Film-Tech Forum ARCHIVE: Blowers: Rooftop or in-booth?

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Posted by David E. Nedrow (Member # 4981) on 04-04-2010, 08:48 PM:

Now that warm weather is upon us, I need to exhaust the lamphouses outside. The way the equipment was left by previous management had a Dayton blower literally laying on top of the projector vent stack. Not bolted, just depending on gravity, though from the amount of dried adhesive around the collar, it looked as though the had it duct taped at some point.

The ceiling duct is clear, though the cap on the roof top needs replaced.

What are people's thoughts on the types of blower installations? I long for the day when I don't have a blower in the booth itself, just from a noise perspective. But if a rooftop unit fails, I'm sure repairing it would be more of a hassle than a ceiling mounted one.

I need to have electrical run either way, so looking for opinions.

-David

Posted by Jeremy Weigel (Member # 4208) on 04-04-2010, 09:03 PM:

See this thread for useful info. Being that far north I would go with the indoor units so you don't have to worry much about clearing snow from around a rooftop unit.

Posted by Monte L Fullmer (Member # 2797) on 04-05-2010, 12:43 AM:

..If you're going in-booth, have the blower away from the machinery so the motor vibrations doesn't resonate into the console or lamphouse.

Posted by Joe Redifer (Member # 3) on 04-05-2010, 01:14 AM:

I've never had any issues with snow on top of the rooftop units here in Colorado.

Posted by Jim Cassedy (Member # 4115) on 04-05-2010, 01:42 AM:

I recently installed a new lamphouse, and the exhaust blower
on the old one was "mounted" (or, more accurately: "sitting")
on top of the lamphouse vent stack in much the same way David
described his installation.

Fortunately, I had access to the attic space between the
booth ceiling and the theater roof, so I simply moved the
blower from on top of the lamphouse up into the attic above
the booth by screwing it to a base and then screwing that
into the metal ceiling joists above the booth.

I also slightly re-routed the flex duct from its' original
path and in doing so I was able to remove two 90deg bends
which greatly improved airflow.

The blower is not entirely "out of sight, out of mind",
since I occasionally have to go up into that attic for
other maintence issues. That will give me a chance to
periodically check it.

Here's A Picture Taken When I
Was Working On The Installation:

Another thing you might want to consider is an "Inline
Exhaust Fan". I used one of these at a theater last year
whose ancient roof exhaust system finially rusted out.
They're relatively inexpensive and come in a variety
of duct sizes and CFM's. It came with brackets which
made it easy to mount it to the booth ceiling above
the projector. They're very quiet, and I got it (new)
on e-bay for around $100 including shipping.

Here's what one looks like:

This worked out so well, they had me install a
2nd one in another booth since it was only a matter
of time before that exahust system failed too.

Search e-bay for "inline exhaust fan" and you'll
find quite a selection. Good Luck!

Posted by Bruce McGee (Member # 131) on 04-05-2010, 12:58 PM:

We have rooftop blowers at my location. They were installed in 1984, and all ran fine until the last couple of years. I am replacing them one at a time as they go bad.

Even with all the snow we have had here on the east coast this winter, I have never had a problem with snow blocking the ventilation system.

Posted by Michael Voiland (Member # 5386) on 04-05-2010, 04:12 PM:

We are at an old GC from the 1980's the hvac guys keep saying they pull 200 cfm i have yet to believe them.

Posted by Monte L Fullmer (Member # 2797) on 04-05-2010, 04:23 PM:

..and in all due actuality, 200cfm's is a bit too low. If you can get it up double the flow past 400cfm's, the bulbs will like you much better...

Posted by Louis Bornwasser (Member # 3063) on 04-05-2010, 08:19 PM:

Cost is worth it in bulb savings. Louis

Posted by Michael Voiland (Member # 5386) on 04-06-2010, 05:36 PM:

They say 200 i say BS i opened one up today to find the belt was falling apart like totally delaminating or splitting to a point were at some parts it was a quarter the thickness. we have 2 projectors that share a roof top can you say cook an egg on top of the lamp house. They are all 2k bulbs to. Trust me I look at the cost of bulbs vs new vents and shake my head they cut our hours back recently.

Posted by Bruce McGee (Member # 131) on 04-07-2010, 05:50 PM:

My blowers are all rated 300 cfm. I get 3000 hours from my 2K lamps.

Posted by Michael Voiland (Member # 5386) on 04-08-2010, 05:30 PM:

Consider yourself lucky. Some of our theaters get a dark spot on the bulb in the first few weeks it just fades dark at the top of the bulb.

Posted by Mike Frese (Member # 4361) on 04-11-2010, 06:16 PM:

Is there a reason to not install these inline blowers on the lamphouse? They do not seem to cause any vibration to the lamphouse.

Posted by Gordon McLeod (Member # 33) on 04-11-2010, 07:21 PM:

The only issue is if there is an existing blower elsewhere on the line as you could cause a change to the overal system draft

Posted by Louis Bornwasser (Member # 3063) on 04-11-2010, 10:02 PM:

You will notice with in line blowers that eventually the Ozone will cause failure. It looks like corrosion. In line is absolutely no good except for a shurt time.

Squirrel blowers are not hard. Louis

Posted by Mark Gulbrandsen (Member # 72) on 04-11-2010, 10:13 PM:

Louis...

I never had that problem with any in lines. The Fntechs are either powder coated or galvanized depending on what you buy. And the air in Salt Lake City absolutely sucks.

Mark

Posted by Monte L Fullmer (Member # 2797) on 04-12-2010, 02:29 AM:

..until the winds blows down out from the canyons to clear the valley out ...