I've managed maintenance for a small commercial building with McQuay HVAC equipment since 2017. I'm not a licensed HVAC tech. I'm the person who schedules the service, orders replacement parts, and answers the call when someone says the thermostat is lying to them.
I've also made—and written down—31 significant mistakes. Those mistakes cost roughly $23,000 in wasted budget. Most of them were avoidable. This checklist is the reason I made fewer of them after 2022.
If you are the entire facilities department for a small office, shop, or retail space, this McQuay HVAC maintenance checklist is for you. Small budgets don't deserve worse service.
Before you call for McQuay HVAC maintenance
I use this quick list before calling anyone. It doesn't replace a real service visit, but it cuts down on preventable callbacks.
1. Check the air filter by spec, not by memory
Why do I always start with the filter? Because the most expensive call I made in my first year was a 'no cooling' visit that ended with a contractor changing a dirty filter. The invoice was $185. The filter was $22. The lesson stuck.
Here's the part that took me longer to learn: don't trust the old filter as the correct filter. Someone before you might have installed a cheap filter, and then everyone kept ordering that same size. Your McQuay unit has either a nameplate on the filter rack or a label inside the access door. Use those numbers, not the dirty filter you just pulled out.
There is also a difference between HVAC filters and vehicle filters. Real talk: a Can Am air filter is designed for an off-road vehicle engine, not for a commercial air handler. I once watched a property owner try to save money by using a vehicle filter in a McQuay system. It didn't fit, airflow dropped, and the unit froze. Use the correct replacement filter and write the MERV rating on the filter housing.
2. Put the McQuay thermostat through a full mode test
Here's something vendors won't tell you: more than a few 'no cooling' calls are actually thermostat settings. A McQuay thermostat doesn't have to be complicated, but it needs to be checked in all modes before the season hits.
Press the mode button until you see Heat. Set the temperature above the room temp and wait for the system to respond. Then do the same in Cool. If your building doesn't use auto mode, leave it off. The important part is to look for a HOLD or OVERRIDE icon. A tenant can set a hold in January, leave in February, and the thermostat will stay in that hold until someone notices the bill.
Change the batteries at the same time. I'm not sure why this is so easy to ignore, but it is. A dead thermostat battery can cause a cold-building complaint in the morning while the system sits there with no power.
3. Give the outdoor fan a pre-season look
McQuay systems that are air-cooled rely on an outdoor fan to push heat away from the condenser coil. When that fan doesn't run, the pressure climbs, the unit trips, and a normal cooling day becomes a service call.
I learned this in 2022. A unit started short-cycling, and I was convinced we had a refrigerant leak. The technician found a plastic bag wrapped around the outdoor fan motor shaft. The system had already tripped on high pressure. That call cost $420 and included a lecture about looking before calling.
Before cooling season, turn off power at the disconnect and inspect the area. Remove leaves and debris from the fan guard and coil. Spin the fan blade by hand—it should move freely without scraping. If you see a cracked blade or a fan motor that smells burnt, call a qualified technician. Anything involving capacitors, refrigerant, or line voltage should be left to someone with the right training. Per EPA Section 608, refrigerant handling is not a DIY job anyway.
4. Look for infrared heaters pointed at thermostats
This is the step most people ignore, and it's the one that embarrassed me.
Infrared heaters are common in small commercial spaces because they heat objects, not the whole air volume. That efficiency is great. But if an infrared heater is aimed at a wall thermostat, it can heat the inside of that thermostat faster than it heats the room. The thermostat thinks it's warm. The HVAC system stops. The rest of the room stays cold.
In 2021, I installed a new infrared heater in a loading dock area. The heater happened to be aimed at the wall where the McQuay thermostat was mounted. The thermostat's reading looked fine, but the people at the other end of the dock were cold. I blamed the thermostat. The thermostat was not broken. It was receiving radiant heat, measuring the surface, and making the wrong decision. Move the thermostat or install a remote sensor; don't just throw a space heater at the problem.
5. Clear the condensate drain before the ceiling says hello
Air conditioning creates condensation. In a McQuay fan coil or air handler, that water goes into a drain pan and out a small PVC line. If algae or dust blocks the line, the pan fills and water finds its way to the ceiling or the floor. Not pleasant.
I once looked up at a ceiling tile that was sagging like a water balloon. The drywall repair cost $1,100. The drain cleaner cost $18. That math still annoys me.
You can reduce that risk without a service call. Turn off the unit, remove the access panel, and look for standing water in the pan. If the drain line has a clean-out tee, use a wet-dry vacuum to pull the blockage from the outside. Add a slow-release pan tablet at the start of cooling season. If you've never opened the unit, ask your technician to show you the safe way before you do it yourself.
6. Write the maintenance story down
The final step is boring, but it's the one that stopped the cycle of repeat mistakes. Keep a log for each McQuay unit: filter size and date, thermostat mode and setpoint, outdoor fan inspection date, drain treatment, error code, and service summary.
When a technician asks, 'How long has that filter been in there?' you should be able to answer without saying 'I think.' If you see a pattern, you can fix the root cause before it costs another $400 visit.
Small building, same standard
Look, I know how it feels to be the small customer. I've had a dispatcher tell me my building wasn't big enough for a rush response, even though the office was sitting at 96 degrees. I handled it by doing the easy checks before I called. You cannot always control a vendor's attitude, but you can control how prepared you are.
Small doesn't mean unimportant. It means your equipment still has to work for the people inside.
This was accurate as of spring 2025. McQuay model numbers, thermostat options, and parts change. Verify everything against your unit's nameplate and the manufacturer documentation before ordering or doing maintenance.
