In this last part of my Series on “Spring Cleaning” (maintenance), we will now actually start the unit and do some checks with the unit operating. You need to remember, SAFETY IS ALWAYS FIRST when working on any live equipment. Make sure you have your personal protection equipment and USE IT!. (Safety glasses, proper gloves, arc flash gear for high voltage equipment, proper meters, a gauge set and good hoses, etc.).
We have done all of our visual and non-operating electrical checks of the outdoor unit and have checked our air flow, filters, coils and drains on the indoor unit. This is also a good time, if you had not done so already, to get the INDOOR WET AND DRY BULB temperatures as we will need these once we go outside to start our refrigerant checks.
We have the disconnect shut off outside and we are now going to turn the unit on with the thermostat. While at the thermostat, if it is not a “hard-wired” thermostat or has batteries for back up or to keep it operating — now is a good time to check and replace the batteries in the thermostat. This is part of maintenance. You might also want to check and verify the schedule in the thermostat, time, set points and when it changes over. This is one little thing a lot of technicians overlook. Once all this has been done, now turn on the stat to cooling and go outside to continue.
Before turning on the disconnect switch, it is a good time to connect your gauges to the unit. You also need to get the OUT DOOR AMBIENT DRY BULB temperature. Also, hook up you temperature probes to the suction and liquid lines so you have them for your super-heat and sub-cooling calculations.
I think we are now ready? Then let’s turn the unit on and see what happens. Before we can take any pressure or line temperatures, we need to let the unit run for 15 to 20 minutes so the SYSTEM can come to equilibrium and everything has a chance to stabilize. Once we have let this run, we can then measure our suction and liquid pressure and our suction and liquid line temperatures. With these readings, we can then see what our super-heat and sub-cooling is and compare them to the manufacturer’s data for that unit. We also need to check the AMP draw on the compressor and on the condenser fan motor to make sure they are per the manufacturer’s ratings.
We now need to go back inside and measure the return air temperature and the supply air temperature. This will give us the “temperature drop” across the indoor coil. On AVERAGE, that should be around 20 degrees but that can vary based on the WET BULB temperature entering the coil. Again, check the manufacturer’s specs.
Now, if everything was within specs, and this was JUST an air conditioner, we could start to button up the unit and remove our gauges and probes. But if this was a HEAT PUMP, there are a few other things that should be checked before closing up the unit.
On the heat pump control, there is usually a way to “force” the unit into a defrost. This is a good item to check while you are there. Also, look at the ‘lock out’ temp for the compressor and the’ balance point’ change over temp and make sure they are properly set for your area. These may be on the control board, they may be part of the thermostat program, or there may be electro-mechanical or solid state controls added to the unit to handle this. Whatever you have, make sure they are properly set.
Lastly, and very importantly, verify the operation of the REVERSING VALVE. Most manufacturer’s energize the reversing valve in cooling (be sure to verify what the particular unit manufacturer’s sequence is) so disconnecting a wire from the valve should de-energize it and the unit should go into heating. Then reconnect the wire and make sure it shifts all the way and you are back in cooling.
With all of this done, we can now close up the cabinet, making sure all the panels are secure and all the screws were put back in or replace any missing panel screws. The one last thing I always did was clean the outside cabinet ( I know some guys that actually take the time to use car wax on it — a very nice touch!).
If you take the time to do proper maintenance and properly perform ALL the checks, this unit should function properly for your customer with few, if any, problems.
Hopefully this series has helped get your mind back into Air Conditioning mode as spring officially starts TOMORROW, Friday March 20th. I’m sure those of you in the south are possibly starting your spring cleanings
already but for those of us up north, it is getting closer. As I said from the start — feel free to create your own start-up list from these points I have presented.
Don’t forget, if you do run into issues, use the SEARCH box above and type in a keyword and chances are, there is a post here to help you. All I can say is AM I GLAD THIS WINTER IS FINALLY OVER and we can all start thinking about air conditioning season!
PS” DON’T FORGET ABOUT “SUMMER SNOW” — COTTONWOOD SEASON — AND MAKING SURE THE OUTDOOR COILS ARE CLEANED AGAIN IF YOU DO YOUR START-UPS BEFORE THIS OCCURS.!
(above picture from last year’s ‘summer snow” in St Louis — compliments of the York St Louis Branch Service Manager –Greg Sims)