Replygotta charge by superheat/subcooling if you wanna do it right
Professional Member
I do controls, but I have been watching and learning the refrigeration side. Plus I have studied the digital gauge issues and watched the videos online. Here is my question. I have never seen the guys I work around charge to a temperature, just pressure. I have watched them on small pack units, large pack units, condensers, chillers, you name it. Some have over 20 years in the business. I am curious as to the pros around here's take on that.
Just Curious.
Regular Guest
gotta charge by superheat/subcooling if you wanna do it right
Professional Member
If you want to do it right you pay attention to saturation temperature of both coils (corresponds to pressure) and to superheat and subcooling. You can easily have a system that is running a low coil temp and has low airflow, or a dirty condenser that is running high head, but correct superheat and subcooling. A technician that does not pay attention to those things will charge to the airflow or the coil conditions. You should be able to determine what the saturation temperature and the pressure are before you even hook up the gauges. Simply put, if you do not know what they should be, what difference does it make what they are? Superheat and subcooling tell you a lot, but definitely not the whole picture. Take a look at these pages, they are geared toward A/C, but the same principals are true with refrigeration.
http://www.trutechtools.com/RefrigerantCharging
JLB,
Professional Member*
Very well put Jim.
I too am an old dude. I see too many techs today that have subcool and superheat so beaten into their heads at Trade/Tech Schools, that they forget about everything else. The proper way to charge is to look at the whole picture. I guarantee that those 20+yr techs are looking at more than just pressure. It may be subtle, but you don't charge chillers without looking at everything.
Keep watching and asking questions. Someone has to do this stuff when us old guys are too worn-out to do it anymore.
Professional Member*
That's funny Jim I was just watching your video on combustion analysis. I just posted a question about it, I would like a better understanding of what I'm looking at.
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Professional Member
Ok I give up. Where did you post your question?Originally Posted by Joehvac25
JLB,
Professional Member*
Oh sorry tech to tech, thanks for responding!
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Professional Member*
It is tech to tech resi, looks like some people posted links to your site.
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Professional Member*
Same here, totally agree
Also your superheat and subcooling isn't some number that someone tells you and that goes for every unit...................
You use the manufacturers SPECIFIED superheat and subcooling info.
Regular Guest
Superheat and Subcooling are necessary for any proper charge. This has never been more true than with today's high-tech/high efficiency equipment. There are a lot of tools today that make it easier and faster than in the past (ie. digital manifolds and system analyzers) but remember that you still have to know what these tools are doing for you. Technology is great but understanding how and why this technology works is much better.
Anytime I want to trust blindly in technology, I just think about those people who try to sue GPS companies because they drove into a lake when their GPS told them to.
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