RD35
Have an installation where I need to have two independent 200A transfer switches fed from the same 16kw generator.  Would like for both switches to be able to, independently, start and stop the generator as well as operate independent based on need.  I have looked at the control wiring diagrams in the manuals and it seems the best I can do, as designed, is to have one switch signal the generator with N1, N2, T1 wires and then have two 23 wires to make both switches transfer based on the "line" condition at the first switch.  I have come up with a proposed control modification, utilizing two control relays, that I believe will give me independent control of the generator based on the "line" condition at either transfer switch and will also allow the generator to only transfer the load at the switch where the outage exists.  Please review the attached diagram and tell me if you see anything wrong with my logic.   Thanks

Generator w-2 switches.jpg 
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patmurphey
Just curious? Under what circumstance would you lose utility power that did not affect both circuits and what would you envision if both needed generator power?
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RD35
A utility outage will take out both service feeds at the same time.  So 99.9% of the time the proposed diagram will be pointless (because the sensing from one switch would suffice for both).  However, in the event I should lose the line side feed (not a utility outage issue) for just one of the two switches, I would like to know that the generator will fire, and the affected switch will operate without transferring the other switch.  I don't want to tell a customer it can be done if it cannot.....or vice versa.
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Goofy4TheWorld
I'll admit I am not familiar with your diagram's CR items, but I have two points.

First, I would post an explanation of what exactly you are using a relay(s) to do (break the 23 wire maybe) and what is that relay's input (240VAC across N1 & N2?), detailing quantity and function (NO/NC) of all relays.  If what you are doing is utilizing a 240VAC relay that breaks the 23 wire as long as the control relay is energized, then you will create a situation where any short-cycle return of utility power (such as power trying but failing to come back on) will violently work the transfer switch back and forth with no delay.  Ordinarily the generator delays the return to utility, but if you use your own relay to break the generator's control, it would AT LEAST require you to put some ON-delay relays to prevent rapid back and forth of the switch.

Second, at the end of the day you can only feed ONE source of N1/N2, you can't tie them together.  I THINK I follow your logic on breaking those wires, but it would be helpful for you to put it into words.

Third, what is your logic controlling T1?  It can only be fed from one source, but it must always be fed to keep the battery charged.  It looks to me like you are tying them together after your control relay which would be a no-go, but then again I am not 100% up to speed on your diagram's lingo.
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RD35
Goofy4TheWorld
Thanks for the reply!  You have interpreted my diagram correctly and you have pointed out the very flaws I was hoping didn't exist....but do...and I now see them very clearly thanks to your response!  Thank-you for the detailed analysis!  I see now how the switch that did not transfer would get hammered as normal power tries to return to the other switch.  This would also hammer the alternator with additional load spikes as well.  So, I think I will simply install the two switches and just connect the control wires to one of them while daisy-chaining the 23 wire to the second switch.  Or....install that time delay function into the two relays as you suggested if I JUST ABSOLUTELY HAVE to make them operate independently.  If there is a better way to make them independent...I'm all ears!
Again thanks!!!
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RD35
Can someone explain the make-up and function of the transfer signal that flows through wire #23?  My guess is that it is either 12VDC or 120VAC and that it is energized when the transfer switch is in the generator (E) position and not energized when the switch is in the utility (N) position.  However, I may be a mile off on my guess.  Thanks
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78buckshot
Wire #23 is a low voltage dc control, nominal 12vdc. Wire #194 is positive 12vdc from the generator controller to the transfer switch terminal strip then on to the transfer relay coil. Wire #23 is the ground or 12vdc common wire from the coil back to the controller and upon a call to transfer to generator the controller sinks #23 to ground or 12vdc negative. This actuates the relay which energizes the transfer coil.
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Brian Baughman
If you have 2 separate electrical services connected to the same generator, your transfer switches have to switch the utility neutral upon transfer and the generator has to be installed as a separately derived system.  Otherwise an objectionable current path will be created between the 2 electrical services through the generator, which is an NEC code violation and extremely dangerous.  If you did not install the optional standby system in accordance with NEC Article 250.30, the best fix and cheapest fix would be to just install a second generator on the other ATS not have one generator on 2 electrical services.  The cost of 3 pole transfer switches are more than the cost of a second generator.
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UPS
Are those transfer switches connected to 2 independent services, with their own meters - or are they both downstream of one meter with a large disconnect / breaker?
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RD35
On the current project, I have a 400A electrical service which feeds 200A to a house and 200A to an out-building 100' away.  I am choosing to use two switches as a cost saving measure.  Just looking at how difficult it would be to make the two transfer switches operate independently.  This current project will be fine with one switch connected to the generator control and the other as a dummy just receiving 23 signal only.  But it got me thinking that if I come across a larger project with multiple sub panels that requires two or more switches, could I make the two switches operate independent.  As a system designer, I want to understand the limitations and options available for these value priced generators.
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Brian Baughman
In that application, there is only one service.  You can use 2 ATS's, and the best option would be 2- 200A service rated switches that are grouped together at a common location.  From the generator to the primary ATS, you need a full set of Class 1 control circuits.  From the primary ATS to the secondary ATS, you need control wires 0, 23, and 194.
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Cobranut
I agree with Brian,

That application with the switches next to each other, would also save having to run two feeders from the genset. 
Couldn't he run the feed from the genset to one switch, and then on to the other switch, as long as everything was sized to handle the full load of the generator?
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Brian Baughman
Cobranut wrote:
I agree with Brian,

That application with the switches next to each other, would also save having to run two feeders from the genset. 
Couldn't he run the feed from the genset to one switch, and then on to the other switch, as long as everything was sized to handle the full load of the generator?


yes
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Geoff Z
The lugs on a 200amp transfer switch are not dual wire rated. We bring the generator power to a junction box. Using Polaris taps we feed into each switch separately.
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RD35
Hey thanks folks for all the discussion and replies.  Geoff Z, Brian, and Cobra I was planning to set the generator next to the building 100 feet away from the service entrance location.  This would place it near the LP Tank and would have it a good distance from the house for noise control purposes.  So this would mean a transfer switch at each building.  However, I have, since, learned a few things as I lay this out.  First, I discovered that I would need a disconnect on the outside of the house "within sight" of the house (within 50 ft and visible) since the generator is not within sight (per'se).  Also learned that the fuel consumption is low enough on these units to keep the gas piping within reason even when upsized for the 100' distance to the house.  Also learned that since these units run so quiet having it located next to the attached 2-car garage (where the electrical service entrance resides) would result in an almost totally undetectable noise level in the home.  So, based on these things, I think I will just locate the generator next to the electrical service and do as you guys suggested.  I'll set the two switches side-by-side and a J-box beneath the two switches with a 3-pole distribution block inside to distribute the generator feed to each switch's E-line terminals.  I'll daisy chain the the 0, 194, and 23 signal wires from one switch to the other.
New question.... what kind of issues will I get into if I attempt to use the load shedding features of both switches.  I assume there is no way to make them work with each other...but can they work independent without causing problems?
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