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Author Topic: Subpanel disconnect?  (Read 4162 times)

frank kayser

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Subpanel disconnect?
« on: February 09, 2017, 11:56:53 am »

I'm sorry. I'm being a bit lazy, but please indulge me.
Does every sub-panel need its own disconnect?
Any such thing as a 220 only panel?


Having someone interpreting for an electrician on premises now putting in a sub-panel with the feeder directly into the bus.  No disconnect.
He is also saying it is a 220 only panel and the 120v circuits should be located in the main panel.
The panel is a three-phase panel.  I'm way out of my league when it comes to the realities of three phase.


My BS alarm is going off.


thanks for the help.
frank
« Last Edit: February 09, 2017, 12:10:33 pm by frank kayser »
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Stephen Swaffer

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Re: Subpanel disconnect?
« Reply #1 on: February 09, 2017, 12:22:14 pm »

That is perfectly normal and acceptable.  He is declining to run a neutral-depending on the use/situation the wisdom of that can be debated, but it is legal. 

The breaker in the panel suppling the feeder provides overcurrent protection, so non is needed at the panel.
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Steve Swaffer

frank kayser

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Re: Subpanel disconnect?
« Reply #2 on: February 09, 2017, 12:30:08 pm »

That is perfectly normal and acceptable.  He is declining to run a neutral-depending on the use/situation the wisdom of that can be debated, but it is legal. 

The breaker in the panel suppling the feeder provides overcurrent protection, so non is needed at the panel.


Thanks, Stephen. A short followup: the way I read your response (and my limited understanding) by omitting the neutral, there would be no way to split the 220 into multiple 120v legs.  Correct?


The feed would be protected by the breaker in the main panel, but there would be no method within the sub panel itself to de-energize the bus. 


OK Legal and proper.  Interesting... BS alarm silenced. 
Many thanks,
frank
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TJ (Tom) Cornish

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Re: Subpanel disconnect?
« Reply #3 on: February 09, 2017, 12:35:31 pm »

The main point is the wiring needs to be protected by some kind of over-current protection device - breakers or fuses.  If this subpanel is rated for less than the ampacity of the main panel or if the wire feeding the subpanel has a lesser ampacity than the main panel, then an OCPD rated for the wiring must be installed to protect the wiring, usually upstream of the wiring.  This may or may not meet a particular definition of a "disconnect".  If the subpanel and feeder wires to the main panel are rated at the full rating of the main panel, sometimes they are fed from the bottom of the bus of the main panel, effectively sharing the main panel's main breaker.

Yes, "220 only panel" presumably means no neutral wire, so no 120v circuits.  Is this for some heavy equipment?  It's clearly not a good panel to use for production.

« Last Edit: February 09, 2017, 12:39:13 pm by TJ (Tom) Cornish »
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frank kayser

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Re: Subpanel disconnect?
« Reply #4 on: February 09, 2017, 12:51:06 pm »

The main point is the wiring needs to be protected by some kind of over-current protection device - breakers or fuses.  If this subpanel is rated for less than the ampacity of the main panel or if the wire feeding the subpanel has a lesser ampacity than the main panel, then an OCPD rated for the wiring must be installed to protect the wiring.  This may or may not meet a particular definition of a "disconnect".  If the subpanel and feeder wires to the main panel are rated at the full rating of the main panel, sometimes they are fed from the bottom of the bus of the main panel, effectively sharing the main panel's main breaker.

Yes, "220 only panel" presumably means no neutral wire, so no 120v circuits.  Is this for some heavy equipment?  It's clearly not a good panel to use for production.


No not a production panel.  The cafe had a "kitchen emergency", and I was asked to bring in an electrician a month ago.  The "good old boys" decided to handle it themself.  My guy found a 40amp subpanel (trying) to feed a 240v 39.5a dishwasher, a 240v 30a water heater, and three 20a 120v commercial kitchen outlets.  The 40a breaker tripped so many times it would no longer hold under no load.  They did not hire my guy.  So the good ol boys were back - We've had some real hacks doing work in here, (including a live 220v open, stripped line discovered under the sink that was sparking when someone bumped it with a bucket) and though I did not like the look of what was being done, it was just my lack of knowledge of things electric (and previous hacks) that led me to you to ask.


I do apologize it was not production related, but you guys are the only guys I trust enough to KNOW.
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Stephen Swaffer

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Re: Subpanel disconnect?
« Reply #5 on: February 09, 2017, 01:39:48 pm »

No neutral is far more common in 480 VAC situations-in those cases normally a panel only has a neutral if it is going to supply lighting-and frequently that becomes a dedicated lighting panel.  But the concept/rules are the same.

With frequent hacks, I don't like a 220 panel with no neutral myself-too easy for some wannabe electrician to wire in a 120 circuit-which will function with the ground (I assume they installed the ground) but is extremely unsafe.

By the way, you might verify where the ground goes-it should go to a grounding bar attached to the enclosure.  If they took it to the neutral bar/bus that would be OK, IF they install the green bonding screw.  This would be the only time you want a bonding screw installed in a panel (in this case it would be bonding the enclosure to ground, not a G-N bond).  Too often people just do what they always do instead of understanding why it is done.
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Steve Swaffer

frank kayser

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Re: Subpanel disconnect?
« Reply #6 on: February 09, 2017, 02:04:17 pm »

No neutral is far more common in 480 VAC situations-in those cases normally a panel only has a neutral if it is going to supply lighting-and frequently that becomes a dedicated lighting panel.  But the concept/rules are the same.

With frequent hacks, I don't like a 220 panel with no neutral myself-too easy for some wannabe electrician to wire in a 120 circuit-which will function with the ground (I assume they installed the ground) but is extremely unsafe.

By the way, you might verify where the ground goes-it should go to a grounding bar attached to the enclosure.  If they took it to the neutral bar/bus that would be OK, IF they install the green bonding screw.  This would be the only time you want a bonding screw installed in a panel (in this case it would be bonding the enclosure to ground, not a G-N bond).  Too often people just do what they always do instead of understanding why it is done.


I've convinced Management to bring my guy back in to consult on some more major work - I'll have him go over the most recent work with a fine tooth comb.  He talked to me and checked the old panel for a grounding screw - and reiterated stuff you guys taught me about neutral-ground bond only at the service entrance.  I'll introduce him to the new one.


Unfortunately there are a couple wanna-be volunteer electricians that want to, and have helped out here - (BIG sigh)
Hell, I do some around MY house, but am smart enough not to touch something in a commercial space.  There are other lives than mine at stake.  Killing myself is one thing, killing others is not on my agenda.


OK, I've learned that the practice of no neutral is legal and sound - now, why would someone want to do it that way in a 220 panel?  Oy vey!
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Stephen Swaffer

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Re: Subpanel disconnect?
« Reply #7 on: February 09, 2017, 04:44:42 pm »


OK, I've learned that the practice of no neutral is legal and sound - now, why would someone want to do it that way in a 220 panel?  Oy vey!

$$$ mainly.

If you have an existing conduit run, you could get 1.73 X the load capacity if you used the maximum conductor size for that conduit and ran 3 phase instead of 2 hots and a neutral (same number of wires)-that would be the one good reason I could think of, but even that comes down to money-though it could be a significant amount in that situation.
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Steve Swaffer

frank kayser

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Re: Subpanel disconnect?
« Reply #8 on: February 09, 2017, 05:02:07 pm »

$$$ mainly.

If you have an existing conduit run, you could get 1.73 X the load capacity if you used the maximum conductor size for that conduit and ran 3 phase instead of 2 hots and a neutral (same number of wires)-that would be the one good reason I could think of, but even that comes down to money-though it could be a significant amount in that situation.


I thought $$$.  This is my first real look at anything 3-phase.  I've got a ton more questions, but I'll research them properly. I've got some reading to do! 
You (plural) have been most generous with your experience and knowledge. 
many thanks
frank
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Tim McCulloch

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Re: Subpanel disconnect?
« Reply #9 on: February 09, 2017, 05:25:15 pm »


I thought $$$.  This is my first real look at anything 3-phase.  I've got a ton more questions, but I'll research them properly. I've got some reading to do! 
You (plural) have been most generous with your experience and knowledge. 
many thanks
frank


You have me going, describing this service as 220v and then as 3 phase.  220v is not a typically specified voltage for either split phase or 3 phase services.

A 3 phase Delta service would have no neutral (unless it's a "high leg" delta or corner-tapped delta service).  Motor loads, resistance heaters, etc need no neutral.  It sounds like that's the kind of applications intended for this new service in the cafe.

I take it this is a non-profit venture that somehow thinks kluging together such things is acceptable?  No permit or inspections?  OY VEY.  After what you found (open hot wires) the board should be petrified of the potential for a fire or personal injury lawsuit and be more concerned about getting it fixed legal and right.  Saving money doesn't help when the building burns down or the dish washing person is electrocuted.

I'm having a deja vu moment here... I think I posted almost those same, exact words in this forum a few months ago....
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Re: Subpanel disconnect?
« Reply #9 on: February 09, 2017, 05:25:15 pm »


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