McQuay Water-Cooled Chiller: A Cost Controller's 6-Step Pre-Approval Checklist

If you're sitting on the budget side of an HVAC decision—facilities manager, plant engineer, or whoever gets asked to "just sign off" on a McQuay water-cooled chiller repair—this checklist is for you. I've managed our plant's HVAC and mechanical budget for about six years now. That's roughly $180,000 in chiller-adjacent spending I've had to justify to leadership, and I've made enough expensive mistakes to start writing everything down.

This is the list I run through every time a chiller proposal crosses my desk. Six steps, in order. Step 4 is the one almost everyone skips, and it's the one that ends up costing the most.

Step 1: Get the serial number before you get quotes

The model number tells you what the unit is. The serial number tells you what it actually is.

McQuay built chiller models across a lot of vintages—WSC, WDC, WMC, and others—and the parts situation looks completely different depending on the year. I've seen two sites with "the same" chiller model where one had easy parts availability and the other needed a 14-week lead time for a control board.

The data plate is usually inside the control panel door. Write down the full serial number, not just the model. Then call the manufacturer's tech support (McQuay operates under Daikin Applied now) and ask for the build history for that serial. The call costs you nothing—well, a few minutes on hold, but nothing in dollars—and it tells you the refrigerant type, the original options, and whether this unit is from an era where parts are still easy to get.

In my first year on this job, I made the classic specification error: assumed the model number was enough to order parts. It wasn't. A $4,100 approved quote turned into a $4,700 total after the wrong part and a restocking fee. I've never repeated that one.

Step 2: Write down the controller password before the previous operator walks away

This sounds too small to matter. It isn't.

McQuay chillers run on MicroTech controllers, and the setup menus are password-protected. If the person leaving your site doesn't hand over that password, you'll pay for it repeatedly. Every time a service tech needs to check setpoints, change a schedule, or pull operating data, that's an extra trip—at service-call rates, not break-fix rates. I've seen the same "chiller locked out" problem turn into three separate visits because nobody had the access code.

So put the password in the handover documents like it's a spare key. If you've already inherited a unit with no one who knows the code, don't pay a vendor a couple hundred dollars to "recover" it. Call Daikin Applied tech support with the serial number and proof of ownership, and they can walk you through the reset. It takes some paperwork, but it's a whole lot cheaper than a lockout call every time you need access.

If I remember correctly, the factory default on the older MicroTech panels was something basic—but most sites end up with a custom password set during commissioning, and that's the one people lose.

Step 3: Run a performance baseline before you authorize anything

When a vendor tells you "this chiller is done," the first thing you need is your own baseline. Otherwise you're negotiating from zero.

This is a day of logging, not a full study. Record entering and leaving condenser water temperatures, evaporator temperatures, refrigerant pressures, and power draw at a steady load. Compare them to the rated conditions under AHRI Standard 550/590, which is the industry rating method for water-cooled chillers.

A useful rule of thumb: condenser approach—leaving condenser water minus refrigerant condensing temperature—should be roughly 3 to 5°F on a clean shell-and-tube unit. If your approach is running 9 or 10°F, the machine isn't necessarily dying; it's telling you there's a water-side problem. That's a different, much cheaper conversation.

That baseline also gives you leverage. I sat in a meeting where a vendor recommended a compressor replacement based on "high discharge pressure." We'd logged the approach temperature the week before, and it pointed hard at a fouled condenser. A tube cleaning and a water treatment adjustment—two weeks and about $800—brought the unit back to normal. That machine is still running three years later.

Step 4: Look at the water side—the part everyone skips

This is the step I'd go back and force on my past self. If you're inheriting, buying, or approving a budget for a McQuay chiller, the water side is where the hidden costs live. At least, that's been my experience with mid-size facilities.

Before you commit to a re-tube, a new condenser, or any major component, do three things:

• Run an eddy current test on the tubes. It's a standard non-destructive test that finds thin or pitted tubes before they fail. It costs a fraction of what a surprise tube leak costs, and it gives you a real number instead of a guess.
• Ask to see the water treatment records. No records? Treat that as a red flag. Poor water chemistry causes more chiller failures than compressor wear, and it's the cheapest thing to fix—if you catch it early.
• Check strainers and flow. Low evaporator or condenser flow is a silent killer. A $100 strainer cleaning has saved me more than one "we need a new chiller" conversation.

I almost signed off on a $23,000 condenser replacement a few years ago. The eddy current test came back clean, and the real problem was a partial strainer blockage and a flow rate that was 40% below spec. We spent an afternoon cleaning the system. Even after we went the cleaning route, I kept second-guessing—what if the test had missed something? The week between cleaning and startup was stressful. Then the approach number dropped back down to around 4°F, and I finally relaxed.

I'm not 100% sure the vendor was misleading me on purpose. I think they just hadn't looked at the water side either.

Step 5: Check parts availability for that specific vintage

Not all McQuay parts are created equal. Some vintages are well covered; others have control boards and compressor parts with long lead times or no stock at all.

Once you have the serial number from Step 1, verify parts availability before you accept a quote that says "remanufactured compressor" like it's a casual line item. Ask where the part is coming from, what the lead time is, whether it's new or remanufactured, and who stands behind it. A $4,000 compressor with a 16-week lead time is a different decision than the same part in four weeks.

I've also seen salvage units become the parts source—same model, same vintage, sitting in another mechanical room. That's legitimate, and sometimes it's the only economically sensible option. Just know what you're agreeing to.

Step 6: Put the real total cost in one spreadsheet

By now you have the vintage, the access situation, the performance baseline, the water-side condition, and the parts reality. That's everything you need for the actual decision—repair or replace—and it needs to come down to one number, not a gut feel.

Build the TCO comparison like this:

• Energy. Use your Step 3 baseline to estimate current kW/ton. Don't let a vendor promise a specific efficiency improvement unless they'll write it into a contract—and even then, read the exclusions.
• Service history. Pull your actual call frequency. If you don't track it, start now. In my experience, the first thing that disappears when a machine is failing is a clear picture of how many times it actually failed.
• Water treatment. This line item never goes away, repair or replace.
• Downtime cost. What does losing cooling cost your building for a day? Use a real number, not an emotional one.
• Fees you can see. Rigging, crane rental, refrigerant recovery, disposal, startup, warranty. Ask any vendor to list what's NOT included—I've learned to ask that before I ask the price. The vendor who lists everything upfront, even if the total looks higher, has been the cheaper partner more than once.

When I built our first real TCO spreadsheet, I found that a solid majority of our budget overruns on mechanical projects came from line items that were never in the original quote. Now our policy is simple: no quote gets approved without a line for unexpected items, and no vendor gets approved without a written list of exclusions. Not because vendors are hiding things on purpose—it's that "standard" means different things to different people.

Notes and common mistakes

Three things to flag before you run off and do this:

1. The password thing isn't a joke. The most expensive words in a chiller plant are "I don't know the code." Put it in writing. And don't pay someone to recover it if you own the unit—the manufacturer's reset process with the serial number is the cheap path.

2. Watch for scope creep in the other direction. A smart thermostat is a great retrofit for a small comfort system, but it does not replace heating and air conditioning at a building scale. I've had that conversation with leadership more than once, and it usually means someone is trying to avoid the chiller budget. Same thing when a project suddenly grows a compressed air dryer or a "shark fan" line item—those are real pieces of equipment, but they belong in the project budget as their own line items, not buried in a chiller authorization.

3. Data beats stories. The first time I went to my finance team with a recommendation, I had a vendor's story. The second time, I had approach temperatures, service records, and a TCO table. Guess which one got approved?

Run the six steps before you sign anything. The number you bring to your finance team will be defensible—which is more than I can say for my first chiller budget.