Compressor Overheating - Short #99
HVAC School - For Techs, By Techs
Bryan Orr
4.9 • 1K Ratings
🗓️ 18 August 2020
⏱️ 13 minutes
🧾️ Download transcript
Summary
In this short podcast episode, Bryan explains what happens to a compressor when it's overheating. He also covers possible causes and troubleshooting strategies.
One of the Kalos techs came across an overheating compressor case that looked like a textbook TXV problem: the superheat was high at the condensing unit on the compressor side. However, the air handler superheat was appropriate, and the suction pressure was low. TXVs, however, respond to the superheat dropping and reduce the pressure even more. Overall, the mass flow rate and velocity drop, meaning that the refrigerant temperature can increase as it spends more time in the suction line.
We were missing a few key measurements to diagnosing compressor overheating. In those cases, we want to know the return gas temperature, discharge line temperature 6 inches out from the compressor, and the compression ratio (absolute discharge pressure / absolute suction pressure). You'll generally want to see a compression ratio between 2.6 and 3 on residential HVAC equipment; the lower the compression ratio, the better the efficiency. A compression ratio higher than 3 can lead to compressor overheating. A return gas temperature consistently above 65 degrees can also make a compressor run hot. The discharge line temperature should not exceed 225 degrees.
Then, you must determine if the charge is correct. (Are you starving the evaporator?) Check if you have restrictions and if your suction line is improperly insulated. Restrictions and heat transfer in the suction line can lead to compressor overheating.
It's bad for a compressor to run hot, but they can go their entire lives without tripping on the thermal limit. Compressors that run hot can have lubrication issues and will have shorter lifespans. The best thing you can do is try to reduce the compression ratio. (Clean the condenser, keep head pressure low, keep good indoor airflow, etc.)
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Transcript
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| 0:00.0 | Why hello this is a short episode of the HVAC school |
| 0:07.1 | podcast and this short episode is about the topic of compressor |
| 0:11.9 | overheating which was something that we, I just had a conversation |
| 0:15.7 | with one of my texts today, I think it was a productive conversation, so I wanted to share some of the |
| 0:20.0 | things that we discussed. But before we do that I want to thank the sponsors, |
| 0:23.2 | supporters of this podcast, the companies that step up and raise their hand and said |
| 0:28.3 | hey we like what you're doing and we want to support you and I appreciate them. First |
| 0:32.2 | one is carrier and carrier.com. |
| 0:34.5 | Second is Navac and Navac Global.com you can find all of your favorite Navac |
| 0:38.9 | tools at true tech tools. TRU tech tools.com the offer code, get schooled at checkout for a great discount. |
| 0:46.0 | Also Field Piece and Field Piece.com, a lot of what I'm going to be talking about here is measuring temperatures |
| 0:51.0 | and some of the best ways to measure temperatures are using their rapid rail |
| 0:55.3 | temperature clamps part of the JobLink family. Find out more at fieldpiece.com |
| 1:00.7 | also refrigeration technologies can't say enough good things about refrigeration |
| 1:04.3 | technologies and everything that they make Mike and John Pasterello salt of the |
| 1:08.4 | earth human beings who just make really good stuff, good chemicals for our industry, |
| 1:13.5 | and they're committed to the trade, |
| 1:14.7 | they're committed to training, |
| 1:16.4 | and so if you haven't tried, |
| 1:17.6 | their Viper Cleaners, their Venom Packs, |
| 1:21.0 | Nylog, so on and so forth, then I would suggest that you give them a shot. |
| 1:25.0 | Go to refrigetech.com to find out more. Also, Blue On, Blue on Energy.com, |
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