Generator with nonessential loads

[100eyeballs]

NEC 517.30 talks about Other Loads not discussed shall be served by their own transfer switches. 700.5 says transfer devices shall only be used for emergency loads.

517.30 seems to imply that nonessential (other) loads can be served by the generator as long as they are on a load shedding separated transfer switch that is designed to not overload the generator.

Is this a correct interpretation?

 

[chris kennedy]

That is correct.

 

[jar546]

Yeah, whatever Chris says goes. He should be an inspector but can't take the pay cut.

 

[RJJ]

So what if the generator is sized to handle all loads? Is a second transfer switch needed to separate non essential loads??

 

[peach]

we did inspections at the new NPR facility in DC; switching to generator power was just like being on normal power.. everything was automatically transferred.

More than one generator, but all switched automatically.

it's a matter of how much they want to spend.

 

[Architect1281]

A Generator sized to handle all loads must have 2 sections one for EMERGENCY SYSTEM POWER, LIfe Safety Fire Alarm Emenrgency LIghting those types of systems and those must be seperated from desired but NON EMERRGENCY SYSTEM (Backup when the power goes out) the semantics of emergency, necessary, etc are treaded differently in in the NEC and our applicants are constantly confused, to them its an emergenct when the power goes out if they can't make the coffee; (me too) but necessary to function life safety items are different and when combined if there is a shift of production or draw the desired power must come down to maintain the emergency (CODE REQUIRED) systems going till the fuel supply runs out

 

[chris kennedy]

Health care facilities around here will normally have 3 ATS's served by one genny. LS, Critical, and stand-by. All is well as long as genny can handle all loads served.

 

[100eyeballs]

So it sounds like a general agreement that as long as the generator is sized to handle all loads, there's no reason why nonessential loads can't be placed on the generator (assuming all the appropriate measures are taken in the system design). How then do we reconcile 700.5 which says transfer devices shall only be used for emergency loads? This implies that nonessential loads can not be on a transfer switch, where 517.30 says they can. What am I missing?

 

[chris kennedy]

700.5(D) is specific to Emergency Systems. Examples of transfer switches used for other systems can be found right down the road in 701.5 and 702.5.

 

[RJJ]

Chris: went back and check some plans from the past and one from last year. They all have multiple transfer switches. I suppose my questions were just lack of memory. So many plans, so many codes sometimes creates confusion.

 

[100eyeballs]

I think I'm catching up. When we look at the nice Figure 517.30 we see that the Life Safety and Critical Branch are the "Emergency System" and the Equipment System is not part of that. So 700.5 is referring only to the Life Safety and Critical branches and those transfer switches can't have nonessential loads on them, but non-essential loads can be brought off the generator as described by 517.30's "Other Loads" section.

 

[north star]

= ~ | ~ =

Recently, I had a dental office project [ anesthetizing ] where a generator was going

to be installed.............I seem to recall that there is a section in NFPA-99 that requires

the generator to activate the LS circuits within 10 seconds of loss of normal power.

Can someone please locate that section in NFPA-99 for me ? ..or is it in Article

517 [ in the `08 NEC ] ?

Thanks !

= ~ | ~ =

 

[Gregg Harris]

= ~ | ~ =Recently, I had a dental office project [ anesthetizing ] where a generator was going

to be installed.............I seem to recall that there is a section in NFPA-99 that requires

the generator to activate the LS circuits within 10 seconds of loss of normal power.

Can someone please locate that section in NFPA-99 for me ? ..or is it in Article

517 [ in the `08 NEC ] ?

Thanks !

= ~ | ~ =

517.31 Emergency System. See related ROP

Those functions of patient care depending on lighting or appliances that are connected to the emergency system shall be divided into two mandatory branches: the life safety branch and the critical branch, described in 517.32 and 517.33.

The branches of the emergency system shall be installed and connected to the alternate power source so that all functions specified herein for the emergency system shall be automatically restored to operation within 10 seconds after interruption of the normal source. [99:4.4.2.2.2.1, 4.4.3.1]

 

[north star]

: 8 : 8 :

Much Thanks Gregg !

: 8 : 8 :

 

[Gregg Harris]

: 8 : 8 :Much Thanks Gregg !

: 8 : 8 :

vobis sunt grata, delectatio mea

 

[JPohling]

totally needed the translator for that, but its good to get a little latin lesson.