A/C Oddity
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Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
A/C Oddity
Hi,
I've observed the following over several years with our A/C.
We keep the temp palmost exactly the same. But, on cooler nights, the indicated temperature goes lower. Ah Ha, you say, it just cools off more before it shuts off.
Not so fast BTU breath. The compressor starts while the indicated temp is still lower than it gets to when it's hotter out.
For example
Daytime -- stays at 72-73.
Nighttime -- goes to 69 or so, starts up at 70 (indicated).
This has happened with 3 different thermostats. (Thermostats were changed for other reasons. )
I realize that the a/c control is separate from the indicated temp, but this has always seemed strange to me.
Anybody?
hj
I've observed the following over several years with our A/C.
We keep the temp palmost exactly the same. But, on cooler nights, the indicated temperature goes lower. Ah Ha, you say, it just cools off more before it shuts off.
Not so fast BTU breath. The compressor starts while the indicated temp is still lower than it gets to when it's hotter out.
For example
Daytime -- stays at 72-73.
Nighttime -- goes to 69 or so, starts up at 70 (indicated).
This has happened with 3 different thermostats. (Thermostats were changed for other reasons. )
I realize that the a/c control is separate from the indicated temp, but this has always seemed strange to me.
Anybody?
hj
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I think I understand what your saying.
At night we set our thermostat at 70. The A/C kicks on when the temp gets to 71 and the unit cuts off when the temp gets down to 69. Is that what you mean?
At night we set our thermostat at 70. The A/C kicks on when the temp gets to 71 and the unit cuts off when the temp gets down to 69. Is that what you mean?
Fleet Owner
Joined: Aug 2001
Posts: 29,941
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From: Drummonds, TN USA
One of the things most people don't think of is that the OUTSIDE heat exchanger on the A/C unit is a lot more efficient when the outside air is cooler - because the air can absorb more WASTE HEAT at a time from the unit.
The HOT exterior heat exchanger is usually called a condenser.
Running in cooler air at night the unit actually DOES achieve a much cooler temperature in it's coils before it shuts the compressor off, in a shorter time.
When it is very hot during the day the unit has to run longer to waste heat into air that is closer to the temperature of the condenser, it isn't as efficient.
So during the night your a/c is actually getting colder internally than it does when running during the day - in high temps like this year especially.
At night it is just plain more effective.
The HOT exterior heat exchanger is usually called a condenser.
Running in cooler air at night the unit actually DOES achieve a much cooler temperature in it's coils before it shuts the compressor off, in a shorter time.
When it is very hot during the day the unit has to run longer to waste heat into air that is closer to the temperature of the condenser, it isn't as efficient.
So during the night your a/c is actually getting colder internally than it does when running during the day - in high temps like this year especially.
At night it is just plain more effective.
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Cargo Master
Joined: Apr 2003
Posts: 3,476
Likes: 224
From: Frequently frozen MN
I'll try once more -- I guess that I wasn't very clear.
Indicated temp is what shows on the thermostat
Hot day A/C set to 72
-Indicated temp goes down to 70/72
-Compressor starts somewhere in that range
Cooler night A/C still set to 72
-Indicated temp goes down to 68/69
-Compressor STARTS with indicated temp at 69 or so
A/C can cool below 70 on a fairly hot day so that's not the reason.
I'm just curious. Only thing that I can figuere is that the indicated temp responds much slower than the one controlling the A/C
Thanks,
hj
Indicated temp is what shows on the thermostat
Hot day A/C set to 72
-Indicated temp goes down to 70/72
-Compressor starts somewhere in that range
Cooler night A/C still set to 72
-Indicated temp goes down to 68/69
-Compressor STARTS with indicated temp at 69 or so
A/C can cool below 70 on a fairly hot day so that's not the reason.
I'm just curious. Only thing that I can figuere is that the indicated temp responds much slower than the one controlling the A/C
Thanks,
hj
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