Anyone know the SEER rating of the AC unit?

Just curious...

Yes

Just answering....

"The SEER rating of a unit is the cooling output in Btu (British thermal unit) during a typical cooling-season divided by the total electric energy input in watt-hours during the same period. The higher the unit's SEER rating the more energy efficient it is"

more details at:

http://en.wikipedia.org/wiki/Seasonal_energy_efficiency_ratio

Yes, we know what SEER means, but that doesn't answer the question. Surely TickTock is asking what the number is for the unit in the LEAF. I'm curious, too. It seems very efficient.

Ray

TonyWilliams said:

Yes
Just answering....

Click to expand...

So the SEER rating of the LEAF's A/C is? (drum roll....)

LEAFfan said:

TonyWilliams said:

Yes
Just answering....

Click to expand...

So the SEER rating of the LEAF's A/C is? (drum roll....)

Click to expand...

Don't know that one. On the two pumps sitting along side my house, yes, I know those

If that data is anywhere, it's probably in the service manual.

OK. It appears to be unknown so I will offer my very rough calculation. I think it is in the 21 range (pretty good). I came to this based on the following assumptions:

1) AC uses 3kW at max (this is the highest I've ever seen it on the Energy Monitor screen when it was running full tilt)
2) The units of the table on page HAC-19 of the service manual is cfs (34.2 total cfs out of the blower at high)
3) This (http://www.engineeringtoolbox.com/cooling-dehumidifying-air-d_695.html) website is accurate

The link computes the epower to cool 1cms (cubic meter per second) of air from 30C to 15C at 60% humidity as 19.3 kW. This example actually lines up pretty well with a datapoint on the chart on page HA-38 of the service manual. 34.2 cfs is equal to 0.97 cms so it takes ~19.3*0.97=18.7kW to maintain the 15 degrees drop. 18.7kW*3.41=63800 btu/h. Divide by 3kW/h and we get an EER of 21.3.

This has, admittedly, a lot of assumptions but I was expecting 16-22 since most home DC inverter AC units are in this range. Since the Leaf is very concerned about efficiency I would expect it to be on the high end.

I suppose they had to make up for the incredibly INEFFICIENT heater somehow...

TickTock said:

This has, admittedly, a lot of assumptions but I was expecting 16-22 since most home DC inverter AC units are in this range. Since the Leaf is very concerned about efficiency I would expect it to be on the high end.

Click to expand...

Yeah. What's up with that? I wonder why they chose to use a separate (inefficient) heating system rather then just making the AC system a full bi-directional heat-pump. Would have saved weight, too.

I would speculate that the compressor they used doesn't have the umph to make a decent heat pump, so a resistance heater element would be necessary anyway - and someone figured the additional cost of engineering the heat pump system was too much to bother with. Designing heat exchangers that work as good evaporators AND condensers is no easy task, and the locations of the components would have to change. A system designed to both heat and cool would necessarily not be as good at either task as a dedicated system. For example, you couldn't include a subcooler with a heat pump.

They were probably banking on heated seats and steering wheel for comfort and the heater was designed more as for defog/defrost than cabin heating.

The inclusion of a water circuit seemed really weird at first, but it makes a little more sense after reading the description in the service manual. The heater is controlled by PWM, so the liquid acts as a nice buffer to keep the temperature steady at the desired setpoint - much easier to control.

I maintain, though, that there could have been a mechanism to heat the cabin air with waste heat from the motor/inverter/charger cooling circuit... I don't know how hot that fluid gets, but if they're actively cooled there just might be something! Anyone willing to measure the main circuit coolant temp this coming winter?
=Smidge=

Another reason to use resistance heat instead of a heat pump is to allow the A/C compressor to run for dehumidification in conjunction with the heater for defrosting.

Gerry

well that a/c compressor will be running at the sime time as the resistance heater in order to keep a windshield clear.

that will be considerable draw and reduction in range during fall/ winter months when both heating and dehumidification are needed. seat heaters or no seat heaters you have to be able to see to drive safely