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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: frank kayser on February 09, 2017, 11:56:53 AM
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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
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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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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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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.
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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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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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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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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!
$$$ mainly.
If you have an existing conduit run, you could get 1.73 X the load capacity if you used the maximum conductor size for that conduit and ran 3 phase instead of 2 hots and a neutral (same number of wires)-that would be the one good reason I could think of, but even that comes down to money-though it could be a significant amount in that situation.
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$$$ 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 $$$. This is my first real look at anything 3-phase. I've got a ton more questions, but I'll research them properly. I've got some reading to do!
You (plural) have been most generous with your experience and knowledge.
many thanks
frank
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I thought $$$. 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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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....
Trust me. When you, Stephen, and TJ talk about electric, I treat it as gospel. Most of this is beyond my current understanding and experience.
Tim, if you think for a moment I do not know what I'm talking about, then you're absolutely correct. I'm clueless, but sometimes I can spot someone more clueless than I.
What I KNOW for SURE: we have three 100amp three phase main panels. (expanded into separate storefronts)
The new subpanel was described as a "220 only" panel, whatever that is. I'm too ignorant to know, but it sounded... off. It sounded to me like "don't worry your pretty little head - us professionals know best". Couldn't have been talking to me, cause no one will accuse me of having a "pretty little...anything"
Again, you're also absolutely correct: this is not a 501(c) (3) organization, but they do consider themselves non-profit. Most of the work until now has been non-permit (poor quality) kludging. This subpanel was put in by a licensed electrician, though, and it was after that work and rewiring the dishwasher when the live 220 showed up under the sink. That's what scares me to death. What else did he miss?
I think my electrician and I have the attention of most of the board. We're meeting with my electrician for expanding, properly, with permitted, inspected work by a master electrician with commercial experience. Tomorrow will be a requirements meeting. We have a builder with his own business on the board that has done a lot, but also thinks he can do it all, and being a board member, throws his weight around a bit. Getting him to back down on anything is a major issue right now. Management is phrasing this as "well, we need a backup electrician in the case the other is too busy". So his guy is not being replaced, just a second, just in case. That appeases the builder.
As I said, not on my agenda to kill anyone. This has to be right.
Again, thank you all.
frank
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DISCLAIMER: I'm not an electrician. I'll defer to those who are.
Service entrances (where electricity enters the building) and subpanels have different rules w/ respect to disconnects and grounding.
The length of unfused wire -- no upstream OCPD -- between where it enters the building and service disconnect is limited (I'm not sure what that limit is). And I think the service disconnect is limited to "6 handles" -- but I don't remember if that's in total, or per service entrance panel. So you could have a service entrance panel with no "main" breaker but up to 6 single- or double-pole breakers -- that don't add up to more than the current capacity of the incoming wire. Practically, I would think that this would eliminate a panel with more than 12 spaces, as someone could add breakers so there's more than 6 handles. (Sure, they *could* use duplex breakers and get more, but if the panel already has 6 standard double-pole breakers, it's full and not easy to add more.)
As long as there's an upstream overcurrent protective device (OCPD) acting as the service entrance or in another upstream subpanel, you don't need a "main" breaker in a subpanel, and the subpanel isn't limited to 6 handles.
As for grounding, the neutral and ground can only be bonded in the service entrance. Also at the service entrance will be a Grounding Electrode Conductor (GEC) that leads to the grounding electrode system, which may include ground rods, rebar in concrete, building steel, piping, an intersystem bonding point (where CATV, phone, etc. tie in to the grounding system),etc. The GEC is supposed to be continuous (no splices) between the service entrance and each ground rod or bonding point.
Any subpanels have to have neutral and ground isolated, which implies that you'll have to run separate neutral and ground (Equipment Grounding Conductor, EGC) wires. In the subpanel, the neutral busbar cannot be jumpered to the grounding busbar, or bonded to the cabinet. The cabinet must be bonded in some manner to the EGC -- possibly to the grounding busbar. Some jurisdictions may allow metallic conduit between the service entrance and the subpanel, but it's safer practice to leave the conduit a "passive" ground and have a separate EGC in the conduit to bond your panels.
In the case of a subpanel with no neutral, if it's equipped with both neutral and grounding busbars, they could both be utilized as grounding busbars if they are properly bonded. The panel should be clearly labeled as having no neutral.
If the subpanel is in an outbuilding protected by an OCPD in the primary building, it could must be treated as either a subpanel grounded through the panel in the main building and having separate neutral and grounding conductors, OR it could be treated as another service entrance, in which case it can and it could have a "main" breaker, a neutral/ground bond, and it must have its own EGC leading to its own grounding system. (Edited; thanks to Stephen Swaffer. I hope I made those edits correctly.)
A service entrance could consist of a panel with a single "main" breaker, and the ground and neutral are bonded in this panel (with the appropriate GEC to a ground rod), and a feeder with both neutral and ground goes to a subpanel which includes breakers for all of the branch circuits. Other systems (plumbing, structural steel, telephone, etc.) may be bonded in the subpanel rather than the service entrance. This is how manufactured homes and modular buildings are typically wired; the service entrance is in a pedestal or pole outside and not attached to the building. The panel in the building is effectively a subpanel, and neutral and ground aren't bonded there.
I don't know if that sheds any light onto your question or if I just took you down an irrelevant rabbit trail! That's my understanding, anyway. It's worth every penny you paid for it.
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Question: is it true that according to the NEC, if a breaker is installed so the handle moves vertically, OFF must be DOWN?
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If the subpanel is in an outbuilding protected by an OCPD in the primary building, it could be treated as either a subpanel grounded through the panel in the main building and having separate neutral and grounding conductors, OR it could be treated as another service entrance, in which case it can have a "main" breaker, a neutral/ground bond, and its own EGC leading to its own grounding system.
Code defines "service" as equipment coming from the serving utility-so it is really not up to the electrician to define how you treat it. If it is a subpanel, it is a "feeder" and as such must have a seperate neutral and ground. 250.52 also requires a building supplied by a feeder or branch circuit to have its own grounding electrode system.
Yes, down must be off for circuit breakers NEC 240.81 This was not always so-you will occasionally find an old panel where one row of breakers is "upside" down.
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Code defines "service" as equipment coming from the serving utility-so it is really not up to the electrician to define how you treat it. If it is a supanel, it is a "feeder" and as such must have a seperate neutral and ground. 250.52 also requires a building supplied by a feeder or branch circuit to have its own grounding electrode system.
Yes, down must be off for circuit breakers NEC 240.81 This was not always so-you will occasionally find an old panel where one row of breakers is "upside" down.
Thanks for the corrections and clarifications!