parallel contactors

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mdshunk

mdshunk

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I have a set of print specs that call for a quiet contactor (less than 20dB) to switch an entire 200 amp 3-phase panel. No model or manufacturer of the contactor is spec'd. I think mercury contactor right away for this application, but they are only available at up to 150 amp, near as I can tell. Is it permissable to switch a 225 amp panel through a set of paralleled 150 amp contactors?
 
Thats a good one Marc.

This is off the cuff... no book handy but IMO the only way you could parallel the contactors is if each one was rated for the entire load. Of course that kills the entire reason for doing it.

Perhaps a solid state unit?
 
iwire said:
Perhaps a solid state unit?
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That's my next search, if I'm not permitted to parallel mercury contactors. I wish they'd have specc'd a certain contactor and had it over with. It's actually work I've won, but I missed this spec. I might end up calling the engineer and find out what he had in mind. I've seen stuff that doesn't exist specc'd more than once in my lifetime. A regular 200 amp contactor will pull-in with quite a thud. Considering the location of this one on the print, I can't really understand why they want it to be quiet. Whatever. We'll give them what they want.
 
Marc,

How about a machinicly (sp bad ) held, power on / power off type? The

reason I ask is, the job I'm on now has excatly that, I don't think they make

any noise at all. I can get the #'s off it tomorrow if you want. They are

SQ'D' if it matters.
 
iwire said:
. . . but IMO the only way you could parallel the contactors is if each one was rated for the entire load.
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I would have to agree. The internal resistance of such a contactor is very small. So a small difference in resistance might force much more of the current to go through one, and next to nothing through the other. In addition, nothing will guarantee that both will operate at the same moment. If one closes before the other, that one gets all the current. If they are not both rated for full load, it is likely that something will fail.

As to code references, all I can offer is 110.3(B).
 
mdshunk said:
a quiet contactor (less than 20dB)
Click to expand...

I am not that familiar with dBs but isn't less than 20dB very quiet?

Like the noise level you would get from an 'ice cube' relay?

I can't think of any 200 amp contactors that do do not sound like a sledge hammer.
 
Charlie and I are thinking alike. :smile:

I was concerned with the opening of the switches while loaded and the slower contactors ability to handle breaking the entire load.
 
benaround said:
Marc,

How about a mechanically (sp bad ) held, power on / power off type? The

reason I ask is, the job I'm on now has excatly that, I don't think they make

any noise at all.
Click to expand...

If you have quiet ones I sure would like to know where you got them. :smile:

In my experience mechanically held are louder when switching contact position than electrically held.
 
iwire said:
I can't think of any 200 amp contactors that do do not sound like a sledge hammer.
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Me either, which is why I thought of a mercury contactor right away. They are basically silent. Even a mechanically held contactor will still slam in with quite a thud before it latches. The print shows a regular snap switch to pull in the coil, and not an on/off/center return switch, which is why I think they didn't have a mechanically held contactor in mind.
 
I believe his intention is for a latching mechanical contactor and not electrically held.
Some electrically held contactors hum while energized.

I would send the engineer a RFI.
If he designed for a silent contactor then one should be available.
When a designer specifies something then it should be feasible and you shouldn't have to invent something.
 
Marc,

So sorry, I thought you meant 20db after it SLAMMED in, oh well. How

often are they going to switch this on/off each day? just curious.
 
tkb said:
I would send the engineer a RFI..
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I may well do that. 'Round these parts, we're a little more informal. A phonecall usually works. I don't know what they want to be honest, as the spec says, "... must operate at 20dB or less". To me, that means pulling in too. I did find 200 amp solid-state contactors just now, from Fuji. I have no idea which of my suppliers (if any) handle Fuji. http://www.fujielectric.co.jp/fcs/eng/product/control/pdf/DEC1901a_P110_128.pdf
 
If you check the contactor datasheets, you may find that you can operate poles in parallel on the _same_ contactor to get increased current handling capability. This eliminates the problem of different contactors operating at slightly different times. There will certainly be derating to allow for imbalance between the poles.

For example:
http://www.telemecanique.com/85256E54006445B8/all/47D676ED58688B6885256E6700652706/$File/tesyscontactorsforutilisationcategoryac1_selectionguide_en4.0_24561.pdf
states that for their contactors you can operate 3 poles in parallel to carry the current of 2.25 times the single pole rating.

You could then use three contactors, one for each phase, to carry the full load.

-Jon
 
Marc the more I think on this I think TKB and Benaround have the answer.

The 20 dB requirement is for when the coil is holding the contactor.

Not for the switching action.
 
As a side note, you can improve contact performance and life by placing contacts in series, rather than parallel. This has the effect of the contacts separating twice as fast, and extinguishing the arc sooner.
 
If the space and budget allow, you could consider splitting the loads into two panels, each with it's own contactor.

Could you split the feeder into two using a six pole contactor?
 
LarryFine said:
As a side note, you can improve contact performance and life by placing contacts in series, rather than parallel. This has the effect of the contacts separating twice as fast, and extinguishing the arc sooner.
Click to expand...
So that's why I've seen 3-pole contacts breaking one hot wired back and forth through it!

Thanks Larry, been wondering about that for years.:smile:

Just previewed this post and thought it looked like sarcasm, but it really isn't.:smile:
 
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