Re: A/C recharge questions

[walter@quattro.corp.inmet.com (Walter Meares)]

> > 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.  

Think about the physics of it.  The static pressure of freon in the system is
60-80 psi under typical temperatures.  The operating pressures are around 30
on the low side, 200 on the high side.  There is *no way* air is going to 
get into the system unless it is a) put in by poor service procedure;
b) diffuses in when the system is completely discharged; or c) gets drawn in
because a blockage in the system, combinded with a leak, allows the low side
pressure to drop below atmospheric.

Auto refrigeration systems are not hermitically sealed; they weep at the hose
connections, through the hoses, and through the compressor shaft seal.  A tight
system will go many years without needing freon added, a bad one only a year,
both extremes fall within the "normal" range for an auto AC 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.

Certification is required to handled refrigerants, discharge to the atmosphere
is an absolute no-no for anyone.  These rules are'nt strictly EPA, they stem
from an international agreement (although I think if you probe under the 
surface you'll find lots of suspicious-looking business and political
goings-on as well).  Pump down is not strictly required, but topping off is
forbidden without checking for leaks and repairing any that are found.  Else
the shop is required to remove the freon and send the owner on his/her way with
an empty 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.

I believe the issue was more that the small cans were being widely used by 
folks to continually top off leaking systems rather than repair minor leaks.
Some minor discharge is unavoidable during R-12 service procedures.  The 
newer R-134 service equipment has some additional features to minimize 
refrigerant loss when connecting and disconnecting service equipment.

> 
> Cheers,
> 
> Bart Chambers


walter

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