Trouble Shooting Your Chiller System

man speaking in front of a wine chiller system

By: Tom Payette – Winemaking Consultant

This should be your first resource before contacting your refrigeration guy/gal or chiller supplier.  It is hoped this document will take you or your winemaking team through some thought processes to help diagnose your chiller problem and to help you know the answers to their questions if you do need to call.   Use common sense in all features of what you do when trouble shooting your chilling unit.  Make sure to employ all proper “Lock out Tag out” procedures and to use all safety procedures known …. plus, good common sense.

  Make sure to have your manual for the unit handy and try to be somewhat familiar with the chilling unit.  If you are not familiar – it’s not too late to start learning your system!  What should your propylene glycol temperature be and what is the unit set on?

Understanding the Unit

  At some point, while your refrigeration person is on the premise already, question him or her about some of the operations of your chilling unit.  You will want to know : where the compressor is; the condenser; the expansion valve; where the transfer of cooling from the refrigerant to the glycol solution is located; cooling fan coil; compressed Freon line; expanded Freon line; the glycol chilling loop, the glycol chilling reservoir, electrical contacts if any etc.  Understand the basics so you can help communicate to your refrigeration person what is happening with your unit once you know something is wrong. Your supplier is also your best first resource in trouble shooting the unit.

So, Your Chilling Unit is Down or not Chilling Properly

Power: May sound silly but check to make sure the unit is getting the proper power.  Perhaps turn the unit off, reset the breaker and turn the unit back on again.  If the unit is not hard wired be sure to check the plug and see if one leg of the power has become weak/loose/disconnected/broken.  Use a volt meter and start to trace the power from the supply to the unit.  Has a phased dropped out from the power company or transformer?   From experience -this is possible.  You will be surprised how many times a service tech comes out to winery and simply traces the power and voila – you are billed for a heavy service charge for the flip of a breaker or resetting the male end of the power supply.  Use a volt meter and be very very safe.

Contacts and other electrical notes: Are contacts (if still equipped) pulling in when they should to engage certain motors or functions?  Do you know how to test them?  Are simple fuses all intact or do they need replacing?  If you “trick” the unit into doing a certain function – does the unit respond?  Do motors function independently when you ask them to?  [More of an over-ride call for use].  Are there any flashing lights indicating a problem?   Your supplier should be able to talk you through much of this.

Amps: Do you have a volt meter and an amp meter?  Do you know how to use them to find out if you have power where you need to have power?  How many amps is the unit pulling?  How many amps should it pull?  Be careful.  These are electrical connection questions.

Sounds: Does the unit sound like it normally has and does?   You should listen for your chilling unit every time you enter and exit the building.   We can often hear our chilling unit from the crush pad.  Did you notice any odd sounds recently?  Did the unit cycle on and off frequently recently?  If equipped with belts – did you hear any belts squeal?

Smell: Has the unit given off any odd smells recently?  Does or did the unit smell hotter than typical.  Does the motor(s) feel the same as when the unit was working properly?  Are bearing areas hot?  “Singing bearings”?

Winery air temperature feel: With cellars and barrel rooms that use “Krack” style units to chill their tank room, barrel room and case goods area(s) one can often “feel” when something is not right with their chilling unit.   Often when visiting clients in the hotter summer months of July and August I can walk in their cellar and know that something is not operating properly.   Perhaps it is even as little as only one of the split units is not operating but it can be felt in humidity and temperature.  They are just limping along on one half of their system and they don’t know it.  This is all part of being keenly aware of your mechanical issues at a winery.

Expanded refrigerant and compressed refrigerant lines: Often the compressor will have a line that carries Freon (refrigerant) to and from the expansion coil.  Have you felt those lines when the unit is working properly?  (Be careful) Do they feel the same as when you felt them during normal operation?  Is one sweating and the other not?  Is one or both frozen?  When was the Freon last checked and charged?  Do you see the Freon sight gauges and do they look proper?  No bubbles, etc.  What are they showing and can you describe what you see to a technician?

Glycol strength: The chilling unit chills the glycol water mix that is pumped through supply and return lines connected to the tanks.  Is that heat transfer happening properly?  What temperature setting is the unit set to chill the glycol to?  Has this been changed as seasonally winemakers may do this?  Has the glycol strength been tested lately?  These are all questions you and your chilling technician will need to answer and explore.  Have solid answers for them when on the phone to help them before they arrive at your place.  It will save you $$.

Simple glycol test: Take a small amount of glycol from the reservoir of the glycol tank.  Make sure it is a representative sample of the glycol in all the lines.  Take a calibrated standard refractometer and place several drops of glycol on the refractometer just as you would checking a brix of grape juice.  If the reading is at or near 27 brix then the glycol strength is about 35%.   If the reading is near 24 brix then the glycol is near 30% strength.   Please double check this quick test with your refrigeration expert to see if they agree.  Suppliers of glycol have been known to, free of charge, receive a 300 milliliter sample of your glycol water mix and with have their lab test it for strength, inhibitor function and several other tests that may or may not be meaningful to you or your technicians.  [ Note : Some units now come with their own dedicated glycol testing refractometer style measuring tools ]

Glycol dye: Many wineries find great application to adding a dye to their glycol system.  This can be blue, orange, red or any other color.  As many off us know water, glycol and white wine often look reasonably similar.  Sweating glycol lines and connections are often tough to distinguish between water or leaks in the glycol line.  If you see, for example, a liquid on the floor of your cellar or on a chilling pipe that is blue – you know this is glycol.

Pump (most likely centrifugal): Is the pump that pumps the glycol working properly?  Has it stopped running?  Is it pulling the amps that it should?  Does it feel hot or is it iced up at the pump head.  Does anything look abnormal?  Do you have pictures of what the pump head should look like when operating properly?   What is the pressure on this closed system loop?  Are you getting ample pressure to move the glycol through the lines, jackets of tanks and krack units?  Did someone open a valve that may have lowered the pressure mistakenly?  Look for the obvious and simple.

Fans: Are all the fans and compressors engaging as they should?  Turn the unit (glycol temperature) down and wait an appropriate time (5 minutes +/-).  Have extra fans kicked in to pull the extra heat load out?   A call for more cooling, while setting this temperature thermostat low, should have more fans that should kick on.  All of the compressors should be functioning and the unit should be trying its best to meet the needs of the thermostat.   Do you know what this full need looks like?  Have your chilling tech show at one of their less urgent visits.


  Get to know your chilling unit.  What a major part of what we do in winemaking.  Walk out there right now and listen to it while watching it run.  Take a video of it.  Do your best to trouble shoot and gather information your own chilling unit before calling your chilling tech.  It can save thousands of dollars.  Often, too, you will discover simple things that have gone wrong while getting to know your chilling unit even better. Often the same thing will go wrong, repeatedly, and lead toward a more final diagnoses of a smaller problem.  Perhaps terms like contacts, set limits, pressure limits switches and a whole host of other higher tech terms. Perhaps the repeated chilling problems will help encourage your winery to stock that part or item that repeatedly gives trouble.  Simply calling your refrigeration guy, in a continuous knowledge vacuum, can lead toward unwanted and unnecessary costs.  Even worse you will still know little about one of the most crucial pieces of equipment in the winery.  Inspect you unit most importantly during certain crunch periods of the year like an upcoming harvest.  Inform yourself and educate yourself about your specific chilling unit(s).  It’s fun and not really that complicated!

•   Know the basic operation of your chiller

•   Build a knowledge and vocabulary base

•   Use common sense and pay attention

•   Become less reliant in case of emergency

  A big thanks to Justin Thomas of G&D Chillers in Eugene Oregon for his assistance.

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