Definite Purpose?

[sparkzilla]

Intermatic has a line of time clocks that "know" sunrise and set, and can combine that with time.
http://intermatic.com/Default.asp?action=subcat&sid=267&cid=50&did=5

 

[steve66]

So the contact kit I put in at 2:00 today in a 30 amp, 3-pole square D contactor didn't really exist?

You deleted the last part of my quote:

(Or at least you don't get many options you can add in the field.)

What kind of contactor? DP or DPA? According to the Sq D catalog, aux contacts are only available as factory installed on DPA only.

The DPA style does have replaceable coils, but neither indicate replacable contacts.

 

[jim dungar]

According to the Sq D catalog, aux contacts are only available as factory installed on DPA only.

Square D Digest 174
Page 16-83 table 16.226 shows field installable aux contacts for 8910 DPA contactors.
Page 16-120 table 16.343 shows the replacement contact kits for the same contactors.

 

[Jraef]

Lisa: Would you like me to explain?
Vinny: I would love to hear this!
Judge Haller: So would I.

When a set of contacts open while conducting current, a good bit of arcing occurs; how much depends on the current, voltage, and type of load. The faster contacts under load are opened, the faster the arc is extinguished. Plus, it takes a higher voltage to initiate an arc than maintain it.

Anyway, when you place two sets of contacts in series, they effectively open at twice the speed, the arc voltage is shared between the two sets of contacts, the arc is extinguished faster, much less contact pitting occurs, because the arc duration is less, and the localized heating is lessened.

When minimal overall contact resistance is paramount, contacts can be placed in parallel, which we all know reduced the resistance, and voltage drop, proportionately to the number of pathways. However, to open a load current, placing contacts in series increases contact life and reliability.

While I have no beef with this statement from a factual standpoint (it's actually a well know principal often used in DC circuits), is it really cost effective to save on contactor life by using twice as many contactors?

 

[Rich Elec.]

Don't forget that even if you are in a state where UL listing is not yet required (i.e. still using the 2002 NEC), UL stands for Underwriter's Laboratories and is directly associated with the INSURANCE industry, not the government.

Hey Jraef,
Does the 2005 code require that all equipment is to be UL Listed?

 

[hardworkingstiff]

Lisa: Would you like me to explain?
Vinny: I would love to hear this!
Judge Haller: So would I.

I love that movie!

 

[Jraef]

Hey Jraef,
Does the 2005 code require that all equipment is to be UL Listed?

Not specifically, but the new Article 409 in thew 2005 version requires a Short Circuit Current Rating from an NRTL (Nationally Recognized Testing Lab), of which UL is the most familiar and easiest to access (with a wheelbarrow full of $100 bills anyway).

 

[wiry]

Reminds me a a job I was on years ago in Florida. It was a restaurant, new construction, and the AHJ insisted that the salad bar was an assembly requiring a UL rating. So the contractor had to fly a guy from Underwriter's in from Illinois to look at the thing and bless it. Put him up in a hotel on the beach, rental car, meals, etc. The actual inspection took all of 15 minutes, most of which was spent BS-ing. I'd hate to think what that piece of paper cost.

 

[jim dungar]

... but the new Article 409 in thew 2005 version requires a Short Circuit Current Rating from an NRTL ...

Not according to the printed copy I have.
Yes, SCCR information is required by 409.110 but there is absoluetly no mention of an NRTL.

 

[petersonra]

I have used DP contactors in small custom systems that will have less than 50,000 operations in 10 years, and the contactors are rated at 500,000 operations. They are typically used at not more than half of rated horsepower and I have never had a failure in more than 10 years of service.

It's a waste of customer's money to spend 6 times as much for a contactor that the customer doesn't need and for which he can't possibly recover the value.

I can get 40A listed IEC motor contactors for about $25, so I don't waste my time on junk. If I needed thousands of them for a specific application, I might well look into something cheaper though.

 

[Jraef]

Yeah, sorry, it isn't a "REQUIREMENT". But here is the text, which states the INTENT by using an FPN (Fine Print Note):

ARTICLE 409
Industrial Control Panels
I. General
409.1 Scope. This article covers industrial control panels
intended for general use and operating at 600 volts or less.
FPN: UL 508A is a safety standard for industrial control
panels.

Then later:

409.110 Marking. An industrial control panel shall be
marked with the following information that is plainly visible
after installation:
(1) Manufacturer?s name, trademark, or other descriptive
marking by which the organization responsible for the
product can be identified.
(2) Supply voltage, phase, frequency, and full-load current.
(3) Short-circuit current rating of the industrial control
panel based on one of the following:
a. Short-circuit current rating of a listed and labeled
assembly
b. Short-circuit current rating established utilizing an
approved method
FPN: UL 508A-2001, Supplement SB, is an example of an
approved method.

Now read article 90.7 (which is not new) and the definition of "Listed" in Article 100, then apply it to the above.

So TECHNICALLY, one could fine another "approved method" for listing besides an NRTL and take the chance that your AHJ will accept it.

Good luck with that.

 

[jim dungar]

So TECHNICALLY, one could fine another "approved method" for listing besides an NRTL and take the chance that your AHJ will accept it.

The FPN notes you refered to offer UL508A as a typical standard. UL508A SB4 does not require any testing to develop an SCCR for a control panel. So, if I use the method outlined in UL508A I have met the INTENT of the 409.1 FPN even though no testing has be performed.

Article 90.7 does not have any INTENT that equipment must be tested/listed. Rather it says if the equipment is listed the it "need not" be inspected unless it has been altered.

 

[Jraef]

OK, I'll print that out and hand it to the next AHJ inspecting a system I have designed when someone forgets to get it UL labeled. I'm sure he will be swayed by the logic as I was.

Seriously though, no argument, you won me over. I was mistaken that it was specifically called for in the NEC. NRTL listing IS however called for in the California Electric Code, as well as in almost all of the Western states I have worked in. So for me, NRTL listing has always been a reality and when 409 was released, I looked upon that as a "back door" way for the NFPA to effectively harmonize the rest of the country to that requirement. But if someone knows what they are doing, it appears as though you can get around it still.

And you appear to now what you are doing.