HVAC Checklist Before Summer: What to Do in February and March

Cooling season in the Rio Grande Valley effectively starts in April and does not really let go until October. Six months of near continuous operation finds every weak point in a system.

The point of a pre-season checklist is to find those weak points in February, when a repair is a scheduled appointment, rather than in July, when it is an emergency call in a 95 degree house.

Here is what to do, in order.

Do it yourself: six tasks, about an hour total#

1. Replace the air filter#

Start here because everything downstream depends on airflow.

Pull the filter and hold it up to a light. If you cannot see light through it, it has been restricting airflow for a while. Note the size printed on the frame so you buy the right one.

For most residential systems, MERV 11 to 13 is the right target: good filtration of pollen, dust, pet dander, and mold spores without excessively restricting airflow. Going much higher than the system was designed for causes frozen coils and blower strain.

If you find yourself changing a one inch filter every three weeks, ask about a deep media filter cabinet. It holds far more dust before restricting airflow and does a better job on fine particles.

2. Rinse the condenser coil#

Turn off the breaker for the outdoor unit first. There is usually a disconnect box on the wall next to it.

Then rinse the coil with a garden hose, spraying from the inside out so debris exits the way it came in. Work top to bottom, all the way around.

Two things not to do: never use a pressure washer, which flattens the fins and permanently reduces the coil's ability to reject heat, and do not spray water into the electrical compartment.

If the fins are visibly matted with cottonwood or grass, a coil cleaning solution from a hardware store helps. Follow the directions on the bottle.

3. Clear space around the outdoor unit#

Two feet of clearance on all sides, several feet above.

Cut back shrubs and vegetation growing toward the unit. Move stored items. If a fence was built close to it since last summer, that is now restricting the airflow the unit needs to reject heat.

4. Flush the condensate drain#

This is the highest value five minutes in the entire list for a Valley home.

Find the drain line access near the indoor air handler, usually a capped PVC tee. Remove the cap and pour in about a cup of distilled white vinegar. Replace the cap.

If the line is already partly blocked, take a wet/dry vacuum to the outdoor end of the drain line, seal the hose over the pipe, and run it for two or three minutes to pull the blockage out before adding the vinegar.

Then put a reminder in your phone to repeat this every two months through October.

5. Test run the system#

Pick a warm afternoon, set the thermostat several degrees below room temperature, and let it run for 30 minutes.

Then measure. Hold a thermometer in the airflow at a supply register near the air handler, and another at the return grille. The supply air should be roughly 16 to 22 degrees cooler than the return air.

If the split is smaller than that, something is wrong: low refrigerant, restricted airflow, or a dirty coil. Finding that in February is very different from finding it in July.

While it runs, listen. Grinding, screeching, rattling, or a new hum that was not there last year are all worth mentioning to a technician.

6. Walk the house#

Go room to room with the system running.

• Is air actually coming out of every supply register?
• Are any registers closed or blocked by furniture?
• Are return grilles clear?
• Do any rooms feel noticeably warmer than the rest?

Note anything you find. A room that has always been warm is usually a duct problem worth diagnosing, and a room that has recently become warm is worth mentioning specifically.

Get it done professionally: three more#

7. Book a cooling tune up#

February through early April is the window. A proper tune up measures rather than inspects:

• Capacitors tested under load against their rated values
• Amp draw compared against the equipment nameplate
• Refrigerant pressures with superheat and subcooling calculated
• Static pressure measured
• Condenser coil cleaned, evaporator coil inspected
• Condensate drain flushed and float switch tested
• Thermostat calibration and configuration verified

Ask for the readings. That is the product. A capacitor rated at 45 microfarads reading 31 is a failure waiting to happen, and only a meter finds it.

8. Have the ductwork looked at, once#

If you have never had static pressure measured, this is the year.

High static pressure means the duct system cannot move the air the equipment needs, and it is the underlying cause of a surprising number of complaints that get blamed on equipment: rooms that will not cool, frozen coils, high bills, and premature blower failures.

You only need to establish this once. If your duct system is fine, you know. If it is not, sealing and correcting it usually produces a bigger comfort improvement than new equipment would.

9. Decide about an aging system before you need to#

If your system is over 12 years old, February is the month to have the replace or keep conversation.

Deciding in February means comparing options without pressure, getting several quotes, arranging financing if you want it, and scheduling the work when it suits you. Deciding in July means making a five figure decision in a hot house from whatever is in stock.

Also worth doing while you are at it#

Check that the fan switch is on AUTO, not ON. Continuous fan operation in a humid climate blows air across a wet evaporator coil after the compressor stops, evaporating moisture back into your house.

Update the thermostat schedule. Set it around your actual routine, with four to six degrees of setback while away rather than turning the system off.

Check ceiling fan direction. Counterclockwise in summer pushes air downward and creates the breeze effect that makes a room feel three to four degrees cooler.

Look at your attic insulation. If you can see the tops of the ceiling joists, you do not have enough, and attic insulation is one of the more reliable improvements in this climate.

The one week timeline#

If you want to just get it done:

• Saturday morning: filter, coil rinse, clearance, drain flush (about an hour)
• Saturday afternoon: test run and measure the temperature split, walk the house
• Monday: book the tune up, mentioning anything you found

That is the whole thing.

The short version#

Filter, coil, clearance, drain, test run, walk the house, book a tune up. Do it in February or March, while a problem is still an appointment rather than an emergency.