multiple motors single circuit overcurrent protection sizing

[DrSparks]

I dont follow none them say you cannot fed one circuit conductor from one breaker which is SCHF to control panel where control panel only has overload for 3 motors?

That's how it's usually done. You have a feeder feeding a control panel which has internal fuses and/or breakers, contactors, overload units and control logic all built in to the cabinet. They are generally designed by an automation or electrical engineer.

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[augie47]

Each motor is required to have properly sized overload and SCGF protection. It is rare when ONE SCGF can protect more than one motor and it will not work in your situation (430.52).

 

[hhsting]

Each motor is required to have properly sized overload and SCGF protection. It is rare when ONE SCGF can protect more than one motor and it will not work in your situation (430.52).

430.55 wont apply to groups of motors? Single overcurrent device sized for overload for groups of motor cannot do both jobs?

 

[augie47]

That's a rarely used Section and it would be more rare for it to apply to multiple motors and certainly not in your case.
If you are doing plans review, keep Post 22 in mind. If you encounter a situation other than that, ask for details.

 

[kwired]

I have three 208V, three phase, 10HP, domestic booster pumps triplex parking basement of high rise building shown in plans.

The booster pump are fed from one circuit breaker in panelboard. The circuit breaker size is 200A.

I am trying to verify the size of the breaker. Where in NEC 2017 section 430 would overcurrent protection for multiple motors fed from one circuit be addressed?


Note: additional question maybe come up depending upon response provided

This is booster for domestic water, right?

Fire pumps becomes a different ballgame.

 

[hhsting]

This is booster for domestic water, right?

Fire pumps becomes a different ballgame.

Yes this is a domestic water booster pumps. No fire pump

 

[paulengr]

Well if the designer placed 3 motors on one circuit then how can NEC stop it?

Because the electrician MUST follow Code. The only time the engineer can override Code is where it allows for engineering supervision or it’s a Listed assembly.

One of the gotchas with Code is the electrician, not the engineer, permit department, or anyone else is responsible for Code violations even if it’s someone else’s screw up.

 

[DrSparks]

Because the electrician MUST follow Code. The only time the engineer can override Code is where it allows for engineering supervision or it’s a Listed assembly.

One of the gotchas with Code is the electrician, not the engineer, permit department, or anyone else is responsible for Code violations even if it’s someone else’s screw up.

How does that work if a home owner pulls an electrical permit?

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[tom baker]

There is a simple solution. Return the submittal with the following comments”provide a listed pump control panel per UL 508A. Resubmit with details on panel, how pumps are sequenced and controlled. Provide a feeder circuit per art 430”

 

[Dennis Alwon]

If you have a 200 amp breaker feeding all 3 motors then the 10 hp motor -- 30.8 amps, will be protected by a 200 amp breaker. The rule is 250% so 30.8 x 2.5 = 77 amps which makes the install illegal unless you tap the feeder to 3 different disconnects then you may be able to meet the tap rules

 

[kwired]

How does that work if a home owner pulls an electrical permit?

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Generally the installation must pass inspection whether an electrician installed things or not.

AHJ's often have the ability to condemn the install and order the POCO to disconnect power if they feel there is enough hazard or if codes aren't met on new installs. Unless something is very dangerous, this often usually means a little back and forth discussion, notices in the mail, etc. between inspector and electrician/owner before that disconnect order occurs. Might have a couple weeks or so to make corrections on initial correction notice before follow up actions begin.

 

[paulengr]

How does that work if a home owner pulls an electrical permit?

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If you even ask then you know that case law has pretty much upheld that property owners can pretty much do what they want with their property. The purpose of the electrical and building codes is to protect “the public” against poor workmanship. So homeowners pulling permits is kind of screwy as they are asking the government to protect them from themselves.

States require contractors to pull permits and contractors work off permits so they really have no choice in the matter. Except that industrial plants as an example pretty much never pull permits except maybe during initial construction and they are pretty much always under construction once they start up. They hire contractors and do their own work. There is no protection of the public here. Not sure why it would be any different if a homeowner hires someone.

 

[kwired]

If you even ask then you know that case law has pretty much upheld that property owners can pretty much do what they want with their property. The purpose of the electrical and building codes is to protect “the public” against poor workmanship. So homeowners pulling permits is kind of screwy as they are asking the government to protect them from themselves.

States require contractors to pull permits and contractors work off permits so they really have no choice in the matter. Except that industrial plants as an example pretty much never pull permits except maybe during initial construction and they are pretty much always under construction once they start up. They hire contractors and do their own work. There is no protection of the public here. Not sure why it would be any different if a homeowner hires someone.

I like that logic to some extent. Doesn't work that way here.

You build a new house you don't get power if you don't file a permit. File the permit you will get inspected at some time. They eventually got to where they decided owner can't file permit on new house though, without ever changing the wording of the laws. Was worded that an owner can pull permit for wiring in his principal place of residence. A new house isn't your principal place of residence until you move in. I'd guess maybe some have challenged that by claiming they are living there while under construction. Doubt they got what they wanted, and in the process possibly made it that much harder for any electrician to want to work for them when they finally decide to get qualified person to do it.

Industrial - the wind farms around here had permit/inspection for every tower. They are not a utility owned operation so not exempt from that aspect. I don't know how I feel about that. Heard through grapevine that mostly all that mattered much was grounding - which I really don't know what to think of either, huge concrete footing with lots of steel reinforcement and we are going to question whether it is grounded? Most everything on those I would guess is cookie cutter from site to site and possibly a lot of it already pre assembled, all they likely need to do is run cables. I can almost guarantee inspector never seen the top of the towers, unless maybe they had an elevator to bring him up there, but I don't think they do. My guess, inspector figured they know what they are doing and didn't really look at much at all, but we have to collect our permit fee regardless. These not initially installed by those that maintain and operate them BTW.