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RE: AC Hook-up

To: <shop-talk@autox.team.net>
Subject: RE: AC Hook-up
From: "Randall" <tr3driver@comcast.net>
Date: Sun, 17 Jul 2005 08:21:07 -0700
> 1. I have A ASC unit that I am Installing in my shop.  The A coil is already
> in the furnace and I would like to hook up the condenser ouotside.  The
> Freon lines are alreasy in.  ONce they are sodered I need to know how to
> "pull a vacuum and start up the system." and start the system up after I
> open the lines and let the freon in.  I have been looking on the net but
> been unable to find any help.

Federal law requires that you be a licensed refrigeration technician to do this
... my suggestion would be to get the technician course, study it, and get your
license.  If you don't, there's a $25,000 penalty if you get caught, and a
$10,000 reward to anyone who turns you in.  And you've just told a whole bunch
of people how they can pick up an easy $10,000 ! <Grin>

But the basic procedure is pretty simple :

1) Hook up your manifold gauges with the high pressure gauge to the high side of
the system and vice versa.
2) Initially charge the system with air or nitrogen (through the center hose) to
at least 150 psi or so, then close the valves and wait to see if there is a
pressure drop indicating a leak.
3) Connect the center hose to a good vacuum pump (which has had the oil recently
changed), open both valves and start the pump.  Run the pump for at least 1/2
hour, overnight is better.  Close both valves, disconnect the pump.  I forget
the definition of "good" offhand, but it's pretty low, something like 100
microns of vacuum, which basically means a rotary vane pump either designed for
AC work or laboratory work.  Those cheap air-powered things at HF aren't going
to cut it !  Nor will an old AC compressor, as some people like to use.  The
goal here is to get and hold the vacuum low enough that any water absorbed into
the desiccant in the filter/dryer will be boiled off and sucked out.  Water,
even water vapor (like in the air) is the mortal enemy of refrigeration systems.

3A) Many automotive systems require that refrigeration oil be added at this
point, but all (AFAIK) stationary units do not.  Check your documentation to be
sure.

4) Connect the center hose to the refrigerant can, with the can upright (so the
valve is at the top, in the vapor).  Set the can on a scale, and note the
initial reading.  Subtract the recommended charge weight, and make a note of the
target weight.  Open the valve on the can, then crack the connection of the
center hose to the manifold just long enough to purge the air from the line.  Or
follow the instructions for your manifold to purge the line.

5) Open the low side valve and wait for the pressures to stabilize.

6) Start the compressor/system and wait for the weight shown on the scale to
drop to the target.

7) Close the valve on the can.  Wait for the system to stabilize, then check the
high and low side pressures to see that they match the air temperatures
obtained.  Also check the sight glass for no bubbles.  Adjust charge as
necessary.

8) Close the manifold valves, disconnect the lines, reinstall the caps on the
service ports.

> 2. Harbor freight is selling a set of manifold gauges, but I'm not sure they
> will work on a home unit?

What refrigerant does your unit take ?  If the manifold set says it will work
with your refrigerant, it will fit.

Randall






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