Battery Charger for Generator

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Shujinko

Shujinko

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Does the battery charger for the start up batteries of an emergency generator have to be on emergency power? From my interpretation of NFPA 110 7.12.5 it would need to be, however some of my colleagues disagree with me. Is there any other codes that address this? As always all help is appreciated.
 
when I say on emergency power I mean connected to emergency power....just a clarification that's it. :0)
 
NEC 700.12 (B)(4) (and it's subsequent explanation in the NEC handbook) basically says that the battery chargers for starting batteries DON'T need to be on emergency power. The only reason the battery charger would have to be on emergency power is if the gen set does not have an alternator that keeps recharging the batteries during operation. In this case the battery charger would have to be on emergency power as it's charging function would be critical for the emergency generator to operate properly. In my situation the emergency generator has an alternator.

Now my question is when wouldn't a emergency generator have an alternator? How would the battery charger and batteries function in that instance? I haven't ever run into that situation? I'm a bit perplexed.
 
If the generator doesn't have an alternator then I would say a battery charger would have to be supplied by both power when the engine is not running and when it is, other wise a lead acid battery will run down on its own.

Also for stand by charging I would recommend using a float type charger, this type maintains the battery at float voltage and extends the battery life the longest.

Putting the charger on the panel that the transfer switch serves to me is the best way so that the charger is charging both when the generator is running and when its not, most generators will have an exorcizer, where the generator starts up and runs like once a week, but these short run times might not fully charge the battery back up.

Also a float charger is also called a battery maintainer.
 
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Shujinko said:
NEC 700.12 (B)(4) (and it's subsequent explanation in the NEC handbook) basically says that the battery chargers for starting batteries DON'T need to be on emergency power. The only reason the battery charger would have to be on emergency power is if the gen set does not have an alternator that keeps recharging the batteries during operation. In this case the battery charger would have to be on emergency power as it's charging function would be critical for the emergency generator to operate properly. In my situation the emergency generator has an alternator.

Now my question is when wouldn't a emergency generator have an alternator? How would the battery charger and batteries function in that instance? I haven't ever run into that situation? I'm a bit perplexed.
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You need to reread 700.12(B)(4)
(4) Battery Power and Dampers. Where a storage battery
is used for control or signal power or as the means of
starting the prime mover , it shall be suitable for the purpose
and shall be equipped with an automatic charging means
independent of the generator set. Where the battery charger
is required for the operation of the generator set, it shall be
connected to the emergency system. Where power is required
for the operation of dampers used to ventilate the
generator set, the dampers shall be connected to the emergency
system.
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I don't know what the handbook says but the hand book is unenforceable. It plainly tells you the generator SHALL be equipped with independent charging means and it SHALL be connected to the emergency system. Most of the generators today are full of electronics that need continuous power. With out an independent source the battery would be drained in a number of hours. On the Generac units we have with the H panel if the charger goes out it will kill the battery in 6-8 hours, the E panels can go for 12-14 hour. The generator engine will have an alternator that will charge while it's running and let the automatic charger drop out until the generator shuts down and the battery voltage drops. Just for clarity what application is this generator going to be use for?
 
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ceb58 said:
You need to reread 700.12(B)(4) I don't know what the handbook says but the hand book is unenforceable. It plainly tells you the generator SHALL be equipped with independent charging means and it SHALL be connected to the emergency system. Most of the generators today are full of electronics that need continuous power. With out an independent source the battery would be drained in a number of hours. On the Generac units we have with the H panel if the charger goes out it will kill the battery in 6-8 hours, the E panels can go for 12-14 hour. The generator engine will have an alternator that will charge while it's running and let the automatic charger drop out until the generator shuts down and the battery voltage drops. Just for clarity what application is this generator going to be use for?
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I would not call it quite as 100% plain as you assert. If it is a cranking battery and the engine, once started, can run without it, the independent charging means must be independent of the generator set. Fortunately, connecting it to an emergency load panel that is powered by POCO with a transfer switch seems to meet that requirement too.
I agree that if the battery is also powering controls and is not recharged by an alternator or generator on the engine, it has to have an AC charger that will operate both when the grid is up and when the generator is running.
 
GoldDigger said:
I would not call it quite as 100% plain as you assert. If it is a cranking battery and the engine, once started, can run without it, the independent charging means must be independent of the generator set. Fortunately, connecting it to an emergency load panel that is powered by POCO with a transfer switch seems to meet that requirement too.
I agree that if the battery is also powering controls and is not recharged by an alternator or generator on the engine, it has to have an AC charger that will operate both when the grid is up and when the generator is running.
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:? I think we are in the same book but not same page. If it is an emergency system, by 700.12 (B)(4), it shall have an independent charging system that is connected to the emergency system. The charger must be supplied from a panel that is powered by the emergency generator in the event of a poco failure.
 
We are relocating an existing emergency generator from inside a building to a small stand alone room separate from the building just for the generator. We are extending all connections from the old location to the new location. However, the EC noticed that the battery charger was on normal power and asked the question if it needed to be on emergency. The problem is the closest availability for a 120V branch circuit on emergency power is clear across the building about 300' away. That's the issue. So I specified on the plans to intercept the feeder of the panel feeding the battery charger and connect it to a Emergency distribution panel about 300' away and the owner was very unhappy with the additional costs. This same panel feeds the battery charger, block heater, and emergency lights that are going in the separate structure for the generator.

There is also a diagram in the NEC 2008 Handbook that points at the battery charger and calls it to be powered from ac normal power. Sorry, I only use the handbook I need to see pretty pictures and analytical explanations. :ashamed1:

Does the code require the block heater to be on emergency power???
 
The diagram is a page or two after NEC 700.12(B)(4) in the NEC 2008 Handbook but is taken out in the 2011 version.
 
Shujinko said:
We are relocating an existing emergency generator from inside a building to a small stand alone room separate from the building just for the generator. We are extending all connections from the old location to the new location. However, the EC noticed that the battery charger was on normal power and asked the question if it needed to be on emergency. The problem is the closest availability for a 120V branch circuit on emergency power is clear across the building about 300' away. That's the issue. So I specified on the plans to intercept the feeder of the panel feeding the battery charger and connect it to a Emergency distribution panel about 300' away and the owner was very unhappy with the additional costs. This same panel feeds the battery charger, block heater, and emergency lights that are going in the separate structure for the generator.

There is also a diagram in the NEC 2008 Handbook that points at the battery charger and calls it to be powered from ac normal power. Sorry, I only use the handbook I need to see pretty pictures and analytical explanations. :ashamed1:

Does the code require the block heater to be on emergency power???
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What is the location of this generator, hospital, rest home, what ? Is the location it serves designated by the AHJ as emergency? The reason I ask is so many times people refer to the generators as "emergency" generators. When in reality they are optional stand by. If it truly is an emergency system then I stand by 700.12 (B)(4). How ever it is silent on a block heater. I see no reason for the block heater to run if the generator is running. The generators at our communication sites have a receptacle in the housing for the heater to plug into but the circuit for the battery charger is taped off of the same circuit, that is feed from a panel, that is powered by the generator in the event of a power failure. Even though our sites are for emergency communications they are still deemed by the AHJ as optional systems.
 
This is an educational type occupancy and the generator feeds life safety loads such as emergency lighting and such.
 
If the battery charger is not required for the operation of the generator, it need not be on emergency power.
 
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