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phuz

Output card for motor starters

13 posts in this topic

I'm trying to decide which output card to use for a new system. The MCC (AB) has about 60 buckets and each has its own control transformer with HOA control. There is a contact in series on the AUTO which has terminals "1" and "1A" which I assume will come back to our control panel. My question is can I use an OW16I to close each one of the contacts or will I exceed the 2A rating per point. I am having trouble finding out the current draw of these motor starter coils. Most of them are 5HP and lower.

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I would use slave relays for this. With output card you have. And don't forget surge protection across the inductive loads. Edited by Mickey

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I would second the option of slave realys and use a 24 VDC coil and 24VDC output card. That way once you Lock and Tag the bucket so there's no 230/480 coming in the on;y remaining voltage is the 24 VC which is outside NFPA 70E. Otherwise you have a 110 voltage from your PLC you'll need to lock out. I might also suggest you look at the 193-E1 Overload Relays which can come with DNET module and output conacts built in. We've used these in our AB MCC and once the DNET is up they're great. There is also an ENET version IIRC.

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Thanks, but from the AB supplied bucket wiring diagram, it looks like the bucket will supply 120vac from its own control transformer and it will need to run through a set of contacts in OUR control panel and then back to the bucket to complete the circuit. So during a lockout/tagout, that 120 would be dead anyway. Any idea where I can find the coil wattages/currents for typical AB starters? I've looked through quite a bit of documentation and nothing refers to the starter's coil. Edited by phuz

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The only problem with that is that your PLC cabinet would have "foreign" 120V in it, with perhaps lots of independent sources (one for each bucket). If you run 24VDC from the PLC cabinet to a relay in the bucket, you can use the relay contacts there to switch your 120V for the coil.

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I agree with the above. If you go with the multiple sources of power in your cabinet make sure you put a big red sign on the outside stating there are multiple power sources. Edited by Mickey

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Put the interposing relay in the bucket and bring 24VDC from the PLC panel. Do not take the bucket 120 voltage back to the PLC panel. The 120 from the bucket control transformer stays only in the bucket.

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And to meet code, your wires to the main control panel are to be orange. The 24V interposing relay placed in the bucket is safer and simpler.

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Great, thank you guys! That makes a lot of sense. How do you handle E-stop circuitry for buckets with HOA control? Let's say I have a safety relay that needs to shut off 5 motors. I plan on putting the safety contactors in the control panel to break the 24vdc that will feed the interposing relay in each of those 5 buckets. But by doing this, we will only stop the motor if the switch is in Auto at the bucket. Edited by phuz

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When did control power conductors become required to be color coded per NEC ? (unless this is something new, I strongly disagree - I'm not saying it's a bad idea, but there's no requirement that I'm aware of as of 2008 NEC).

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NFPA 79 13.2.4.1 The color ORANGE shall be used to identify ungrounded conductors that remain energized when the main supply circuit disconnecting means is in the off position. This color identification shall be strictly reserved for this application only. If he brings 120V from the MCC bucket to a control panel then those wires are still energized even when the control panel supply is off. This isn't a new code requirement, however a long time ago yellow or orange was allowed, but yellow had been depricated to eliminate confusing with the IEC yellow/green ground standard. The requirement doesn't apply to low voltage. Edited by TConnolly

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You will need an interposing relay to break the 120 hot in the bucket before it goes to the Auto/Manual Switch. Another option is to structure your MCc Section so that a High Amperage Contactor connected to your safety relay interrupts the 230/480 to all five buckets. Not feasible if you've already ordered and bought the section. Very Doable if AB is still building it for you.

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The MCC is already built and in operation, unfortunately. The customer decided on controls AFTER the fact. :)

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