coil Archives - HVAC School

In commercial HVAC you will find several different types of multi-stage evaporator coils, intertwined (like shown above), horizontal face split (one coil on top of another), and vertical (side by side).

Pay attention when staging a horizontal evaporator to ensure that stage #1 is on the bottom and stage #2 is on the top. If stage #1 is on top you risk condensate being pulled off of the coil when the water runs down the wet fins and then hits the dry second stage on the bottom.

By keeping stage #1 on the bottom the moisture adhesion will stay consistent as condensate drops no matter if one or both stages are calling.

You can also have this same effect when stage #1 fails and stage #2 keeps running on a stacked horizontal coil.

— Bryan

Tech Tips

Checking Evaporators on Furnaces

March 3, 2018 By Bryan Orr 2 Comments

In Florida, there are not many gas furnaces, At least not as many as up North. Sometimes we can look like real dummies compared to techs who work on them everyday.

One thing to know about 80% gas furnaces with cased evaporator coils is that you can often check the evaporator coil by removing the high limit and running an inspection camera up through the opening.

You may also be able to use a mirror and flashlight but you usually won’t see much due to the heat exchanger being in the way. Otherwise, you are stuck removing the entire blower assembly… and that’s no fun at all.

Another practice is benchmarking the static pressure drop across a new coil when it is dry and wet when installed or during the first service call. You can then easily watch coil loading over time without the need to look at the coil visually.

— Bryan

Tech Tips

Maintenance During Major Repairs

January 17, 2018 By Bryan Orr 2 Comments

Every contractor is different, I get that. we don’t all need to do everything the same way or include the same services with repairs but there are some “best practices” that can save you a lot of heartache before, during and after you make a big repair.

Catch it During Diagnosis

Let’s say you find a failed, shorted compressor on a 7-year-old system that still has manufacturer parts coverage. If you simply quote the compressor and leave you may be missing a lot of other maintenance related issues that can affect operation once the compressor is replaced. A short list of items to check would be –

Look at the accumulator for signs of corrosion
Acid test to see if a burnout protocol should be used
Check the air filter
Inspect the condenser coil cleanliness
Look at the underside of the evaporator coil
Perform a static pressure test on the system to check for duct issues
Check the crankcase heater (if it has one)
Inspect the contactor
Check condenser fan and blower motor amps
Test all capacitors
Visually inspect wires and cap tubes
Check high voltage electrical connections

And this is just for cooling side issues. If the system is a fuel-burning appliance you would inspect every part of the furnace operation as well.

Testing all of these things is commonplace AFTER a repair, but it makes so much more sense to do it beforehand so that you can either charge appropriately for any of these items that need to be addressed or let the customer know you are including them to differentiate you from the competition.

Things to Do Along With Major Repairs

There are a few things you need to do as a matter of course during major air conditioning or refrigeration repairs that just make good sense to prevent callbacks. You can include them in the price or not or not but either way, it will save you more than it costs to do it.

Clean the drain line and condensate pan (seriously…. do this)
Wash the condenser coil
Clean the blower wheel (if it is dirty)
Change the air filter
Test both modes of operation

Do these things along with all of the standards tests you perform to make sure that you have no issues and that whatever caused the fault in the system has been rectified and you will save a lot of problems. When the customer spends a lot of money getting a system fixed, they don’t want to turn around and have it fail for an “unrelated” reason.

While this list is clearly tailored to the residential and light commercial air conditioning market, every piece of equipment has its common maintenance items. So what do you do every time when you make a major repair?

— Bryan