Thank you for this video! It’s a very typical scenario and I do see this pretty much every week during my March/April clean-and-check maintenances. Typically it will be a brand new customer that has never had this system checked/cleaned and it will be a piston, not a TXV. I don’t see this freezing evaporators on my regular customers equipment because everything was cleaned and checked last year and not a lot of surprises happen here. Long story short, I don’t like to take new customers for these clean-and-check maintenance simply because I am starting with evaporator/condenser coil cleaning, but ending up with new TXVs, additional return air ducts, evacuating the system and charge it to its a correct refrigerant and correct amount of refrigerant, add acid scavenger into the compressor’s oil…. It’s like a Pandora box… I had one guy with non-cooling R-22 walk-in cooler; two refrigeration condensing units that were grossly oversized for the cooler’s cooling validators, running non-stop and still…. Inside temperature wouldn’t go below 44F-46F. So, standard list of findings; neither evaporators or condensers were ever cleaned, ~40%-50% over charge, plugged screens/retainers on both TXVs, wrong motors and fan blades on both condensing units, of course burned compressor’s oil and by-passed defrost timers… So, instead of regular 2-3 hours clean-and-check it took me 2 days to resuscitate that walk-in cooler. The temperature inside dropped to 33F and both condensers were now going OFF by the thermostat. The store owner was happy with the temperatures, but he complained that this repair took too long…!!!! Previous guys would get everything done in 30-40 mins and don’t charge him so much… … I still don’t know how to handle such complaints… Well, a year later he called me about another store.. he said something like: “…. I know that you charge too much, but I cannot find anyone that will be able to repair my walk-in cooler…”. Ha-ha-ha! I told him that I am busy.
Liked the story. Your videos are excellent. I did scratch my head "why would cleaning the evap coil not be part of the maintenance routine?" You don't have to answer.
Great question. With proper filtration, an evaporator coil should never need to be cleaned. If it is cleaned, proper filtration should be installed so it does not get dirty again. Cleaning a coil is hard on it. Even the safest chemicals have a reaction on the metals and increase the risk of leaks. Accessing it in place is difficult, can damage the fins and does not get the dirt from deep between the fins. Pulling it and cleaning it is very expensive and time consuming.
Great information. I'm new to the trade n learned a lesson real fast. I was working on a reach-in freezer that was 20yrs old. The owner kept putting band-aids on it to keep it goin. They probably had 6 previous companies do work on it. I come along n did some work to keep it going but also mentioned we could try installing some needed parts to the unit which could help. Now I did suggest buying a newer one but he said to install some parts. Long story short the unit died n the manager went off on me. Luckily I know the owner he was cool but I did some other work for free for him cause I felt bad, but next time I come across a relic I'm saying call someone else. Thanks ty appreciate the work u do for us thermal dynamic energy specialists rookies!
Not an HVAC guy, just really enjoy your videos and learning. I remembered your experience with this from another video and I was saying, " Don't do it!, don't do it!" Lol, Thanks Ty.
These are great videos! I'm not a service tech, but I do deal with HVA/C on occasion and at times, my friends and relatives ask me for help with maintenance and small repairs. (I guess that means that I'm the worst element. Someone with just enough learning to be dangerous.) Anyway, please make more videos with scenarios where we have to figure out the issue, just like this one. Keep up the great work!
At the end of the course I will add in diagnostics. Diagnostics is just specific application of the fundamentals. Once you have a solid fundamental foundation , understanding how it works, diagnostics is just what's missing in the sequence of operation.
Wow, that was an interesting experience! Thank you for sharing. It's positive now, but back in the day, it was quite a bit stressful. That's why it's a must-have to understand the refrigerant cycle and be able to see the whole picture. A lot of techs don't understand it. They work for years. Your lessons have a deep point of view. A lot of new information to me also. Never stop learning! I'm a residential-small commercial repair /maintenance technician.
Ty, thank you so much for your time, effort and passion in providing your viewers with excellent instruction and well thought out content. You've helped me be a better instructor for my students and I greatly appreciate and respect your talent and abilities.
@@love2hvac Can't thank you enough! I would love your opinion on what I feel is a very unusual HVAC system installed on a transit rail car. Do you have an email that you wouldn't mind receiving a schematic of this package unit made by a Chinese company called "King"? I think you might find this one very interesting. And, I have system operational questions that I really think you could help answer. Thanks again.
I say let them know before doing anything else. Dealing with the public is not fun and they will blame you for everything. I've had a few run in's over the years
So obviously cleaning the evaporater coil was the correct solution, but if you had wanted to cheat, could you have added more refrigerant to the system, which would raise the pressure in the evaporater and consequently the temperature also, which would prevent the freezing?
You could have added more refrigerant to get the evap saturation temp above 32F, but you would only be making the situation worse. Because of the dirty evaporator coil, the refrigerant is not picking up the proper heat from the air and there's a decent chance you're getting some liquid slugback at the compressor. If you add more refrigerant to the system at this point, you're just making it worse and there will then be even MORE of a chance for saturated liquid making it back to the compressor.
I replaced a control board today and the blower fan didn't start immediately. I second guess myself for a minute and went to the t-stat to check. The blower was on a time delayed from the t-stat.
Disconnect one connection line from condenser fan and re connect it to the ground wire!!!! then plug and prey!!!...and put a scull singe on the condenser!!!
Hi Sir Ty! Highly appreciate your videos. I have a question! Why evaporators on refrigeration like freezer don’t Ice up or freeze although saturation temperature much below 32 degrees F???
That is a great question. The issue is the compressor running for a long time on a dirty coil reduces capacity and it also (slugs) floods the compressor with liquid. After the coil is clean the compressor is now running back at full capacity/full load and also dealing with the damage and abuse from the liquid slugging over _ years. It's sometimes too much for the compressor to handle. Also many tech's over charge them to compensate for the dirty coils low pressure. When it's running again techs dont remove the charge to put it back like its suppose to. Also when the system is opened up it's possible for contaminated to get in the system or a tech to not pull a proper vacuum that grates acid that can eat away at the winding on the compressor.
That's one thing I'm trying to learn how to tell without looking at the evap coil if it's dirty. Low superheat high subcool? Or low superheat normal subcool?
Hello Ty, quick question if you don't mind. When pressure testing lines + evap coil with nitrogen, do I need to use bubbles on the joints if the pressure isn't budging after an hour? 300 psi for 1 hour . Thanks
Yes, remember it's easier to do extra steps now vs returning later. When pressure testing I use a digital guage that peak in decimal of an inch and with the temperature clamp. As the temperature change the pressure will change to. For example, the tempersture goes up and the pressure stays the same it could be a leak and the tech never knows. Another example the temperature drops and the pressure drops and a tech will spend time looking for a leak that's not there.
Hi sir, Thank you for your videos. I am writing to enquire about. There is a page said that If there is a high charge in ac system ( its metering device is capillary tube), it would start freezing from the compressor suction. Is this right? Thank you in advance.
Overcharged will damage the compressor but not cause it to freeze. #1 cause is airflow Also Refrigerant restrictions, indoor outdoor temp and low on charge
For that unit which it got freezed evaporator, if u have let it run for enough Time, utill gets the normal pressures on both sides, will that fix the problem, if not how u fix it?
