Although I've previously posted, wanted to jump in with another question. In the colder days here in Colorado, I've notice when I have had the ECO on and heater on AUTO that the A/C light is on. I can push the button and the light goes off, but was just wondering if the pump actually running and using electric energy? I understand the A/C pump would be on if I were using the defrosters.

 

Most likely the A/C compressor is running. (If the light is on...so's the compressor.) However, its probably cycling infrequently due to the cold ambient temperatures. Most of the HVAC systems shut down the compressor when the outside temps approach the upper 30s .. low 40s to prevent the coil from freezing up. They do work when the defroster is on to pull moisture out of the air ... and keep it from collecting on the cold windows. Well, most of it anyway.

 

High moisture content inside the car is another reason to keep the RECIRC button off. The excess moisture from clothes, bodies, breathing saturates the air and it will then collect on cold surfaces... like the windows. A bit of circulation ... with the RECIRC off ... keeps the air flowing through the cabin.

 

Thanks ... tend to agree that if the light is on that the pump is running some, and also agree it wouldn't be much because of the colder tempature. Guess I can just push the button and shut it off. The only time I've seen the RECIRC light on is in the summer when the car is hot and it reculates for a while until the car cools down, then shuts itself off automatically. I've never seen it come on in the cold. I do find myself using the heater a lot less or at a very cool tempature in the winter ... most the times just shut it off when stopped at a light so the ICE will shut off.

 

This system does use the AC to dehumidify the inside air while heating. It takes less energy to dehumidify recirculated air than it would to adequately heat air from outside. The recirculated inside air needs to be dehumidified, to remove the water added by human breath. Without dehumidification, it will quickly fog the windows.

I have also noticed that on not-too-warm days (mid 70's), the automatic system likes to use outside air for the AC. When it is very humid, I see fog coming from the AC vents. Turning recirc on eliminates that fog, too.

 

Steve,

The 'fog' you see coming from the vents is due to the very cold air from the vent hitting warm moist supersaturated air in the cockpit. You see the same things in some aircraft cockpits and cabins ....

Our SOP is to leave the RECIRC off as much as possible. With the HYCAM it has to be on most of the time when using the ECO setting. Even that doesn't cut it on a 90F+ sunny Texas day. Then its RECIRC on/ECO off.

Still trying to figure out what we're saving here. If its juice out of the battery that's easily replaced when you go into regen mode. Maybe its best left on when you are in very heavy city traffic where you don't regen as much and the ICE would have to make up the losses???

Happy Holiday!!

 

I don't think it saves much, if anything. To remove the same number of BTUs from the cabin, using the same AC equipment, takes about the same number of Joules of energy to operate that AC equipment, no matter when or how rapidly you do it. Running the compressor and fan at slower speeds might gain a SEER point. It might delay the ICE restart by a few seconds. But neither of those would make a big difference.

I think the real purpose of the "ECO" button is so the marketers can make a claim in their advertising. The feature-list in the brochure can have a check beside the "has ECO button" feature.

 

I'm in agreement here.... Theoretically, it would take a system working at 50% effiency (ECO ON) twice as long to condition the same cabin space (given the same light and outdoor temperature) as one working at 100% (ECO ON). As we already know, the ECO managed HVAC doesn't cool worth a hoot above 90F on a sunny day.... so that means the puppy is working its guts out. Probably better to have it ECO OFF and let the system work at 100% and use the A/C systems 'throttle itself' using as much or as little freon as it needs to cool the cabin.

Since ECO OFF allows the resistance cabin heater (and maybe an engine block heater) to operate, it would seem to be a better strategy to leave it ECO ON in cool/cold weather to take advantage of the energy stored in the battery. Which, is easily replaced by regenning.

Next tank, I'm going to leave the thing ECO OFF for a full tank and see what that does.

Cheers!

 

The ECO button seems to be for the 'average' 35-85 F range. When you start going outside of that range then it makes sense that the car needs to work a lot harder at keeping the interior at an appropriate temp. I seldom see temps over 90, but I do see temps in the -40 range, and yes mileage takes a big hit when we get out of those 'average' conditions.

 

I seldom (never?) see temps below +40, here in South Florida. Actually, it does happen, but only for a few days each year. We have trees that will die if the temp gets down to 32 for even one night. They are predicting a low of 50 today. Most years, we get about six months of above-90-degees, with high humidity.

The AC does not work well in hot summer conditions with the ECO feature engaged. Summer here requires the AC on full-blast for at least the first ten minutes of each trip. In winter, it doesn't take nearly as much AC to keep it comfortable. Over two years so far, I get about 35-36 mpg in the "winter", but only about 32-33 in the summer. I sometimes feel embarrassed about that mileage, after seeing lots of people here getting much better. But, of course, I forget that most people don't have both 95 degree heat and insane city traffic.

I am sure my summer mileage would be lower than my "winter" mileage, with or without the ECO feature. I still don't think the "ECO" feature does anything useful.