Electric AC compressor

It's amazing how much current just a thermo fan can draw, I had one of those battery monitors connected to my brother's car on the weekend and it was showing green with the alternator running but when the second stage fan kicked in it briefly changed to yellow!

@tins then I think that indeed if you can optimize the system without being limited to the constraints of the engine bay you might win some here and there. This does remind me of another topic here about the TD5 efficiency and other topics about after market AC/s in defenders and such. It's not just the condenser that has to do it's job (and the compressor having to make sufficient RPM when the engine is at idle) but it also very important to have a decent evaporator and blower(s) inside the car.

As mentioned before; I basically ripped the original belt driven compressor and VC fan out of my range rover, but kept all the rest of the system intact @scarry so yes I have a TXV just before the evaporator inside the range rover which at that point already was dual zone so it has two blowers, one for each side.

In short, my entire system was already very capable of keeping the car cool on even the hottest days, with the exception of slow traffic where the VC fan would not pull enough air and the two thermofans would have to help and even then I got to points where the over pressure switch would simply kill the AC for a while. With the large thermofan I do not expect that to happen again (and the much smaller electric compressor can probably never get to that point...). This in my opinion goes to show/prove that with a decently sized condenser, evaporator etc. even a smallish sized DC compressor can provide ample cooling, although it will never be as much as the belt driven one. If you put the smaller compressor on a less properly sized system, I doubt you will get great results.

@randlover yes, and do not forget the blower(s) that keep the interior cool/warm. My range has two and both of them are rated (well fused) up to 40A. I doubt I will ever see them do that under any circumstance but let's put all the theoretical maximums together: 100A compressor, 80A thermo fan, 80A blowers... and then the rest of the car to work. I had a victron shunt in my car for a while that measured -everything- and just the car running pulled 30A. So yeah ;)

Cheers.
-P

Quote:

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Originally Posted by scarry;[URL="tel:3258646"

3258646[/URL]]Lower head pressure will to some degree,but it is higher back pressure that pushes the amps up very significantly.

The higher the back pressure,the more capacity and work the compressor has to do.

Which is why we use MOP TX valves,and CPR valves on low temperature refrigeration systems,and a few other applications,such as large DX AC plants.


We actually came across a freezer room today,at a school,4 yrs old,a faulty compressor,they wanted another opinion.It is on its third compressor.[bigsad]
No MOP TX or CPR valve,are the main issues,there are others.
I wish fan mechanics(AC techs),would stick to AC......

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Hey Paul, when you get time how about a car A/C 101 for us muppets? My early learning did not include it ( Army didn’t use it below the rank of General) and we always used to farm it out in my post military life. I would like to have a basic understanding. YouTube may be the younger generation’s centre of learning, but you never know who the teacher is.