Hello guys,
I enjoyed reading the conversation about the air conditioning, even if at some points was a bit too... Anyway, I think I heard that is better to have the air conditioner run 24/7 for mantainance and cost... is that true of conventional air conditioners and a work enviromnent where the space is used for half of the day... (I'm working in Malaysia... hot and humid!)
Thank you, R.
Dear ri:
Unless you sell electricity, replacement units, or service on existing units, then *of course* it is a good idea to spread this rumor. ;>)
No it is NOT better to leave the air conditioner running at the same temperature setpoint 24/7. If the compressor can be started with a VFD or "soft start", then you will save wear and tear on that component. A good unit probably already has this feature (or one that bypasses the expansion valve on startup, or some such "load limiter"). If the system is well designed and implemented, and has the proper refrigerant charge, then liquid ingestion issues are non-existant.
It is not necessary to keep the plant air "cold" off shift. There are "electronic thermostats" that can alter the temperature setpoint based on a schedule. This will be probably your best bet. The plant doesn't have to become supersaturated with heat/humidity, and then the A/C unit has to climb out of the hole... Might be good to limit what exhaust fans can run when the A/C is off also, as they will provide high loads.
Lastly, the air filters can/will provide a negative air pressure in the ducting between the filter elements and the fan, and this too can carry a penalty if the fan is left running continuously.
David A. Smith
This brings up another question I had. Wouldn't setting the thermostat to a low temperature at say around 3AM, so it slowly cooled the building off to a pretty low temperature help? That way it wouldn't require as much energy to keep it cool during the day? Kind of like letting your car build up speed going down the mountain and then slowly bleeding it off as you climb up the next. Would this be efficient? My guess is that it may require too low of a setting in the mornings, or too high of a setting in the afternoon, to be comfortable, if it is going to have a significant effect.
Only if the unit were so undersized that it couldn't handle the daytime load.
You could "store the cold" in a reservoir, much as is done in passive cooling systems. Then add heat to the reservoir during the day. But you would need really good insulation on the reservoir...
It would not be efficient, since A/C unit efficiency is really "tuned" to a particular outside/inside temperature gradient. Also, the colder you drop the internal temp, the higher the ambient heat transfer into your building. No it is most efficient to have the "road ise to meet your feet", and the building gets to temp just as employees arrive.
David A. Smith
Assuming that the Air Conditioning is for that room only and the room is used at a set time every day, you would be best off using a programmable thermostat. With the thermostat you can set it up to turn on about 1 hour before people begin to work, and shut off when the room is no longer being used.
You may also want to consider connecting dehumidifiers to your HVAC system. That way you remove more humidity than the AC unit alone. Without the humidity people will be able to cool down in a more natural way.
Here at my job in SoCal the company does this. During the summer months they run the airco hard all night when power is cheap. It's cold as hell in the morning. They shut if off for the peak hours and the building slowly warms up.
Saves money and saves brownouts, but you look funny wearing a parka in to work when it's 85F at 8AM.
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