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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 <u>fairly</u> clear that we are not required to vent any
batteries to the outside. <br><br>
<b>"480.9 Battery Locations<br>
</b>Battery locations shall conform to 480.9(A), (B), and (C).<br>
<b>(A) Ventilation. </b>Provisions appropriate to the battery
technology<br>
shall be made for sufficient diffusion and ventilation of gases<br>
from the battery, if present, to prevent the accumulation of an<br>
explosive mixture.<br>
Ventilation is necessary to prevent classification of a battery
location<br>
as a hazardous (classified) location, in accordance with<br>
Article 500.<br>
Mechanical ventilation is not mandated. Hydrogen disperses<br>
rapidly and requires little air movement to prevent accumulation.<br>
Unrestricted natural air movement in the vicinity of the battery,<br>
together with normal air changes for occupied spaces or heat<br>
removal, normally is sufficient. If the space is confined,
mechanical<br>
ventilation may be required in the vicinity of the battery.<br>
Hydrogen is lighter than air and tends to concentrate at ceiling<br>
level, so some form of ventilation should be provided at the<br>
upper portion of the structure. Ventilation can be a fan, roof ridge<br>
vent, or louvered area.<br>
Although valve-regulated batteries are often referred to as<br>
“sealed,” they actually emit very small quantities of hydrogen gas<br>
under normal operation and are capable of liberating large
quantities<br>
of explosive gases if overcharged. These batteries therefore<br>
require the same amount of ventilation as their vented<br>
counterparts."<br><br>
I think that the confusion come is with the statement "These
batteries therefore<br>
require the same amount of ventilation as their vented<br>
counterparts." <br><br>
As we see from the statement "Unrestricted natural air movement in
the vicinity of the battery,<br>
together with normal air changes for occupied spaces or heat<br>
removal, normally is sufficient," the concern is with explosive
gasses being restricted to a small area, where explosive concentrations
of hydrogen can build up.<br><br>
The article also has the statement "Provisions appropriate to the
<u>battery technology</u>" which should be taken into account. In
practice, liquid electrolyte batteries stink and emit toxic fumes, so we
do vent these outside. <br><br>
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. <br><br>
Drake <br><br>
<br><br>
<br>
At 12:06 AM 6/22/2014, you wrote:<br>
<blockquote type=cite class=cite cite="">Bob,<br>
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.<br><br>
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.<br><br>
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.<br>
Allan<br><br>
<b>Allan Sindelar</b><br>
<a href="mailto:allan@sindelarsolar.com">allan@sindelarsolar.com</a><br>
NABCEP Certified PV Installation Professional<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
Founder (Retired), Positive Energy, Inc.<br>
<b>505 780-2738 cell</b><br><br>
<br>
On 6/21/2014 1:30 PM, Bob Clark wrote:<br>
<blockquote type=cite class=cite cite="">RE-Wrenches: <br><br>
2014 NEC 480.9 (A) has two informational notes that seem to point to the
possibility of not having to vent AGMs.<br><br>
Here is what I was going to do with 8 Concorde SunXtender Batteries, 6V,
405Ah, L16, PVX-4050HT:<br><br>
1. Put them in a Midnite Solar, MNBE-CL16 Battery Enclosure (which
is not a sealed box) in a “battery closet."<br>
2. Vent the box out of the top of the box and through the wall of
the house with pipes like Kevin Pegg suggests.<br><br>
Do any of you see any problems with this? Venting
unnecessary?<br><br>
One consideration is the “next guy” who occupies this house may want
flooded batteries, in which case, the vent system would definitely be
necessary.<br><br>
Bob Clark<br>
<a href="mailto:bclark@solar-wind.us">bclark@solar-wind.us</a><br><br>
<br><br>
On Apr 4, 2014, at 2:49 PM, Kevin Pegg
<<a href="mailto:kpegg@energyalternatives.ca">
kpegg@energyalternatives.ca</a>> wrote:<br><br>
<blockquote type=cite class=cite cite=""><font size=2 color="#0000FF">Hi
William, <br>
</font> <br>
<font size=2 color="#0000FF">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. <br>
</font> <br>
<font size=2 color="#0000FF">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. <br>
</font> <br>
<font size=2 color="#0000FF">
<a href="http://www.bdbatteries.com/hydrogenventing.php">
http://www.bdbatteries.com/hydrogenventing.php</a><br>
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. <br>
</font> <br>
<font size=2 color="#0000FF">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! <br>
<Outlook.bmp><br>
</font> <br>
<font size=2 color="#0000FF"><Outlook.bmp><br>
</font>
<dl>
<dd><font face="Tahoma" size=2>-----Original Message-----<br>
<dd>From:</b>
<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">
re-wrenches-bounces@lists.re-wrenches.org</a>
[<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" eudora="autourl">
mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]On Behalf Of
</b><a href="mailto:william@millersolar.com">william@millersolar.com</a>
<br>
<dd>Sent:</b> April 4, 2014 9:29 AM<br>
<dd>To:</b> RE-wrenches<br>
<dd>Subject:</b> [RE-wrenches] Batteries in a dwelling<br><br>
</font>
<dd>Friends:<br>
<dd> <br>
<dd>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.<br>
<dd> <br>
<dd>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? <br>
<dd> <br>
<dd>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.<br>
<dd> <br>
<dd>Thanks in advance for the forthcoming, always expert advice.<br>
<dd> <br>
<dd>William Miller<br>
<dd> <br><br>
</dl>_______________________________________________<br>
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