[RE-wrenches] Batteries in a dwelling - Venting Concorde AGMs

Glenn Burt glenn.burt at glbcc.com
Tue Jul 29 11:10:05 PDT 2014


Also look to see if the fire code in your state has additional restrictions.

In New York Stat, the 2010 Fire Code contains a section (608) with more
regulations to be heeded when installing 'stationary storage batteries'.

 

-Glenn

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of Drake
Sent: Tuesday, July 29, 2014 12:01 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Batteries in a dwelling - Venting Concorde AGMs

 

This is a reply to a post by Alan from June 21st. I'm replying because I've
had to deal with this issue also. It seems to me that the 2014 NEC Handbook
is fairly clear that we are not required to vent any batteries to the
outside. 

"480.9 Battery Locations
Battery locations shall conform to 480.9(A), (B), and (C).
(A) Ventilation. Provisions appropriate to the battery technology
shall be made for sufficient diffusion and ventilation of gases
from the battery, if present, to prevent the accumulation of an
explosive mixture.
Ventilation is necessary to prevent classification of a battery location
as a hazardous (classified) location, in accordance with
Article 500.
Mechanical ventilation is not mandated. Hydrogen disperses
rapidly and requires little air movement to prevent accumulation.
Unrestricted natural air movement in the vicinity of the battery,
together with normal air changes for occupied spaces or heat
removal, normally is sufficient. If the space is confined, mechanical
ventilation may be required in the vicinity of the battery.
Hydrogen is lighter than air and tends to concentrate at ceiling
level, so some form of ventilation should be provided at the
upper portion of the structure. Ventilation can be a fan, roof ridge
vent, or louvered area.
Although valve-regulated batteries are often referred to as
"sealed," they actually emit very small quantities of hydrogen gas
under normal operation and are capable of liberating large quantities
of explosive gases if overcharged. These batteries therefore
require the same amount of ventilation as their vented
counterparts."

I think that the confusion come is with the statement "These batteries
therefore
require the same amount of ventilation as their vented
counterparts."  

As we see from the statement "Unrestricted natural air movement in the
vicinity of the battery,
together with normal air changes for occupied spaces or heat
removal, normally is sufficient," the concern is with explosive gasses being
restricted to a small area, where explosive concentrations of hydrogen can
build up.

The article also has the statement "Provisions appropriate to the battery
technology" which should be taken into account. In practice, liquid
electrolyte batteries stink and emit toxic fumes, so we do vent these
outside. 

It does sound like different voices have worked their way into this code
section, which can open the way to various interpretations. But, if you look
at the photos in the NEC Handbook of batteries, they are on unenclosed racks
inside of a building. 

Drake 




At 12:06 AM 6/22/2014, you wrote:



Bob,
We had a case in February in which an AHJ insisted that we vent a Midnite
cabinet with a dozen 2V 9150T batteries. We fought it all the way to the
state Technical Advisory Committee, the top arbiter of Code issues. We
fought to a draw: we finally agreed to put in the vent to get our final
passed, and the committee permanently tabled the issue so there is no
precedent set. To continue to fight this would have required bringing in
professional engineers, as some of the committee members were reluctant to
make their own decisions about the issue and wanted to pass the buck. As I
recall, the Zephyr Power Vent was ultimately never hooked up to the Classic
controller's auxiliary, as the necessary work was handled by the GC (rather
than by us) at a quite remote location. The challenge to the AHJ was a pain
in the butt, although we were paid by the clients for the effort, as they
agreed with the absurdity of the inspector's demand.

I have attached a few documents I gathered and prepared in this case. You do
not need to vent AGMs if the larger space in which the battery enclosure is
located has a typical and normal amount of natural air circulation and
convective air exchange. Also, you can't duplicate what Kevin describes
below with a vented enclosure - Kevin's approach requires a "sealed and
vented battery enclosure". By design, your enclosure is unsealed.

Putting in vents "for the next guy" also makes no sense. If you install 8
flooded L16s on two shelves in a Midnite MNBE-Cl16 enclosure, you won't be
able to routinely add water to the cells. The cabinet was designed and built
for VRLA batteries. So any venting you install now would have to be redone
to fit a cabinet built for flooded batteries with top access.
Allan

Allan Sindelar
allan at sindelarsolar.com
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
505 780-2738 cell

 
On 6/21/2014 1:30 PM, Bob Clark wrote:



RE-Wrenches: 

2014 NEC 480.9 (A) has two informational notes that seem to point to the
possibility of not having to vent AGMs.

Here is what I was going to do with 8 Concorde SunXtender Batteries, 6V,
405Ah, L16, PVX-4050HT:

1.  Put them in a Midnite Solar, MNBE-CL16 Battery Enclosure (which is not a
sealed box) in a "battery closet."
2.  Vent the box out of the top of the box and through the wall of the house
with pipes like Kevin Pegg suggests.

Do any of you see any problems with this?  Venting unnecessary?

One consideration is the "next guy" who occupies this house may want flooded
batteries, in which case, the vent system would definitely be necessary.

Bob Clark
bclark at solar-wind.us



On Apr 4, 2014, at 2:49 PM, Kevin Pegg < kpegg at energyalternatives.ca
<mailto:kpegg at energyalternatives.ca> > wrote:




Hi William, 
 
In the cold north here in Canada, this is the most common way we install
batteries - within the heated envelope of a home or shop, installed in a
sealed & vented battery enclosure.  
 
Hydrogen is easy to vent as it is lighter than air. We use a process similar
to below. I see a lot of installations with power vents that are not done
properly - exhaust only but no intake as example. They can also fail. Or
installed in such a way that outside wind influences could actually reverse
the flow and pressurize the battery box! Air flow needs to be balanced. 
 
http://www.bdbatteries.com/hydrogenventing.php
To remove the thermal air currents present in a battery box venting system,
you must create a natural heat sink between the vent tubes to neutralize the
difference in temperature. This in turn will stagnate the air, allowing the
hydrogen which is lighter than air, to rise and escape the battery box. Make
sure the smaller tube, the one inside, extends to the bottom of the box.
This will allow "heavier" fresh air to fall to the floor of the box and
retard hydrogen entry. The intake for the hydrogen is at the top of the box,
the exterior tube in the system. Hydrogen will travel in the opposite
direction through the larger outer pipe as it is lighter than the air
surrounding it. Several good methods for constructing this vent system
exist, we particularly like to see 1/2 inch copper pipes inside 1 inch pipe.
Any highly conductive metal pipe will work it will transfer heat quickly.
Galvanized, steel, and other pipes that spark when rubbed aren't as great.
DO NOT USE THESE IN EARTHQUAKE ZONES. 
 
DO NOT USE PVC FOR THIS VENT SYSTEM....PVC DOES NOT CONDUCT HEAT WELL
ENOUGH! Copper, aluminum, and other non sparking conductive metals are
great! 
<Outlook.bmp>
 
<Outlook.bmp>

-----Original Message-----

From: re-wrenches-bounces at lists.re-wrenches.org [
mailto:re-wrenches-bounces at lists.re-wrenches.org
<mailto:re-wrenches-bounces at lists.re-wrenches.org> ]On Behalf Of
william at millersolar.com 

Sent: April 4, 2014 9:29 AM

To: RE-wrenches

Subject: [RE-wrenches] Batteries in a dwelling

Friends:

 

I am proposing installation of vented batteries in a first floor garage of a
dwelling.  The dwelling areas are on the second floor.  I am nervous about
the cohabitation of batteries and humans.

 

I reviewed the NEC and could not find any prohibition.  Do any of you have
any advice on how this is accomplished in the mot safe manor?  

 

I presume good ventilation and an otherwise sealed room are advised.  I will
propose additional smoke detectors, locked doors and I will research
hydrogen detectors.  A good spill kit and all PPE will be staged as usual.

 

Thanks in advance for the forthcoming, always expert advice.

 

William Miller

 

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