Panel Construction Question - re: multiple disconnects

Slightly off topic:

I am currently designing a panel for a pump control station. There are 5 motors (40hp) involved. Each motor is operated by an SMC-3 soft starter, all controlled by a ML1500. Once commissioned, the system will never be down except for a power outage. However, there must be a provision to allow for maintenance on one pump or motor at a time. The customer does not want an MCC style panel with separate buckets for each motor, but the customer does want each motor individually disconnectable and lock-out-able. The enclosure is to be NEMA 4 (IP67). The customer does not want their maintenance people to open the control cabinet to operate a breaker to disconnect a motor. Two of the motors are 80 feet from the main panel and are outside. Each of those will have a disconnect switch mounted next to the motor. However, the other three motors are on the pump skid and their starters are in the main control panel. This is where I am looking for some ideas.



The panel will have a main disconnect switch interlocked with the door, but the other three motors have to be disconnectable. The customer does not want separate disconnects, but wants it all in the main panel. I don’t want to put three disconnects through the main door of the enclosure (imagine the alignment problems, as well as trying to operate three cheaters at once to get the door open. Since there is a main disconnect, the individual motor disconnects don’t need to be interlocked to the door. My current idea is to use C-H cable operated disconnects to operate the 3 breakers and to mount the disconnect operators on the side of the cabinet.



Has anyone else encountered something like this? Or is there a better way to do this?

Assuming I'm following the description correctly, can you use the IEC door mount style disconnects (where the operator is on one side and the switch on the other) through the side of the panel? Assuming they are available in that current range (PS: AB has them in the 194E series)?

I have used or seen used the following:
1, Individual isolators at each motor (you discounted this option)
2, Cuttler hammer (or similar) 3 phase plugs at each motor. These often have extra pins that can be wired back to the PLC to prevent starting if the plug is disconnected or to drop out the motor if someone tries to unplug while the motor is running. We also modify the plugs to allow a padlock to be fitted, this prevents them being plugged back in if they are locked out.
3, Same as 2, but mounted on the side of the panel. - only did this once, since most of our motors are remote from the panel and the maintenance crew like to be able to see that the motor is correctly isolated.

Hope this helps,

Doug

2, Cuttler hammer (or similar) 3 phase plugs at each motor. These often have extra pins that can be wired back to the PLC to prevent starting if the plug is disconnected or to drop out the motor if someone tries to unplug while the motor is running. We also modify the plugs to allow a padlock to be fitted, this prevents them being plugged back in if they are locked out.

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I have been using plug lockouts for over 20 years, they are made in different sizes for 120v-600vac plugs up to at least 60amps. I have also used them for cam-lok (the twist and turn type connectors you find on welders) and similar, these may fit connectors rated up to 1000A....maybe higher but I never went over 800A.

RSDoran's suggestion will work, but I am confused about this quote.

1, Individual isolators at each motor (you discounted this option)

Where was this discounted in his post? He never says that these disconnects could not be located on the skid, or mounted externally on the door or side of the cabinet. We have these all over the place here. I'm not talking about big fused disconnects, simply 3 phase switches that are lockable. They fit right in a traditional outlet box and are quite handy for mounting close to the motor without taking up a lot of space. Just thought I'd throw this out there, since I hadn't seen where this was discounted. If you want more info I can get a part # and man. name for you to check out, as I am unsure who makes the ones we use. Good luck whatever you decide.

Russ

russrmartin said:

Where was this discounted in his post?

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Alaric said:

The customer does not want separate disconnects, but wants it all in the main panel.

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I like the cable operated disconnect idea. I've used the rotary IEC disconnects, but I don't really like them. IMO, there's usually too much 'give' in the external operator before the actual switch rotates, making them feel too 'mushy' (for lack of a better description). I like the good old lever-operated devices... :nodi:



-Eric

I normally use Merlin Gerin circuit breakers with a door mounted handle. An auxiliary contact feeds the PLC input. These things are positive.

Also use Telemecanique or Sprechur+Schuh (read AB if S+S are not available) motor circuit breakers with a door mounted handle. They are positive also.

Alaric,

I have never had to have separately lockable disconnects inside a box, but I have used cable-operated circuit breakers. I found them to be easier to install and align than any other type. Once the switch handle is mounted in the door, the circuit breaker can be mounted ALMOST anywhere in the box, with no worries about aligning the operating mechanism. The cable resembles the brake cable on a bicycle, and works very well. You need to route the metal cables so that they cannot cause a short circuit by rubbing against an exposed terminal screw. The bending radius of the cable is limited, so your arrangement must minimize the amount of bending in the cables.

Lancie1 said:

I have never had to have separately lockable disconnects inside a box, but I have used cable-operated circuit breakers. I found them to be easier to install and align than any other type. Once the switch handle is mounted in the door, the circuit breaker can be mounted ALMOST anywhere in the box, with no worries about aligning the operating mechanism. The cable resembles the brake cable on a bicycle, and works very well. You need to route the metal cables so that they cannot cause a short circuit by rubbing against an exposed terminal screw. The bending radius of the cable is limited, so your arrangement must minimize the amount of bending in the cables.

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I have used these before, but have this to offer...

Use the cable-operated mechanism to work a switch only, not a circuit breaker. Wire the circuit breaker "downstream" of the switch. The disconnect for a circuit breaker gets funny because you are not only turning the breaker on and off, but in the case of a "trip", the mechanism must be able to force the tripped breaker down to "reset", then up to "on" again. The play in the cable can sometimes be difficult to make this happen. Also, the switch handle rarely reflects the "trip" position.

Alternately, I would mount a separate, small disconnect enclosure to the main enclosure for each motor desired. This way each enclosure has a clear box to lock off and tag out. Even better is to locate these right at the respective motor. I think this is the safest way.

I cannot see a problem with mounting a circuit breaker on the base plate and using an extension handle mounted in the door to operate/reset the breaker. As a control panel builder, I do this all the time and have no problems. You just have to be careful to align the handle and circuit breaker properly at installation. If you do not then there are problems.

If there are several to mount, it is better to place them on the side of the door opposing the hinges. They are easier to line up when closing the door. If on the hinge side, the handles can present problems when closing the door even if they have been installed in alignment. I generally find the Merlin Gerin (Schneider) ones are easier to install and have a better appearance.

Most of the circuit breakers I mount this way are a minimum of 250 amps up to 630 amps and also have 4 pole RCDs attached. Man, does that limit space and make alignment more difficult, not to mention the weight of the things.

BobB said:

I cannot see a problem with mounting a circuit breaker on the base plate and using an extension handle mounted in the door to operate/reset the breaker. As a control panel builder, I do this all the time and have no problems. You just have to be careful to align the handle and circuit breaker properly at installation. If you do not then there are problems.

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I don't disagree. My earlier point is that there is an additional consideration (resetting a trip) when using a disconnect for a circuit breaker instead of a switch. Sometimes, not always, this adjustment can be tricky.

I just wish I had more guys like Bob working for me when I had my panel shop...

Sometimes, not always, this adjustment can be tricky.

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Once the handle is in place and correctly aligned, resetting is just performed by turning the breaker off and then back on again. I see many tradesmaen struggling with alignment of the handles when building panels. The secret an even older bloke than myself taught me was to make up some good jigs. I only use plastic binders for continuous US fanfold printouts. The plastic is quite thick and I mark the jig up and then cut it out with a pair of scissors, punch suitable holes in it and all is well.