Emergency Generator Ventilation
Emergency Generator Ventilation
(OP)
I'm new to this forum, and I can't find the code reference I'm looking for. A little background: We have a generator room that is using unconditioned outside air for cooling and combustion air, powered in using fans. There are three (3) generators in the room. I have a good idea of the airflow required, and selected my fans appropriately. However, I know there needs to be a discharge damper on the outlet of the fans. Through using projects with similar scope around the office, I saw that the requirement for the motorized discharge damper is "spring open/power close" as opposed to most dampers on the market. I received a submittal that shows "spring close/power open" which is opposite of what I specified. I seem to remember seeing the "spring open/power close" requirement in NFPA something or another. I haven't been able to find it in NFPA 110, 90, 92, or 70. Any ideas where I could find this control damper requirement, or am I just making this thing up?





RE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
In your case as this is inlet air for an emergency gen set, when, presumably, power has been lost before you fire up the emergency gen sets, the dampers need to be fail open, not fail closed. I doubt this is regulated as each site and location could be different.
Can't see a big deal about reversing the action.
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RE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
kahnman (Mechanical)
Most generator rooms I have worked on have had louvered dampers that have been airflow open, gravity close.
B.E.
You are judged not by what you know, but by what you can do.
RE: Emergency Generator Ventilation
I can't imagine there are many clients who would be happy if their generators failed due to a fault on the low voltage control circuit which energizes the dampers.
On another note, it is a little unusual to have air inlet fans. I guess if you're in a basement or away from accessible exterior walls this might make some sense. The normal design strategy is to have as few active/powered components in the system in order to minimize the risk of failure.
Finally, you want to pay attention to the operation sequence at start up. If your generator and radiator fan start up too quickly you risk damaging the dampers.
RE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
1. prevent sucking in the damper/walls
2. provide some heat to the space when it is very low ambient conditions.
These dampers are normally set to normally open. when the generator has started and the inlet air dampers are open, these dampers will modulate down to maintain a space minimum temperature (closing if it is exceeded)
RE: Emergency Generator Ventilation
- When there is loss of power the generator will start up but it will take time for it to come up to speed AND there is a timer before generator power is transferred to the MCC via the robonic transfer switch. Therefore there will be no power to operate the combustion air fans or the exhaust dampers.
- Meanwhile, combustion air is needed for the generator and during this time the room also kind of gets smoky and hot.
- That is why when there is a power loss the outside air dampers need to spring open to allow combustion air to come in immediately by gravity without the use of power to open a motorized damper
I don’t think there is a code for thisRE: Emergency Generator Ventilation
RE: Emergency Generator Ventilation
Admittedly my applications never had dampers fitted, and it was one generator per room, so making sure that the fans are powered by the correct generator is much easier. Its a different argument in a generator hall with 3 sets, in that case you'd want it the way its specified.
As an aside, are there any competing requirements for dampers and fire suppression, or does that not come up much as no one fits fire suppression (in my case it was never done either)?
I don't have any code references unfortunately, I don't think the codes you referenced were applicable to my location either.