Climate control for xmtr site

[SamBuca]

Could use a little help here from those who've been there, done that, and ran the numbers.

I'm trying to figure out the expense vs savings for installing air conditioning at the transmitter building. In the engineering log, I see entries saying the temp inside the building is over 110 F (small building...20x20 or so).

Xmtr is older (1985) and almost all the components were recently replaced (boards, caps, etc), but since the xmtr is older, it's not efficient...we burn through a lot of power for 5kw.

We can probably trade out a 1 ton standup a/c unit, but I need to figure out whether the added cost of electricity (with an energy hog xmtr) to run the a/c is worth it when compared to the cost of ruining the newer components in the xmtr.<P ID="signature">______________
</P>

 

[RadioDoc]

> Could use a little help here from those who've been there,
> done that, and ran the numbers.
>
> I'm trying to figure out the expense vs savings for
> installing air conditioning at the transmitter building. In
> the engineering log, I see entries saying the temp inside
> the building is over 110 F (small building...20x20 or so).
>
> Xmtr is older (1985) and almost all the components were
> recently replaced (boards, caps, etc), but since the xmtr is
> older, it's not efficient...we burn through a lot of power
> for 5kw.
>
> We can probably trade out a 1 ton standup a/c unit, but I
> need to figure out whether the added cost of electricity
> (with an energy hog xmtr) to run the a/c is worth it when
> compared to the cost of ruining the newer components in the
> xmtr.
>

That's a tough one...it could go either way. Would your transmitter be happier at a cooler temp? Sure. It is entirely bad to run up to 100 degrees? Yes, but if it's occasionally, that shouldn't be a problem.

I can tell you that you could do just fine with a good exhaust system. I have two sites here in Wisconsin that do just fine with blowers, even on the hotter days. In fact there are LOTS of sites that have nothing more than a simple exhaust fan. Much cheaper to run than A/C. If you can keep the ambient temp between 80-95 degrees on the hot days, you'll be fine. The key is to keep the air moving!<P ID="signature">______________
</P>

 

[rfry]

Here is a link to a good paper from BE about tx cooling...

http://www.bdcast.com/papers/cooling.pdf

 

[tpt]

I would agree.

We have an FM 10 K & use a system of three attic fan type blosers in, and three out. Each has its own thermostat setting (steggered) so they don't all run until it gets real hot.

Advantages: Failure of one blower won't compromise the system, as would happen if you had an air conditioner (they only fail on th e hottest weekend of the year). Also if it goes from 80 to 40, as it is wont to do here in the midwest, a blower won't freeze up. Our transmitter seems happy so long as there is air blowing through.

Disadvantages: Obviously when it is 95 outside it willbe somewhat warmer inside. Not a great system in the deep south, or anywhere where it gets how and stays hot for long periods of time.

We have furnace filters on the air intake, but these get clogged easily when they mow the grass. Filters still can't keep out all of the no-see-ums and coal dust from the coal trains.

 

[CW]

> Could use a little help here from those who've been there,
> done that, and ran the numbers.
>
> I'm trying to figure out the expense vs savings for
> installing air conditioning at the transmitter building. In
> the engineering log, I see entries saying the temp inside
> the building is over 110 F (small building...20x20 or so).

Thats not good & what is the rise through the stack?? Whats the max temp
allowed by the manufacturer for the xmtr? Personally I dont like using outside air...except as a backup...An AC makes a cleaner room as well as a cleaner xmtr cabinet....positive air pressure keeps bugs, dust, etc out of the room..
of course if you put a vent in, you need to make sure it closes properly and completely (and most dont in my opinion)...so you can NEVER have it completely closed if you have a backup air supply in case the AC dies.

> Xmtr is older (1985) and almost all the components were
> recently replaced (boards, caps, etc), but since the xmtr is
> older, it's not efficient...we burn through a lot of power
> for 5kw.
>
> We can probably trade out a 1 ton standup a/c unit, but I
> need to figure out whether the added cost of electricity
> (with an energy hog xmtr) to run the a/c is worth it when
> compared to the cost of ruining the newer components in the
> xmtr.

Well you can figure the KW-H draw of the AC unit, multiply that by an average
run (with a 50% duty cycle, say 12 hours a day that the compressor is on) then go to 365days for a year's total usage and factor in the KW-H charge of your electric utility. Personally, if the components were not rated for 150 degrees or so to be conservative, you will do better with some cooling...

IMHO....

 

[Les]

The cost of AC will floor you.

AND, depending on the climate where you are, there's a good chance
of icing that will destroy any beneficial effects.

I've had good luck with installing two air intakes, each with a
coarse screen, fine screen, furnace type filter and a HEPA filter.
One has a thermostatically controlled motorized louvre; the other
(blocked off in winter) has no louvre.

Then on the opposite side of the building (place these so prevailing
winds help you), a pair of very large industrial grade fans blowing
air out. Separate thermostat for each, staggered by about 5
degrees. Ideally one fan would have sufficient flow to do all the
cooling and the other is there ONLY for backup if the first one
fails. If conditions don't absolutely demand it, don't even use
a motorized louvre on your intake; it's just another potential
failure mechanism. OR, consider using a louvre (separate thermostat)
on the second air intake.

Keep the fans well oiled and all the pivot arms on the louvres
well lubricated. Check filters at least once a week.

IMPORTANT:

Industrial type fans generally don't have over-temperature
protection for the air passing through, though they probably
have thermal protection for internal heat. I always install
what are called "fire-O-matic" switches just overhead of the
fans. These are devices commonly installed just above
oil burners on heating systems. They'll cut off power to the
fan if the temperature reaches 160-degrees F and can be wired
to produce an alarm. That way the fans won't boost a fire
in the building...though it'd probably be too late to matter
all that much. I have done it with line voltage thermostats
but prefer low-voltage stats running commercial AC contactors
rather than common relays.<P ID="signature">______________
When you're done impeaching the prez, keep on going; recall every member of congress and lock 'em up! Let's try NO govt. for a while.</P>

 

[SamBuca]

> If you can keep
> the ambient temp between 80-95 degrees on the hot days,
> you'll be fine. The key is to keep the air moving!

Building was 80-85 when the outside temp was in the mid to upper 60s...with 2 industrial fans going. It's clear to me why the PA modules were all burned when I replaced them.

My concept was to run the a/c unit and set the fans at like 90 degrees, so that if the a/c should fail or be unable to cope, they'll kick on as a backup to keep air moving. A little ammeter on the a/c unit tied into the arc-16 can keep me alerted to an a/c problem.

I was considering getting one of those standalone floor units...position the exhaust/intake tubes, plug 'em in, and set the temp. No water reservoir, no HVAC, no heat pump, etc...it'll just add another 20 amps. If my math is right, that's another 60kwh per day to the bill for june/july/august.

$800 for a unit plus another $30-40/mo in electric. That's what I've come up with.<P ID="signature">______________
</P>

 

[zachm]

> > Could use a little help here from those who've been there,
>
> > done that, and ran the numbers.
> >
> > I'm trying to figure out the expense vs savings for
> > installing air conditioning at the transmitter building.
> In
> > the engineering log, I see entries saying the temp inside
> > the building is over 110 F (small building...20x20 or so).
>
> >
> > Xmtr is older (1985) and almost all the components were
> > recently replaced (boards, caps, etc), but since the xmtr
> is
> > older, it's not efficient...we burn through a lot of power
>
> > for 5kw.
> >
> > We can probably trade out a 1 ton standup a/c unit, but I
> > need to figure out whether the added cost of electricity
> > (with an energy hog xmtr) to run the a/c is worth it when
> > compared to the cost of ruining the newer components in
> the
> > xmtr.
> >
>
> That's a tough one...it could go either way. Would your
> transmitter be happier at a cooler temp? Sure. It is
> entirely bad to run up to 100 degrees? Yes, but if it's
> occasionally, that shouldn't be a problem.
>
> I can tell you that you could do just fine with a good
> exhaust system. I have two sites here in Wisconsin that do
> just fine with blowers, even on the hotter days. In fact
> there are LOTS of sites that have nothing more than a simple
> exhaust fan. Much cheaper to run than A/C. If you can keep
> the ambient temp between 80-95 degrees on the hot days,
> you'll be fine. The key is to keep the air moving!

Here in Wyoming, we simply run industrial fans to draw air in, and a smaller fan to use for exhaust. The key is keeping positive pressure in the building; not only will it keep the air moving in room, but it will also do a fairly good job of keeping dust and the elements out.

Run more than one fan though...and don't duct the exhaust directly to the top of the transmitter. My predecessor did that, and I wound up replacing a transmitter.
>
<P ID="signature">______________
Zach Morton
Chief Engineer
Legend Communications Of Wyoming, LLC.
KGWY/KAML/KIML/KLGT/KZZS/KBBS
Office (307) 686-2242
Cell (307) 660-9101</P>

 

[ironbear]

> I'm trying to figure out the expense vs savings for
> installing air conditioning at the transmitter building. In
> the engineering log, I see entries saying the temp inside
> the building is over 110 F (small building...20x20 or so).

Good grief. I've actually had tenants threaten to sue for building temps which barely reach 90F here in the northern mountains of Arizona. Clearly, stuff like STL's, FMT's and TV microwaves will misbehave by losing afc lock and drifting, and sharply tuned cavities wander.

I bit the bullet and now run AC 24/7/365, but ultimately the tenants pay through reimbursements and higher rents.

 

[EncSpy]

> I would agree.
>
> We have an FM 10 K & use a system of three attic fan type
> blosers in, and three out. Each has its own thermostat
> setting (steggered) so they don't all run until it gets real
> hot.
>
> Advantages: Failure of one blower won't compromise the
> system, as would happen if you had an air conditioner (they
> only fail on th e hottest weekend of the year). Also if it
> goes from 80 to 40, as it is wont to do here in the midwest,
> a blower won't freeze up. Our transmitter seems happy so
> long as there is air blowing through.
>
> Disadvantages: Obviously when it is 95 outside it willbe
> somewhat warmer inside. Not a great system in the deep
> south, or anywhere where it gets how and stays hot for long
> periods of time.
>
> We have furnace filters on the air intake, but these get
> clogged easily when they mow the grass. Filters still can't
> keep out all of the no-see-ums and coal dust from the coal
> trains.
>

I say go the AC route...lets just say i've seen a vintage RCA BTA 1R burn up ALL 4 of its 4-400 tubes on one very hot summer day when a carbon resistor cracked....the owners got wise and installed AC....

 

[MrMissRadio]

Sam, you didn't say, but it sounds like you may not be exhausting the transmitter ventilation to the outside. Any A/C contractor can do that for you quickly. That will really take a lot of heat out of the building.

Also, if you go the inexpensive way (no A/C) there are 15 inch attic fans with thermostats and no finger guards available at Home Depot that move a good bit of air and are cheap (35-40 bucks 10 years ago when I bought mine). You can mount one in the wall (at the top, heat rises, you know), set it, and forget it.

I filter the incoming air and the air intake of the transformer.

No doubt A/C is better, it might not be more cost effective.

 

[DFWRadioJock]

> Could use a little help here from those who've been there,
> done that, and ran the numbers.
>
> I'm trying to figure out the expense vs savings for
> installing air conditioning at the transmitter building. In
> the engineering log, I see entries saying the temp inside
> the building is over 110 F (small building...20x20 or so).
>
> Xmtr is older (1985) and almost all the components were
> recently replaced (boards, caps, etc), but since the xmtr is
> older, it's not efficient...we burn through a lot of power
> for 5kw.
>
> We can probably trade out a 1 ton standup a/c unit, but I
> need to figure out whether the added cost of electricity
> (with an energy hog xmtr) to run the a/c is worth it when
> compared to the cost of ruining the newer components in the
> xmtr.

[smaking my forehead against the wall]

Sam, are you SERIOUS???? That poor transmitter's temperature must be well over 200 degrees, practically hot enough to cook breakfast. Running a transmitter with a room temp that high is just asking for trouble. The cost of running AC vs. the price of poor performance and expense from constant replacement of overheated xmtr parts (and eventually the transmitter itself) is the difference between night and day.

My personal feeling is, keep the transmitter temperature no higher than 130 degrees, preferrably no higher than 120. The room temp should be around 70. I'd put the life of a transmitter high up on the priority list, even if it means having to spend a little more money to run AC.

 

[radiosaur]

When superpower WMC-FM Memphis replaced the transmitters last (1990) I decided to go with the fan / filter intake wall then vent it all out the exhaust fans to the outside. The transmitters were actually built into a wall so the backs of them and the power supplies were in their own self contained room. The front of the units were in the main air conditioned room. We ran the BE 35B's at 36.5 KW with a hot standby during ratings periods. Even on the 100 degree days, it seemed to work OK. We'd lose about 2-3% efficiency in the summer heat, but never had a heat related failure. There's about as many thoughts on this as there are engineers...


<P ID="signature">______________
Never hold a cat and a dustbuster at the same time.</P>

 

[Engineer]

Agreed. You will kill this transmitter by letting it run so hot. I would not accept an ambient air temperature any higher than 80 on the hottest day of the year. Also, all of your ancilliary gear will suffer too. STL receivers, processors, remote controls, etc. Also, I've had problems with Burk remote controls failing in the worst way in overtemperature situations by refusing to call out an alarm. Even a big window-mount unit from Sears stuck in a cutout in the wall is better than nothing.

> > Could use a little help here from those who've been there,
>
> > done that, and ran the numbers.
> >
> > I'm trying to figure out the expense vs savings for
> > installing air conditioning at the transmitter building.
> In
> > the engineering log, I see entries saying the temp inside
> > the building is over 110 F (small building...20x20 or so).
>
> >
> > Xmtr is older (1985) and almost all the components were
> > recently replaced (boards, caps, etc), but since the xmtr
> is
> > older, it's not efficient...we burn through a lot of power
>
> > for 5kw.
> >
> > We can probably trade out a 1 ton standup a/c unit, but I
> > need to figure out whether the added cost of electricity
> > (with an energy hog xmtr) to run the a/c is worth it when
> > compared to the cost of ruining the newer components in
> the
> > xmtr.
>
> [smaking my forehead against the wall]
>
> Sam, are you SERIOUS???? That poor transmitter's
> temperature must be well over 200 degrees, practically hot
> enough to cook breakfast. Running a transmitter with a room
> temp that high is just asking for trouble. The cost of
> running AC vs. the price of poor performance and expense
> from constant replacement of overheated xmtr parts (and
> eventually the transmitter itself) is the difference between
> night and day.
>
> My personal feeling is, keep the transmitter temperature no
> higher than 130 degrees, preferrably no higher than 120.
> The room temp should be around 70. I'd put the life of a
> transmitter high up on the priority list, even if it means
> having to spend a little more money to run AC.
>

 

[MikeF]

I've run a BE FM-30 for 20 years very similarly in the northeast with no heat related failures and very long tube life.

The trick is to make sure you have plenty of positive pressure into the back of the transmitter by using the sealed self contained room, and a hefty intake blower going into it that exceeds the transmitter's air flow spec. I also use double air filtering with pleated filters to keep the dust & dirt down as much as possible. As long as you're pouring large volumes of air through the transmitter, it will be happy, even if it's 95 degrees. Then the top of the transmitter and stack exhausts outside, on the same wall but not too close to the big blower intake. That way outside wind is less likely to screw up the air flow. Below 50 degrees the big blower turns off, so it doesn't get too cold in the winter.

Works as well as and much less expensively than air conditioners with their large initial cost (you'd better have two), and subsequent electric and maintenance costs. It's especially true if your trying to cool a large 20 - 30 kilowatt rig.

The front of the transmitters and all other equipment are in an air conditioned space, but with a much smaller air conditioning requirement.

I'll definitely concede that the (double) air conditioning method is much better for a small solid state transmitter where the air requirements are lower.


Mike


> When superpower WMC-FM Memphis replaced the transmitters
> last (1990) I decided to go with the fan / filter intake
> wall then vent it all out the exhaust fans to the outside.
> The transmitters were actually built into a wall so the
> backs of them and the power supplies were in their own self
> contained room. The front of the units were in the main air
> conditioned room. We ran the BE 35B's at 36.5 KW with a hot
> standby during ratings periods. Even on the 100 degree days,
> it seemed to work OK. We'd lose about 2-3% efficiency in the
> summer heat, but never had a heat related failure. There's
> about as many thoughts on this as there are engineers...
>

 

[SamBuca]

> Sam, you didn't say, but it sounds like you may not be
> exhausting the transmitter ventilation to the outside. Any
> A/C contractor can do that for you quickly. That will really
> take a lot of heat out of the building.

These are old pics...I've changed a lot of stuff and installed some new gear since then.

Front of xmtr building. Those are the 2 intake fans.

Xmtr and rack. Inside the front door looking left. The grey thing behind the xmtr is the intake duct which vents downward. The grates in the back are the exhaust ports...no fans on them.

2 portable a/c units rated for 10k-12k btu @ 10 amps each would give me the 20k-24k btu of cooling for about $400 each. Saves me the trouble of running duct work or cutting a hole in the wall...plus we can trade out the a/c units.<P ID="signature">______________
</P>

 

[ElectricNoodle]

Another couple cents thrown in.... I just shake my head when entering a site for the first time and see the exhaust fan blowing the air through the wall vent - and it's mounted on the NORTH side of the building, sucking in all that nice warm SOUTH side air. It's very easily overlooked but try to remember to mount the exhaust fan on the SOUTH side and pull in the cooler NORTH side air.

EN

> Works as well as and much less expensively than air
> conditioners with their large initial cost (you'd better
> have two), and subsequent electric and maintenance costs.
> It's especially true if your trying to cool a large 20 - 30
> kilowatt rig.

 

[tpt]

> My concept was to run the a/c unit and set the fans at like
> 90 degrees, so that if the a/c should fail or be unable to
> cope, they'll kick on as a backup to keep air moving. A
> little ammeter on the a/c unit tied into the arc-16 can keep
> me alerted to an a/c problem.
>
> I was considering getting one of those standalone floor
> units...position the exhaust/intake tubes, plug 'em in, and
> set the temp. No water reservoir, no HVAC, no heat pump,
> etc...it'll just add another 20 amps. If my math is right,
> that's another 60kwh per day to the bill for
> june/july/august.
>
> $800 for a unit plus another $30-40/mo in electric. That's
> what I've come up with.
>
Sounds like a plan, especially if you can trade out the AC units.
Nothing wrong with AC, as long as that is not the only cooling system available.

 

[tpt]

> The trick is to make sure you have plenty of positive
> pressure into the back of the transmitter by using the
> sealed self contained room, and a hefty intake blower going
> into it that exceeds the transmitter's air flow spec.


One mistake that is often made is to build ductwork from the transmitter's air output to the outside. Not that this can't work, but it is not that easy to design a system that works properly. The risk is that the duct-work causes too much back-pressure to allow for adequate air flow thorugh the transmitter.

Another problem is to have too small of an air intake. One TV transmitter site I remember had this problem--when you opened the door to the place the in-rushing air would literally suck the door knob out of your hand.

 

[zachm]

> Another couple cents thrown in.... I just shake my head when
> entering a site for the first time and see the exhaust fan
> blowing the air through the wall vent - and it's mounted on
> the NORTH side of the building, sucking in all that nice
> warm SOUTH side air. It's very easily overlooked but try to
> remember to mount the exhaust fan on the SOUTH side and pull
> in the cooler NORTH side air.
>
> EN
>
> > Works as well as and much less expensively than air
> > conditioners with their large initial cost (you'd better
> > have two), and subsequent electric and maintenance costs.
>
> > It's especially true if your trying to cool a large 20 -
> 30
> > kilowatt rig.
>


Oh I was amazed when I first walked into our shack and discovered that the only ventilation was a small home window air conditioner and nothing but the internal blower on the transmitter running, and the stack bolted to the TOP of the transmitter. It's no wonder I'm replacing this tramsmitter next week. The air conditioner just barely cools the air in front of it, and definately not enough to cool the tetrode in the transmitter.

On top of all that, the electrical wiring is completely wired wrong, and there is no grounding straps on the coax anywhere along the tower.

So, when I replace this with our brand-spanking new FM25T next week, I'm having the building completely reducted and vented...and rewired!

Ahhh...inheriting stations is such a thrill!<P ID="signature">______________
Zach Morton
Chief Engineer
Legend Communications Of Wyoming, LLC.
KGWY/KAML/KIML/KLGT/KZZS/KBBS
Office (307) 686-2242
Cell (307) 660-9101</P>