arnis wrote:Above freezing temperatures heat pump is more than 300% efficient. During near freezing
weather (few degrees above) keeping Leaf at comfy temperature takes less than 300W.
Efficiency drops considerably at -10C/14F. I suspect no more than 200%.
At -15C (+/-2C) heat pump stops working, fan stops, only resistance heater is used.
Sometimes it doesn't start with vehicle at all (most likely temperature sensor data). Sometimes it
starts for up to a minute and then stops. Sometimes it doesn't start but if I drive into warmer
places it will start later. It is not based on outside temperature reading we see on the dash.
In some scenarios heat pump also stops working at temperatures below freezing above -10C/14F.
This is due to evaporator icing. Heat pump will stop, outside fans will stop. Only way to deice is
to start charging process. Process will start about 1-2 minutes after charging has started,
will take about 5 minutes (will run heat pump in closed cycle, just gets hot). Process will not start
until SOC is above 15%. Deicing is not possible while driving. Maybe it will deice even without
charging. Haven't tried jet.
I've not measured efficiency but others can report how much does resistance heater consume
(after vehicle fully warmed up, takes about 15 minutes) at near freezing temperatures.
PS. Heat pump is more efficient at higher speeds. Due to the fact that outside fans should stop
(never heard that but manual says that happens) and more air is pushed past evaporator.
I have a question: does anyone know heat pump electric motor maximum power rating?
I've seen it draw 2250W. At the same time resistance heater draws ~3750W. That should translate
to about 10 000W of heat. This is not sustained for long due to fact that air resistance heater is PTC
based and will not be able to consume that much energy when it gets hot. Neither of those numbers
is the maximum rating, I think...
Intrigare wrote:Thanks for the useful info, arnis.
Look for the A/C compressor maximum power rating. The heat pump "electric motor" IS the A/C compressor. Perhaps you already know that a heat pump is essentially an air conditioner running in reverse.
When you say the heat pump runs in closed cycle to de-ice, do you mean its running in Air Conditioning mode? Is it blowing air into the cabin when it does this?
arnis wrote:Defrost cycle runs with weird valve combination mode (normal split-type heat pumps don't have that second valve AFAIK). It doesn't blow anything at all. Only after defrost is done it purges water with fan (outside evaporator).
arnis wrote:There is something wrong with C - D and E - F positions. I've tried min and max temperature settings
and during cold weather PTC element and inner condenser have airflow
Also between A and B there is also a half-position (active if AUTO or hold recirculation=double-blink)