Generator Loading Question?

[steveng]

we have a 28kw 480/277 generator for primarily emergency lighting, it has a 100 amp 3 pole brkr, broadcrown is manufacturer. neutral is switched
ats is asco 100 amp, 2 lighting loads 1 auto switched and 1 manually switched in another bldg.


what is the total load i can put on this 28 kw generator?


28 X 1000 = 28000 / 830 = 33a per phase @ 480vac

28 x 1000 = 28000 / 360 = 77a per phase @ 208vac

i want to feed approx 1600 sq ft area with power and lighting circuits, i am calculating feeding a 10 to 15 kva xfmr 208 3 ph for this additional load.

do i have enough power to do this?

thanks

 

[RUWired]

what is the total load i can put on this 28 kw generator?
thanks

Steve, with a 28 kw generator and a 80% power factor, you have a 35 kva generator.At 480, the maximum load would be 42 amps.A 15 kva transformer at 480 has a full load of 18 amps.

 

[iwire]

we have a 28kw 480/277 generator for primarily emergency lighting, it has a 100 amp 3 pole brkr, broadcrown is manufacturer. neutral is switched
ats is asco 100 amp, 2 lighting loads 1 auto switched and 1 manually switched in another bldg.

If it is really used for 'Emergency Lighting' (Legally required egress lighting) it sounds like you are already in violation of the NEC.

To supply both 'emergency' and 'optional standby' loads with one generator would require a generator with more then one output breaker. Emergency loads must be entirely separate from optional loads, separate panels, separate raceways, separate ATS.

 

[steveng]

iwire,

iwire,

If it is really used for 'Emergency Lighting' (Legally required egress lighting) it sounds like you are already in violation of the NEC.

To supply both 'emergency' and 'optional standby' loads with one generator would require a generator with more then one output breaker. Emergency loads must be entirely separate from optional loads, separate panels, separate raceways, separate ATS.

thanks iwire for the help, what is the violation?

we have 1 gen supplying egress lighting in 2 bldgs, via ats, bldg 1 is auto, bldg 2 is switched manually after gen is on via double pole switch.

 

[bob]

thanks iwire for the help, what is the violation?

we have 1 gen supplying egress lighting in 2 bldgs, via ats, bldg 1 is auto, bldg 2 is switched manually after gen is on via double pole switch.

Iwire stated the violation. Quote "To supply both 'emergency' and 'optional standby' loads with one generator would require a generator with more then one output breaker. Emergency loads must be entirely separate from optional loads, separate panels, separate raceways, separate ATS."

 

[iwire]

Thanks Bob.

The relevant code section is 700.9(B)

Here is a small portion.

2005 NEC part of 700.9(B)

.....Wiring from an emergency source or emergency source distribution overcurrent protection to emergency loads shall be kept entirely independent of all other wiring and equipment....

Further more you said

1 auto switched and 1 manually switched in another bldg.

A manual transfer switch can not be used to supply legally required egress lighting.

Take look at all of Part IV of 700, for that matter I suggest a read of both Article 700 Emergency Systems and Article 702 Optional Standby Systems.

To the NEC there is a major difference between true emergency systems and optional standby systems.

Generators at peoples homes, for data centers, or for the registers and security systems at stores are all examples of 702 optional standby systems.

Generators that supply egress lighting are 700 emergency systems.

At the very least take a look at 700.1 and 702.2, those to sections spell out the differences.

 

[steveng]

thanks for your help guys

thanks for your help guys

thanks bob, thanks iwire.:grin:

iwire, what would be the best way to make this code compliant?

any suggestions?

 

[TDN]

Generator Load

Generator Load

The power factor of the load affects the capability of the generator to hold up its normal voltage. For example if your generator rated 480VAC, 28KW at 0.8 pf (35KVA), and if the pf of your load is lower than 0.8, the generator can no longer deliver its rated full load KVA and KW at rated voltage.

 

[steveng]

The power factor of the load affects the capability of the generator to hold up its normal voltage. For example if your generator rated 480VAC, 28KW at 0.8 pf (35KVA), and if the pf of your load is lower than 0.8, the generator can no longer deliver its rated full load KVA and KW at rated voltage.

thanks tdn,