Gen in condenser bay question

Paladin · October 04, 2012, 05:37:29 PM

Another active question made me think of this. Many have placed their gensets in that bay as I'm considering doing and some have mounted fans in the expanded metal doors or even downward facing through holes in the floor of the bay.

I'm assuming that they also used a hole in the floor of the bay to either pull or vent air from.

For those who did this, what size and type gen do you run?
Did you use pusher fans or puller?
What size (dia) and cfm fan did you use and are you happy with them?
Did you use a thermal switch or does it run non stop with the gen?
Lastly, did you really need the fan?

What was your main point? To draw fresh air into the bay or to vent heat out?

Tenor · October 04, 2012, 06:50:24 PM

Paladin,
My generator radiator is in the condenser bay, about in the middle, facing the front of the bus. There is an aluminum box/shroud behind it connecting it to the first bay. Inside the shroud is a large squirrel cage fan. The fan has the side openings facing the radiator and the generator. There is a factory hole in the bulkhead between the 2 areas. The fan draws air from the generator enclosure and the radiator and dumps it out the original condenser floor duct. Worked real good except when driving. I ended up putting an automotive fan behind the radiator as well. Now it works perfect. Several possible reasons for this airflow issue. Squirrel fan draws too much air through the generator enclosure. Squirrel cage fan too far away from the radiator. Radiator perpendicular to the side of the bus and the bus causes a vacuum near the compartment. Before I added the 12v fan, you could feel the air draw over your hand on the way over the radiator. Now, it will hold paper and small animals against the condenser bay screen!

Mex-Busnut · October 04, 2012, 07:08:25 PM

Edit: Ours is air-cooled, not water cooled.
===========================
Most honorable Mister Paladin:

We have ours mounted there as well. Let me suggest totally emptying out the compartment, clean and paint it, then insulate it (all walls, floor, ceiling) to lower noise and heat transfer to upstairs.

I got a large section of steel grate from a local recycling place. it was placed in the already-existing hole the the OTR A/C compressor breathed through.

Generator is 6.5 kilowatts. Our two one-ton mini-split A/C units peak at only 980 watts maximum each.

When you are going down the road, there is higher air pressure on the outside walls of the bus than under the bus. When stopped, it is opposite. My paint-and-body shop friend gave me a double electric fan unit off a totaled Dodge van radiator. I plan to use a switch to reverse its polarity when parked.

Tomorrow maybe I can post a pix of the genny in place.

Paladin · October 04, 2012, 07:48:54 PM

That's awesome Dr Steve! Please do show me anything that you have since it looks like I'm leaning exactly where you are.

Mex-Busnut · October 05, 2012, 05:18:22 AM

Quote from: Paladin on October 04, 2012, 07:48:54 PM
That's awesome Dr Steve! Please do show me anything that you have since it looks like I'm leaning exactly where you are.

Yikes! I hope you don't weigh too much!

Just kidding. I will try to get you some more pictures today.

gus · October 05, 2012, 02:25:25 PM

Steve,

Just curious, how did you find out "when you are going down the road, there is higher air pressure on the outside walls of the bus than under the bus"?

When you're parked there is no measurable difference in the pressure top, bottom or side.

Mex-Busnut · October 05, 2012, 09:00:42 PM

Quote from: gus on October 05, 2012, 02:25:25 PM
Steve,

Just curious, how did you find out "when you are going down the road, there is higher air pressure on the outside walls of the bus than under the bus"?

I found it out from several of the air-conditioning gurus on some forums called www.busconversions.com, when I was asking a lot of questions before installing our mini-splits.

RJ · October 05, 2012, 10:44:10 PM

Quote from: gus on October 05, 2012, 02:25:25 PM
Just curious, how did you find out "when you are going down the road, there is higher air pressure on the outside walls of the bus than under the bus"?

Gus -

If you'll notice, nearly every coach builder has placed the HVAC condensor approximately two feet behind the front axle. Crown & Gillig mid-engined skoolies placed their radiators in that same spot.

Why?

Because from wind tunnel testing (primarily by GM in the '40's) it was discovered that's where the "bow wave" coming off the front of the coach at speed collapses back against the side of the bus. Pure and simple physics!

This was shared with me by a fellow Corvair nut's father, who happened to spend 35 years as the GMC Coach Warranty Service Tech for Northern CA, OR, WA, ID & NV, the late Tony Newell. It actually started as a conversation about the cooling air intake location for the Corvair Greenbriar, Rampside and Corvan models.

Amazing the trivia we learn from our crazy hobbies, isn't it?

Glenn & Steve -

I'd like to suggest that you both consider hanging a "mud flap" in front of your under coach discharge opening. That will help create a lower pressure area directly under the opening when moving, thus assisting in drawing the hot air out of the compartment. Same principal GM used to assist cooling their highway model's engine compartment.

FWIW & HTH. . .