Operating instructions

TM 11574A-OI
3-28
2
Capacitor analyzer.
a.
The function of the analyzer is to read the microfarad value of a capacitor and to
detect insulation breakdown under load conditions. The important advantages
of an analyzer are its ability to locate capacitors that have either failed to hold
their microfarad ratings or those that are breaking down internally during
operation. It is also useful in identifying capacitors when their microfarad rating
marks have become unreadable.
(14) Suction Modulation Valve
NOTE
On start up of the unit, the valve will reset to a known open position. This is
accomplished by assuming the valve was fully open, driving it fully closed, resetting the
percentage open to zero, then opening to a known 21% staging position.
Figure 3-12. Suction Modulation Valve (SMV).
(a) Pre-check Procedure. To check the suction modulation valve, perform the following
steps:
1
Check unit for abnormal operation.
2
Check charge. If refrigerant is low repair as required and again check operation.
3
If sufficient capacity cannot be maintained or unit is tripping excessively on high
pressure switch (HPS) in high ambient temperatures, check coils and clean if
required.
4
If capacity or control cannot be maintained, turn unit OFF, then back ON. This will
reset the valve in the event the controller lost communication with the valve, and may
correct the problem.