Equipment Enclosure Ventilation

Roger Thoms · May 2015

I'm in the process of installing a new off grid system and am trying to figure out the best solution for ventilation for the equipment enclosure. The enclosure, which is basically a small shed built onto the back of the house, holds a Magnum MS4024PAE inverter and two Tristar TS-MPPT-60 charge controllers.

I'm thinking of using 24V fan with a simple thermostat to turn it on and off. That way the fan could run while the inverter was in stand by and keep the charge controllers cool.

So far I have found quite a few pancake/computer style fans. I was thinking one or possibly two 4" dia. fans at the top of the north facing wall with corresponding makeup vents at the bottom of the wall. Am I on the right track? I would also appreciate any recommendations on fans and thermostats.

Roger

BB. · May 2015

Can you just have screen vents (one set down low, a second mounted high) and get natural air circulation--When you add fans, thermostats, etc...-- Things can go wrong; Plus fans are an electrical draw--And if you can avoid the electrical fans with natural air circulation, the better off you would be.

-Bill

Dave Angelini · May 2015

If there are batteries in there you will need to do this safely also ! Even sealed batteries must have some form of protection in small spaces.

Roger Thoms · May 2015

The batteries (sealed AGM) are in a seperate enclosure. I'm planning on venting that too. I don't know if heat will be a problem in the battery compartment.

The passive approach sounds good and I will try that first, then add a fan if needed. My gut tells me that I'm going to need a fan which is why I was hoping to find out what other people are using. I should have the everything up and running this weekend so I'll have a better idea of what is needed.

BB. · May 2015

Batteries "want" to be around room temperature... For every 10C (18F) increase in temperature, they age 2x faster (a battery bank at 35C or 95F will last 1/2 as long). And near freezing and below, the batteries have much less energy available.

In general AGM batteries are much more efficient and therefore generate less internal heat (unless you are over charging them).

And are you keeping the cables between the battery bank and your solar charge controller & AC inverter as short as practical? You do not want very long cables and much voltage drop if you can avoid it.

-Bill

Roger Thoms · May 2015

54" 4/0 cables, which is as short as possible. Shouldn't over charge them unless I set the charge controllers up wrong. The compartment is insulated so I don't think freezing will be a problem. This system is located at 6000' near Flagstaff so it does freeze, hence the insulated compartment. The other consideration was the location on the west side of the house which gets strong afternoon sun. The nice thing is that both the equipment shed and battery compartment stay nice and cool in the afternoon. This is with highs into the mid 80's and no equipment running. I am going to put thermometers in each compartment so that I can keep an eye on the temperature. Roger

BB. · May 2015

South and west facing walls for equipment room, unless you have shading for the equipment room, is something I would avoid unless you need winter sun to keep things warm.

-Bill

Roger Thoms · May 2015

The location is not ideal for the summer but very good in the winter. They are also located close to the solar array. I considered a seperate out building possibly below ground but the would have been a lot more labor and expense. I also wanted to avoid another out building. The back of the house (west) was the only practical location.

Roger

Photowhit · May 2015

Lower right bottom of my power center has a 12x12 filter (with a scrap of 2x4 on it) and I have a 3" Fan in the upper left side wall, can't be seen here, but note the extra over hang of roof. I powered the fan directly off a small solar panel 5 watt 6v, which worked fine until eating the wasp now doesn't work at 6 volts, fan is a 12v nom fan.

This worked well last year until the fan caught a wasp. I should have put a bit of screen around it. This lives under my array so doesn't get any (or at least very little) direct sun.

The battery lives outside as well, no concern in keeping the battery warm, it won't freeze in most of the lower 48, an 80% SOC battery will go down to 10 below without issue. It does have diminished capacity. I have little need for my large capacity other than long periods of clouds sometime in winter, and summer AC.
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Roger Thoms · May 2015

Photowhit &K4KMG thanks for the pictures and info about your systems, this helps.

Roger

sawmill · May 2015

I use a couple of 3" screened computer fans that blow across the top of the battery box with screened vents on the other side. Also use a 4" fan to help cool the inverter. These are wired direct from their own 10 watt panel with an on & off switch. During the warmer months I leave them on 24/7. Once the Sun comes up they start running and have worked great. With the onset of Winter temps the battery fans are turned off and passive venting is used. Hope this helps.

SolarMusher · May 2015

Photowhit wrote: »

Lower right bottom of my power center has a 12x12 filter (with a scrap of 2x4 on it) and I have a 3" Fan in the upper left side wall, can't be seen here, but note the extra over hang of roof. I powered the fan directly off a small solar panel 5 watt 6v, which worked fine until eating the wasp now doesn't work at 6 volts, fan is a 12v nom fan.

This worked well last year until the fan caught a wasp. I should have put a bit of screen around it. This lives under my array so doesn't get any (or at least very little) direct sun.

The battery lives outside as well, no concern in keeping the battery warm, it won't freeze in most of the lower 48, an 80% SOC battery will go down to 10 below without issue. It does have diminished capacity. I have little need for my large capacity other than long periods of clouds sometime in winter, and summer AC.
Attachment not found.

Hi Photowhit,
How did you insulate your outdoor battery box? Would you have a pic to share? Here a friend of mine has lost his new AGM bank last winter at his cabin, I'm thinking to build him a new box using at least a 4 inches foam insulation. Temps dropped really too low last winter with -20/-25°F every night and his panels were surely covered by snow until april..
Thanks,
Erik

SailorThor · May 2015

SolarMusher wrote: »

... Temps dropped really too low last winter with -20/-25°F every night and his panels were surely covered by snow until april..
Thanks,
Erik

My solution for unattended winter systems is to turn off the large tare loss inverter and solar charger at the breakers, mount a reasonably sized panel on a vertical south wall that gets lots of sun, and connect it via a Genasun boost controller (for 48V banks). Its tare losses are tiny, the unit will up-convert to temperature compensated 57.6V from down to 5V input from the panel, and it saved my friend's battery bank @ -50F,when the snow just wouldn't shed off the main panels on the roof.

I have since done the same installation at my place with an oddball panel on the south wall to avoid the unattended-covered-in-snow-problem.

Works great.
Michael

Equipment Enclosure Ventilation

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