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Thread: Compressor cycle on and off
06-23-2011, 12:27 AM #1Regular Guest
- Join Date
- May 2010
Compressor cycle on and off
I'm trying to learn a little bit about my air conditioner system. I was trying to find out how the compressor in the outdoor heat pump is controlled. So here is the question, does the compressor in the outdoor heat pump cycle on and off based on the pressure on output of the compressor even when the thermostat is telling the outdoor unit to stay on? Or does the compressor on the outdoor heat pump just stay on all the time? If it stays on all the time how does the compressor prevent overpressure? Is it just that the compressor is leaky enough that it can only compress to a certain level, or is there some valve?
Maybe someone could point me to a website. I can't seem to hit on the right combinations of words to find anything on google.
06-23-2011, 06:51 AM #2
I'd recommend that you align yourself with a reputable, established HVAC company that will do routine maintenance on your system. Many people are under the mistaken impression that this stuff is easy. That anybody can look at the system and make it work. That has some small element of truth but just working and working properly are two entirely different things. In fact, many of the wannabe professionals in the trade are anything but. The errors of their work are displayed all over the country and repaired (sometimes) by other techs who really know their stuff.
This is not a DIY site so we can't give you specifics. There are many HVAC educational institutions of brick and mortar where you can learn and there are even more books on the subject.
To actually work in the trade and be good, requires a substantial investment in both time and equipment. Most states require some form of licensing as well. License requirement vary from state-to-state so check on yours if you're looking to be a pro. If you're not looking to be a pro, I'd dissuade you from even attempting to learn the nuances as "a little knowledge is a dangerous thing" as evidenced by many of the posts to this site.
06-23-2011, 07:35 AM #3Professional Member*
- Join Date
- May 2011
- Ripley, WV
In a standard a/c unit when the thermostat calls for cooling it brings on the blower and the outside unit (compressor and condenser fan) but will run for the duration of the cycle and shut of at the same time. If your compressor or fan either one is kicking on and off or the outside unit is short cycling you need to call an HVAC pro because it will take a pro to fix it.
06-23-2011, 09:31 AM #4Regular Guest
- Join Date
- May 2010
Sorry, let me explain, there is nothing wrong with my air conditioner (I get it serviced each year by a pro). I was just trying to understand how it works. (If this isn't the place to ask how it works type questions, then I apologize).
I had recently seen an article that putting some shade over your outdoor heat pump can increase efficiency 10%, and was trying to understand how that happens. I was thinking of few possible scenarios (but couldn't really find any articles):
1. While the outside blower may run all the time, the compressor could turn on and off on the outside heat pump to maintain pressure. Thus, the compressor would run at a lower duty cycle when the air is colder outside, and take less energy.
2. The compressor stays on all the time, and there is some bypass from the high pressure side to the low pressure side. In this way as the outside air gets cooler, the pressure differential across the air compressor would decrease. I guess this would mean the compressor (while still running) wouldn't have to work as hard and thus would save energy.
3. The compressor stays on all the time, and it is leaky enough at higher pressure differentials that it can only build to some maximum pressure. The problem with this would be that the compressor has to keep working just as hard or harder even with the cooler air. (It would be kinda like those pumps for air mattresses where you can hear it working harder as the mattress gets full, and it will only pump up so much). This doesn't seem to fit with the better efficiency in the shade though.
Or maybe it is something else entirely. If this isn't the place to ask, is there another place I should go?
06-23-2011, 11:19 AM #5
Not sure you'd see that 10% increase in efficiency.
All other factors being equal (a HUGE assumption) pressure is controlled by temperature. Since a shady spot is typically cooler, theoretically, the pressures would be lower.
With a system that is running "perfectly" (again with the assumptions) shading the outdoor unit might gain you a tiny amount of efficiency, but I think it would be difficult, if not impossible, to quantify.
Better for increasing and maintaining efficiency is regular and complete system maintenances. Keep in mind that just because someone can hook up a set of gauges to a AC unit doesn't mean they have all of the knowledge requires to get maximum efficiency from that same unit.
Things like indoor airflow, coil cleanings and proper system charge are vital to maximum efficiency.