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Forced air ventilation for the electrical bay

May, 2008

Our electrical bay is a fairly small compartment (about 8 cubic feet) with a 2,000 watt inverter/charger (Xantrex RS2000) that generates lots of heat in this small compartment even when running at less than 1,000 watts for a few hours. We have observed the compartment temperature elevate to about 120 degrees F after a day on the road which is right at the upper operating limit for the Xantrex inverter.

The heat accumulation in this bay has always concerned me, and after a summer of travel in the coach in 2007, I was determined to try and solve the problem. The solution (at least I hope it is the solution) is to install a small marine bilge ventilator above the compartment (which happens to be under the bed.)

So - on with the project in pictures!

Pilot hole

The idea is to make a 3" hole from the electrical bay to the inside of the coach to draw cooler air from the inside of the coach and force it into the bay. As you can see, I made a pilot hole first to verify my rough measurements. As it turned out, the hole was oriented satisfactorily

pilot hole topside

Here is the other end of the drill bit nicely protruding in the middle of the under bed storage

three inch hole saw

Getting ready for some action! Here is my old DeWalt drill with a 3" hole saw in the chuck. If you don't have a hole saw of the proper size, consider investing in one - it is a great addition to the tool box

bottom view of the hole

Ah - now we have a nice 3" hole! Drill from the bottom up since you don't want to begin your hole in the carpeted area under the berth. As soon as I felt the hole saw break through the wood of the floor, I stopped.  Then it is fairly simple to use a razor knife to trim away the carpet

top view of the hole

Notice the carpet plug I cut out with a box cutter

the parts

The parts - the blower is a Jabsco model 35115-0020 3" flange mount and is sold for the marine market to ventilate bilges and engine rooms. I ordered mine from West Marine (about $60 May 2008), but if you have a boat store in your town, they should have them. I believe Jabsco is a little better product than Attwood, so buyer beware if you think you can buy a quality blower for $20

As far as the other parts - any auto parts store (or marine store) will carry a fuse or circuit breaker (fuse size is six amps for this particular blower) and some sort of switch. This blower draws less than five amps, so 14-16 gauge wire is plenty okay for a short wiring run

power source

Pick up 12V anywhere it is convenient. We happened to have two beautiful 12V buses that supply 12V to the various circuit breakers on the end of the berth. I found an extra blade fuse holder in my parts box and used it instead of the circuit breaker I bought (since the breaker was rated for 10 amps - the store didn't have any six amp breakers.) I found a 7.5 amp blade fuse which should be close enough to the recommended six amp fuse

Completed installation

The completed installation. I could have run a 3" hose from the blower inlet to the edge of the berth, but the easiest thing to do will be to simply flip open the access panel for that storage compartment (the "forward" arrow points to the access panel) and leave it open while we are using the blower

You might be wondering where all that air goes when it is pumped into the electrical bay (if you aren't, you should be!) I was considering cutting an exhaust vent in the bay but thought I'd see what happens with no vent since it seemed like there was a wiring channel/opening from the inside of the bay which would permit the air to escape somewhere. Sure enough, the air must be getting out somewhere since opening and closing the bay door with the blower running produces no perceptible change in the blower noise level or motor load

We have had a water intrusion issue when driving in the rain - water would be forced into the cable opening at the bottom of the bay. Now with the blower operating, it will be impossible for water to enter since the compartment will be pressurized

Update May 2010: water will still enter the compartment, but we have much less intrusion with the blower operating. Our Xantrex RS2000 is running nice and cool now - this was a worthwhile project