MICROSENTRY™ REFRIGERATION MONITOR
If low side pressure is below pressure in Table B, check for the following:
A system leak1.
Capillary tube is restricted2.
Insufficient compressor (does not pump properly)3.
If low side pressure is above pressure in Table B, check for the following:
Restricted air flow1.
Dirty condenser coil2.
Overcharged system3.
Low side leak4.
2.8 Re-charging
Re-charging of the unit should be done only after diagnosing and repairing the system. Be sure to flush the system
with dry nitrogen gas and evacuate to 50 microns before re-charging.
The method for re-charging the unit is by weight using vapor refrigerant. Using manifold gage set-up, hook up
charge hoses to the access valve on the compressor’s process tube. If any access valve is attached to the high side
process tube, remove it and then seal the tube by brazing before charging. Charge the unit to specified amount
(see Section 1.1, Unit Specifications for charge specifications per model).
After re-charging the system, check pressures and refer to Table B for corresponding temperatures and pressures.
If pressures are incorrect, check the sealed system, recover the charge, repair, evacuate, and then re-charge.
It is normal to have some condensation or slight frost on the suction line. Typically this will occur towards the end of
a run cycle. If the frost continues down the suction line to the compressor, the system is overcharged. It is impor-
tant that the insulation remains on the suction line and the capillary tube together after any repair and that it is
sealed on both ends. Be sure to replace the refrigeration putty in the hole of the foam where the refrigerant lines
go through the back of the unit. Spread the putty out evenly filling in the cracks to prevent air from leaking in and
out.
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