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

Tue Jul 29 10:02:08 PDT 2014

Hey Wrenches

I've run into this on several times, usually this is an installer looking for our help with an inspector...  Most often there isn't much you can do once the inspector digs his heels in.

At Rolls, we suggest that you use active ventilation (aka something like a Zephyr fan installed) with a sloped roof enclosure (to funnel Hydrogen) with Flooded, but with AGM's passive ventilation should be just fine, but again once the inspector has dug in his heels sometimes they'll force you to put in active ventilation regardless of what battery type.

Anything more than a 4% saturation in Hydrogen gases can be explosive, so you want to avoid that number.

I know this doesn't help with the Concorde's, but the rates should be pretty close... With our AGM's we gas at:

When the battery is float charged at 2.3V/cell, the amount of the gas generated will be approx. 0.0187 cc/hr/AH/cell.

When the battery is charged above 2.4V/cell, the amount of the gas generated will be approx. 0.0366 cc/hr/AH/cell.

1cc (Cubic Centimeter) is equivalent to 0.0000353146665722 Cubic Foot.
1 Cubic Meter is equal to 1,000,000 cc or 35.3146665722 Cubic Feet.

Steve Higgins
Technical Services Manager
M: +1.206.790.5840
F: +1.902.597.8447
Surrette Battery Company
Exclusive manufacturer of
[cid:rolls9fd1d0]<http://www.rollsbattery.com>

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Drake
Sent: Tuesday, July 29, 2014 9:01 AM
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<mailto: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<mailto: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<mailto: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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