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
<mailto:al...@sindelarsolar.com>al...@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
<mailto:bcl...@solar-wind.us>bcl...@solar-wind.us
On Apr 4, 2014, at 2:49 PM, Kevin Pegg
<<mailto:kp...@energyalternatives.ca>kp...@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>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:
<mailto:re-wrenches-boun...@lists.re-wrenches.org>re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org]On Behalf Of
<mailto:will...@millersolar.com>will...@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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