Motor Control Center

[BlaineVT]

My mechanical contractor decided to build a motor controller/disconnect for a 7.5HP, 3P, 480V chilled water pump instead of purchasing a package. All of the parts are Square D and UL labeled, but when the parts are arranged in a NEMA Type 1 enclosure I feel like something is missing as far as spacing between parts. I can't find anything wrong with the device other than as a whole it does not have a UL rating and not tested to NEMA ICS 18.

Does anyone have any good tips/links for approving a motor controller? Please let me know if need any further information.

This is my first post, but I have been reading forums here for a while. TIA

 

[itsmoked]

Wow you are asking for a bruising. If you don't need a UL listing on the panel don't bother!

You need a box with the appropriate weather/atmosphere rating.
Nema 12/13/1/etc.
Preferably a "DISCONNECT ENCLOSURE"

You need the disconnect.
Big lever outside the box that works the power switch inside the box.

A short circuit/ground fault protection device.
Fuses<yuck!>
or a circuit breaker<pricey>

Motor overload protection.
Solid-state overloads<superior>
or
heaters

matched with a paired contactor
which is the switch that controls the ON/OFF of the motor.

This all needs to be wired neatly in a clean manner with reasonable space around the components, with proper sized and rated wire.

A good electrician can probably confirm the adequacy of your result.

If you really are a glutton for punishment, you could find a "UL Panel Shop" and see if they will certify your box for money.

Otherwise throw it all away and purchase a "motor starter unit".

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[LionelHutz]

If it is field installed you would need a field inspection. In the US I believe the hydro inspector or UL are your 2 main options. I know that to get a UL field inspector in is quite pricey, I believe over $1k.

You could go the UL certified panel shop route, but they will want the enclosure in their shop because they are not allowed by UL to field label an enclosure. I know I wouldn't do it. As a minimum, you will also have to provide documents showing the short circuit rating of the combo of parts.

So, as Keith says, don't bother unless there is a need for it.

 

[dpc]

If you decide you must have a UL label, I agree it will be less expensive and much faster to simply order a combination starter in an enclosure. But the only difference will probably be the label. There really isn't much to building up a starter.

 

[jraef]

If component spacing is your issue however, there are specific rules in UL, then there are different rules in the NEC, which often differ from the UL listing rules. In other words, a UL label may trump NEC rules, but without it, the NEC rules may leave you with more stringent requirements than your "starter" has.

With regards to UL being necessary, that is up to 3 things:

1) Many states' electrical codes require it. If you are anywhere west of the Rockies, you will need it if you are going to have the installation inspected or you think anything else will be inspected at your site in the foreseeable future. East of the Rockies there are still a few states who have not added this to their codes, but they are fewer and fewer each year. They never specifically say UL by the way, they refer to it as needing a listed and labeled assembly from an "NRTL", Nationally Recognized Testing Laboratory. UL is the biggest and best known of the NRTLs, but definitely not the only one. The way it is typically described is that any assembly of 3 (maybe 5) devices including an enclosure must have an overall NRTL listing in addition to all of the interior components being listed. Breaker/disconnect + contactor + overload + box usually qualifies. The specifics will be in your state's electrical code as a codicil to their acceptance of the NEC.

2) The local NEC version you are using. In the 2005 NEC, they added a section (article 409) that now requires all electrical equipment to show an SCCR, Short Circuit Current Rating, on the outside. If you cobble together loose parts and pieces, the assumed SCCR is going to be the LOWEST withstand rating of any component. In the case of a non-tested motor starter combination, that will be 5kA. This means if you have an available short circuit current of more than 5kA (and virtually everyone does), your starter will now be "illegal". Had you bought a complete factory assembled starter, the same combination of components may be rated for 100kA, but unless you have that label on the door, you cannot claim that. Your only possible out is that not every state has yet adopted the 2005 NEC.

3) Your insurance company. Most, if not all, industrial indemnity / assurance companies will require underwriting, i.e. they have an underwriter review your plant when you first buy insurance. In the insurance policy they give out at signing, there is usually a clause that states any further additions, modifications or expansions will either be inspected again by their underwriter (for a fee) or you can use UL listed equipment (and/or FM). UL is short for Underwriter's Laboratories; meaning it is all about insurance risks, not government approval. You need to follow their rules. FAILURE TO DO SO CAN LEAVE YOUR ENTIRE PLANT UNPROTECTED! For example, if you have a fire and the insurance company's inspector finds non-UL listed equipment that was not part of their official underwriting report, they can just say "Sorry Charlie" and walk away. Check with whoever is in charge of your company's loss prevention and they can look that up in your policy.

 

[dw51]

UL 508A and NFPA 79 have the information you are looking for in terms of what is acceptable for this unit.

But the everyone else is correct in terms of acceptance by an inspector or AHJ. No listing or label on your controller / disconnect and you stand a good chance of being shot down. If you are committed to using this one then a field evaluation is your best shot.

Any of the NRTL's can provide a field evaluation and IF the unit is acceptable, apply a label. That label is good for that unit only. If you electrical contractor decides to build an exact duplicate, you'll have to get it labeled as well. Unless he wants to go through the process of becoming a "UL" shop for listing purposes, he should really stick to buying listed units.

Field Evaluations tend to get pricey and can be unpleasantly surprising if your unit does not meet the applicable standards.

Good Luck!

 

[jraef]

...and can be unpleasantly surprising if your unit does not meet the applicable standards.

Been there, done that, got the T-shirt and the hat! The last UL field inspection I got was $2000, but that was in 1990, so I have a feeling it would cost just a wee bit more now.