Emergency Lighting Load for Generator Sizing
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Re: Emergency Lighting Load for Generator Sizing
Square feet won't work. Try counting the fixtures.
Generators don't have much wiggle room.
Square feet won't work. Try counting the fixtures.
Generators don't have much wiggle room.
Re: Emergency Lighting Load for Generator Sizing
Can't count fixtures. Problem is that someone a few years back took out the em lighting for the 5th and 6th floors and replaced with battery packs. This does not currently meet code and this load will need to be accounted for in the sizing.
Can't count fixtures. Problem is that someone a few years back took out the em lighting for the 5th and 6th floors and replaced with battery packs. This does not currently meet code and this load will need to be accounted for in the sizing.
Re: Emergency Lighting Load for Generator Sizing
Also, this is a building that is over 100 years old. There is no telling if the existing em ltg is actually equal to the current footcandle requirements of the code. Which is what we want to size the generator for so that as they renovate parts of the building, the new EM ltg will be able to comply and still fit on the generator.
We use the 1/3 va/sf for rough sizing of generators when we start projects, before the actual lighting load is known. I can't recall it ever being low, but in some cases it does come out a little high. So that is why i am asking for what others do.
Also, this is a building that is over 100 years old. There is no telling if the existing em ltg is actually equal to the current footcandle requirements of the code. Which is what we want to size the generator for so that as they renovate parts of the building, the new EM ltg will be able to comply and still fit on the generator.
We use the 1/3 va/sf for rough sizing of generators when we start projects, before the actual lighting load is known. I can't recall it ever being low, but in some cases it does come out a little high. So that is why i am asking for what others do.
Re: Emergency Lighting Load for Generator Sizing
typically use a .5W/sf for the emerg ltg. In MA we only need to provide 1FC of lighting for egress. why are the battery packs against code? is this a local code?
[ April 07, 2004, 12:30 PM: Message edited by: bwyllie ]
typically use a .5W/sf for the emerg ltg. In MA we only need to provide 1FC of lighting for egress. why are the battery packs against code? is this a local code?
[ April 07, 2004, 12:30 PM: Message edited by: bwyllie ]
Re: Emergency Lighting Load for Generator Sizing
high rise in chicago. Has to have 4 hour gen or inverter. The load is too much to make an inverter practical. We are also going for 1 FC. It has been our experience on new jobs that equals about .33 va/sf. I have heard other engineers say .5 va/sf though also.
high rise in chicago. Has to have 4 hour gen or inverter. The load is too much to make an inverter practical. We are also going for 1 FC. It has been our experience on new jobs that equals about .33 va/sf. I have heard other engineers say .5 va/sf though also.
Re: Emergency Lighting Load for Generator Sizing
I don't have floor plans for any floor but the basement. I know the SF and the type of space that they are. I walked through the building. But it is kind of like sizing a service for a building, the code gives you a VA/SF as minimum service size, no matter how little lighting you actually put in. The space layouts change from open office to many small offices with corridors. The layout of em lighting will change also. I have some extra power on the generator anyways, just because of the sizes between generators. I actually end up closer to .5va/sf of power available.
I don't have floor plans for any floor but the basement. I know the SF and the type of space that they are. I walked through the building. But it is kind of like sizing a service for a building, the code gives you a VA/SF as minimum service size, no matter how little lighting you actually put in. The space layouts change from open office to many small offices with corridors. The layout of em lighting will change also. I have some extra power on the generator anyways, just because of the sizes between generators. I actually end up closer to .5va/sf of power available.
Re: Emergency Lighting Load for Generator Sizing
I don't understand how an existing building can have a undetermined load.
Is this a remodel? Has the design engineer ever done a building like this? Or is this a design and build? If this is a design and build, there should be enough money in the budget to hire a design engineer.
I don't understand how an existing building can have a undetermined load.
Is this a remodel? Has the design engineer ever done a building like this? Or is this a design and build? If this is a design and build, there should be enough money in the budget to hire a design engineer.
laengineer
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Re: Emergency Lighting Load for Generator Sizing
I'm not sure what building code Chicago is under, but I presume that this high rise building will have to have at least one elevator, stair pressurization fans and a fire pump on the generator as well as the emergency lighting. If you assume 0.5va/sf or 1va/sf, the lighting load will have a negligible impact on the size of the generator. The proper way is to obtain floor plans and spot the fixtures that you want to be on emergency and run new circuits to each of those fixtures.
I'm not sure what building code Chicago is under, but I presume that this high rise building will have to have at least one elevator, stair pressurization fans and a fire pump on the generator as well as the emergency lighting. If you assume 0.5va/sf or 1va/sf, the lighting load will have a negligible impact on the size of the generator. The proper way is to obtain floor plans and spot the fixtures that you want to be on emergency and run new circuits to each of those fixtures.
Re: Emergency Lighting Load for Generator Sizing
chicago has its own version of the 1999 NEC. They require all high rise buildings to have 4 hour source(generator or inverter) for EM power. For buildings built before 1975, you only need em ltg and exit signs on the EM source. The load on this building is too large to make an inverter practical.
Bennie, there is never enough money in the budget for engineering fees. The owners only want to pay the bare minimum.
The point is, that the use of the building changes and the space gets built out differently. So spotting lights only gives you what would work today as configured. So that is about as useful as a SF estimate. We are increasing the overall em service from a 100A, 1phase to 100A, 3phase just because of generator sizes, voltage availabilities and the such. So I am confident that the generator is plenty big for the load.
chicago has its own version of the 1999 NEC. They require all high rise buildings to have 4 hour source(generator or inverter) for EM power. For buildings built before 1975, you only need em ltg and exit signs on the EM source. The load on this building is too large to make an inverter practical.
Bennie, there is never enough money in the budget for engineering fees. The owners only want to pay the bare minimum.
The point is, that the use of the building changes and the space gets built out differently. So spotting lights only gives you what would work today as configured. So that is about as useful as a SF estimate. We are increasing the overall em service from a 100A, 1phase to 100A, 3phase just because of generator sizes, voltage availabilities and the such. So I am confident that the generator is plenty big for the load.
Re: Emergency Lighting Load for Generator Sizing
Real easy, the meter is not a demand type meter. There are no existing plans of what was installed. The building has been changed many times, it is over 100 years old. And no one has done a complete survey of every single lighting fixture to determine the circuit it is connected to. Therefore it is undetermined. Could it be determined? Yes, but at an expense that the owner does not want to pay for.
Re: Emergency Lighting Load for Generator Sizing
I know what the best way is. That would be to determine all the loads and size the generator. But the question is, WHAT DO YOU AS AN ENGINEER USE AS A VA/SF FOR EM LIGHTING LOADS TO SIZE A GENERATOR UNTIL THE LOADS ARE KNOWN?
This is useful also for budget pricing when an architect asks how big a generator is needed for a certain building. YOu can give them a guestimate based on the SF they give you.
I know what the best way is. That would be to determine all the loads and size the generator. But the question is, WHAT DO YOU AS AN ENGINEER USE AS A VA/SF FOR EM LIGHTING LOADS TO SIZE A GENERATOR UNTIL THE LOADS ARE KNOWN?
This is useful also for budget pricing when an architect asks how big a generator is needed for a certain building. YOu can give them a guestimate based on the SF they give you.
Re: Emergency Lighting Load for Generator Sizing
All that is needed to determine the lighting load on the Empire State Building is a clamp on ampmeter, pencil, paper, screwdriver, a forefinger, and some time.
This is a piece of cake for a 5 story building.
I must be missing something.
All that is needed to determine the lighting load on the Empire State Building is a clamp on ampmeter, pencil, paper, screwdriver, a forefinger, and some time.
This is a piece of cake for a 5 story building.
I must be missing something.
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Re: Emergency Lighting Load for Generator Sizing
How can there possibly be a sq ft number.
Every building we do with generators applies them differently.
One building may use the generator to light just the bare minimum fixtures to keep the AHJ happy, the next building may light 50% of the fixtures so power failures do not effect normal operations.
Bennie's suggestion, Data loggers or making a list are the only way I would think you could do it.
How can there possibly be a sq ft number.
Every building we do with generators applies them differently.
One building may use the generator to light just the bare minimum fixtures to keep the AHJ happy, the next building may light 50% of the fixtures so power failures do not effect normal operations.
Bennie's suggestion, Data loggers or making a list are the only way I would think you could do it.
Re: Emergency Lighting Load for Generator Sizing
I agree the BEST way to do this is to meter the lighting however the building is over 100 years old so who knows if the lighting is fed from a one panelboard or multiple panelboards. Plus, there is no em ltg on the 5th and 6th floors so metering will not help you there. The metering of the other floors would give you a base va/sf, but who knows what the em ltg was designed to on that floor. The original question is what is typical va/sf that is used to size the em ltg load for a generator when the lighting is not known. Sometimes the best way of doing things is not always practical or can be time consuming and you must use good engineering figures, such as the .5va/sf. which would give you a good ballpark load for the lighting.
I also agree the va/sf number will change based upon what you are lighting for , i.e. em egress ltg or normal bldg operation. but the question that was asked, that we have gotten away from, is what is a typical va/sf for em ltg when sizing a generator when the lighting is not known.
[ April 21, 2004, 09:52 AM: Message edited by: bwyllie ]
I agree the BEST way to do this is to meter the lighting however the building is over 100 years old so who knows if the lighting is fed from a one panelboard or multiple panelboards. Plus, there is no em ltg on the 5th and 6th floors so metering will not help you there. The metering of the other floors would give you a base va/sf, but who knows what the em ltg was designed to on that floor. The original question is what is typical va/sf that is used to size the em ltg load for a generator when the lighting is not known. Sometimes the best way of doing things is not always practical or can be time consuming and you must use good engineering figures, such as the .5va/sf. which would give you a good ballpark load for the lighting.
I also agree the va/sf number will change based upon what you are lighting for , i.e. em egress ltg or normal bldg operation. but the question that was asked, that we have gotten away from, is what is a typical va/sf for em ltg when sizing a generator when the lighting is not known.
[ April 21, 2004, 09:52 AM: Message edited by: bwyllie ]
Re: Emergency Lighting Load for Generator Sizing
When I Do Electrical Budgets For New Construction Or Remodels And The Narrative States That They Need A Generator But Do Not List A Size I Will Plug In 1 va/SF And Then Round Up To The Next Higher Standard Size. This Ususally Covers All MDF / IDF Rooms And Anything Else That The Owner May Want. If I am Just Doing Emergency Lighting I Will Use About .3 va/SF.
-Ed
When I Do Electrical Budgets For New Construction Or Remodels And The Narrative States That They Need A Generator But Do Not List A Size I Will Plug In 1 va/SF And Then Round Up To The Next Higher Standard Size. This Ususally Covers All MDF / IDF Rooms And Anything Else That The Owner May Want. If I am Just Doing Emergency Lighting I Will Use About .3 va/SF.
-Ed
laengineer
Member
Re: Emergency Lighting Load for Generator Sizing
What does the Chicago code require for a high rise building? Is there a fire pump? I agree with the 0.5 VA/SF criteria. It is a very conservative quantity. I suspect that you will have other large motor loads on the generator. What does the building code require? For example the Standard Building Code which is the governing code in Louisiana says that at least one elevator be connected to emergency power with the capability to transfer the power to any other elevator in the building. It also requires a fire pump and stairwell pressurization fans. With this load, the amount of emergency lighting load is not really relevant. Something to consider, you may want to check into the motors that the generator has to supply.
What does the Chicago code require for a high rise building? Is there a fire pump? I agree with the 0.5 VA/SF criteria. It is a very conservative quantity. I suspect that you will have other large motor loads on the generator. What does the building code require? For example the Standard Building Code which is the governing code in Louisiana says that at least one elevator be connected to emergency power with the capability to transfer the power to any other elevator in the building. It also requires a fire pump and stairwell pressurization fans. With this load, the amount of emergency lighting load is not really relevant. Something to consider, you may want to check into the motors that the generator has to supply.
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