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post #1 of 6 (permalink) Old 11-13-2003, 11:40 AM Thread Starter
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Default Climate control

As I have been given to understand the climate control in the '04 Prius uses an electric motor driven air conditioning compressor so the A/C will continue to function when the gas engine is switched off at a long light or train crosssing.

What I am wondering is what aout heat?

Most cars get the heat to run the defrosters and to heat the cabin from rejected waste heat "borrowed" from the cars coolant by running it through a water to air heat exchanger (heater core.)

Since the Prius will shut the gas engine off for significant periods of time, where does the climate control system get heat to keep your tootsies warm in the winter time while in stop and go slow speed traffic?

Could it be they use the electrically driven compressor as a reversable heat pump? That would certainly work but I haven't a clue what they actually did or if the heater works worth a darn under the conditions that allow the gas engine to shut down.

Ideas? Thoughts? Anyone driven in those conditions with heater on who could report the reality of their experience?

Winter is coming and hopefully so is my Prius so I care a bit.

Pat

A blah day in the country beats a whoopee day in town!
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post #2 of 6 (permalink) Old 11-13-2003, 01:55 PM
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Default heat

for the classic Prius in the US, there
are small electric heaters that do
give some heat when you first start
the car.

Afterwards, if you have the heat on
and you're stuck at a long traffic
light or behind construction, the
car will start the gas engine up just
to keep itself and you warm. That's
one of the reasons that gas mileage
is lower in the winter for Prius in
colder climates - at times when otherwise
the gas engine would be off (stopped
at a light, coasting down a hill, etc.),
but you want cabin heat (and therefore
also want to heat the batteries), the
gas engine will come on to provide heat.




-- Michelle Vadeboncoeur, [email protected]
2001 Aqua Ice Opalescent
2004 Black BC
fuel stats: http://www.kluge.net/~felicity/prius.php
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post #3 of 6 (permalink) Old 11-14-2003, 06:34 AM
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Default Re: Heat

I will just add that the Prius has a small, electrically powered pump to keep the coolant flowing through the heater core when the gas engine is off.

2002 Blue Moon Pearl
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post #4 of 6 (permalink) Old 11-29-2003, 06:06 PM
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Default Re: Climate control

Quote:
Originally Posted by patrickg
What I am wondering is what aout heat?
Me too. Maybe I'm missing something somewhere, but is the air conditioner the heat? I mean, if you want heat (it's going down slightly below freezing here tonight), do you just turn the A/C on and set the temperature higher? I didn't see a specific heat setting, and didn't see it in the manual either, unless its just all A/C and the temp setting.
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post #5 of 6 (permalink) Old 11-29-2003, 07:09 PM
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> but is the air conditioner the heat?

"Air Conditioning" has always meant "conditioning of air".

At some point though, some people starting implying it only meant "cold".

But since climate-control systems, like the one in Prius, automatically toggle between the cold & hot for you to achieve the specificed conditioning of the air, the proper terminology is coming back.

So now cold is labeled as "A/C" to help avoid long-term confusion.
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post #6 of 6 (permalink) Old 11-30-2003, 10:23 AM Thread Starter
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John, I am in complete agreement with your A/C definition feelings. I get bugged when perfectly good expressive terms are misused and then the "wrong" usage becomes the accepted usage. The talking heads took "DECIMATION" which means literally to be reduced by 1/10 (Romans started the term with their practice of killing every tenth male in a village as punishment for some transgression against the conquerors.) Now the talking heads have "sold" it to the TV audience as meaning TOTAL DESTRUCTION!

Oh well.

Sometimes in order to communiate with the general public you have to use terms "their way." Still the question regarding heating and cooling went unanswered. The automatic climate control may alternatively use either heating or cooling "mode" to try to achieve the setpoint temperature but that doesn't say where the heat came from. I suggested at one point that if the A/C compressor were utilized as a reversible heat pump that it could heat or cool more or less independently from the gas engine as a heat source. A heat pump could get heat from the engine or from the environment or whichever worked.

I suspect that in the Prius the "A/C" compressor is used only for cooling and the engine's waste heat is used for the main heat source. It is possible that there is some electric suplemental heat as another poster mentioned he had in his "classic" Prius.

In "other" cars the defrost mode engages the A/C irrespective of the selected temperature and of course works best at a high temp setting. This serves to dry the air by first cooling it below the dew point to condense out a lot of the moisture and then heating the air via the heater core, further reducing the relative humidity, prior to blowing it on the glass where this warm dry air is efficient at removing "fog".

I suspect this is the same for the Prius and await confirmation or denial from "hip" owners. If I am right then the truly relilgious technogeeks will use the defrosters as little as possible due to the energy consumption and gas mileage reducing effect. Driving with a window open could come back in vogue.... BUT does it disturb the aerodynamics such that mileage will be reduced?

Pat

A blah day in the country beats a whoopee day in town!
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