Regards, Jim > -------- Original Message -------- > Subject: RE: [EE] Ghost in the (AC) machine - Broken AC > From: > Date: Thu, July 21, 2011 3:08 pm > To: "Microcontroller discussion list - Public." > > > Herbert, > > Just a thought I had while reading this. If for some reason when the > compressor turns off at the end of > one cycle, and then the thermostat calls for more cooling and the > pressure hasn't bled down on the > compressor, you may have a condition where the compressor is trying to > start while there is still a > pressure head on the high side of the line. If this is the case, the > compressor either won't start at all, > or will struggle to start, and wind up tripping the overheat sensor and > cutting power to the compressor. If > that happens, you'll have to wait for the heat to subside before the > thermal switch can reset. This might > take anywhere from a few minutes (warm outside - 75F) to maybe an hour > or More (hot - 90F+) > > I don't know if this is what's happening, but the symptoms sort of > support the theory. Maybe it's > something you could watch for in your investigation with all of the > sensors you have available. > > Just food for thought. > > Regards, > > Jim > > > -------- Original Message -------- > > Subject: Re: [EE] Ghost in the (AC) machine - Broken AC > > From: Herbert Graf > > Date: Thu, July 21, 2011 1:05 pm > > To: "Microcontroller discussion list - Public." > > > > > > On Thu, 2011-07-21 at 11:15 -0600, YES NOPE9 wrote: > > > I started watching *ghost in the shell* yesterday at a friends house.= .... > > > I plan to return and finish watching it. > > > > > > What was the ultimate ghost in your machine ? > > > > I'm still "collecting data", I didn't want to bother the list till I ha= d > > enough data. > > > > It hasn't actually happened "as bad" as the first 2 times. > > > > Since I'm rarely home when strange stuff happens, I've added additional > > sensors. > > > > I now have proper gauges of both cold air temp in the furnace, and the > > low side line coming out of the furnace. I also have a sensor on the > > thermostat cooling signal, and I have a webcam trained on my power mete= r > > monitor (so I can confirm when the compressor is actually running). > > > > So, some stuff I've learned: > > > > when it's "warm" outside (say about 75F), and the compressor hasn't run > > for a while it takes about 5 minutes between when the thermostat tells > > the AC to engage, and when the compressor actually starts up. > > > > Unfortunately I don't know if this is normal behaviour? The last home A= C > > unit I had was about 20 years old, and the compressor started > > immediately with the condenser fan started (which is when the thermosta= t > > told it to cool). Perhaps high efficiency AC units act differently? Can > > anybody comment on their experiences? It's a Fedders outdoor unit, I > > believe 1.5ton, operating on R22. Can anybody on the list with a simila= r > > unit comment on when there is any delay between the condenser fan > > turning on, and the compressor turning on? > > > > When it's REALLY hot, things are different. I haven't noted an exact > > correspondence, but this is the "feel" I get: > > > > - if it's really hot (say in the 90s) and the thing hasn't run for a > > while, it take about 5 to 10 minutes for the compressor to start > > - if the thermostat is cycling at a set point, the compressor will star= t > > within about 5 minutes the first time, more then 10 minutes the second > > time, and up to an hour the third time > > - once the compressor is running it will run for HOURS without issue, > > it's the cycling the seems to be the issue. > > > > I think the reason I only noticed the problems on weekends is due to ho= w > > I have the thermostat set: > > > > - on weekdays I let it go up to 78 during the day and then at 6pm I hav= e > > it set to 73. On warm, but not hot days, there is pretty much no > > cycling, by the time recovery mode kicks in on the thermostat (usually > > around 3 or 4pm) the house hadn't yet reached 78F > > - on hot days the house reaches 78F before the recovery mode triggers, > > and I see the 1 hour start time after a few cycles > > - on the weekends I have it set to 73 pretty much during the whole day, > > so it's always cycling, that's why I think the problem was more > > prevalent on the weekends > > > > I'm still kinda at a loss as to what to do. I'm going to call some AC > > people in the area and see if this situation sounds familiar to them. I > > just don't want to get ripped off, so I'd much rather have someone tell > > me what's going on who DOESN'T have an incentive to rip me off! :) > > > > Thanks for any comments/insight/critisism! > > > > TTYL
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