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Old 07-24-2016, 08:13 AM   #1
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
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Year: 1991
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Chassis: International 3800
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roof hatch without passive vent??

does one exist? my roof hatch is definitely SHOT on my bus... not only was it the type you could pop for vent it also has a passive always-open vent which on paper sounds nice.. but causes negative pressure on the bus.. sucking in more air from outside sources when driving... ie engine compartment heat that I have yet to seal..

I cant seem to find any non-vented roof hatches.. I dont mind the fact that they can be opened.. but ai dont want that possive vent.. I dont need to worry about humidity in the bus, I have Air-conditioning and can even pre-refrigerate the defrost if I need to for humidity control..

my current one is a Transpec so thats the ones ive been looking at since it would be an easy drop in replacement....

-Christopher

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Old 07-24-2016, 08:26 AM   #2
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I thought they only vented if you popped up one side, allowing them to say "vented roof hatch." Mine are the normal ones too and I don't think they have an open air channel unless I pop one side up.

I was looking into getting one with an integrated fan, but that's a little pricey for my taste and I never thought about it sucking in air instead of exhausting it. Hmmm.
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Old 07-24-2016, 08:34 AM   #3
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when I had mine apart iot mentions passive venting and theres a channel from inside the bus up to the top and I notice the ones I find online have vent-holes..

the hatch itself doesnt suck air in.. it creates a negative pressure on the bus at road speed which will tend to suck air in from other sources...

negative pressure is also created by your mirrors.. thus why when you open your driver window you may actually be Hotter in your bus as it is creating more negaitive pressure which will exploit any holes in the firewall and other places in the bus... the passenger windows starting a row or two back are out of the mirror draft and will usually bring in air when opened..

wind deflectors on car windows work on the same principle to create negative pressure so you can have your window down but not get wind in your face...

in my case I dont want negative pressure on the bus as im running windows closed with the A/C on when its hot like now.. or if I want my driver window open I want the mirror pressure relieved so I can have air blowing on me (I love a nice sultry evening drive windows open and AC blasting...).. so I made a temporary reverse deflector i can place on the driver window when I open it to snag some outside air..

-Christopher
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Old 07-24-2016, 08:58 AM   #4
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Not sure if large bus escape hatches are different from small buses,... e350 corbeil...but mine that I am working on , see thread can be fully closed.

With the four spring loaded arms you can set it up the way you want. You can lift it up a s scoop, positive pressure so air will be blown in or as a negative pressure as your is.

The piece i cut out to make a skylight out had another vent in that also could be set up as positive or negative pressure. That was a steel add on.

What do you mean with a channel inside the bus? Is it hooked up to some duct work in the ceiling?

Later J
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Old 07-24-2016, 10:17 AM   #5
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Join Date: May 2009
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Rated Cap: 7 Row Handicap
my hatch has a permanent channel open from outside to inside.. it appears baffled.. but I havent ripped it apart till I get a new hatch.. the transpec hatches ive been seeing all have that "vent" hole in the hatch itself.. this vents even when the hatch iod l;atched and closed.. not when its in a vent position..

my guess is that they are ,made this way because when carrying a bus load of people in col or damp weather you have a high amount of humidity..
-Christopher
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Old 07-24-2016, 11:56 AM   #6
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Christopher, can you simply block/plug the channel with a bit of butyl or silicone caulking?
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