# Adding an ATS to an existing service



## Hippie (May 12, 2011)

I have a job Im trying to plan out and its not something Ive dealt with before. Office building with 1200A 208 service, old late 60's GE panelboard. 3 4" rigids coming from above with service conductors. My plan is to cut them back, run a 12x12 gutter across the top of the existing panel and along the wall to pick up the ATS and the pipes that will be coming in from the generator. Splice onto existing service conductors and run them into ats. At some point the service will have to be disconnected and I think a rental genset may have to be brought in to power the building while i reconfigure the service into the new ATS, even if i do it at night. I should hopefully be able to unscrew the last length of rigid and cut it without too much trouble. 

There is basically the genset and ats sitting there, no plans of any sort. Ive done a lot of big new generator jobs but never tying one this large into an existing service, and before they were all engineered jobs and not on my own. Am i approaching this the right way or am i missing something simpler?


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## Bbsound (Dec 16, 2011)

Around here that would require engineered drawings to get a permit.
What city?


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## SteveBayshore (Apr 7, 2013)

First, is there a service disconnect or is the new x-fer switch service entrance rated? 
Second, trough must be sized properly for the 4" conduits and I assume 500kcmils.


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## Hippie (May 12, 2011)

Virginia eastern shore. And its going in a county building that actually houses the building department. So.....


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## Hippie (May 12, 2011)

SteveBayshore said:


> First, is there a service disconnect or is the new x-fer switch service entrance rated?
> Second, trough must be sized properly for the 4" conduits and I assume 500kcmils.


It's a service rated ats. The old service is just a mdp with 4 breakers, no main

I was planning on 3 runs of 500 cu. I havent actually sized the trough yet so that's just kind of what I was picturing


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## xlink (Mar 12, 2012)

Have you thought about cutting into the load side of the main? It would avoid the splice on the service conductors.


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## Hippie (May 12, 2011)

xlink said:


> Have you thought about cutting into the load side of the main? It would avoid the splice on the service conductors.


There is no main.. service conductors straight to bussbar


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## xlink (Mar 12, 2012)

Hippie said:


> There is no main.. service conductors straight to bussbar


Oh yeah. You said that.

Your wires from the generator can go directly to the transfer switch. That will reduce the clutter in the trough. I'm sure it depends on the transfer switch, but it would be a hard day to terminate all that 500 copper. (Three runs per phase, three phases per circuit (plus neutral?), in from the service and the generator and out to the load.) I used acwu (aluminum teck) on a similar job. 750 Aluminum is way easier to handle than 500 copper, and cheaper.

Just a reminder. 4 inch rigid is over 100 lbs per stick. There is nothing easy about 4 inch rigid.

You need to find a way to have everything ready for the final change so all that is left is terminations on the changeover night. The only thing worse than still working when the sun comes up is still working when the sun goes down again.


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## Hippie (May 12, 2011)

xlink said:


> Oh yeah. You said that.
> 
> Your wires from the generator can go directly to the transfer switch. That will reduce the clutter in the trough. I'm sure it depends on the transfer switch, but it would be a hard day to terminate all that 500 copper. (Three runs per phase, three phases per circuit (plus neutral?), in from the service and the generator and out to the load.) I used acwu (aluminum teck) on a similar job. 750 Aluminum is way easier to handle than 500 copper, and cheaper.
> 
> ...


The lugs on the ats definitely won't take a 750 unfortunately. The ats will be between where the wires enter from the genset and the service but I will have 24 500s plus grounds and splices in one section.. ouch probably will need more than a 12x12..


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## xlink (Mar 12, 2012)

Hippie said:


> The lugs on the ats definitely won't take a 750 unfortunately. The ats will be between where the wires enter from the genset and the service but I will have 24 500s plus grounds and splices in one section.. ouch probably will need more than a 12x12..


Can you splice parallel runs or do you need buss bars?

750 lugs were a special order for me.


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## Hippie (May 12, 2011)

xlink said:


> Can you splice parallel runs or do you need buss bars?
> 
> 750 lugs were a special order for me.


I dont see why they cant be spliced, ive never heard anything to the contrary as long as they stay the same length.

do you know the cost of the 750 lugs and savings of aluminum vs. the cost of 500 copper? the ats is already on site so getting another set of lugs would probably be pretty costly... but so is all that copper


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## Hippie (May 12, 2011)

Also, as a side issue, there is a 600A breaker in the panel that feeds the building next door. That building already has a smaller generator and ats. My thought is that it will be ok to leave that as it is, since in the event of a power failure the existing ats will switch over and no longer be connected to the panel that will be fed through the new ats. However it would be possible for the new genset to come on before the existing one, causing the smaller one to not run and putting the full load of both buildings on the new generator. So i think i will need to interlock them somehow?


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## xlink (Mar 12, 2012)

Hippie said:


> I dont see why they cant be spliced, ive never heard anything to the contrary as long as they stay the same length.
> 
> do you know the cost of the 750 lugs and savings of aluminum vs. the cost of 500 copper? the ats is already on site so getting another set of lugs would probably be pretty costly... but so is all that copper


The lugs were special to fit the ats equipment and had to be purchased from the ats supplier. They were really pricey and a bear to install. Still, I prefer aluminum. It hurts less the next day.

Does your generator have a breaker in it. I'm wondering if you need to size the wires between the generator and the transfer switch for that breaker or for the load.


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## xlink (Mar 12, 2012)

Hippie said:


> Also, as a side issue, there is a 600A breaker in the panel that feeds the building next door. That building already has a smaller generator and ats. My thought is that it will be ok to leave that as it is, since in the event of a power failure the existing ats will switch over and no longer be connected to the panel that will be fed through the new ats. However it would be possible for the new genset to come on before the existing one, causing the smaller one to not run and putting the full load of both buildings on the new generator. So i think i will need to interlock them somehow?


I suppose if it were simple, you wouldn't be asking for ideas.


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## Hippie (May 12, 2011)

That's another thing I was wondering about. It has a 1200a breaker in it but rated output is like 1050 amps


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## SteveBayshore (Apr 7, 2013)

Hippie said:


> That's another thing I was wondering about. It has a 1200a breaker in it but rated output is like 1050 amps


1200 amp breaker is OK, but you cant protect (3) 500s on a 1200 amp breaker any more. Existing might be OK, need 600s now. Over 800 amps can't go up to next size CB, 240.4(B). 500s only rated at 380a at 75c.


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## Hippie (May 12, 2011)

SteveBayshore said:


> 1200 amp breaker is OK, but you cant protect (3) 500s on a 1200 amp breaker any more. Existing might be OK, need 600s now. Over 800 amps can't go up to next size CB, 240.4(B). 500s only rated at 380a at 75c.


youre right, i never thought about that. im definitely going to have to look into the bigger lugs for the ATS.

on second thought, maybe ill just pull a #6 along with them from the roll i already have to make up for the extra 60 amps lol:jester::thumbup::laughing:


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## nolabama (Oct 3, 2007)

They make reducer crimp pins. New. Panduit I think. I will look for link


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## nolabama (Oct 3, 2007)

http://www.panduit.com/wcs/Satellit...tion_id=1981&locale=en_us&pagename=PG_Wrapper


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## nolabama (Oct 3, 2007)

Hippie said:


> Also, as a side issue, there is a 600A breaker in the panel that feeds the building next door. That building already has a smaller generator and ats. My thought is that it will be ok to leave that as it is, since in the event of a power failure the existing ats will switch over and no longer be connected to the panel that will be fed through the new ats. However it would be possible for the new genset to come on before the existing one, causing the smaller one to not run and putting the full load of both buildings on the new generator. So i think i will need to interlock them somehow?


Can the new ats send the start/run signal to the old genset? Should be easy. Most have a set of nc no contacts.


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## Bbsound (Dec 16, 2011)

nolabama said:


> Can the new ats send the start/run signal to the old genset? Should be easy. Most have a set of nc no contacts.


It's not just the start circuit he needs to worry about.
When the new genset comes online, the old ATS will see normal power available and transfer back to normal. 
So it does need to be interlocked somehow.
We would need more specifics on the ATSs.


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## Hippie (May 12, 2011)

Bbsound said:


> It's not just the start circuit he needs to worry about.
> When the new genset comes online, the old ATS will see normal power available and transfer back to normal.
> So it does need to be interlocked somehow.
> We would need more specifics on the ATSs.


That's what I was trying to say sorry if I wasn't more clear. The new one is cutler hammer, I haven't looked into the other one yet all I know is that its there. I'll be back there Friday ill check all that stuff out then


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## nolabama (Oct 3, 2007)

Bbsound said:


> It's not just the start circuit he needs to worry about.
> When the new genset comes online, the old ATS will see normal power available and transfer back to normal.
> So it does need to be interlocked somehow.
> We would need more specifics on the ATSs.


Oh. Your gonna have to trick the old ats.


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## Hippie (May 12, 2011)

nolabama said:


> Oh. Your gonna have to trick the old ats.


Yeah. I was thinking if it can't be done with the existing controls then the simplest thing would be to break the voltage sensing circuit in the old ats with a relay that pulls in when the new gen starts so it won't see line power.

The old service is 500 cu so I don't see why the new wiring thru the ats would have to be upsized. The inspector is pretty easygoing I think he would be ok with it.


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