Re: A/C recharge questions

["Barton P. Chambers" <bchambers@atlantic.nos.noaa.gov>]

In message <199409081346.AA27418@mailhost.nexus.comm.se>  writes:
> > From: "Barton P. Chambers"  <bchambers@atlantic.nos.noaa.gov>
> > Reply-To: quattro@swiss.ans.net
> > X-Charset: LATIN1
> > X-Char-Esc: 29
> > 
> > Hi Vladimir,
> > 
> > > Why the Bentley recommends to evacuate system before recharging?
> > 
> > This procedure applies to *all* conventional air conditioner systems using 
> > refrigerant under vacuum.  If you wish to successfully charge one of these 
> > systems, it is *absolutely* essential to pump out the remaining refrigerant
> > under vacuum, or you *will* get air in your system, and lose the ability
> > to cool.
> > 
> 
> What do you mean by "refrigerant under vacuum"? Conventional (R-12, R134A)
> A/C:s are under pressure when correctly charged.

Hi Thom, et al,

Guilty as *charged*.  Boy, is my face red!  Doubtless, this confusion of
vacuum with Pressure is the result of an intermittent short in the cerebrum,
the inevitable consequesce of a cerebral-rectal inversion.  (blush)

> Unless you have a leak and the whole charge has vanished it is
> possible to recharge without evacuating the remainder. 

au contraire.  If you don't/didn't have a leak, you would not be in the
position of needing to add refrigerant.  I spent an expensive summer
acquiring conclussive evidence that loss of refrigerant will always
equal air in system.  also, just BTW, I've been advised that EPA regs now 
*require* pump-down, and prohibit the self-charge.  I'm not on real
solid ground here, but I will check with EPA & get back if you desire.

> If there is a
> leak and air (= moisture) has gotten into the system the moisture must
> be evacuated, after fixing the leak of course, as R-12 reacts with
> water into some acid.

also true.

> One reason I can see to evacuate the system is to know exactly how
> much refrigerant you have in the system.

I am certain that EPA has prohibited discharges of R-12 to the atmosphere.
It may be that it is virtually impossible to hook-up the old DIY 1 lb can
recharge w/o some discharge, thus the prohibition.

Cheers,

Bart Chambers
(who *is* aware of the wisdom that...

it is better to be thought a fool than to open mouth and 
remove all doubt...)