HVAC - Isolate to Diagnose
Bryan Orr talks about how HVAC technicians can isolate problems to diagnose faulty systems. He particularly focuses on using isolation diagnosis on a grounded compressor and in the low-voltage circuit. This presentation was given at the HVAC Conference in Birmingham, AL, presented by BTrained, LLC.
Isolation diagnosis requires us to make a hypothesis about the system and isolate our testing to the problematic part of the system. Instead of going in and testing every single wire, you have to develop a process of elimination to get to the bottom of the issue efficiently.
At Kalos, when our techs find grounded compressors, we make our techs pull the wires off, isolate the wires, put the top back on, and see if everything else runs when power is applied once again. (We call that the "redneck compressor test," and it's an alternative to bringing out your ohmmeter.) If everything else runs, then we can be confident that the compressor is grounded and proceed with further diagnosis. However, if nothing else runs, then we will know that we have a problem elsewhere.
In cases with grounded compressors, we would bring out the megohmmeter to check resistance at the compressor terminals after we confirm that the problem is indeed isolated to the compressor. The lacquer in compressor motors can wear down and cause issues with the motor windings.
In cases with time-delay issues on the low-voltage circuit, we do isolation diagnosis by checking for shorts in the Y or G circuits. We can rule out the red circuit and reversing valve immediately when we experience time delay issues.
Once you have all your tools and an idea as to how you'll tackle a problem, you can use isolation diagnosis to troubleshoot the system. In cases where we have voltage, we need to make sure that the voltage doesn't drop. We can use components to test the voltage drop; for example, we can see if 24v power will energize the contactor at various points (though things get tricky when the common gets involved).
Isolation diagnosis can help you solve all sorts of weird problems that your meters alone can't help with.
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Пікірлер: 41
The information you give is so great,started doing HVAC a year ago with no experience and I’ve watched your videos almost everyday while working in the field and I’ve learned a lot,Thanks man!
Good guidance, Thanks
Great video toms of info
The megohm tools is not used to diagnose a bas compressor. It is used to measure Insulation resistance. If you read "bad" on a megohm then you want to talk to the customer that their compressor is close to being on its way out. As in they should start saving for a new unit or compressor.
This man is a HVAC god
I’m a 45+ year tech and find your videos interesting sometimes reminding of things and the occasional well da Ghost voltages in many cases will drive ya crazy in systems with massive electronic controls Thank You
Essentially, an electrician back in the day was a guy that volunteered to get shocked. My actual nightmare. Lol, love the content.
10:45 Reminds me of something my dad said when I was about 14 years old. I was tagging along on an AC service call and I pointed at the capacitor and asked "What's that?" He said, "That's the capacitor, don't worry about those, they never go bad." At that time, that was a true statement! That was when the compressor and fan motor each had a separate capacitor and the compressor capacitor was about a foot tall and weighed 5 pounds!
@austrianpainterhidingfromt5920
2 жыл бұрын
That is funny. Nowadays even the biggest brands are putting cheap, Chinese caps on their equipment, it seems like we replace them once a year. And with everybody going away from the PSC blower motors for the modules it's even more of a pain.
@chrisdeanndavison3626
2 жыл бұрын
@@austrianpainterhidingfromt5920 I've been using the Titan HD USA-made capacitors exclusively for about 4 years now. Unfortunately, I haven't seen a drastic decline in capacitor failures with them either. I've had quite a few of the ECM modules fail too. Manufacturers tend to blame power surges, but I'm not convinced.
@metal2444
2 жыл бұрын
They where all thrown out with kitchen scraps in the landfill to rust leak p.c.p. out into the dirt , should have saved them a lot of old caps had red dot for line incoming shorts to case not load start winding connection.
I believe I found this at Heating Help: “The two best tools a troubleshooter can have are a bright flashlight and an open mind.”
Always makes my day watching these vids. Thank you for your time and knowledge. 🇺🇸
Indoor fan running: 1)power ✅ 2) control power ✅ 3) check safeties 👍🏽
Grear video Bryan. Thank you.
Excellent video. My dad used to test electrical with his hands.
Thanks..very useful information.
Thank you Bryan for posting this video, it was excellent!
We were just taking about this at work with the new guys yesterday. Gonna show this to them.
Wow bro your so smart with this stuff appreciate all the info you give every vid!
Why was that free app that Brian came up with again?
Thanks again for the videos! 🍺🍺🍺🥃🥃⛳🎳
Great video. For low voltage shorts I’ll put an ammeter on the secondary and sometimes I’ll jump across the fuse but it’s not always necessary. I’ll have all my wires disconnected and just momentarily, I’ll touch one wire at a time to hot. I’m just looking to see if it sparks or not. If there’s a short to ground, there’s gonna be a spark. The transformers will last a few seconds under a very high load so they won’t burn up in just the time it takes to momentarily touch the wires. Doing this, you won’t waste a single fuse.
love it
Thank you for an excellent presentation on the practical aspects of troubleshooting. Between your videos and "Pine Hollow Auto Diagnostics" automotive troubleshooting videos, you really provide an excellent overview on troubleshooting along with real life experiences in the field. I find all your videos very informative - Thanks (from an Aerospace Engineer who troubleshoots spacecraft both prior to launch and on-orbit).
That's coors not miller.
Love it keep them coming now I need a Beer 🍺
ghost voltage...makes me crazy. Like your contactor tip.
Thank you so much!!! I like it Nice video I was hypnotized watching the video 👌 😂
Hey 👋 how about moving to Barbados😌 so I could be an apprentice under you.
If you want to work on VRF equipment, You need this mentality.
I like learning about HVAC when I watch a comedy special.
It’s tuff when 4 18/3 wires are ran in a commercial building for a heat pump and both Technicians are new to the “Service “ part of the Trade
Sounds like "hop scotching" that I was taught.
What is a time delay?
How can I get one of those beer can cool t-shirts
Take them socks off, poor smuck, haha, but seriously great information Bryan Orr.
I met a young guy who asked me to teach him the tricks of the trade. I told him there were no tricks.
👍
Dude I want a beer can cold shirt please
First comment ❤️