Auto Transfer Switch Question

[quogueelectric]

ats switch

ats switch

Is the ats also connected to an emergency generator??

 

[mkgrady]

Is the ats also connected to an emergency generator??

Nope. The ATS will send one feeder to one of two loads. Right not it is a manual transfer switch and the customer wants it wo work automatically

 

[charlie tuna]

sounds to me that your gettin ready to build half a$$ motor starter using relays -- now your asking for problems if you don't match everything and include overload protection-------code wise??? a reversing contactor is just two relays that are mechanically interlocked--no overload protection. when you start using different manufactured parts and pieces and there's a problem somebody's gonna be asking you for a manufacturer's engineering stamp. if you didn't want or are afraid to get into the vfd's program -- just start the second compressor on loss of pressure or at some lower than normal setpoint and interlock the vfd with aux. contacts on the secondary compressor's "motor starter"... when you get a price from asco --- take a deep breath before reading it!!!!

 

[jim dungar]

sounds to me that your gettin ready to build half a$$ motor starter using relays -- now your asking for problems if you don't match everything and include overload protection-------code wise??? a reversing contactor is just two relays that are mechanically interlocked--no overload protection. when you start using different manufactured parts and pieces and there's a problem somebody's gonna be asking you for a manufacturer's engineering stamp. if you didn't want or are afraid to get into the vfd's program -- just start the second compressor on loss of pressure or at some lower than normal setpoint and interlock the vfd with aux. contacts on the secondary compressor's "motor starter"... when you get a price from asco --- take a deep breath before reading it!!!!

Charlie, he does not want a motor starter, he simply wants to automatically switch two different motor loads motor overload protection is provided by other devices.

Personally I see no reason to got to ASCO or to adjust the VFD programming when mechanically interlocked motor contactors are available from every major manufacturer in both NEMA and IEC (which would be my preference) designs.

 

[mkgrady]

Charlie, he does not want a motor starter, he simply wants to automatically switch two different motor loads motor overload protection is provided by other devices.

Personally I see no reason to got to ASCO or to adjust the VFD programming when mechanically interlocked motor contactors are available from every major manufacturer in both NEMA and IEC (which would be my preference) designs.

I like the mechanically interlocked motor feeder contactors because I don't want to get into the guts of the packaged systems. There are already problems with the internal controls so I see the contactors as a way to shift power from the main compressor to the backup. You know, the KISS system.

 

[charlie tuna]

wiregaru had mentioned buying a "fuji" 285 amp contactor --- and mounting it in a hoffman box --etc.. ---thats what i was refering to.. as you say, there is a very simple way to handle this---electrically---you want mechanical interlock your gonna be buying a ats or a reversing contactor---this isn't cheap... don't be afraid of these programable controls in the vfd --- you can do anything with them --they have auxilaries like motor starters and you can set them to actuate at many parameters......

 

[jim dungar]

wiregaru had mentioned buying a "fuji" 285 amp contactor --- and mounting it in a hoffman box --etc.. ---thats what i was refering to.. as you say, there is a very simple way to handle this---electrically---you want mechanical interlock your gonna be buying a ats or a reversing contactor---this isn't cheap... don't be afraid of these programable controls in the vfd --- you can do anything with them --they have auxilaries like motor starters and you can set them to actuate at many parameters......

I am not afraid of VFDs or PLCs I have worked with them for more than 29 years. I don't change someone elses logic design if I don't have to. Yes contactors are more expensive than simply changing the VFD (if it was supplied with the corrcet options) but the mechanical interlock is fool proof for preventing simultaneous operation

 

[wireguru]

wiregaru had mentioned buying a "fuji" 285 amp contactor --- and mounting it in a hoffman box --etc.. ---thats what i was refering to.. as you say, there is a very simple way to handle this---electrically---you want mechanical interlock your gonna be buying a ats or a reversing contactor---this isn't cheap... don't be afraid of these programable controls in the vfd --- you can do anything with them --they have auxilaries like motor starters and you can set them to actuate at many parameters......

you mentioned code problems from putting different bits and pieces together and 'manufacturing' this. how is it any different than putting a lighting contactor in a box?

you guys are right about the mechanically interlocked reversing being the way to go. with the setup i recommended the potential exists for both contactors being able to be energize if the auxillary contact used for the electrical interlock were to fail. an appropriate size reversing contactor will only be a couple hundred dollars more than the solution i had originally proposed

 

[quogueelectric]

two speed contactor

two speed contactor

Has both mechanical interlock and separate heater sections. Could easily build logic for automatic with pressure switch . I personally would prefer an alternator switch which would alternate each compressor at each start wearing them evenly and maintaining assurance that they will work properly after not being used for a long time

 

[mkgrady]

Has both mechanical interlock and separate heater sections. Could easily build logic for automatic with pressure switch . I personally would prefer an alternator switch which would alternate each compressor at each start wearing them evenly and maintaining assurance that they will work properly after not being used for a long time

The alternator would't be good here. The main compressor runs on a VFD and the backup is just a line voltage starter. 50% of the time they would loose the advantage of having a VFD. However, I do agree that there should be a way to run the backup unit often enough to keep it running trouble free.

 

[mkgrady]

I dont why you couldnt use a three pole double throw ASCO switch and some simple control wiring? Whats the problem? It can only feed one compressor at a time.

I agree but I got a quote for an ASCO switch. About $3,600. The price doesn't bother me but it is all set up to take two feeds and use them to serve one load. I'd have to modify all the controls and labels to have one feed and two loads. And I'm sure there will be no warranty if I modify the switch. There is also a problem with the dimensions of the enclosure. It's too deep.

Jim Dungar suggested some heavy duty three phase contactors and to electrically and mechanically interlock them so only one contactor can close at a time. I've headed down that road by looking at GE and Seimens catalogs showing list pricing. While I realize there are substantial discounts off list prices the prices I'm finding would put the parts cost above 10 grand! I also have been unable to locate any mechanical interlocks in the catalogs.

Wireguru suggested some very reasonably priced 285 amp relays by Fuji at $490 each but they do not make a mechanical interlock for it so that's no good.

I'm hoping someone can point me in the right direction. Does anybody know of a contactor supplier that sells a reasonably priced 300 amp +/- contactor (the FLA is 225) that can be interlocked with a sister contactor?

 

[jim dungar]

I've headed down that road by looking at GE and Seimens catalogs showing list pricing. While I realize there are substantial discounts off list prices the prices I'm finding would put the parts cost above 10 grand! I also have been unable to locate any mechanical interlocks in the catalogs.

You can easily use IEC style devices in this application (basically no load switching and not even once per day). Why do you want a 300A contactor when all you are switching is a 75HP load?

Take a look at something like the Telemecanique mechanically interlocked contactor from Square D (LC2D150F6 rated 100HP @480 for $1,598 list) . Of course you will need to put it into your own enclosure. Or use their 330A unit but you build this from parts (2 - LC1F330F6 + LA9FJ970 for about $3,500)

Siemens, AB, Fuji, ABB, Eaton, and others all make similar devices.

 

[mkgrady]

You can easily use IEC style devices in this application (basically no load switching and not even once per day). Why do you want a 300A contactor when all you are switching is a 75HP load?

Take a look at something like the Telemecanique mechanically interlocked contactor from Square D (LC2D150F6 rated 100HP @480 for $1,598 list) . Of course you will need to put it into your own enclosure. Or use their 330A unit but you build this from parts (2 - LC1F330F6 + LA9FJ970 for about $3,500)

Siemens, AB, Fuji, ABB, Eaton, and others all make similar devices.

The motor FLA is 225, (208 volts) so I rounded up to 300 amps. I'd shoot for anything above 250 amps. Thanks alot for the part numbers. That really helps.

 

[jim dungar]

The motor FLA is 225, (208 volts) so I rounded up to 300 amps. I'd shoot for anything above 250 amps. Thanks alot for the part numbers. That really helps.

My bad, didn't look at the voltage.

The 265A, 75HP @ 208V Square D numbers would be: (2) LC1F265G7 + LA9FH976 + LA9FJ970 + DZFH6 for about $2,500 list. This includes the contactors, connecting bus bars, mechanical interlock, and lugs. Again there are other manufacturers, just remember that IEC style devices have "some assembly required".

 

[mkgrady]

My bad, didn't look at the voltage.

The 265A, 75HP @ 208V Square D numbers would be: (2) LC1F265G7 + LA9FH976 + LA9FJ970 + DZFH6 for about $2,500 list. This includes the contactors, connecting bus bars, mechanical interlock, and lugs. Again there are other manufacturers, just remember that IEC style devices have "some assembly required".

I'm very grateful to receice such precise information. You just saved me alot of time. THANKS. I hope I can return the favor.

 

[jim dungar]

I'm very grateful to receice such precise information. You just saved me alot of time. THANKS. I hope I can return the favor.

Thanks,

But do not assume that the parts I listed are the actual ones that suit your specific project. Use these as a reference.

 

[quogueelectric]

did you see

did you see

The two speed starter? I do not have prices for you it has separate heater sections is mechanically interlocked and will only operate one at a time

 

[mkgrady]

The two speed starter? I do not have prices for you it has separate heater sections is mechanically interlocked and will only operate one at a time

Sounds like it could work but I don't need thermal overloads so I assume contactors will be less cost and more compact. I don't want to make the enclosure any bigger than it needs to be.

 

[benaround]

Make sure this stuff is HP rated, not just current rated.

I'll pass this on as it was passed to me long ago.

control relay

lighting contactor

motor starter

 

[jim dungar]

Make sure this stuff is HP rated, not just current rated.

It only has to be horsepower rated if it is going to be used to Start-Stop the motor. No load switching devices only need to be current rated. Are there any "large" automatic transfer switches which are horsepower rated?