generator question e lighting/optional loads

[steveng]

i want to use 1 gen to feed 2 seperate bldgs for egress lighting and some optional loads, what is the most cost effective way to do this?

the 2 bldgs are fed from the same distribution transformer 1500kva pri 12kv
secondary voltage is 480 3ph

any suggestions, comments from someone who has done this?

thanks

steve

 

[mdshunk]

Two transfer switches.

 

[iwire]

Two transfer switches.

Maybe four if he needs both optional and emergency in each building.


It is worth pointing out there is a change in 2008s 700.9(B) that allows the use of a single distribution breaker to supply both kinds of loads.

 

[chris kennedy]

any suggestions, comments from someone who has done this?

I did one last year. The genny was a 750kw 480V and I used two service rated transfer switches to handle the entire loads of both buildings. Works sweet and the genny under load is at under 50% of its capacity.

 

[mdshunk]

I did one last year. The genny was a 750kw 480V and I used two service rated transfer switches to handle the entire loads of both buildings. Works sweet and the genny under load is at under 50% of its capacity.

Let me ask a couple quick questions....

You'd have the gen start wiring coming from each ATS to the generator, so that any or all of them can start the genset. It's just a dry contact anyhow. Q: If just one building has a problem that needs gen power, will the second ATS squalk or alarm out because it's now got power on its E terminals for reasons unknown to that second ATS?

 

[iwire]

I used two service rated transfer switches to handle the entire loads of both buildings.

That will not fly with him supplying egress lighting.

the genny under load is at under 50% of its capacity.

This may not be as good as it sounds, under loaded gen sets can wet stack (Diesel fuel pools in the exhaust system.)

I really do not know if a 50% load will prevent it. We have installed load banks and we have ordered gensets with factory installed load banks in front of the radiator in order to load the generator up for exercising or for lightly loaded conditions.

 

[chris kennedy]

Q: If just one building has a problem that needs gen power, will the second ATS squalk or alarm out because it's now got power on its E terminals for reasons unknown to that second ATS?

Since both are fed from the same POCO tranny, someone would have to run a car into one service for only one building to have a problem.

There is only one remote annunciating (sp?) panel in one building. If only one service has a problem, then the other transfer switch will show EM and Normal power available, as during exercise. BTW this genny exercises under load.

 

[chris kennedy]

That will not fly with him supplying egress lighting.

Why not? The EM and Life safety panels never lose power.

This may not be as good as it sounds, under loaded gen sets can wet stack (Diesel fuel pools in the exhaust system.)

I really do not know if a 50% load will prevent it. We have installed load banks and we have ordered gensets with factory installed load banks in front of the radiator in order to load the generator up for exercising or for lightly loaded conditions.

Get this. They also bought a gas assist system for 70 grand. Genny needs at least 60% load for this to kick in. I wanted to put a 3rd sister building on this genny but was overruled by the powers that be.

 

[iwire]

Q: If just one building has a problem that needs gen power, will the second ATS squawk or alarm out because it's now got power on its E terminals for reasons unknown to that second ATS?

I see no reason the ATS would squawk about the power on the e-terms the 'available' light should come on.

In any multiple ATS setup I have worked with I did not observe any problems. Most of those supermarkets I work in have multiple ATS.

The power on the e terminals would be no different then what happens every time the gen set is exercised.

As far as the start wiring we have always just paralleled them all together, but only one ATS will have the exercise clock installed, programed or enabled.

One battery charger as well.

 

[mdshunk]

I see no reason the ATS would squawk about the power on the e-terms the 'available' light should come on.

Since these things are becoming more and more electronic, and software driven, I figured it was worth an ask. I know that a fairly mechanical ATS, like the old-school ASCO 300's wouldn't care.

 

[iwire]

Why not? The EM and Life safety panels never lose power.

The required egress lighting can not be supplied from a transfer switch that also supplies optional loads per 700.9(B).

Though you may find a way to do it with the changes in the 2008 700.9(B)

 

[iwire]

Since these things are becoming more and more electronic, and software driven,

I am so much happier with the software driven versions. Assuming I have the instructions.

You can change all sorts of perimeters easily and accurately, you can get histories etc.

There are often field definable alarm contacts available that can be used for all sorts of things, I am sure you could set it up to close a contact the when correct and clean power was detected on the e terminals.

At one site they had an ATS that for over 4 years had seemingly randomly started the gen set and transferring. This was dropping out HIDs to the restrike lamp. The odd thing was the store had two transfer switches with identical control systems both fed from the same panel but it was always the same single ATS that acted up.

Anyway I found that someone had set the voltage imbalance % much tighter on that switch then the other. I restored it to the factory default setting and all has been good since.

 

[chris kennedy]

The required egress lighting can not be supplied from a transfer switch that also supplies optional loads per 700.9(B).

I'm sorry Bob, I'm not following you here. 700.9(B) applies to branch circuits. And whats up with 700.9(B)(1)?

 

[iwire]

I'm sorry Bob, I'm not following you here. 700.9(B) applies to branch circuits.

I don't see the word 'Branch'.

700.9(B) in my words Wiring from an emergency source to emergency loads shall be kept entirely separate unless allowed

And whats up with 700.9(B)(1)?

If 700.9(B)(1) was not there you could not bring the utility power into the emergency transfer switch to land it on the normal terminals. :smile:

 

[chris kennedy]

I don't see the word 'Branch'.

700.9(B) in my words Wiring from an emergency source to emergency loads shall be kept entirely separate unless allowed

I know you love to talk headings.:grin:

II. Circuit Wiring
700.9 Wiring, Emergency System.

Does that say feeders? I know the word branch isn't there but...

If 700.9(B)(1) was not there you could not bring the utility power into the emergency transfer switch to land it on the normal terminals. :smile:

Well I'm glad its there so I don't have to land them all on the neutral bar.

 

[iwire]

Does that say feeders? I know the word branch isn't there but...

Exactly, neither word is there as that section applies to all the circuit wiring from the emergency source (as described in 700.12) all the way to the emergency load.

Well I'm glad its there so I don't have to land them all on the neutral bar.

Well it is handy if you want a working system. :grin:

The rules for emergency systems are much stricter then for legally required or optional standby systems.

 

[iwire]

This image from the IAEI may help

In a nut shell for 2008 they loosened the rules up a little bit.

The IAEI commentary for the above image.

Revision: 700.9(B) Wiring

The general requirements and concepts behind Section 700.9(B) relate to separation between emergency circuits from other than emergency loads, unless in accordance with the allowances provided in this section. Action by CMP-13 results in a new list Item (5) in Section 700.9(B). This additional text clarifies that the original separation requirements from the source to the loads, or from the source-distribution overcurrent protection to the loads, is to be required unless modified by any of the provisions in items (1) ? (5). The revised text will further clarify that it is permitted to supply any combination of emergency, legally required, or optional loads from a single feeder, or from multiple feeders, or from separate vertical sections of a switchboard that are supplied by either a common bus or individually. The use of an overcurrent protective device at the standby source or for the equipment is related to reliability and design. While the new requirements in (5)(b) maintain the highest degree of reliability, the exception to (5)(b) will also permit the use of an overcurrent device at the source or for the equipment. The coordination of the overcurrent protection at the source or for the equipment with the downstream overcurrent protection requirement in this exception will maintain the highest degree of reliability possible while allowing protection for conductors and equipment. The revised text in the main paragraph clarifies that circuits supplying emergency loads are not to be combined in panelboard enclosures with circuits supplying other loads (see figure 17).

From September/October 2006>Analysis of Changes

 

[steveng]

bob, how does this work?

bob, how does this work?

The required egress lighting can not be supplied from a transfer switch that also supplies optional loads per 700.9(B).

Though you may find a way to do it with the changes in the 2008 700.9(B)

if i knew how to draw a single line diagram to describe this wiring.
i would, so here's my attempt to explain what i see, this was wired and has been in use for yrs now. i know its not code, i am changing it to meet code, but i dont understand how it is working now,

1 gen, 480 3ph with ats, 3 pole, neutral not switched, feeding 2 seperate 480 volt panels in 2 seperate bldgs, the gen feeder is tapped before landing on the e terminals in the ats,
the tap feeder goes to bldg a 300 feet underground rmc to double throw switch, the neutral in this feeder is not attached to the panel. this is what is concerning me, this panel is a lighting panel 480 3 phase.

question?

when switched to e power, how can the 277 lighting work with no neutral attached from the gen. is the return current going to the service panel neutral ?


thanks for any help

steve

btw, i did not wire this, someone before my time.