Need more than 1 OL contact

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dnyman

Member
Location
Logan, Ut
Hello All,
I'm wanting to use one OL contact to turn on a light that indicates the motor OL is tripped, and the other to drop out the motor. Problem is the starter has only one OL contact (NC). I'm planning top add a DPDT relay that is pulled in by the OL contacts on the starter, then use one NC relay set of contacts to turn on the light and one NO set of relay contacts to drop out the motor on overload. Does anyone see any safety or code concerns with doing this?
The motor starter is a 509AOD930 Allen Bradley
Thanks for your feedback.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I'm a bit confused. On the A-B 509 Starters I am familiar with, the OL contacts are internal with terminations on the bottom. The contacts on the side are auxiliary contacts.
In any event, my opinion would be that if you altered the OL wiring in any way you would be altering a UL (NRTL) piece of equipment which is not acceptable by many AHJs.
I would think you need to add an auxiliary contact block to the starter or use an existing auxiliary contact and relay to perform any function other than OL protection
 
K

K2500

Senior Member
Location
Texas
dnyman said:
Hello All,
I'm wanting to use one OL contact to turn on a light that indicates the motor OL is tripped, and the other to drop out the motor. Problem is the starter has only one OL contact (NC). I'm planning top add a DPDT relay that is pulled in by the OL contacts on the starter, then use one NC relay set of contacts to turn on the light and one NO set of relay contacts to drop out the motor on overload. Does anyone see any safety or code concerns with doing this?
The motor starter is a 509AOD930 Allen Bradley
Thanks for your feedback.
Click to expand...

What's your control voltage?

Got a one line?

Sounds like it might work, but will it be reliable?

I like justdaves idea better.
 
D

dicklaxt

Senior Member
The overload relay output contact is set/coordinated to function directly with the action of the overload heaters so if you were to control an aux control relay rather than a motor shutdown with this overload contact it would work electrically but other conditions would also take the motor down that would not be due to an overload condition as seen by the phase conductors.They might be aux relay failure,wiring problems,under voltage etc to name a few.

IMO this would have to be a no-no.

If you are stuck with this particular starter then you are stuck ,however,newer electronic overload modes may be able to be configured to do what you want.If my memory serves me correctly they have a SPDT output contact for overload protection but then again you would be using the output contact in this case for something other than it was designed for.I don't recall if they have other aux contacts or not.

You may have to just use a run status light motor running not tied to the OL condition.

Let us know what you end up doing.

dick
 
R

ronaldrc

Senior Member
Location
Tennessee
The pencil drawing is very good.



I like your idea it would do the job.
And very simple and down to earth.



http://www.flickr.com/photos/34242310@N07/4825259717/

I had the idea of jumpering the seal and start button with a 10 K ohm resistor and
putting a neon pilot light across the OL.

But simple ideas like my and yours are apparently not very acceptable to most on this forum.

Some one always finds a way to fault them.

Not a thing wrong with that way.
 
P

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I don't know that there is any requirement that the overload contact be connected directly to the contactor coil, either in the listing or in the NEC, or anywhere else for that matter.

Its actually not all that uncommon to wire all the overload contacts into the estop circuit to shut down all the motors in a simple machine with more than one motor.
 
P

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
runrun401 said:
http://www.flickr.com/photos/34242310@N07/4825259717/



I think this will work as well but Justdave's solution is probably more elegant.. in the attached diagram, the overload contact still opens up the control circuit instead of going through a contact on the added relay.
Click to expand...

There is an exception allowing you to break the control cicruit on the neutral side with an overload contact for motor contactors. Not so for relays.
 
R

runrun401

Member
petersonra said:
Te here is an exception allowing you to break the control cicruit on the neutral side with an overload contact for motor contactors. Not so for relays.
Click to expand...

Ahh, so if the coil voltage was 208, it wouldn't be an issue? Out of curiousity, what article forbids it?

That's the best part, I don't see a single problem with your idea.
Click to expand...
The coil of the added relay is held in all the time, prone to failure.
 
J

justdavemamm

Senior Member
Location
Rochester NY
K2500 said:
That's the best part, I don't see a single problem with your idea.
Click to expand...

Neither do I. But I think it's better to get a N.O. / N.C. OVLD contact block and wire as such and avoid mounting and wiring a relay.

Can we get some feedback from the OP (Original Poster) as to the course of action taken ?
 
C

CIECO

Senior Member
I don,t see a big problem. Cheep and simple. I cant count how many times I have seen OEMs parallel a coil of a starter and if you are concerned about switching a nautral ( you should be if it is grounded ) place the overload contact at the begining of the stop string
 
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D

dnyman

Member
Location
Logan, Ut
I like this idea

I like this idea

I think adding the relay per the pencil sketch is the best route. It would have a relay energized all the time, but this panel is not used continuously. The voltage is 120VAC controlling a 480 VAC motor. The starter has a NC set of contacts for the overload and I don't think a second set can be added. This NEMA starter has been around for along time, and I'm sure that I'm not the first one wanting to add some indication or PLC input for MOL status.
Thanks all for your great input.
 
J

justdavemamm

Senior Member
Location
Rochester NY
dnyman said:
... I'm sure that I'm not the first one wanting to add some indication or PLC input for MOL status.
Click to expand...

Overload status is done in the PLC by using an AUX contact and logic. If the starter is energized and the Aux is off, the the OL is tripped (or a coil problem). Conversely, if the AUX is on and the starter is not energized by the plc output, then the starter is stuck. Either condition is alarmed.

The starter has a NC set of contacts for the overload and I don't think a second set can be added.
Click to expand...

The part # I mentioned is to replace the existing single contact with a dual set.
 
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