ECM, VFD, and Inverter – What’s the Difference?
Ever since Nikola Tesla invented the modern induction motor, we have been struggling with varying the speed of motors efficiently and reliably. The trouble in the HVAC industry is that there are several different types of technologies in play, and they can easily get confused. ECM (Electronically Commutated Motor) In residential and light commercial HVAC, […]
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Work Vehicle Entropy
Have you ever noticed that the more you're required to speed up to get all your work done in a day, the more the cleanliness of your work vehicle suffers? Some techs won't clean their vans, no matter how slow or busy the schedule gets, but most of us prefer a clean and organized vehicle. […]
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What Should My Superheat Be?
  The most common—and often most frustrating—questions that trainers and senior techs get asked sound something like this: “What should my ______ be?” or “My _____ is at ______. Does that sound right?” Usually, when the conversation is over, both the senior and junior techs walk away feeling frustrated because the junior tech just wanted […]
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This is Not a Soft Start
I used to call PTCR devices a "Soft Start". I was wrong.
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3 Ways to Reduce Compression Ratio in a Heat Pump
We’ve talked about compression ratio a lot over the years. Compression ratio is the number you get when you divide the absolute head pressure (PSIG + 14.7) by the absolute suction pressure (PSIG + 14.7). It measures the efficiency of a compressor, and lower numbers indicate that the compressor is moving more refrigerant while consuming […]
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Best Practices to Conserve A2L Refrigerants in a Shortage
If you own your HVAC company or are involved in management, you may have realized that our industry is currently facing a shortage of new A2L refrigerants, particularly R-454B and R-32.  Our own company has faced limited availability and long lead times, mainly due to supply chain disruptions and the increased demand now that our […]
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Wet Bulb and Enthalpy – The Left Side of the Chart
It's incredibly useful to understand wet-bulb temperature and air enthalpy when calculating actual system capacity and human comfort. Dry-bulb temperature is a reading of the average molecular velocity of dry air. However, it does not account for the actual heat content of the air or the evaporative cooling effect of the air. When air is […]
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High-Pressure vs. Low-Pressure Shell Scrolls: A Deeper Dive
I want to share something that came up in a recent discussion with Roman Baugh about VRF systems, and it made me realize I might have had a blind spot regarding scroll compressor designs. We were talking specifics, and he brought up high-pressure shell compressors. My immediate thought was, “Hold on, aren't scrolls low-pressure shell […]
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Should the Float Switch Break R or Y?
There are three things we never discuss at the dinner table: religion, politics, and which wire to break with your float switch. A float switch fills with water whenever there is a drain backup, and it breaks power to one of the low-voltage wires. We clearly want the HVAC system to stop producing more condensate, […]
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