Uh oh. Your walk-in is warm again 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. They are useful words but too many might be less than helpful.
10 common reasons why your walk-in isn’t working. Part 2
3. Defrost Time Clock:
The defrost time clock can fail and cause a few things to happen. Most notably it can fail causing the coils on your evaporator to freeze up preventing air flow which eventually will cause your walk-in to warm up. It can also prevent refrigeration from coming on, causing your walk-in to warm up. NOTE: For our Lubbock customers you might not have a defrost time clock for your walk in coolers because you live in an arid place. Our Austin customers are in a humid climate and require a defrost timer on a walk-in cooler because the moisture in the air freezes to your coil. How do we tell what is going on with your defrost time clock? I’m glad you asked.
The first thing we check is if all of the pins are in place and if the defrost time is long enough to defrost the evaporator. The standard for a walk-in cooler is 30 minutes 4 times a day. The standard for a walk-in freezer is 45 minutes 4 times a day. Sometimes the pins fall out or the defrost time can get changed. Not enough time or frequency of defrost will cause your coil to freeze and your box to warm.
The next thing we check is if the time clock is rotating. We put a mark on the time clock dial and watch it for ten minutes to see if the mark moves. If it’s not turning we make sure there is power coming to it with a voltmeter. If there is power and it is not rotating, we replace it.
Sometimes the internal switches that are activated by the timer stop working. That requires more time as we watch and test to see if power is being sent to the right places at the right time. If it’s not we’ll check the wiring to be sure that it is correct. If the wiring is correct we replace the defrost time clock.
Sometimes the motor that rotates the dial can slow down, speed up or work when it feels like it. This is harder to diagnose because you may watch the time clock for an hour and as soon as you leave it may stop acting normally. This is one of those situations where we may have to visit more than once to find the issue.
You might be asking yourself how do pins fall out, how do time clocks get set to a new time and how does something that worked last week have wiring that is screwed up today? Who knows for sure. This is one of those situations where no one wants to take responsibility. It could be your employees trying to figure out what is going on. It could be another company who didn’t know what they were doing and kept trying stuff until they had screwed it up royally. It could be people who gained access to your roof and just started tinkering. We don’t know why it is this way. It just is this way.
The contactor is a large switch that turns on your condenser and in some cases your defrost heater and condenser fans in your walk-in. The contactor is activated by an electromagnet that turns the switch on and off. This allows us to control a high power device with a low power device. What are the symptoms? The condenser isn’t running and the walk-in is warming up. What do we look at to diagnose the issue?
First we should check the wiring to the contactor. Is it loose? Is there something burned on the contactor? Are the connectors coming apart and not making a good connection? Is a wire completely disconnected?
Is the contactor activating? To test this we can test if voltage is going through the contactor with a voltmeter. We can also typically see that the contactor has been pulled in by the electromagnet. If it were quiet you could also hear the hum from the electromagnet but it’s not usually that quiet.
Is voltage being applied to the contactor? If voltage is not being applied to the contactor then it will not work. You’ll need to find out where the power was lost. It could be a disconnect or a breaker somewhere else.
Is there voltage to the contactor coil? Check the voltage going into the coil to see if the coil is even getting power to it. If it is not, your problem lies elsewhere. If it is and the contactor is not pulling in there is a problem.
Contacts can develop pitting and will no longer make good connections consistently. In this case we pull apart the contactor and examine the contacts. If they are heavily burned they may still function but they may function inconsistently. The metal contact wears down due to arcing as the contactor turns off which is what causes the issue. When we perform PMs for customers in Austin or Lubbock the contactor contacts are always examined to see if they are wearing out.
We’ll continue this series of 10 common reasons your walk-in isn’t working next week when we talk about the fan motors and the pressure switches. Check back in 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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