did a damn good job, and they would hook them to the panel, no problem. If I can do it, you can, save money for the service upgrade.

Why 200 Amps, when 100 Amps would likely be more than enough? I have a shed outside I want to electrify with a subpanel in the future. 200 Amps gives me plenty to spin off for future use.


:tiphat:Nelson