[alfa] Mechanical vs electric fans

[Graham&Joan Hilder <graham.joan@xxxxxxxxxxxxxxx>]

In Digest 404, Biba wrote:
"Whilst I'm more concerned with originality, I have wondered what the True
hp difference between running a mechanical fan and the additional drag on
the alternator from running an electric fan is. I'm guessing, on average,
about 1 to  2 hp difference."

On this, well I wouldn't think the electric fan would add very much
alternator load at all. Let's say the fan draws 5A, which I think is
probably in the right order, and we have say 70W or about 0.1HP. Let's be
generous and allow the alternator only 50% efficiency (disgraceful!), and we
have an added 0.2HP alternator load. I think belt-driven fans are generally
thought to use several HP at high revs so the potential saving from
converting to electric looks like several HP, unless I'm talking through my
hat (not at all impossible!)

An important extra benefit (apart from the better cooling at low RPM in
traffic jams) is that the elec fan doesn't run when not needed, which is
usually at high speed (and high revs) which is just when you are probably
wanting any extra HP you can get!

Regards,
Graham in NZ
GTV, Alfetta , Alfasud
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