openinverter forum

Cabin heat!

Now in general it’s not very efficient to heat the air around us, than to just heat us. But beyond that for cabin heating we have

• Recirculating waste heat

• PTC heater (matrix/liquid)

• Petro heater

• Ac system in “reverse”?

a ptc heater is great 100% efficient! but at some point it’s a huge range killer.

Can we do better(without using a petro heater)?
so what about taking heat from the outside? Using an ac system in reverse! if the ac evaporator is colder than the outside air, then it will pull heat into the system. Then we dump that heat into the cabin.

Now the colder it gets outside the less “efficient” the system becomes.
But the would never drop bellow 100%, would always =<.
Condenser get cold, like -20 cold. equilibrium, evaporator temp = outside temp

I think for most of our climates,
this is a non issue!

*edit

This is essentially what a heat pump is, new leafs and model y have this system.

Heat Pump efficiency drops off at temperatures below about -10*C, this is not a "hard line" and depends on the individual system. Colder than that, some direct heating mechanism is needed, but it some form of dino-based fuel, or electrical.

I am going with a PTC heater element as I simply need it for "demisting" above freezing as my conversion does not have 4 Season or long range intent.