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Normal HVAC behavior?

CommodoreAmiga

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I'm not an HVAC specialist but I think the issue they have is balancing efficiency while using a resistive heater. There no low setting on a heater it just cycles on/off, so to have warm vs hot air running the resistive heater would have to be on 100% of the time mixing with cabin/outside air. Whereas in an ICE they can grab as much/little engine heat anytime. Granted, this is an issue for any EV without a heat pump and Tesla still seems able to hold a setpoint so... hopefully they fix that.
They could use thermal mass to their advantage.... Two easy options:

A metal heatsink provides thermal mass. You the resistive heater heats the heatsink, and the HVAC blows air across the fins to transfer the heat. The resistive heater is duty cycled, so it can be switched on/off as necessary. The thermal mass of the heatsink provides smooth, consistent heat to the air which continues to blow, even when the resistive heating element is unpowered.

A heat exchanger and coolant loop is heated by a resistive element. Coolant flows through the loop and air blows through the heat exchanger. The heating element is duty cycled, as necessary.

These are not new concepts. These are used all over the place!

Also, this is yet another reason that a heat pump is great.
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Dark-Fx

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I'm not an HVAC specialist but I think the issue they have is balancing efficiency while using a resistive heater. There no low setting on a heater it just cycles on/off, so to have warm vs hot air running the resistive heater would have to be on 100% of the time mixing with cabin/outside air. Whereas in an ICE they can grab as much/little engine heat anytime. Granted, this is an issue for any EV without a heat pump and Tesla still seems able to hold a setpoint so... hopefully they fix that.
Resistive heaters are typically capable of being controlled with a PWM signal though. You don't have to have 100% or 0%.
 

SSteveEV

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Resistive heaters are typically capable of being controlled with a PWM signal though. You don't have to have 100% or 0%.
Thanks, That'll give me more to research while I'm sitting at a RAN later today. Do you know if that is a linear break on power for the duty cycle? I would have assumed that just to get the coil warmed up would take a lot of initial power to turn it on but glad they can regulate it better than I thought. That'll keep me warmer on my drive as I manually move my HVAC from 72 to off to 73 to off or however we are supposed to stay warm ;)

@CommodoreAmiga Also thanks, good point about the thermal mass. That's the concept I was trying to use while preheating while plugged in this morning which is why I was so annoyed at the temp dropping so quickly. Figured if I load up all the seats and cabin before setting off I'd have a bit more heat stored vs blowing at me on battery power.
 

JohnB R1T

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If there are any bored people out there, please do the math on how terribly inefficient it would be to plug a space heater into our 120v ;)
Technically speaking, it wouldn't be any less efficient as long as that heater provides adequate circulation of the heat within the cabin.

Once you get past the inefficiency of turning fuel into electricity, all electric resistance heating is "100% efficient" in that it is all converted to heat...it's the "starting with a lump of coal" or "puff of wind" that is where inefficiency enters into it.
 

SSteveEV

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Technically speaking, it wouldn't be any less efficient as long as that heater provides adequate circulation of the heat within the cabin.

Once you get past the inefficiency of turning fuel into electricity, all electric resistance heating is "100% efficient" in that it is all converted to heat...it's the "starting with a lump of coal" or "puff of wind" that is where inefficiency enters into it.
I was thinking in terms of the DC battery to AC outlet conversion before it gets to the newly installed back seat turbo heat mode vs whatever Rivian runs their heater off of. But I'm glad you saved me the research and guilt over adding another warm fire hazard.

(to be clear, I will not be attempting that terribly dangerous idea, though I was tempted to put one in the bed while star gazing)
 

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JohnB R1T

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I was thinking in terms of the DC battery to AC outlet conversion before it gets to the newly installed back seat turbo heat mode vs whatever Rivian runs their heater off of. But I'm glad you saved me the research and guilt over adding another warm fire hazard.

(to be clear, I will not be attempting that terribly dangerous idea, though I was tempted to put one in the bed while star gazing)
Yeah, I'm thinking any inefficiency in going from DC to AC would end up as heat...but it's unknown (to me) whether that heat would be released in a manner that would warm the cabin. Remember, that DC to AC conversion also occurs when conditions would warrant cooling, so it stands to reason that it wouldn't automatically "dump" inside.

I see absolutely NO reason to not run your little heater in the bed while stargazing. A 1200 watt heater will be drawing 1.2 kWh per hour of use...not too many miles shaved off of your range to do that for a while.
 

SSteveEV

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I see absolutely NO reason to not run your little heater in the bed while stargazing. A 1200 watt heater will be drawing 1.2 kWh per hour of use...not too many miles shaved off of your range to do that for a while.
Frankly it was bed length that killed that idea, though one day I'll probably try that. Had hoped to keep the liftgate closed and just crack the tonneau for my cocoon. Certainly worth the range!

And good point about the AC/DC losses also being heat.
 

JohnB R1T

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I once spent a sub-freezing night camping with a buddy. We decided it would be a good idea to drape a heavy green canvas tarp over the bed of my '71 Ford Step Side 4x4 pickup (wish I still had that one). As we slept (mostly) through the night, our breath condensed and froze on the bottom of the tarp. Being South Texas boys, this had never occurred to us. When the sun rose enough to hit the tarp, we were awakened by ice water dripping from above. I've never set up and lit a campfire that fast in my life.:)
 

Indy avocado

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Unfortunately, mine (VIN 17xxxx) works exactly the same.. it's not very relaxing to have to constantly work the system on longer drives. In our other EV's and ICE vehicle you simply set the system at 68deg and the cabin gets up to 68deg and stays there without any additional driver input.

Rivian could solve this embarrassing issue so easily they probably can't see it... put a dedicated screen icon for "HEAT" and one for "A/C" ... done! Old school easy ;)
Here to keep bumping the thread because the current "auto" climate is absolutely infuriating to use.
When it's cool/cold out and I set the HVAC to 68F, it blows (seemingly) cold air aggressively at me while the actual cabin temp is in the 60F range. I have never seen the fan below "2" when in auto. If I override fan speed to minimum it's better, but then it won't warm up the cabin in a reasonable amount of time.

Adding "heat" "Vent" and "a/c" buttons would help.
 

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Driving my kids to school this morning in rare for LA freezing rain I was dangerously trying to manage the HVAC system while driving down the 2 with two chatty children behind me and I still couldn’t understand how to make it comfortable and manage the fogging on the windows without the fan at full blast. Sucked!
 

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Interesting side note: if you look closely at Doug demuro’s video on EDV “quirks and features”, it seems like Rivian implemented simplified HVAC controls with a hot/cold slider.

when hvac in our truck goes rogue, I put it in manual mode, low fan, recirculate with the temp set above 70F. When windows start to fog up, I switch to outside air for a few minutes. That’s my coping strategy for now.
 

MXA121

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Today, long enjoyable drive in the R1T. 45F and we're a bit chilly in the cabin. Every other vehicle I have works perfectly fine on Auto - Not the Rivian..
Still love it! But quirks it has.
 

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Am I going crazy or is my defroster blowing nearly ALL the time?

Why are my fans making so much noise when they are on 1/7 and auto is on?!

I’m turning Auto OFF ALOT because it just making obnoxious sound lately.
 

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Rivian R1T R1S Normal HVAC behavior? 24D56951-9DCF-4257-B10B-2BCD9446F8EF

45 windy and some snow in Los Angeles and I’m driving around with the windows cracked because it’s hot as fuck in this truck.
 

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I love my truck which I've had for about 4 months with no mechanical issues, but I have to say I've had the same frustrations as others have described with the HVAC system. Because it's so nonintuitive (and a bit noisy when running on anything above the lowest setting), 90% of the time I drive it with the HVAC off and either crack the window if it's warm or run the seat heater if it's cold. The few times it's been too cold to get by comfortably with just the seat heater I've had to crank the temp to 73 F or above, like others have reported. It's a very quirky system. I agree with others that it's in great need of improvement. I'm kind of concerned about what it will be like in the summer.
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