Can 20 year compressor overheat the 20V?

[Huw Powell]

Just to play with numbers a bit...

a 6500 BTU house window unit, recommended for a 250 sq ft room would use 
about 50 amps on 12 volts:

5.7 a at 110 v = 627 w

627 w at 12 v = 52.25 a

To make a huge assumption, that running one off house AC is roughly as 
efficient as running the compressor directly, that's like adding "half 
an alternator on full load".

Plus whatever the interior fan uses on "high cool" mode.

So while it is certainly a load on the engine, it shouldn't feel like 
towing a trailer.

Another random note, the numbers above are for a new, modern, Energy 
Star* AC unit.  The 20 year old system under discussion is probably less 
efficient to start with, and might be quite a bit worse by now.

*My new (ten years ago) Energy Star refrigerator was about 30% larger 
than the late 70s era unit it replaced, and my electric bill went down 
$20 a month (135 kwh at my nuclear rates).  Your mileage may vary.  It 
might not be possible to match modern efficiencies of that sort in an 
automotive system, especially a retrofit.

On 7/30/2012 2:35 PM, George Selby wrote:
> At 01:56 PM 7/30/2012, you wrote:
>> Regarding the drag: my compressor is pumping fine, but when it turns
>> on, it
>> feels like I'm hauling another type44 on my back. Any remedy for this?
>
> Double the boost?
>
> In actuality AC is a huge drag on the engine (Maybe not in Canada, but
> down here in the southern US it is.)  Due to losses in converting
> energy, the engine bay probably sees 4 times as much heat added when the
> AC is engaged as is removed from the interior.  And most auto AC systems
> do produce an icy blast, in fact the average car system would cool a
> house quite well.
>
>
> George Selby
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