Uh oh. Your walk-in is still warm isn’t it? Sometimes you just can’t catch a break. In Texas’ unrelenting summer heat a warm walk-in is never good news. Well we’re going to go over ten things to check on your walk-in that could be the problem. Hint, 80% of the time it is not low on refrigerant. The information below is for educational purposes. If you attempt any diagnosis on your own based upon what is written here, you are responsible for your actions but you know that already, don’t you? This began as a short list of possible problems with short descriptions and morphed into thousands of words about what could be wrong with your cooler and what steps we take to solve the problem. Considering this, I broke this post up into multiple blog posts rather than overwhelm readers with thousands of words. If you’ve made it this far you are considerably more knowledgeable about what makes your walk-in cooler or freezer cold.
10 common reasons why your walk-in isn’t working. Part 3
5. Condenser or Evaporator Fan Motor:
Fan motors make all the air move. If they have burned out it is time to replace them. Fan motors come in all shapes, sizes, speeds and horsepower and are fairly easy to determine if they are at fault. There are a couple of things that trip people up when diagnosing a bad fan motor.
The first thing we look for is a fan not spinning. That’s easy enough to see, but what is causing it not to rotate? If it is an evaporator with three fans and one is not rotating either the fan motor is dead or the power has been cut to that motor. We verify power is going to that fan motor. If power is getting there and it is not spinning then it’s time for a new motor. If power is not getting to the motor then it’s time to do some wire tracing to see if there is a break, burned wire or bad connections.
Just seeing a fan not rotating is not a cause for alarm. Sometimes that is a planned part of the refrigeration system. Your walk-in freezer shuts all of its evaporator fans off during the defrost and that is totally normal. The condenser fan motor may be on a pressure switch and may only operate when the refrigerant inside of it gets hot enough which increases the pressure.
6. Safety Pressure Switches:
Pressure switches can cause a warm box like many other problems. Pressure switches are for safety. The pressure switches in a walk-in refrigeration system also control when to turn the system off and on. How? How, indeed! A regular condenser for refrigeration has two safety pressure switches: A high pressure and a low pressure switch. The high pressure switch is 100% for safety. If the pressure gets too high then it shuts the system off so the unit doesn’t commit suicide. Imagine what happens if you keep filling a balloon with air: POP! The low pressure switch is there for safety too but it also serves the purpose of turning the condenser on and off. When the pressure rises the unit will turn on. If the pressure gets too low the unit will shut off. If one of these pressure switches gets stuck off, it can cut off power to the condenser no matter the pressure. It can also get stuck on causing the opposite situation. What do the pressure switches power when they are both on? They power the coil in the contactor which turns on the power to the condenser. Is this clear as mud? How do we determine how it is not working?
To start we check voltage at the contactor coil. If there is no voltage there we look to the pressure switches. With a voltmeter we will verify that there is power to the pressure switches and then test each one to see if power stops at one of them. If we find power stopping at either of those pressure switches we will replace it and get you up and running again. If your walk-in is mission critical the broken pressure switch can be temporarily bypassed to get you running until the correct part can be acquired. No one should ever leave it bypassed.
7. Fan Cycle Switch:
Another pressure switch is the fan cycle switch. As its name indicates it is a pressure switch that turns on a fan. It turns on the condenser fan to be more specific. As the pressure rises it turns the fan on and as the pressure falls it goes off. The fan cycle switch keeps the unit operating at constant pressure even when it gets cold outside. If the fan ran all the time even when it was cold outside it would create problems with enough pressure being maintained and your walk-in box would get warm. Alternately if the fan never ran, your walk-in box would also get warm. This is fun isn’t it. Diagnosing refrigeration issues is like those times that you feel sick and you look up your symptoms on the internet and find out that you have any of 50 different diseases. Anyway, to check the operation of the fan cycle switch we check the pressure of the system to see if it is in the range of the fan cycle switch. How do we do this?
We start by checking the voltage while the unit is operating. If the pressure in the system is high enough to turn on the switch and there is voltage then it is more than likely operating normally. If the pressure is high enough to turn on the switch and there is not voltage there is a problem and the fan cycle switch should be replaced. Not all pressure switches are the same. Since they operate on pressure instead of temperature, what refrigerant is in the system is an important factor. Choose the wrong pressure switch and things start acting crazy.
If the fan is always on we may find that the fan cycle switch is stuck OR more than likely some past technician bypassed it without putting in a new pressure switch. During the heat of the summer that works fine because the fan is going to be running all the time anyway. But as soon as it cools off that will come back to haunt you unless that switch is changed out.
We’ll continue this series of 10 common reasons your walk-in isn’t working next week when we talk about the compressors and the solenoid coils. Check back in next week or add us to your RSS feed so you don’t miss out. If you are having trouble with your refrigeration equipment in Austin, TX or in Lubbock Texas give us a call for service or new equipment. We are always happy to help! 512-651-4565 in Austin and 806-787-4985 in Lubbock, Texas Or Visit our website at www.tripointrefrigeration.com
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