ATS FEEDS

[Alwayslearningelec]

Ok...scenario. You have ATS that is fed(obviously) by both a norm and em source and the ATS feeds a panel. Would working on/changing the EM feeder that is feeding the ATS be considered working on it as "hot"(while it is fed from norm power) ? I don't know how this technically works but it would seem that the "norm" side of the ATS would be live if this makes sense but again...I don't know how the bussing or insides of ATS are connected. Oh, and this is based on the fact you shut the breaker or switch from the em panel/board feeding the EM side of the ATS. Thanks.

 

[ron]

Most ATS's have the norm and em feeders adjacent to each other. That would normally mean that you are working near energized electrical equipment (no barrier) so I would recommend PPE.

 

[Alwayslearningelec]

Most ATS's have the norm and em feeders adjacent to each other. That would normally mean that you are working near energized electrical equipment (no barrier) so I would recommend PPE.

I figured that but just wasn't sure if you could safely work on the em feeder? But then again what happens if there is an situation while working on it thst requires transfer of power....uh oh..but then again you can do all the work adjacent to the run and then do the final terms etc. leaving minimal "off/down" time.....I'm assuming.,

 

[Joethemechanic]

In the Transfer switch you are going to be working very close to energized components, just like Ron said. There will be energized components on the normal power side and the load side.

But , the feeders from the generator will not be hot until the generator starts.

If you are working on the feeders from the generator, but you are not going inside the transfer switch, and you disable the generator, you will not be working hot.

I guess a better answer isn't possible without knowing exactly what you are doing

 

[Alwayslearningelec]

In the Transfer switch you are going to be working very close to energized components, just like Ron said. There will be energized components on the normal power side and the load side.

But , the feeders from the generator will not be hot until the generator starts.

If you are working on the feeders from the generator, but you are not going inside the transfer switch, and you disable the generator, you will not be working hot.

I guess a better answer isn't possible without knowing exactly what you are doing

THanks, but to disconnect is to go inside the ATS...

 

[Joethemechanic]

THanks, but to disconnect is to go inside the ATS...

Yeah that is working pretty hot.

If you want to disable the generator and be sure about it, the best way is to disconnect the starting batteries, but throw the breaker or pull the plug on the battery maintainers/chargers first.

 

[MEP_PM]

can do all the work adjacent to the run and then do the final terms etc. leaving minimal "off/down" time.....I'm assuming.,

I have been involved with several jobs in which a Pull box were set above/beside the equipment and wires pulled to the box. Then during the shut down the last 8-10ft of wires were pushed into the equipment and terminated. Also be sure you know where power is derived for any related control circuits inside the ATS. I've seen ATS control circuits connected to UPS in a large system. You don't want to be surprised by 110V control circuit when you think the equipment is isolated.

Also triple check phase rotation and document it. The same person with the same meter should check it before and after. I also try to find a motor/fan to use as the triple check. Before the shutdown, with a marker, place an arrow in the direction of rotation on the equipment. Then after the shutdown, turn only that motor/fan breaker on and see if it's rotation is correct while the ATS is being fed from the feeder you've replaced. Then turn everything else on.

 

[Alwayslearningelec]

I have been involved with several jobs in which a Pull box were set above/beside the equipment and wires pulled to the box. Then during the shut down the last 8-10ft of wires were pushed into the equipment and terminated. Also be sure you know where power is derived for any related control circuits inside the ATS. I've seen ATS control circuits connected to UPS in a large system. You don't want to be surprised by 110V control circuit when you think the equipment is isolated.

Also triple check phase rotation and document it. The same person with the same meter should check it before and after. I also try to find a motor/fan to use as the triple check. Before the shutdown, with a marker, place an arrow in the direction of rotation on the equipment. Then after the shutdown, turn only that motor/fan breaker on and see if it's rotation is correct while the ATS is being fed from the feeder you've replaced. Then turn everything else on.

Great info MEP, thanks. Cant you just run the conduit close to the ATS run the last few feet during the shutdown and term?

Phase rotation ... Isnt that or motors only?

 

[ActionDave]

Phase rotation ... Isnt that or motors only?

The phase rotation of the generator needs to match the utility power or you could have trouble with any connected motors.

 

[iwire]

Most ATS's have the norm and em feeders adjacent to each other. That would normally mean that you are working near energized electrical equipment (no barrier) so I would recommend PPE.

If you are even allowed to do the task hot.

 

[MEP_PM]

Cant you just run the conduit close to the ATS run the last few feet during the shutdown and term?

Phase rotation ... Isnt that or motors only?

You can just run the conduit near the ATS and connected the last few feet during the shut down. Just depends on the time you are allowed to shut down the system. If you had multiple long runs of paralleled large feeders, it could take a long time to finish the conduit runs and pull the large feeders.

To follow up on what ActionDave said, you don't want the motors to spin one way on the normal feed and then backward when the ATS transfers to the emergency feed. Depending on the speed of the ATS transfer and the sizes of motors in the systems you could cause some damage if that happened.