Case Study 4:The Night the Headmaster Blew

Welcome to the HVAC Mentors Podcast. This is the show where we talk about the attitudes, habits, and professionalism that shape great technicians. It's also a place where we talk about how to help the newer people overcome obstacles that can stand in the way of success. Whether you're just stepping into the trades for the first time or you've got decades in the rearview, this is the place for you. Welcome to the HVAC Mentors Podcast. Welcome back to the HVAC Mentors Podcast. This one is titled The Night the Headmaster Blew. It was a walk-in freezer that had gone down at a chain restaurant. The condenser rack on the roof, which served this unit, it also served the walk-in cooler as well as several other refrigeration units within the building. When I arrived, It was already dark. I think it was about 8 o'clock when I received the call. It was probably, probably going on 9 o'clock by the time, by the time I arrived at the customer's location. I was gonna have to do most of the diagnostic work at night. That particular location does have some lights on the roof, but really they're so you can find your way to the equipment. They don't really help you with diagnosing the equipment. When I got to the Um, when I got to the unit, I found that inside the freezer, of course, was running just above freezing, and the evaporators were running. So that told me we had power. The solenoid was energized, and the thermostat was calling. So clearly, control side was as it should be. So, when I got to the rooftop unit, I went to the rack condensing machine and connected my gauges. Instantly, I saw that the charge was flat. There's not A drop of refrigerant, or if there is, it's just a trace. Even in the dark though, I could see that something wasn't right. So when I walked up, I could see that one fan wasn't turning. Well, that didn't make sense. I had a walk-in freezer that was above freezing, so both condenser fans should have been on. The inside of the cabinet was covered in oil, which of course, that is a big indication of a leak. The secondary fan motor was still operating intermittently. Cycling on and off on the fan cycle control. Uh, when I checked it more closely after I de-energized the fans, I actually found that there was excessive play in the shaft. So clearly we had some bearing wear, and I could just tell by the way the shaft felt as it turned that there was definitely something up with the bearings. One condenser fan was still trying to run. The other one was completely locked. Over in the area around the receiver for the walk-in freezer, there was an excessive amount of oil. splattered everywhere. It was obvious that something happened. There was a major, major hemorrhage. Because it was dark and there was limited visibility, I was forced to wait until the next morning to perform a leak check and a full diagnostic. When I arrived the next day, I returned with my nitrogen tank, gauges, leak bubbles, and attempted to pressurize the system. I could immediately hear a very loud hiss near the receiver, near where all of the oil had been found inside of the cabinet. Following the sound and using my hand, I was able to feel nitrogen flowing from out of the Headmaster. Upon closer examination, the head of the Headmaster was split open, revealing how the entire refrigerant charge was lost. With daylight, I was able to see the whole system and the larger problem at play. Namely, the condenser coil was absolutely jam-packed with dust. The condenser had not been cleaned in quite some time, and clearly there was a major air restriction. It was A little sad, honestly, to see that one condenser fan motor trying its best to continue to reject heat, but obviously it had burned out due to high heat load in that coil and its inability to pull against that pressure. The secondary motor again was trying its best to keep the system alive, but it was also fighting against a clogged coil. And so with airflow collapsing, then Condensing pressures would have increased significantly during operation. So under those conditions, the headmaster would have basically become the weakest point in the system, and eventually the head would have ballooned out and fractured at the seam, and it failed. I replaced the headmaster, recharged the refrigerant, and cleaned the condenser coil to restore airflow. With those corrections, the system was able to run again Um, to get by. I still had to order the condenser fan motors and wait for them to arrive. On a third visit, I was able to replace both condenser fan motors and clean the coil. And after the repair, airflow across the condenser was back to normal. Head pressure stabilized. Um, system returned to normal operation. There were no more problems. So just for some background context, how did we get to this position that we are literally blowing up the system because our head pressure are so high because we're not rejecting heat, and that we're killing fan motors because our condensing coil is full of dust. To give a little background, that customer had been on a preventive maintenance program with my company. That service had been canceled. They figured they were going to do it in-house, or have another vendor do it. It hadn't been done in quite some time. In fact, I'd be willing to venture that we were the last ones that maintained that, uh, coil. If the condenser had been cleaned regularly, the fan motors would not have failed. The system would not have been forced into high pressure, and the headmaster valve would not have ruptured. So the result is, after this incident, that customer returned to regular preventative maintenance. We talk about preventative maintenance— clean your coils, change your filters— and sometimes a failure like this really drives home the necessity of doing preventative maintenance on both residential and commercial equipment. It's absolutely vital that we keep our coils clean. Because it doesn't just wear the compressor. Yes, that's kind of the primary thing, but pressures can go so high that you're literally exploding components within the system. Coming back to this system, approximately 6 months later, I returned for preventive maintenance. I remember that it sounded like a helicopter failing to take off. I mean, it was so loud you couldn't have a conversation standing next to this unit. But now you hear the fans, you hear the compressors. You could talk in a normal voice, normal tone of voice with no problem and be heard standing next to the system. It ran smooth, it ran quiet. It was obviously well within its capabilities. When I first encountered the system, it sounded like it was dying and it was, but now it was steady, smooth, and balanced, just like it should have been. The takeaway from this is that preventive maintenance doesn't just increase efficiency and keep the system from wearing out prematurely. It literally stops catastrophic failures from happening. What causes a big failure like that is a lack of maintenance. Every big problem usually started as a small problem. If there's a major failure, it's because something little was not addressed while it was a small problem. And in this case, that small problem was just simply cleaning the condenser coil. It wasn't just replacing a valve. If we work to maintain our customers' systems, then we're doing a good job for them. They may ask us, you know, do I really need to get this cleaned every year, every 6 months? The machine doesn't break down. Why am I paying you to keep coming out and looking at this machine? That, that is evidence itself that you should keep coming out and looking at that machine because nothing catastrophic has happened. Just remember, as you're out there performing your job, servicing and diagnosing and performing preventative maintenance, that many of the most expensive failures are preventable and you are preventing them. This was the lesson the machine had for us today. Thank you for listening to the HVAC Mentors Podcast. If you enjoyed today's discussion, feel free to continue the conversation in the comments below. Sharing experiences and lessons learned is how we all grow in this trade. Until next time, keep learning, keep improving, and keep showing up ready to do the job right. I'll look forward to seeing you next time on the HVAC Mentors Podcast.