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MANIFOLD GAUGE SET
A typical manifold gauge set (Figure 9-7) has two screw
type hand valves to control access to the system, two
gauges and three hoses. The gauges are used to read
system pressure or vacuum. The manifold and hoses
are for access to the inside of an air conditioner, to
remove air and moisture, and to put in, or remove,
refrigerant from the system. Shutoff valves are required
within 12 inches of the hose end(s) to minimize refrig-
erant loss.
A gauge set for R-134a will have a blue hose with a
black stripe for the low side, a red hose with a black
stripe for the high side, and a yellow hose with a black
stripe for the utility (center) hose. The hoses use a 1/2
in. ACME female nut on the gauge end. Special quick
disconnect couplings are normally combined with a
shutoff valve on the high and low side hoses. The free
end of the center hose contains a 1/2 in. ACME female
nut and a shutoff device within 12 inches of the hose
end. These special hoses and fittings are designed to
minimize refrigerant loss and to preclude putting the
wrong refrigerant in a system.
NOTE: When hose replacement becomes necessary,
the new hoses must be marked "SAE J2916 R-134a".
Functions of the manifold gauge set are included in
many of the commercially available recovery or recov-
ery/recycle stations.
M9-10
FIGURE 9-7. MANIFOLD GAUGE SET
Low Side Gauge
The Low Side Gauge, registers both vacuum and pres-
sure. The vacuum side of the scale is calibrated from 0
to 30 inches of mercury (in. Hg). The pressure side of
the scale is calibrated to 150 psi.
Never open the hand valve to the high side at
anytime when the air conditioning system is oper-
ating. High side pressure, if allowed, may rupture
charging containers and potentially cause per-
sonal injury.
High Side Gauge
The High Side Gauge is used to measure pressure only
on the discharge side of the compressor. The scale is
calibrated from 0 to 500 psi.
Air Conditioning System
for HFC 134a Refrigerant
M09010 6/97
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