chimp1
Member
- Location
- Palm Bay, FL US
Would a shut off at the motor be required by NEC standards or would a shut off at the motor just be the preference of the operator?
NEC rules
- Thread starter chimp1
- Start date
- Status
- Location
- Massachusetts
A disconnecting switch is required within sight of the motor in almost all applications.
See 430.102(B).
See 430.102(B).
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
Unless needed for a specific operational safety issue, industrial applications rarely ever put an extra disconnect in sight of the motor.
See 430.102(B), Exception 1.b
ice
See 430.102(B), Exception 1.b
ice
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Do you mean a disconnect switch? If so, in general the answer is yes, with some exceptions.
Or do you mean some kind of stop push button? The NEC does not address this issue at all.
In general operators would rarely need to operate a disconnect so I fail to understand why their preference would be at issue at all.
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- Location
- Massachusetts
Must be a regional thing
Where I am I would say they always put a disconnecting means with an early break aux switch for signalling the control system that the switch is about to open. Also a stop, start station beside it.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
Comments limited to industrial only:
Interesting. S/S buttons out in the field, next to the motors were in vogue 40 - 50 years ago. It was considered okay to push in the STOP, slide in a pin and use that as a maintenance lockout. That went out in the late 70's. And that was the end of the field S/S unless there was an operational need.
As for local disconnects:
Commercial buildings - yes
Industrial - emphatic No. Unless there is an over-riding maintenance issue, usually non-electrical. Why put them in? No one is going to interupt an industrial process - no sense to it. (Note to nits: Yes, I'm sure someone can come up with a contrived reason)
This regional thing you speak of: Are you thinking East Coast, Northeast only ....
I have not seen much east of the Mississippi - and little east of the Rockies. Still, .....
ice
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I concur that as often as not some kind of aux switch is typically used these days if there is a local disconnect switch for the things I am involved in. I can't say as I see them all that often these days. They take up a lot of room and add cost that does not usually serve much of a purpose.
For most of my work there just are not many operators out near the equipment anymore so the desirability of having local controls is limited to a few special cases.
- Location
- Massachusetts
Uh .... would you call refinery commercial or industrial? I would call it industrial.
Why put one in? Just stupid safety for those that have to put their fingers into potentially moving parts etc. I find it intresting you consider those with differing view points 'nits'. :roll:
Region? New England.
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Having people like that at a refinery makes me very nervous!
There was a psych study that found that the higher a person's level of formal education, the more likely they were to test a Wet Paint sign though.
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- Location
- Massachusetts
I just don't get the EEs that do not see the value of a local switch for servicing the equipment unless of course the switch turns off a containment field holding the aliens left over from area 51 in place.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
Yes, industrial - I've worked a few.
That is what MCC lockouts are for. Again, nobody is going to pull open a field disconnect in a runing refinery. Operation will shut down the offending equipment. LOTO done at the MCC. Work commences.
And yes, I would have to say not locking out the MCC is pretty stupid - although not illegal if there is a local disconnect. None of the techs I know would consider that. Hummm ... well, okay, not exactly true, there are Lefty and Stubs. They are dumb enough to do that.
No, not "differing" - "contrived"
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
Bob -
That is a disgusting, personal attack - arrogant, demeaning ... (you fill in the rest)
You want to discuss the merits of local disconnects - I will.
You want to throw rocks - I have no interest.
ice
- Location
- Massachusetts
I guess we see things differently, I do not believe my post was anything like that.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Many of the places I do work in there is barely enough room for the equipment much less anything extra like a disconnect switch. Keep in mind that if you have a disconnect switch you need working space for it which can quickly eat up a lot of area.
I too work in Mass. and we try to install disconnect at each motor if MCC is not within sight of motor. Alot of times in different places we work a particular motor may be fed from a MCC, but that particular motor/section of "line" is not in operation for some time for inspection/cleaning/adjustments/etc while it would be expensive to shut the entire MCC/operation down for that one motor. If I've never been in a certain factory before and I'm working on a motor/machine etc I'd much rather have a clear disconnect right at the equipment.
One job we did there was 4 motors on a section of equipment were all fed by VFD's, all about 150' away from the control cabinet. Owner of the facility wanted disco's on the line side of the VFD's at each motor so as to never chance "blowing" the drive by shutting the load off while running. Lots of extra wire and pipe on that one.
One job we did there was 4 motors on a section of equipment were all fed by VFD's, all about 150' away from the control cabinet. Owner of the facility wanted disco's on the line side of the VFD's at each motor so as to never chance "blowing" the drive by shutting the load off while running. Lots of extra wire and pipe on that one.
- Location
- Illinois
- Occupation
- retired electrician
Around here, it is very rare to see a local disconnet at a motor in an industrial application. If there is, it is likely there because plant operations require frequent lockout for cleaning or something like that.
When we install a VFD with a disconnect on the load side, we make sure there is an early break aux switch to shut down the VFD to protect it from "blowing"
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