Jan 14, 2014 HVAC
TROUBLESHOOTING HEAT PUMP SYSTEMS…R-22 VS R-410A
Unless you’ve been living under a rock for the past several years, you know R-22 is on the way out and R-410A appears to be the manufacturer’s weapon of choice for heat pump and comfort cooling equipment. If you’ve already encountered a 410A system and had a less than pleasant experience, possibly attempting to correct or understand what appeared to be abnormally high system pressures, your confusion may be with a misunderstanding of mechanical refrigeration, rather than the refrigerant.
Mechanical refrigeration is all about heat transfer and temperatures, especially boiling and condensing point temperatures. The whole point of a refrigeration system is that of creating a heat sink or low heat energy level, causing heat to transfer from a higher energy level. For comfort cooling applications, the indoor coil operates at a temperature lower than that of the indoor air temperature, and I’ll say in the 40ish degree range. When the system is in operation, the indoor air is pulled through the coil, where some of it’s heat is transferred to the coil. That heat is then carried to the outdoor coil, where it is transferred to the outdoor air. When heat pumps are operating in the heat cycle, the outdoor coil has a temperature less than the outdoor air temperature. Then the heat in the outdoor air transfers to the refrigerant in the outdoor coil, is carried to the indoor coil, where it is transferred to the indoor air. So, the dynamics of a mechanical refrigeration system simply control the refrigerant temperatures within the indoor and outdoor coils, maintaining a continuous process of heat transfer, in whatever direction is needed.
I don’t claim or even pretend to know, the engineering details necessary for the design of refrigeration systems. But I have a reasonably good idea of how they’re supposed to operate, relative to system pressures, subcooling and superheat, and particularly with comfort cooling and heat pump applications. And so long as I know what refrigerant the system uses, and have a way to convert pressures to saturated temperatures, I’m comfortable with the system. We’re all probably guilty of becoming familiar with system pressure measurements, and forgetting what we’re actually measuring, which is the saturated refrigerant temperatures in the evaporator and condenser coils. Once we see what those numbers are, we then measure the suction line and liquid line temperatures so superheat and subcooling values can be calculated. With the system pressures / saturated temperatures, superheat and subcooling values, we can make an intelligent decision about the operation of the system.
An R-22 system operating in the cool cycle on a hot summer day will usually run a suction, or low side pressure, of 75 psi or so. And the superheat could range from 5 to 15 degrees depending on the type metering device, equipment brand and outdoor temperature. An R-410A system would be running around 120 psi low side, but would have a similar superheat range, again depending on the metering device, brand and outdoor temperature. The difference in pressures is due simply to the difference in saturated temperature / pressure characteristics of the two refrigerants. So long as your gauges have a “temperature conversion scale” for the type refrigerant you’re working with, and you know what the evaporator temperature is supposed to be, you can analyze the system for proper charge and operation, whether or not the pressures are “familiar”.
Author: Wayne Shirley HVAC Tips
Jan 13, 2014 HVAC
TROUBLESHOOTING HEAT PUMPS SYSTEMS…REFRIGERANT LEAK DETECTION DEVICES
No doubt, my most frustrating service issue has been locating refrigerant leaks. And I’ll be the first to admit it was due to my own ignorance, from simply not doing a little research. I started out with a cold sensor technology electronic detector, bought a second cold sensor electronic detector and eventually concluded electronic detectors were pretty much worthless, at least for my desires and needs.
Next , I let someone talk me into the ultrasonic detector method. I never found the first leak using it. In fact, I couldn’t find a leak in my truck tire with the thing…so much for ultrasonics.
When I discovered the fluorescent dyes, I thought my leak search headaches were over. And to a certain extent, locating some leaks did prove to be much easier. So long as the black light would shine on the leak area, and it was reasonably dark around the suspect area, and the dye was actually coming out of the leak, I was in pretty good shape. But then there’s the waiting period between injecting the dye, and actually seeing it exit the puncture…and the mess…and all the paraphernalia required to actually locate a leak…
At some point I walked into my favorite wholesale house and told the manager, “Today is the day I buy my last leak detector…if it doesn’t do what I need it to do, I’m just gonna’ slit my wrists, and let my wife collect the insurance…” I bought another electronic detector with heated sensor technology…I had done a little research. That turned out to be one of the finer moments in my service career. It worked so well and was so reliable, I didn’t believe it for a while. But once I finally gained some confidence with the tool, my leak search issues were mostly a thing of the past. I can find most leaks now about as fast as I can access the equipment…especially those pesky indoor coils. Add to the detector’s capabilities my knowing where to look, and my batting average is close to 1000. The biggest problem I’ve had recently was a 410A leak that didn’t want to sniff out well.
Before I get too many people overly irritated with my conclusions, let’s back up a minute or two and pay some due respect to the aforementioned devices and methods. I’m sure there is some useful purpose for electronic detectors that use cold sensor technology. I just don’t believe it’s the residential sector. They will indeed detect refrigerant…but they also detect other stuff, so you never know for sure if the alarm is refrigerant or some other unknown something.
The ultrasonics are revered by some folks, who claim good success in finding leaks. I’m not gonna’ call those same folks liars.
The dyes are absolutely an option for some situations. If for whatever reasons you need to pinpoint the location of a leak, that’s the way to go, unless you want to try the bubble solutions.
But for me, most of the time, I just want to know if a coil is leaking, or an accumulator, or a service valve, or a liquid line filter or whatever. If the coil is leaking, I’ll replace the coil…if the accumulator is leaking, I’ll replace the accumulator.
Most of the repairable leak sources are visible via oil deposits. The electronic detector will usually get you in the general vicinity, and the oil, along with some bubble solution will show you the target.
Author: Wayne Shirley HVAC Tips
Dec 20, 2013 Sponge
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Dec 14, 2013 Home Automations
- Works with X-10 Controllers & Timers
- Replaces existing wall outlet – No special wiring!
- Top outlet is X10 controlled, Bottom outlet is always on
Product DescriptionTo get the plug-in X10 control of devices with a custom look just replace the existing receptacles with them. bottom outlet behaves like a regular non-controlled outlet. High output responds to commands as X10 Appliance Module 3 pin. Responds to ON / OFF OFF all units. No answer to ALL LIGHTS ON or BRIGHT commands Sun /. Local manual control is possible. With manual, when the container is connected equipment to turn on the light and again the receptacle on the meaning and OFF cycle and the output forces. Very useful when you are near an X10. White only.
SR227 Or PA011 X10 Split Receptacle Module X10 Usa