Air intake to maximize cooling of roof fans (not A/C)

daveola · September 28, 2011, 01:58:56 AM

I have a Fan-tastic Vent fan in my roof, and it helps a great deal, though it only exhausts, and as we all know, I need air intake for this to work well. It's great if I open one of my windows, but I don't like the security involved with leaving the window open while gone, and regardless, I'd prefer something automated.

The Fan-tastic Vent fan is thermostat controlled with a powered cover and a rain sensor. This is pretty important to me so I don't have to worry about being at the bus or being awake to operate things just because it gets hot. My cat appreciates the temp control as well.

So I need an intake. I've thought about getting another fan for the back of the bus that blows in, though my bus is 24V or 110V, and the 110V Fan-Tastic vents are not reversible, and I don't have 12V.

Perhaps it's unnecessary, since in this thread:

http://www.busconversions.com/bbs/index.php?topic=11123.30

People talked about the fresh air intakes in the floor.

Where is the intake on the outside of the bus, and how do I open/close it? I haven't noticed any air flow when I turn on the roof fan with the windows and hatch closed. And has anyone put a fan in the fresh air floor intake?

And if not, any suggestions on where I can find a 24V or 110V *intake* roof vent that is fully automated (powered vent with rain sensor)?

RJ · September 28, 2011, 02:48:50 AM

Dave -

The main coach air intake for the OEM HVAC system is located just about at eye level in the "billboard" area above the A/C condenser compartment on the street side, and the battery compartment on the curbside. Bunch of little holes punched in the aluminum in a rectangular pattern about 6"x4" in size. Has ductwork on the inside to direct the airflow down into the HVAC components underfloor. There are no provisions for opening/closing these, you'd have to do your own.

Here's a thought - since the A/C motor on the Fantastic Fan is non-reversible, what about flipping the fan blade over? Study the fan you've currently got, and see if that's feasible. If it works, bingo! If it doesn't:

I've heard that Fantastic's customer service dept is really excellent. Maybe a call to them might bring a reversible A/C model like yours to light in their product line? Or a 24V model that would work. Give their 800 number a call and ask.

Interesting challenge!

FWIW & HTH. . .

scanzel · September 28, 2011, 03:28:25 AM

Food for thought. If you don't have a fresh air intake now so you are not seeing air movement then if you do reverse the fan to feed in, where do you expect the air to go to create an air flow. All you are going to do is create a positive pressure and the fan will basically not be able to do its function. A friend of ours years ago decide to turn his whole house ceiling fan on to cool it down but forgot to open a window slightly. What happened is that his fireplace screen and damper were still open. Because of the volume of the air the fan could draw it sucked all the ashes out of the fireplace before he caught it. Guess what the inside of his house looked like after. Good thing the ashes were out and not glowing. If a fan is drawing out it needs an air intake, if forcing air in it needs a vent.

Marcus · September 28, 2011, 04:22:10 AM

I have a fantastic fan in bus bathroom. It is reversable, in or out. It is 12volt. Reduce your 24 to 12volt very simple. Marc

robertglines1 · September 28, 2011, 06:14:12 AM

Your drivers air/outside air vent won't let enough air in? the one hooked into the front defroster/heater box and fan. bob

luvrbus · September 28, 2011, 07:50:45 AM

Talk to Fantastic they will come up with something for you, the way most use those they have one pulling air in and the other pushing air out that has worked for me over the years,same idea as yours

good luck

06 Bill · September 28, 2011, 08:51:46 AM

Flipping the fan does not reverse air flow, just makes the fan less efficient and noisy. 06 Bill

daveola · September 28, 2011, 02:13:14 PM

I suppose at only 24W I could drop 24V down to 12V without too much extra cost, and that might solve my reversing problem.

scanzel, I wasn't planning on replacing my current fan with one that would draw air in, that would be silly - I was planning on putting in a second fan.

robertglines1, where is the intake on the outside for the drivers air vent? Because most of the hoses for it by the driver are gone.

I think that possibly using the intake that RJ mentions might be a good bet, though it's in the front of the bus, where my current Fantastic vent is, so it wouldn't really circulate much air unless I piped it to the back of the bus.

I'll have to call Fan-tastic and see what they have to say.

buswarrior · September 28, 2011, 07:44:28 PM

A coach that is air tight enough to need an air intake to feed a fantastic roof fan?

Oxymoron or heretical?

I don't think that fan is starved for air.

happy coaching!
buswarrior

daveola · September 29, 2011, 12:54:16 AM

Probably not starved, but when I open the window, I definitely feel the breeze. The real problem is that I don't have air circulating through the bus from the outside - hence the idea of putting a push fan on one end of the bus and a pull fan on the other.

So at this point, it's probably a fan in the ceiling, unless anyone has an idea for an air intake in the back of the bus, preferrably one that I can put a fan in. I suppose I could cut a hole in the floor and then find some way to pipe air into one of the bays and through the floor, but that's a bit of a modification.

DMoedave · September 29, 2011, 07:27:29 AM

5 stars for the Warrior.

gus · September 29, 2011, 04:02:33 PM

As Steve says, if you want air flow and have anywhere near an airtight bus you need two holes, simple high school physics.

With only one hole you are pressurizing the bus one way and the other way you are decreasing the pressure. Slightly, true, but you aren't moving air either.

The way to solve the rain problem is not with a rain sensor but with with one of the many inexpensive vent covers available.

TomsToy · September 29, 2011, 07:32:23 PM

Can't tell for sure but that looks like an MCI, if so you have two fresh air inlets in the front of the bus. The control for one is at the bottom of the dash just to the left of the steering wheel and the other is on the front of the door (if you have a single piece door) eighteen to twenty four inches from the bottom.

HTH

Tom

daveola · December 24, 2011, 03:46:19 PM

For some reason I stopped getting notified of replies on this topic..

I've looked into some fan options, and I agree that a cover makes far more sense than a roof sensor, so I think I'm going to just find a different fan that can do intake.

Speaking of fresh air intake, it is an MCI (102A3) and the door is a single door, but it doesn't have any air vent or controls for fresh air on it. Maybe that's a different model MCI?

Busted Knuckle · December 24, 2011, 05:36:21 PM

Dave you have several fresh air vents for when your rolling.

As Tom's toy mentions there is the one below the steering wheel that looks like an eyeball.
Also in the front luggage bays are a pair of knobs (one on each side that can be pulled in the event of an A/C failure that will allow fresh air to flow into the A/C vents. Doesn't do a great job of cooling, but at least some air flow is better than nothing when ya got a load of hot people on board(for when it was in revenue service)

BK