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Car Forum / Australian Car Forums / General Car Topics (Australian group) / February 2007Dual-zone climate control
How does dual zone aircon work? Obviously, the air coming out one side of the car is a different temperature (or different flow rate?) to the air coming out the other side. I'm wondering how this is controlled, particularly when cooling the air in summer. I can see three possibilities. Least likely is two separate HVAC systems operating independently. It's probably what most car buyers imagine, and it's easiest to understand, but it would be way too expensive. It could be that the regulation is done just by flow rate. If the left side of the car is set colder than the right, then the left gets all the air direct from the HVAC system; the right gets only a little air, and relies on "second hand" cool air flowing across from the other side of the car to maintain target temperature. The last option is the one that I fear is used: a single aircon system and two separate heater matrices. The air coming in to the car (or being recirculated) is cooled by the aircon coil to the cooler of the two settings, split between the two zones, and the air for the warmer zone re-heated to the target temperature. That would be affordable - two small heater cores and a couple of control valves wouldn't be much more expensive than a single large heater core and control valve. But it would also be grossly inefficient, using engine power to drive the aircon to cool the air, then heating half of it up again. Anybody know the workings of these things? fs > How does dual zone aircon work? > [quoted text clipped - 28 lines] > > fs Pretty much the last one. That's what even non-dual CC systems do even when you ask for heating-only. The A/C runs anyway. It's done to de-humidify the air. So would I be correct in thinking that if I have my A/C on and the temperature set to something other than full cold, the A/C is still operating at full capacity anyway and all I've done is opened the heater tap to heat some of the dehumidified air coming through the A/C system? Marco > So would I be correct in thinking that if I have my A/C on and the > temperature set to something other than full cold, the A/C is still [quoted text clipped - 3 lines] > > Marco In a CC system, yes. In a 'manual' system, it depends. Many of the new cars do it this way, the older ones usually don't. >> So would I be correct in thinking that if I have my A/C on and the >> temperature set to something other than full cold, the A/C is still [quoted text clipped - 8 lines] > In a 'manual' system, it depends. Many of the new cars do it this way, the > older ones usually don't. All the cars I've owned with climate control give you the option to switch the aircon off manually. Fraser > So would I be correct in thinking that if I have my A/C on and the > temperature set to something other than full cold, the A/C is still > operating at full capacity anyway and all I've done is opened the > heater tap to heat some of the dehumidified air coming through the A/C > system? On A/C systems with variable stroke compressors the load determines the rate of cooling. The load is based on the outside temperature and the temperature inside the cabin. On older systems the rate of cycling of the compressor could alter the rate of cooling. But basically yes, warm air is mixed with the cold air. > So would I be correct in thinking that if I have my A/C on and the > temperature set to something other than full cold, the A/C is still > operating at full capacity anyway and all I've done is opened the > heater tap to heat some of the dehumidified air coming through the A/C > system? Not necessarily. For example the VT onwards commodores are supposed to have a variable compressor. So, if the required cooling is less than max theoretically the compressor won't work as hard.  SignatureThe Raven http://www.80snostalgia.com/downloads/batfink/sounds/wings.mp3 No, you don't get two separate HVAC systems at all, unless this is specifically stated in the car's list of features. Usually you find two such systems on large people movers, but some luxury cars have it too (the 2nd gen. Lexus LS400 being one example - it had a button you push called "rear A/C" (or something similar) which turns on the second unit). > How does dual zone aircon work? > [quoted text clipped - 28 lines] > > fs > But > it would also be grossly inefficient, using engine power to drive the > aircon to cool the air, then heating half of it up again. > > Anybody know the workings of these things? I believe you answered your own question.... Signaturesome stupid sig... |
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