ThosEM
Space Weatherman
Maybe they are only heating the house to 10F?
Extraordinary claims require extraordinary evidence.
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Maybe they are only heating the house to 10F?
Extraordinary claims require extraordinary evidence.
He's not far off, the best mini-split that Mitsubishi makes has a HSPF of 13.5 which is 440% efficient. I don't think anyone is concerned with efficiency at -40 degrees, however at -13F/-25C its efficiency they are still over 400%.
HSPF of 15.4 is 13.5/3.41 = 396% output to input.
Which unit are you refering to? MSZ/MUZ-FH High Efficiency Heat Pumps have 13.5 HPSF @ 47F. At 17F, the rated HPSF is ~11. And don't forget defrost..
I'm going to toss this out there before even making through the first page of the thread....
The 2002 Toyota Rav4EV (same as when it started in 1997 model year) had a lot going for it in the heat/defrost department
1. It has no resistance heater for cabin air
2. It has TWO heat pumps, and so would dehumidify AND heat the air via heat-pump when needed
3. The windshield itself is resistance-heated with a thin film. This worked edge-to-edge almost instantly, using full pack voltage
(I use present tense because there are still so many of these cars running around all these years later!)
I can tell you that the heat worked quite well (with varying efficiency of course) down to the coldest it ever gets in my area–about 22F.
Wow. That's something new for me
What if condenser and evaporator are both inside HVAC box. First, air passes through cold surface to
condensate and then through hot surface to warm up. Exterior condenser is not even activated (valve shut).
Extremely closed cycle
That is how heap pump clothes dryers and dehumidifiers work. As long as you don't mind net heating, its a useful system with no outside ducts.
The car would need two heat pumps, one with a modicum of back up resistance for heat defrost/defog and the other for dedicated cooling. Also, this allows for the passenger to select a different temperature than the driver (secondary issue). But there might be advantages in this arrangement in that the heating side of the two heat pumps could scavenge heat air from car components that are already producing waste heat in operation for the outdoor section of the compressor to improve COP. Infrared examination of the car in motion could help determine such locations.
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nwdiver
Well-Known Member
Why? There are plenty of heat pumps out there that heat and cool. All it takes is a $10 valve. The EV1 could do it....
It literally does both at the same time. What you want to heat/cool/defrost is just a matter of plumbing and valving.
There is no HEAVY need to pump heat from outside and dry it up simultaneously on daily basis.
I've noticed that this is only necessary in case of really wet weather. In that case, I use
heat pump as AC to dry the air and just PTC to heat it.
I know that Tesla always uses compressor to dry the air by default, even in winter (except if AC forced off).
But HP equipped vehicles use compressor in heating cycle.
With the help of some plumbing and additional internal radiator, HP can do both.
I've noticed that this is only necessary in case of really wet weather. In that case, I use
heat pump as AC to dry the air and just PTC to heat it.
I know that Tesla always uses compressor to dry the air by default, even in winter (except if AC forced off).
But HP equipped vehicles use compressor in heating cycle.
With the help of some plumbing and additional internal radiator, HP can do both.
So the driver gets an evaporator/ condenser the passenger gets an evaporator/ condenser, the battery pack gets an evaporator/condenser, the drive unit gets an evaporator/ condenser, and the front intake gets an evaporator/condenser. I think that covers everyone.
Oh wait, the HVAC gets an evaporator and condenser to dehumidify the air and heat it for defrost/defog...
This is a real issue in winter due to tracked snow melting in the cabin. Need to prevent condensation (or frost) on the inside of the windshield along with reducing interior moisture content (venting being another option).
Can do it all with 2 valved coils on the inside with mix-doors. It's not like you get 2 heater cores so you can have split controls. Just a mix-door.
Water on the floor mats is way too much for even an ICE vehicle. Blasting air is how they deal with it. In case of EV, that is a massive waste.
And actually, many vehicles have multiple heater cores. Pretty much all bimmers since 90-s for example.
And bimmers even have left and right PTC heater in the HVAC box.
And actually, many vehicles have multiple heater cores. Pretty much all bimmers since 90-s for example.
And bimmers even have left and right PTC heater in the HVAC box.
hill
high fiber member
So - in conclusion, answering the OP's question from long ago.
no one knows why, for certain
.
no one knows why, for certain
.
There are many reasons.
a) Tesla is a "sunny climate vehicle". It's not "above average" in cold weather compared to all other EV's
b) Simplicity - HP system is more complex.
c) HP system is also slightly less efficient in AC cycle compared to AC-only system
Two compressors is definitely overkill. Extra plumbing is sufficient.
Only my 2 cents here, but I have some experience from a BMW i3 which had a heat pump.
Cold weather around zero Celsius they don't work good at all, heating consumption of i3 was crazy even with heat pump
They consume a certain amount of energy to just heat their own circuit, means it all takes time and energy, not good on a short trip
They also need a resistive system to back them up, means you need both anyway
To be honest when I changed over to Tesla, I was happy to learn they don't bother with the heat pump approach.
Maybe on exactly the right day, with exactly the right temperature and a long trip the heat pump would be worth it. Otherwise, with a big battery and supercharging its a waste of time.
Get a nice coat
Cold weather around zero Celsius they don't work good at all, heating consumption of i3 was crazy even with heat pump
They consume a certain amount of energy to just heat their own circuit, means it all takes time and energy, not good on a short trip
They also need a resistive system to back them up, means you need both anyway
To be honest when I changed over to Tesla, I was happy to learn they don't bother with the heat pump approach.
Maybe on exactly the right day, with exactly the right temperature and a long trip the heat pump would be worth it. Otherwise, with a big battery and supercharging its a waste of time.
Get a nice coat
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