McQuay Air-Cooled Chiller Maintenance: A 7-Step Parts Checklist That Won't Blow Your Budget

I've been managing the parts budget for a 40-person commercial HVAC service company for the last six years. We spend roughly $180,000 a year on replacement components, and a significant chunk goes to McQuay air cooled chiller units in older commercial buildings. This checklist came out of that experience.

Before you start, one honest boundary: this list assumes you’re working on a McQuay air cooled chiller with a screw compressor, and that the same mechanical room has a refrigerated air dryer on the instrument air system. If you’re maintaining a water-cooled centrifugal or a residential heat pump, your part numbers and pressures will be different. I can only speak for the commercial line—the air-cooled screw machines we’ve serviced since about 2010.

There are seven steps. Read them all once, then use them as an order-and-inspect checklist.

The 7-Step McQuay Air-Cooled Chiller Parts Checklist

Step 1: Pull the actual nameplate data

Don’t order anything from memory. McQuay’s part numbering has gone through several revisions, and many chillers now carry Daikin Applied nameplates. On a typical air-cooled screw chiller from the 2000s, the oil filter is the 7384-188 McQuay oil filter HVAC parts item. But I’ve seen the same housing use a different gasket after a mid-production change.

Take a photo of the chiller nameplate and the compressor nameplate. Note the serial number. Then call a supplier with that number. This sounds obvious, but in 2023 I approved a $400 filter kit using the unit’s model number alone, and the gasket didn’t fit.

Step 2: Order the 7384-188 McQuay oil filter HVAC parts before opening the loop

If you verify that you’re working on a McQuay screw chiller from the 2000–2015 generation, the filter you’ll likely get is the 7384-188 McQuay oil filter. Wholesale pricing I’ve seen in Q1 2025 is roughly $55–$85, but verify current rates before budgeting. The OEM filter includes the proper bypass valve and gasket. A generic “universal” filter might save $20 until it opens the bypass at the wrong differential.

Counterintuitive, but true: you usually don’t need to drain the entire oil charge to change the filter. Following McQuay’s IOM manual (available through Daikin Applied), with the service valve closed, you can swap the filter and keep the oil in the sump. That saves time, oil, and disposal fees.

When you open the old filter, look at the media. Fine metallic gray dust is normal. Chips or flakes mean serious wear. If you see chips, don’t just replace the filter and close up—tell the owner to schedule a compressor check before it fails.

Step 3: Diagnose the solenoid valve before replacing it

Solenoid valves control hot gas bypass, liquid injection, and fan staging on McQuay chillers. When they fail, symptoms include erratic capacity control, low suction pressure, or a compressor that short-cycles.

Test the coil resistance first. The most common failure I see is a 24V coil on a 120V circuit, because someone swapped the coil last year and guessed. It burns out almost instantly. Also check the pilot port for debris. A dirty pilot port can make a perfectly good valve act dead. In those cases, cleaning the valve and replacing the filter drier is one-tenth the cost of a full valve assembly.

If you do need a replacement, record the valve model number from the nameplate, not from the old part, because the valve body may have changed over the years.

Step 4: Clean the intake filter—including how to clean a K&N air filter

This is the step that disappears from most PM checklists because it isn’t on the refrigerant loop. On a McQuay unit, the control panel cooling fan pulls room air through a filter. If that filter is clogged, the controller cabinet runs hot. On some installations, the washable filter is a K&N HVAC filter—not the automotive kind.

Here’s how to clean a K&N air filter for an HVAC application:

1. Turn the unit off and remove the filter from the housing.
2. Vacuum loose dirt from the outside with a soft brush attachment.
3. Rinse with low-pressure water—from the clean side to the dirty side. Don’t use a power washer.
4. Let it dry completely before reinstalling.
5. If it’s a K&N home HVAC filter, don’t oil it after cleaning. That’s a common mistake among techs used to automotive K&N filters.
6. If the media is wrinkled, torn, or missing its rubber frame, replace it.

One caveat: K&N’s official instructions differ by product generation, so check the label on the filter. This is the basic routine that works for the washable home filters we’ve used, not a substitute for the manufacturer’s directions.

Step 5: Don’t ignore the refrigerated air dryer next to the chiller

In many commercial plants, the refrigerated air dryer supplies dry air to the controls that run with the chiller. It isn’t part of the McQuay package, but it protects the solenoid valves and actuators. If moisture gets through, the plunger in a solenoid valve can rust and stick.

On each PM visit:

• Record the dryer’s inlet and outlet air pressure.
• Check the condensate drain operation. A drain stuck open will waste purge air and keep the dryer’s refrigeration compressor running continuously.
• Clean the condenser coil on the dryer. Dust is the number one reason these units short-cycle.
• Note the dew point if the dryer has a readout.

I learned this one the hard way. I assumed an automatic drain meant self-cleaning. Then our refrigerated air dryer’s drain failed open, and the unit ran for two weeks without cycling. That caused a frozen evaporator and a damp building. Now the drain test is on the checklist.

Step 6: Track total cost, not line-item price

Here’s where my procurement hat comes on. I’ve compared vendors on the same McQuay parts bundle—oil filter, solenoid coil, dryer filter—and seen price differences of 30–40%. But the lowest quoted price wasn’t the lowest total cost when freight, lead time, and minimum-order fees were added.

For the 7384-188 McQuay oil filter, for example, Vendor A may quote $65 with free freight, and Vendor B may quote $55 plus $22 freight and a $50 minimum order. If you only need one filter, Vendor A is cheaper. If you’re ordering a quarterly kit, Vendor B might win. That’s why we use a simple spreadsheet with columns for part number, vendor, order date, promised date, actual date, freight, and a “notes” column.

After tracking nine orders in 2024, we found that 14% of our maintenance budget was going to freight and special-order fees. We consolidated part deliveries to one scheduled weekly order and cut those fees in half.

Step 7: Capture startup readings before you leave

After any oil filter or solenoid valve replacement, start the chiller and write down the baseline readings: oil pressure differential, discharge pressure, suction pressure, liquid-line sight glass, and amp draw on each compressor. The numbers matter less than having them on the same work order as the part replacement.

In my 2023 audit, 20% of our callbacks on McQuay units had no startup readings on the ticket. When the tech returned, there was no baseline to compare against. Add a photo of the pressure display to the service record if you can. It costs 60 seconds and saves hours later.

Common Mistakes That Expire Budgets

Here are three patterns I see repeatedly:

• Mixing filter compatibility with bypass rating. An incorrect oil filter can have a different bypass valve setting, which may send unfiltered oil through the compressor when the oil is cold.
• Guessing the solenoid coil voltage. A 120V and a 24V coil can look identical until smoke appears. Read the label.
• Skipping the K&N air filter twice. If you clean it only when it looks dirty, you’re likely cleaning too late. Add a calendar reminder at the same interval as the condenser coil cleaning—usually semi-annual.

When This Checklist Doesn’t Apply

I want to be honest about limits. If you’re managing a water-cooled McQuay or an older reciprocating chiller, this list will only get you partway. The solenoid valve locations, oil filter housing, and air dryer relationship are all different. If your building uses packaged rooftop units, the refrigerated air dryer step probably doesn’t apply at all.

For critical facilities like hospitals or data centers, I’d use genuine McQuay OEM parts and match the exact serial number. For a warehouse comfort unit with a good PM schedule and no acid contamination history, a well-documented compatible filter is a reasonable choice. The point is to make that decision consciously, not on a Friday afternoon with a service call waiting.

If you’re in doubt, call Daikin Applied with the McQuay serial number. That costs nothing and keeps you from buying the wrong part for a 20-year-old chiller.