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Ventilation/Air-conditioning system for battery room

Ventilation/Air-conditioning system for battery room

Ventilation/Air-conditioning system for battery room


I just found this site helpful and I hope you guys can help me too.

I am not familiar with the air-conditioning system and exhaust fans.

There's a battery room that will be designed to have a forced ventilation ( using exhaust fan ) and air-conditioned to maintain the temperature within the battery room.

Is it possible that the design for the battery room is having an exhaust fan and its exhaust air, 80% of it, will be recirculated through ducts as an input for A/C, while the remaining 20% of exhaust air will be drawn out from the room. Is there any standard that allow this kind of design?
What kind of air must be inputed to the A/C?

Battery emits hydrogen gas and has a lower explosion limit of 4% by volume. I'm just afraid that there will be a tendency that some H2 gas will go through ducts and accumulate inside the ducts and to the A/C. Though battery type is AGM that emits minimum H2 gas, I'm still afraid if this is a possible design based on standards.

Please advise me. Thanks!

RE: Ventilation/Air-conditioning system for battery room

Put Hydrogen gas sensors in the space, if the concentration hits 2% by volume eliminate the recirculation.  Shut down A/C units and exhaust the space entirely.  You may want to review the appropriate NFPA documents for your situation.  The battery room sounds similar to a telecommunications facility (see NFPA 76).

RE: Ventilation/Air-conditioning system for battery room

What you need to do is figure out what the CFM (cubic feet per minute) requirements of exhausting for this type of room is.  Then be constantly exhausting that amount, and replacing the exhausted amount with outdoor air.  Also, have an H2 sensor connected to a make-up air unit and a second exhaust fan.  So, when the H2 sensor is triggered, the second exhaust fan will turn on with the make-up air unit, to bring the H2 levels down.

RE: Ventilation/Air-conditioning system for battery room

this like a rectifier room in a telco?

RE: Ventilation/Air-conditioning system for battery room

I agree with Walkes...

Design a passive exhaust system to be activated when the H2 sensors alarms at 1% or 2% H2 concentration by volume and also shut down the AC system.

During normal operation the room can be 100% recirculated.

A simple formula we use to calculate the minimum required exhaust CFM is:

CFM = G / P / 60
G = Gassing rate of batteries at worst case condition [ft^3/hr](gassing rate provided by battery MFR)
P = Maximum percentage of H2 concentration allowed. (Our local codes mandates a 1% or P = 0.01)

RE: Ventilation/Air-conditioning system for battery room

Also, make sure the exhaust fan is of spark/explosion construction and the powered by emergency power (if available).


RE: Ventilation/Air-conditioning system for battery room

Whilst AGM batteries tend not to do this, Flooded batteries, when over charged will sometimes emit an aerosol spray of sulphuric acid.
 Can the materials around the area handle this?

RE: Ventilation/Air-conditioning system for battery room

Thank you guys for your replies. Those are very informative.

Though A/C unit cannot be shutdown as it is required to maintain the room temperature for the battery.

Usually, one air flow is used for battery rooms and discharged all air outside. But in this case, large capacity of A/C unit is needed. So to save energy and to reduce the capacity, air is recirculated. Unfortunately, H2 is mixed with air.

Is it possible to have a valve in the duct to close if set percentage of hydrogen is reached then discharge it into the air? And open it once H2 level goes down?

Is it allowed and safe for operation?

Thank you for your time.

RE: Ventilation/Air-conditioning system for battery room

It is possible to have the H2 sensor activate a damper actuator but the important question is whether your local jurisdiction will allow it. Check with your building dept & fire dept.


RE: Ventilation/Air-conditioning system for battery room

Wow! Thank you so much for your replies. I told my boss about putting a hydrogen gas detector. And they are considering and proposing it to the plan. Though I haven't found in NFPA standards that allow for recirculation, but they stated proper ventilation. So I believe, we could work it out.

Thank you guys for your help and God bless!!

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