ERV in Battery Room

[getitdone91]

Looking for thoughts about using an energy recovery ventilator in a VRLA battery room application.
The system will be exhausting to the outside at 1 CFM/sq.ft. continuously, so recovering that energy seems like a no brainer. However, this is a battery room, so certain precautions need to be taken into account, i.e. hydrogen generation. Brief description of my proposed system:
300 sq.ft. room, yields 300 CFM OA & exhaust directly to the outside. Under normal operation, battery room exhaust would go through the ERV prior to exhausting outside. Hydrogen concentration sensors placed inside the room; upon detection (1% by volume), the ERV is powered off and appropriate dampers close, and an spark proof exhaust fan is activated (at 600 CFM) to evacuate the room.
Thoughts?

 

[dbill74]

Are you providing conditioned air to the battery room?
If not, then the ERV application becomes questionable. Need more information about the application, where is this located, are batteries in use or just stored, etc.

 

[getitdone91]

Thanks dbill.
To give a bit more information: this is a UPS room with a battery room adjacent. The UPS room will be conditioned via recirculating air handler. Means of ventilating the battery room is through transfer air from the UPS room. Region is Atlantic City, NJ.

 

[lukaiENG]

Firstly take a read of the code again. It seems like you are using IMC or ASHRAE.
The code(s) present 2 compliance paths, paraphrased these are:
1. the prescribed approach - ventilate to 1 cfm per sf; OR:
2. The engineering approach: prove that you can maintain the H2 concentration below 1% by ventilating at a lower rate (continuously or intermittently on H2 detection) or intermittently at the prescribed rate upon H2 detection.

If you do the prescribed approach you do not need hydrogen detection, you have chosen the simple compliance method and can therefore keep it simple.
There is no need to ventilate over and above the 1 cfm/sf in any circumstance I have ever come across.

I have taken the engineered approach a number of times with different ventilation strategies. This calculation is quite onerous and should be avoided unless it's hugely advantageous (for example a small battery deployment in a large room)

In your case I would put in the constant volume 300 cfm exhaust with your HRV and MUA. Forget the separate exhaust fan, forget the higher flow rate, forget the hydrogen detection.
This ventilation rate is designed to keep you well under the 1% guideline. Unless you have a cruel AHJ this should not be classed as a hazardous exhaust therefore you shouldn't have any issues with fire rating or spark proof motors. Remember the LEL for Hydrogen is 4%.

Fun fact: this section of the code does not actually use the word exhaust. I concede it is in the exhaust section, but all other sections within the exhaust section refer to exhaust whereas for batteries they refer to ventilation.

 

[lukaiENG]

Apologies, I only read the OP.
to dbill74's point, the batteries require close temperature control, typically 77F +/- 2F. a HRV is highly unlikely to achieve this unless you have a super cold UPS room and thermostatic control on your HRV.
If you're making up from the UPS room what is the point of the HRV?
I would put small AC units in the battery room, sized based on the battery heat gain during a discharge/charge event.
I assume you're not exhausting into the UPS room? I assume this is being ducted out of the building.

I'm assuming this is connected to some sort of data center or trading floor. I would revise my original recommendation and state that keep it real simple and just exhaust the space, constant volume. The heat you are throwing away our the exhaust is tiny compared to the other loads in the building. Further to this, in these building types you are typically trying to get the heat out as effectively as you can, the heat discharged by the battery exhaust will be helpful, albeit a drop in the ocean.
If you really want to minimize the heat loss, take the engineering approach.

 

[getitdone91]

Thanks @lukaiENG:
You are spot on with your assumptions. To "clear the water" a tad more... the plan is to have a small A/C unit in the UPS room for purpose of cooling the UPS equipment. The purpose of the ERV is a source bringing OA into the UPS room, as well as exhausting (ventilating) the battery room.

Attached is a quick diagram that hopefully explains the system.
Orange = Air handler and duct work
Red = ERV with supply and exhaust duct work

 

[lukaiENG]

What benefit does the HRV give you though?
in the winter you're better to bring in OA directly as it will aid your cooling. (unless you have extreme cold conditions)
in the summer you might sensibly trim the OA condition slightly but this will be pretty negligible as your HRV approach will be small.
It won't hurt to include it, but it seems like you have a lot more equipment/complexity than you probably need.

 

[SAK9]

These days sealed batteries are in use so they do not give off hydrogen.Please speak to your electrical engineer and first understand what type of batteries are used.As already said there is no need for HRV unless mechanical cooling/heating is used in single pass systems.There is no justfication to use HRV air qty is less than 1000 l/s

 

[lukaiENG]

SAK9. your first statement is incorrect.
"Sealed" lead acid batteries is a common term for valve regulated lead acid batteries. VRLA batteries which require ventilation per every code I know.
VRLA batteries release significantly less hydrogen than flooded lead acid however this does not mean you don't need to ventilate them. The NEC references battery room ventilation and actually required you treat VRLA batteries the same as FLA.
VRLA is the current industry standard battery technology for UPS battery systems although Li-ion are slowly being adopted as the battery monitoring/control technology is developed/proved for the application.

I agree that the HRV is overkill

 

[SAK9]

LukaiENG:

VRLA battery rooms do not require mechanical ventilation.Please see attached recommendation from a manufacturer.

 

[getitdone91]

@SAK9: thanks for the replies. I'm familiar with that white paper, and am aware that the H2 generation from VRLA batteries is minimal. Like the white paper states, the ventilation of an occupied space is typically greater than the ventilation requirements for H2 generation from VRLA (1% by volume). However, this doesn't apply in unoccupied spaces where mechanical ventilation is not required and may not exist. Therefore, per IMC, ventilation must be provided to keep the H2 concentration less than 1%, or simply ventilate at 1 CFM/sqft.

 

[lukaiENG]

SAk9. you miss the point. There are code requirements to ventilate (or prove you don't need to) battery rooms for hydrogen, even if it is technically not required. The white paper you cited actually echos this if you read until the end.

I'm all for taking the engineered and practical approach, but you still have to obey your local codes.

IMC code reference (as an example)

http://publicecodes.cyberregs.com/icod/imc/2012/icod_imc_2012_5_par017.htm

 

[miningman]

Never mind the codes...... what happens when the hydrogen concentration sensors mal function???

 

[SAK9]

I have worked on projects in Australia,UK,Singapore and the Middle East where IMC is not in use.The battery rooms were air conditioned with an FCU and there was no ventilation air supply.This is just a case of codes not keeping with changes in technology.

 

[SAK9]

Have a read through this report as well which questions the need for dedicated ventilation for sealed battery rooms

 

[FreddyNurk]

SAK9, the relevant battery installation standards in Australia (AS3011, AS2676), which are typically called up by the governing electrical standard (AS3000), still require ventilation for VRLA installations. Admittedly, the standards have not been updated for some time, and do not provide any guidance for lithium chemistry types, but are still required to be complied with.

 

[SAK9]

AS 2676 has really kept pace with technological evolution,it was last updated in 1992

 

[urgross]

Instead of asking for opinions, have you considered doing a life cycle cost analysis?

 

[lukaiENG]

BS EN 50272-2 covers battery room ventilation. It's actually more prescribed than the American standards (IMC etc). I had to use the methodology outlined in here to prove the battery rooms I designed were not going to blow up on my last project in the UK.
As FreddyNurk pointed out there are Australian standards as well. I'm sure with a little digging you would find standards for Singapore and Middle East locations as well.

My point is, you are professionally/legally/ethically obliged to follow the codes for your jurisdiction. You can prove that you don't need ventilation for some spaces - I've done it myself - you need to prove it though. You can't just ignore the code and say "she'll be right".