Summer is here! Time for the Transmitter to get hot!

[alabamamic]

Summer is here and the temps will be getting brutal. We have 2 window AC units and they barely keep the building cool at our station in Georgia. Any other tips of the trade from you engineering types to keeping the equipment (mainly the transmitter) cool during the summer? Nothing sounds more professional than the transmitter cutting off for five minutes to cool off!

 

[techie2]

Get some more AC tonnage?

 

[TomT]

Maybe some exhaust fans? Pulls the cool air from the air conditioner through the transmitter, and shoves the hot air out. After all, unlike the usual home environment, you not only have heating from outside, but also heating from inside (the transmitter).

 

[ChiefEngineer]

Check to make sure your exhaust port opening isn't facing the normal incoming wind and exhaust the stack out for a few bucks with rigid vent. This helps a lot.
If wind usually comes from the west don't exhaust directly into it. Inexpensive louvered vents that close when not pumping air are available everywhere.

Insulate around the garage door with vinyl weather strip to at least seal it.

The problem with the window ac units is that every 3 years they need to be replaced. We paid 3 grand from a local heating and cooling guy for a 6 ton unit. Runs forever and has an air filter to lower particulates and dust.

Insulate the building. Close of the attic. A little osb board and that stuff is still inexpensive does a couple things. Keeps rodents out if it is installed in a proper way. reducing the room to exclude the attic and the insulation make it easier to heat and cool.

Put a thermometer on the stack to check the output from time to time. like the end of summer sale to get the meat thermometers for a buck.

 

[kyscott]

Here's a question for you. What do you do if one of the AC units die? Do you have any temperature alarms that will alert you the building is getting hot?

I would suggest what both techie and Tom suggest. Get bigger AC units. Also, hook up an exhaust fan with a couple of motorized louvers that will kick on and open on a preset temp (say 90*). If you don't have a temperature alarm, get one. You can buy a temp sensor or build one. Set it to alarm at 90* with the fan. That will buy you some time before things REALLY start to get interesting in that tube cavity.

If you don't have a backup to those AC units, you are playing Russian Roulette with your signal.

 

[rrsounds]

Air conditioning can be a tough battle. I have worked in just about every possible scenario:
• no AC, no blower (really bad!!);
• no AC, with a blower to the outside, and no transmitter ductwork (free-standing);
• no AC, with a blower to the outside via ductwork at output of transmitter;
• no AC, with ductwork from outside to intake of transmitter, along with a blower to the outside via ductwork at output of transmitter;
• AC with a blower (free-standing transmitter);
• AC, with a blower to the outside via ductwork at output of transmitter;
• closed-loop AC (free-standing transmitter).

The ductwork can work well, but will be a BAD thing if it in ANY way constricts the ability of the transmitter to blow heated air exhaust out. A blower, while useful in such situations, will most certainly result in disaster if it fails, as it will result in constriction of air flow.

As for ACs, I've seen everything from residential window ACs (trade outs!) to dual-redundant industrial ACs.

IMHO, the last example above, closed loop AC, while the most expensive, is the best, mainly because it is the cleanest.

It's a given that you have to get rid of the transmitter-created heat, along with fighting additional outside heat. But bringing in outside air has serious side effects, the most important of which is the amount of dirt that is brought in by incoming air that is replacing the air blown outside by the blower. Never mind that that air may be really hot, and useless for cooling.

By creating a closed-loop, and exchanging heat externally, the overall cooling efficiency is a bit lower than typical AC but you can keep dirt WAY down because you're not bringing it in in the first place. When your filtering requirements are only for re-circulated air, the filter can be a static-electricity type, which will remove even the finest dust particles. You couldn't use this type of filter with outside air, because it would soon be overwhelmed.

When the transmitter's air is clean, its efficiency does not deteriorate as when it accumulates a layer of dust on internal parts. So long-term transmitter reliability goes way up. Maintenance requirements for closed loop are nearly the same as for traditional AC, but the need for transmitter maintenance can be greatly reduced.

In the interest of absolute reliability, you can of course have a blower as an automatic backup in case of AC failure.

The reason I'm so gung-ho about this type of system is that the first time I ever visited a closed-loop installation, I was simply amazed at the cleanliness of the entire operation. It was in one of the rooms at the World Trade Center. The CE told me he had never had to clean out the transmitter! You could have eaten off the sparkling interior of the PA cavity. This, in direct contrast to the non-closed-loop AC I had at Z100 at the Empire State Building, where fine black dust coated everything.

While I hate to generalize, and I realize that in many cases the capital simply isn't available for such an investment, when it is, closed loop is highly recommended.

One final word: if you can afford a good system, you can also afford to have an expert design it. Unless you have experience in HVAC, outside help can prevent mistakes that can have long-term consequences.


Kind Regards,
David

 

[kyscott]

While I hate to generalize, and I realize that in many cases the capital simply isn't available for such an investment, when it is, closed loop is highly recommended.

A $100 fan and louvers from Grainger is better than nothing. I agree with you that a closed system with enough tonnage to keep it cool now and for future expansion is the ideal way. I have seen too many owners and engineers try to cheap out and it did nothing but cost them money having to constantly maintain the system. Keep in mind, if you have an exhaust hood over your transmitter, the hood does NOT attach to the transmitter itself. There needs to be about 6" of space between the transmitter and hood.

I would have loved to have seen the WTC site.

 

[mr_elbows]

the problem with the window units is not that they 'have to be replaced every three years'

the problem is that the outside coil is full of dirt on the side facing the outside fan

dust, dirt, pollen, bugs, (around here) 'fuzz' from cottonwood trees, other crap gets packed solid there, restricts airflow thru the coil, head pressure rises, the compressor kicks out on thermal switch, and the unit is 'condemned'

you can do it yourself if you have some help getting it out of the wall..........take off all the covers around the coil that you can, if it is encased in molded plastic you will need to use a 'cutter tip' on an old Weller soldering gun to slice thru the plastic (and that silvery AC sealing [NOT 'duct'] tape to reseal it with)

mix up a 1-in-5 solution of Formula 409, and soak down the gunk with it and let it sit a while

then using a garden sprayer (pump-up type) wash from the top down with clean water, the layer will literally 'peel off'

repeat as necessary, then flush it from the back side with a garden hose to remove the last bits

be sure to wash out the bottom pan with the hose and make sure none of the gunk is plugging the condensate drain for the inside coils

resist at all costs the temptation to 'take 'er to the car wash' because the pressures there will fold the fins over and you will spend HOURS straightening them one at a time

once it's clean, take it to an HVAC shop and have them install a charging tap on the low-pressure line and check the charge (most units DO leak a bit over time) and re-charge as necessary (which depends on air temp and humidity, among other things)

have them lube the fan motor and check the start capacitor for bulging top (sure sign of impending doom!) while they have it

check the power plug for signs of overheating, if you see that, replace the plug AND the receptacle into which it plugs

keep a filter on the inside coil, make sure it is slightly tilted outwards in re-install, and you're good to go

Gary

 

[littlejohn]

Haul the offending unit out of its case and put it in the bed of your (or the stations) pickup. Hie yourself to the local Ace Hardware and get a gallon of coil cleaner (which will work better than regular cleaners). Hie yoursel;f then to the localo carwash or station backyard. I favor the car wash. Soak the coils down using a pump sprayer, and then let the stuff foam for five - ten minutes. Blast it clean with the hose or car wash wand. Repeat till the coils look new. While you have access, take the front off and do the evaporator coil as well. If you don't have a set of service guages, or the unit doesn't have guage ports (many newer ones don't), take your AmpCamp<tm> and measure the compressor surrent before and after the cleaning. On a really dirty machine, you can knock 50 - 100 pounds off the head pressure, and 15 - 20% off the current draw.
Compute the heat load in the transmitter room, and install twice this in A/C capacity. In at least two units. Matters not they are window units or big systems as long as you have sufficient capacity. Close the place up and alarm it by putting a thermostat high on the wall set to like 90 degrees. Let it tally an alarm on your remote control.
Put you a purge fan with maybe three times the transmitter blower capacity high up, and across the room an air - loaded louver/filter. Set it on a thermostat by the first one, to come on at a slightly highwer temp.
Voila! Cool clean RF plant with alarm and redundancy.

 

[busyradioguy]

RE: Taking the unit to a car wash. Please see what Gary wrote above:

resist at all costs the temptation to 'take 'er to the car wash' because the pressures there will fold the fins over and you will spend HOURS straightening them one at a time

 

[OKCRadioGuy]

A guy does need to be careful to not bend the fins up. Car wash power levels can do it, but if a guy is careful it won't. Just don't get too close and pay attention. Call me a Okie, but I just put mine in the back of the truck bed and get after it at the car wash. I haven't bothered with coil cleaner but that would be a great idea as it would clean things a bit better. The main thing is get all that clogged crap out without soaking the electronics. Also, make sure and let the thing dry out for a day before plugging it in! It pays to start this project actually BEFORE summer hits so you don't have to worry about having to be without for a day for it to dry out.

I really like the exaust fan idea and the thermostat. I've used the thermostat at a station I used to work at. We didn't have a budget to get a real sensor so my 15 bucks at Ace Hardware saved me a lot of headache when their old junk air conditioner failed. Sure beat being off the air and having to jump in run because the temp was 100 plus in the room.

One thing the original poster might do is go out and feel how hot the air is on the outside fins and how much air is coming out. If the outside fins are very hot and have very little air blowing out than there's the problem: RESTRICTION.

I recently had a stopped up coil issue at my transmitter site where it's pretty rual and dust and pollen had stopped up things. There is no water at the transmitter. After thinking about it for a while I got the nitrogen bottle with regulator out to the air conditioner and gave it a nice 25lbs blast. WORKS GREAT (making sure I didn't damage the fins of course!!)

Good luck!

 

[littlejohn]

I wrote on the assumption this gent is engineering in a small marklet. He knows how to be careful if that's the case.
But the point is well taken..... go gently. I airhose them and then turn them back on, haven't had a problem.
Coil detergent has a fair amount of phosphoric acid in it, which gets the crud right off the aluminum and copper in the condensor and evaporators. Helps the efficiency measurably.
We clean coils every year here on four stations. I schedule for second quarter, but hold the guy off till the dandelions bloom. That way, we get the dandelion fuzz along with the crud.

 

[NE Miss Radio]

Alabamaniac, do you exhaust from transmitter to outside? Are you sure that not only the main blower, but also any IPA or other fans inside the transmitter are operational? You could have some other, smaller fan with problems. My transmitter had 3 fans in addition to the main blower.

In Mississippi, I ran the exhaust to the outside thru ductwork. I had a thermostat-controlled attic fan (about 40 bucks) at the top of the transmitter bldg set on about 85 degrees, with intake at floor level. I put filters on the intake to the building and the transmitter.

I was able to run without A/C. However, it was just the transmitter shed (not the studio location).

 

[kyscott]

This is an excellent way because it also keeps heat from building up in your attic (if you have one).

I would like to make one point about the exhaust fan. If you have a side of the building that is facing, or close to, a wooded area, put the intake louvers on that wall. I worked at a transmitter site that had one side of the building up against a wooded area and the other side faced the afternoon/evening sun. Guess what walls they put the fan and louvers on. If not this, put the intake louvers on the east side of the building with the rising sun.

 

[rfry]

I had a thermostat-controlled attic fan (about 40 bucks) at the top of the transmitter bldg set on about 85 degrees, with intake at floor level. I put filters on the intake to the building and the transmitter. I was able to run without A/C. However, it was just the transmitter shed (not the studio location).

Pulling or pushing filtered cooling air into the building, and venting it out with a fan leaving a slight positive pressure in the room will tend to keep the equipment and building cleaner, because this avoids inhaling dust/dirt/bugs through the gaps around doors and windows.

//

 

[rrsounds]

One thing I think should be mentioned is that the for a given air flow, the larger the cross section, the less pressure and velocity. This can be used to advantage.

For example, in a location that had a bad problem with dirt/airborne crap gumming up a set of window ACs, they built a large box entirely surrounding the external part of each AC, made up of a simple open wood frame covered only by relatively open filter material. Since the filter area of this box is many times that of the intake of the AC, it gets much less clogging than the AC would by itself. The reduced pressure of air drawn in being distributed over a larger area means the particles don't get too wedged into the filter fibers. By making it removable, it also can be cleaned without needing to take the AC out of the wall, or even discarded if it gets too ratty.

Obviously filters with too high of density could be counter productive, overloading the AC. But once again, the larger the surface area, the less likely this is to happen.

As usual, YMMV


Kind Regards,
David

 

[Dr. Bob]

There are some excellent ideas in this thread but I need to add something that was not discussed.....

If you cool air below its dew point the water in the air will condense. The condensation of the water in the air requires significant amounts of energy. This is important in areas (like the Southeastern U.S.) where the temperature and relative humidity can be high.

Under conditions of high temperature and high humidity, less energy may be required to cool down the transmitter exhaust than to bring in air from the outside and subsequently cool it. This is a straightforward calculation if the temperatures, dew point and volume of air are known.

Dr. Bob

 

[The Beave]

Some of the transmitters here in Arizona have been configured to draw in cool air from a central air unit outside the transmitter and an exhaust blower out through a wall or roof of the building. The idea is to keep the building at about 65, and the inside transmitter at around 78 degrees. I have seen transmitters at stations have blower failures when the AC kicks off for some 3-4 hours at 100+ degrees F. Now they are meticilously maintained, aswell as the Aux. Transmitter and Back-up Generator.

 

[Jim Graham]

And small market stations wonder why they can’t find a good engineer to work for them. When I WAS doing part-time work, around ’91 I was building a Class A and installing a 5 KW Continental FM transmitter. I specifically told the “Manager” (not the owner) to install a 3-Ton AC unit and a whole house fan with louvered, filtered intake in case the AC failed. He gets an HVAC guy up there who asked why we wanted a 3-ton AC in such a small building (approx. 12’ x 10’) and that a window unit would be more than sufficient. Guess who the Manager listened to. At least the back up ventilation was in place. Sheesh...... JG

 

[busyradioguy]

Here's one question about window units... Aren't those things easy targets for vandals? Yeah I know, the shack is fenced and the warning signs are posted. But there have been stories in the past about transmitter room break-ins. Seems to me a window unit would be serving as an "Enter Here" sign for those vandal idiots.