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Old 05-16-20, 09:51 AM   #3
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There are a few obstacles and hurdles to overcome with automotive systems. Cooling mode has been practicing for 50 plus years in cars, so it is the easy part. The challenges come with heating mode.

I encourage you to read the thread in this group entitled "heat pumps for dummies". Not saying anything about you, but we threw it together to help people quickly get a grasp on the concepts and terms involved. Especially from a DIY approach.

Traditional automotive systems have been driven mechanically by a belt and pulley from the rotating engine. The new EV designs are using an electronic control and an electric compressor. I'm not familiar with the new compressor designs, so any background information here would be appreciated. I do know that the BMW, Tesla, Nissan, Toyota and a few other designs are using heat pump technology for heating.

In the proven and practical designs, the reversal of refrigerant flow from heating to cooling mode is accomplished not by reversing the compressor rotation, but by electric solenoid valves. With most split and minispli home systems, there is a single 4 way reversing valve that reverses the direction of refrigerant flow on command. With the automotive designs I've seen, they use more than one valve to accomplish this task. The main reason for the multiple valve approach is because they employ different strategies to heat, depending on environmental conditions and climate control settings.
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