Xmtr Rack Dirt Problem - Best practice?

[DJ-TG]

I'm currently helping my old student radio station at ConglomU clean their engineering act up, both as a favor to the kids coming up on a license renewal, and for feel-good community service.

The transmitter site is in a normally-locked penthouse on top of a 9-story building. All components are mounted in a fairly new-ish rack, with a wood-frame wire mesh cage around 3 sides of the rack to prevent unauthorized access, the fourth being an external concrete wall with their leased pair termination.

Since it's ConglomU, their NPR station's engineers have to physically perform any maintenance on the transmitter site, no contractors or students allowed. While at the transmitter site during break, they noticed that the entire contents of the rack were covered in dirt/dust from what appeared to be a gutting/renovation of the building. The NPR guys took the xmtr, optimod, remote control, and mod monitors out for bench cleaning and replaced them later in the week (yes, seriously). I'm gathering nothing else was touched, though admittedly the rest is pretty irrelevant. Apparently this is the second time in 10 years this has been performed.

The kids now have it in their heads that to prevent that kind of downtime in the future, they'll need to get the ConglomU physical plant guys to put a vent fan in the external wall, and cover the cage in some type of fabric, at some insane hourly cost. To me, this seems like a really expensive band-aid to the situation. Any suggestions on a better way?

 

[RadioDoc]

Could you give up more information about the size/layout of the room? How is the dust getting in?

I think we can help you out if we have a little more info...

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[radio8z]

> I'm currently helping my old student radio station at
> ConglomU clean their engineering act up, both as a favor to
> the kids coming up on a license renewal, and for feel-good
> community service.
>
> The transmitter site is in a normally-locked penthouse on
> top of a 9-story building. All components are mounted in a
> fairly new-ish rack, with a wood-frame wire mesh cage around
> 3 sides of the rack to prevent unauthorized access, the
> fourth being an external concrete wall with their leased
> pair termination.
>
> Since it's ConglomU, their NPR station's engineers have to
> physically perform any maintenance on the transmitter site,
> no contractors or students allowed. While at the transmitter
> site during break, they noticed that the entire contents of
> the rack were covered in dirt/dust from what appeared to be
> a gutting/renovation of the building. The NPR guys took the
> xmtr, optimod, remote control, and mod monitors out for
> bench cleaning and replaced them later in the week (yes,
> seriously). I'm gathering nothing else was touched, though
> admittedly the rest is pretty irrelevant. Apparently this
> is the second time in 10 years this has been performed.
>
> The kids now have it in their heads that to prevent that
> kind of downtime in the future, they'll need to get the
> ConglomU physical plant guys to put a vent fan in the
> external wall, and cover the cage in some type of fabric, at
> some insane hourly cost. To me, this seems like a really
> expensive band-aid to the situation. Any suggestions on a
> better way?
>

From your description this sounds like a one time problem due to construction. My experiences with penthouses is they get dirty because they are frequently passively ventilated with louvers to the outside. If that is the case, a fan will make things worse by drawing in unfiltered outside air. Maybe a furnace filter installed over the vents with no fan will help.

Neil

 

[mr_elbows]

> I'm currently helping my old student radio station at
> ConglomU clean their engineering act up, both as a favor to
> the kids coming up on a license renewal, and for feel-good
> community service.
>
> The transmitter site is in a normally-locked penthouse on
> top of a 9-story building. All components are mounted in a
> fairly new-ish rack, with a wood-frame wire mesh cage around
> 3 sides of the rack to prevent unauthorized access, the
> fourth being an external concrete wall with their leased
> pair termination.
>
> Since it's ConglomU, their NPR station's engineers have to
> physically perform any maintenance on the transmitter site,
> no contractors or students allowed. While at the transmitter
> site during break, they noticed that the entire contents of
> the rack were covered in dirt/dust from what appeared to be
> a gutting/renovation of the building. The NPR guys took the
> xmtr, optimod, remote control, and mod monitors out for
> bench cleaning and replaced them later in the week (yes,
> seriously). I'm gathering nothing else was touched, though
> admittedly the rest is pretty irrelevant. Apparently this
> is the second time in 10 years this has been performed.
>
> The kids now have it in their heads that to prevent that
> kind of downtime in the future, they'll need to get the
> ConglomU physical plant guys to put a vent fan in the
> external wall, and cover the cage in some type of fabric, at
> some insane hourly cost. To me, this seems like a really
> expensive band-aid to the situation. Any suggestions on a
> better way?
>

portable air tank and a nozzle ?

 

[DJ-TG]

> Could you give up more information about the size/layout of
> the room? How is the dust getting in?

Room size is about 75' x 60'. Layout is irregular, usable space kind of L shaped, with elevator engines creating the L. There's a base tier for entry from inside, then a platform step to the roof exit. The rack and leased pair are terminated on this platform, some distance away from the exit door, near an external wall, opposite the engines.

There were very large air movers in the room at one time; those seem to have disappeared with the renovations, though I'm not sure when. That would be the biggest source of airborne dirt/dust in my estimation, obviously. The elevator engines and from the HVAC vents (not even sure they're in use anymore) would also be problem points. I am told that there were much worse dirt/dust problems in their rack previously, so the air movers disappearing might have helped things somewhat.

I think the plan is to have the fan installed on the wall, blowing out of the room to remove the hot air and dust from the cage.

They're really looking to just keep it as clean as possible, and functioning, without human intervention. I realize we're trying to address a personnel/access issue with equipment and not personnel, but it doesn't seem like we're going to get access to the room on a regular basis.

 

[rfry]

> I think the plan is to have the fan installed on the wall,
> blowing out of the room to remove the hot air and dust from
> the cage.
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That tends to inhale a lot of outside dust and dirt from whatever source is providing makeup air for the air that the vent fan is trying to remove from the room. And such a planned air inlet is essential, otherwise the vent fan won't work.

An air filter on an air inlet port into the room is typical for these systems, but there are usually plenty of other ways for dirty air to enter the room when it is under a partial vacuum like this (ie, under doors, around windows/pipes etc).

Better to put the fan at the (filtered) air intake, and pull air into the room -- so as to put the room under a slight pressure (~0.1" of water). That will push air out of the cracks under doors etc, and keep the room cleaner. With sufficient air movement, the temperature in the eqpt room can be held to within several degrees of the outside ambient air temperature.

Any qualified HVAC firm should be able to design a ventilating system like this at a reasonable cost.