Seems I dabbled in this a while ago, but few folks agree with what I came up with.. kinda felt like the messenger running for his life.. I forget the exact verbiage, but As I recall, all the NEC really requires is that "all live parts be protected", and that Batteries be provided with a positive means to disperse flammable gases (Ventilated). It also defines an environment that contains flamable vapor as a Class I location, and an environment that rely solely on mechanical means (which could fail and create a Class I location) as a Class I Division II location. (please don't make me relookup these code references-- I want to go outside and play). Seems I looked into it some, and in some other Code section (NFPA 70?), they require that if you do rely on a fan to mitigate an explosion hazard, it must be rigged with a monitor, and a warning light to indicate a failure.
I will tell you that the nasty battery messes I've gotten to honors of squeegeeing up, have been ones where the vent fan failed or was never set up right to begin with. It defies logic to button up a battery box and expect a $2.00 fan to toke enough on the seals to disperse nasty vapors (especially from a larger battery bank). these things need inlet air from someplace. they need an air flow... and to compound things, being in the cellar, they usually get to duke it out with the heating systems or kitchen/bathroom exhaust.. or the rest of the house in general.. like an open window on the third floor?
If I can swing it, I try to incorporate my battery ventilation program into the whole house air flow (Fire Fighting 101).. I also try to make it "fail safe", I'd rather have "bad smells" if it fails, rather than allowing it to concentrate and create an explosive condition.
My battery "Enclosures" usually look more like a screened in range hood.. with the fixed part of the hood hinged (protecting "live" parts of the battery) and slanted so's folks can't stack things on top of it.
I'd rely more on mechanical ventilation, to enhance existing air flow, rather than fight it. My goal (and I believe the intent of the NEC) is to simply disperse battery gases to a non volatile state.
As for creatively interpreting the the NEC, it just seems wrong to apply the code when it's convenient, and get defensive when it's not. Let's be rational. Flammable Vapor is Flammable Vapor. and Explosive condition is an Explosive condition.
I'm gonna go play.. . Happy new year everybody. the Sun returns
db
Dan Brown
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564
www.Foxfire-Energy.com
NABCEP #092907-44
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564
www.Foxfire-Energy.com
NABCEP #092907-44
-------- Original Message --------
Subject: [RE-wrenches] battery venting
From: JRQ <quackkc...@yahoo.com>
Date: Sun, January 01, 2012 1:03 am
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
So, is it best to use a DC fan or an AC fan? Should I run it on a relay, or just run it all the time? What conditions would a relay be set to: whenever the battery is at the absorption voltage or higher? A small 12V fan (which may or may not be brushless) wouldn't be a big power draw, but I'm worried something larger would be a bad parasitic load if run all the time. Would the main thing that it be near the diameter of the vent pipe?Also: does anyone have a rule of thumb for the maximum angle of the vent pipe from plumb? 45˚? 60˚?Thanks,Jeffrey Quackenbush
NABCEP Certified PV InstallerPeripatetic Solar Technician
From: bob ellison <reelli...@gmail.com>
To: 'RE-wrenches' <re-wrenches@lists.re-wrenches.org>
Sent: Sunday, January 1, 2012 5:06 AM
Subject: Re: [RE-wrenches] battery venting
Mount a BRUSHLESS fan inside the box blowing out into the pipe, do not
pressurize the box, that will blow gasses into the room, it is bound to
leak. Use screened vents to keep out the critters.
I use a Carlon 6x6x4 box to mount the fan and vent, also don't mount the
relay if you use one, in the battery box. Things night go bang!
Going back to the woods!
Happy New Year!
Later,
Bob
-----Original Message-----
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Exeltech
Sent: Saturday, December 31, 2011 5:17 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] battery venting
Hello Jeffrey,
Since you're working under constrained conditions for the install, and
apparently have little option on using the flooded/vented batteries, here
are some suggestions that may help:
1) Do your best to ensure the battery enclosure is reasonably sealed except
for the outlet vent.
2) Use non-corrosive vent pipe of as large a diameter as is practicable for
your circumstances.
Angle it upwards at all times. A 4% hydrogen concentration can be
explosive.
3) Install corrosion-resistant screening at the vent outlet, and with the
vent oriented in a manner to discourage entry of unwanted anything.
4) Install the vent fan on the fresh-air inlet side of the box. The inlet
itself should be located below the tops of the batteries, and at the
opposite end from the vent. Screen the inlet to keep critters and anything
else from getting in.
This accomplishes several goals:
a) Keeps the fan and its mechanics out of the corrosive flow; b) Eliminates
any possibility of a spark occurring in the hydrogen; c) Locates the fan
into a "friendlier" atmosphere, reducing its exposure to insects and other
accumulating junk;
d) Makes the fan easier to service/replace if it
*should* fail.
Happy New Year to all.
Dan
> --- On Sat, 12/31/11, Richard L Ratico <richard.l.rat...@valley.net>
> wrote:
>
> From: Richard L Ratico <richard.l.rat...@valley.net>
> Subject: Re: [RE-wrenches] battery venting
> To: re-wrenches@lists.re-wrenches.org
> Date: Saturday, December 31, 2011, 1:47 PM Huh??? I'm probably
> missiing something here.
> What happens when the powervent fails???
> I replace it with another, the same thing I do when other equipment in
> our whiz bang industry fails.
>
> The difference with the powervent is that it is easy and relatively
> inexpensive. I've also had good luck using screens on the vent inlet
> and outlets, per the instuctions, albeit a high tech solution. :-)
>
> Seems inverters, charge controllers,
> batteries, DC breakers, even modules fail more frequenty.
> Rant off.
>
> Dick Ratico
> Solarwind Electric
>
>
>
> --- You wrote:
> Jeffrey,
>
> I'll second Jay's suggestion that sealed AGM batteries are the best
> choice in this circumstance. Presumably this is a grid backup system
> so the poor endurance of AGMs for cycling applications shouldn't be an
> issue. If you use a Zephyr power vent horizontal runs shouldn't be
> problem, but what happens when the power vent fails?
> It will fail. I've seen the bearings wear out on one and another that
> failed when insects got into the blades and gummed it up to the point
> that the motor stalled.
>
> Kent Osterberg
> Blue Mountain Solar, Inc.
> www.bluemountainsolar.com
> t: 541-568-4882
>
>
> On 12/31/2011 6:59 AM, JRQ wrote:
> > Wrenches,
> >
> > I'm looking at a potential battery backup system wtih a 200 AH @48V
> > flooded battery bank in the basement electrical room of a 3 story
> > building.
> > There is a window in the electrical room. The batteries will be
> > located about 10' from an outdoor wall. The building is all
> > reinforced concrete, so I can not run a vent pipe vertically from
> > the batteries. Does anyone have a rule of thumb for how much the
> > vent pipes can be angled from the batteries? Would it be more
> > lenient for short sections of pipe (say <2') versus one long angled
> > piece from the batteries? My instinct would be to keep the pipe no
> > more than 45? from plumb.
> >
> > Or with bending the vent pipe: does anyone have a best-practice rule
> > for the sum of the angles of bends?
> >
> > Thanks,
> > Jeffrey Quackenbush
> > NABCEP Certified PV Installer
> > Peripatetic Solar Technician
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