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Air Conditioning ideas for Broadcast Engineers

HVAC ideas for the Broadcast engineer.  Or anyone else that cares about equipment cooling.

Chances are you'll also be the local Heating, Ventilation and Air Conditioning (HVAC) guru at your station.   At least the GM will call you before the A/C company to avoid another trade out.

Items you might want to include in a new station install or retrofit into your existing systems.

A/C systems can generate a lot of water quickly.   Leave a door open on a humid day and you'll be amazed at how fast the water will flow out of your system.   Keep in mind that things grow in this water.  Green things.  Sometimes green things gang up and become brown things.   Before too long you have a blockage.   If you planned well, the water will harmlessly flow out of your back up pan and send you a page.  Oh, how you ask?   You need to do some design work.

First, assume every A/C air handler WILL leak water.  It's not 'if' it's 'when'.  Make sure you have a full tray under it with a separate drain out to an exterior wall.  No need for a down spout on this one.  You want it to look odd that something is dripping from it.   Don't share anything with the primary system or that will be the  part that gets the clog.  Make sure the pan covers the entire width and depth of the air handler.  You can never predict where the water will come out first. Having that tray there will save a lot of water damage some day.

Get a device in the drain line that gives you a contact closure when the water gets too high.   Most of the time you want this to open the lead to your compressor contactor.  That stops the cooling which stops the water.  When people get hot, you get the call and then you figure out why the A/C stopped working. 

Get another device that goes into the condensate line at the hair handler to facilitate flushing.  The easier it is, the more often you'll do it.  I like this one from AirWaterTech:  http://www.airwatertech.com/ezkleenwater.html   You connect a simple garden hose, turn off the valve toward the air handler, then let it rip.   All the crud in your drain line is flushed out without backing up into the air handler.  Just be ready for odd looks as you walk down the hallway pulling a garden hose. 

You may have heard of using chemicals to keep drains clear.   I think I lost a coil to some tablets that went into the tray at the bottom of the coils.  After it had a gas leak, I could clearly see a color change where the tablets rested.  Moral of the story, use chemicals if you want, but OUTSIDE of the air handler and away from anything metal.   This device adds the chemicals in the PVC line so they can keep your line clear but not adversely effect your coils:  http://www.airwatertech.com/chemkleen.html

Or you could combine both ideas and use this part:  http://www.airwatertech.com/dualkleenwater.html

Most A/C systems run everything on a 24 VAC control system.  Your thermostat is switching this safe voltage, not the 208, 240 or 440 VAC that's doing the heavy lifting.   Use this to your advantage.  Add LED pilot lights to show you the status at a glance.   Is it warm?  Is the compressor being told to come on?  If it's pilot light is dark, you may need to check the thermostat.   If you connect some of these lines to your remote control, you could even tell if your site has problems.   If the duty cycle on the compressor is 100%, there's a good chance something is wrong.  Could be a total lack of cooling because you lost all your gas or maybe just dirty filters.  Either way, you'll start saving on your power bills as soon as you clear the problem.  You can also put warning lights across any cut-outs.  Larger systems usually have high and low gas pressure switches.   A big red light wired across one of these will show you exactly why the system isn't cooling.

You should already have a float switch on the condensate drain to shut down the compressor when the water is about to overflow.   But if you add a second one with a slightly lower trigger point, you could get an advanced 'heads-up' that the water is higher than usual. 

Differential air pressure gauges can show you when your filters need attention.   I've seen one busy open house clog the filters in a day.  A dust storm or sloppy contractor in the building can do the same thing.   Let a device show you the filters need cleaning, not your calendar.  For a local air-handler a device like this would be mounted on a wall:  http://www.dwyer-inst.com/htdocs/pressure/Model25-40Price.cfm  And at a remote site this could give your remote control a warning that the filters need cleaning: http://www.dwyer-inst.com/htdocs/pressure/SeriesADPSSpec.CFM  Just allow for some time delay for avoid extraneous readings during air handler startup/shut down. 

As good as these are, keep in mind that your filters are only as good as they were installed.   Are you using the right filters?   The ones you found when you got there might be totally wrong for the air handler.  Check the specs.   Even with the right ones, are they installed right?   Do you see gaps?   Is there a filler at one end or a gap?   If there are multiple filters, should you link them with duct tape?  I've seen filters that were perfectly flat at install time totally caved in a month later.   The constant suction pulls them toward the coils.  Once one of them bows in, you have a big gap.  The dirty air will take the path of least resistance and go straight for the coils.   Dirty air and the condensation on the coils means mud and crud in no time.   If you see signs this ever happened, you need to wash the coils.   If you're lucky, they're easy to get to.   After a few hours inside an air handler, you'll be checking the filters real often.   Your system will also work more efficiently when it's clean.  Clean coils mean better heat transfer so the compressor will run fewer hours a month and your power bill will be lower too.  Hose down the outdoor coils too.  Make sure there's no grass growing in and around the outdoor coils.   Nothing should slow down or divert the flow of air from the outside through the coils and out.  If you have a older system that's had filter issues for a long time, there's a good chance your air handler fan is dirty.   Time for a professional.   As bad as the crud may be, it's likely balanced crud.   Try taking some off and you'll have wobble in no time.

Another device I like to have at my facilities is a sight glass on the refrigerant line.   As long as you ask at installation or when you're changing a compressor, the A/C guys will usually solder in one at the cost of the part.  Once the system is charged with refrigerant, it will be an expensive upgrade.  When you suspect your system isn't cooling as well as it used to, take a look in the glass.   An occasional bubble rushing by is fine.  But if you see a steady stream of air or, worse yet, a few squirts of fluid going by, you've lost refrigerant.  Time for a service call including a leak check.   Scroll to the bottom of this page to see one:  http://www.rparts.com/Catalog/Major_Components/filterdryers/filter_dryers.asp   This isn't as good as connecting a set of gauges, but it's easy to read in a hurry.

Another thing... how OLD is your system?  If more than 10 years change it and thank me later.  No matter how nice it looks it's not efficient.   Major advances have been made in the last few years.   Believe it or not, the pay back could be measured in months thanks to a much lower power bill.  

Another trick from my past... We had to increase the capacity of the A/C in the server room.   We got a price from the A/C guy but a footnote mentioned a licensed electrician would have increase the power at the compressor from 20 to 30 amps.   I asked to see the spec sheets for the system they had spec'ed and all others in the same cooling capacity.  For an extra $200 I got a the model with highest SEER.   Why?  It was the one with the same cooling capacity that still required a 20 amp breaker.  Net result was we saved hundreds in electrical costs up front and maybe hundreds more later in reduced power bills.    Especially in system upgrades, ask for a listing of all the options.   A catalog page might open your eyes to a lot of improvements. 


A quick suggestion about the A/C compressors. I've had good luck with installing time delays on the compressors. Very easy to install when you install it on the 24 VAC line going to the contactor. I install mine in the outdoor unit, but as long as you interrupt the compressor lead, you could even do it inside next to the thermostat. Just be sure to label the thermostat so someone following you doesn't assume there's a problem with the compressor when it doesn't come on right away.

This is just one example. There are many flavors.


The idea is that this time delay will allow pressures to equalize after a brief power glitch. Another BIG plus is they can allow you to stagger the heavy loads coming up on your genset. At one location I had 2 compressors so I set one to 5 minutes and the other to 7. That allowed to load on the generator to come up in steps rather than all at once. These also protect you from the thermostat twidlers in the office that like to wiggle the thermostat while a contactor outside buzzes with surges.

While you're at it, think about adding some of these devices also to protect your A/C system from power problems (like the imbalance you mentioned):


Real good article by Clay Freinwald on page 34 of the Jan/Feb 2008 Radio-Guide about this.

(side note, Radio-Guide.com seems to be down with this message: "radio-guide.com expired on 11/23/2009 and is pending renewal or deletion." Note to self, get all domains off Network Solutions ASAP since they seem to think it's 2009)

You might want to use the same idea for other heavy loads like water pumps, heaters or building fans.

Another tip I learned from the A/C guy... check the current on your A/C blower motor regularly. Too low could indicate you're not moving enough air over the coils which will lead to ice. Too high and it could be working too hard. Add a CT connected to your Remote Control and you can keep and eye (and log) on it.


>Date: Mon, 25 Feb 2008 06:13:53 -0500
>From: Edwin Bukont <ebukont@msn.com>
>Subject: [RT] Three phase to single phase transformer
>To: <radio-tech@broadcast.net>
>your note on 3-phase power configs was timely. well known to most of us I
>I have a situation where someone purchased a 1-phase, 240VAC, 5kW solid state
>transmitter (TPO 3kW) and supplied it from a 3-phase, 208VAC service. The
>transmitter for the most part runs, but the low voltage keeps the supply fan
>from running correctly at low speed, thus it faults and the fan goes to high
>(Incidentally, the site keeps loosing compressors in its 3-phase air
>conditioners. I wonder if the imbalance in the load presented by the TX is
>causing issues for the compressors?)

Except for portions owned by others, Copyright: Ray Vaughan, 2008