Johnson Controls YORK YVAM 0350, Operation & Maintenance Manual

Page: 136 / 162

• Test the motor windings annually to check for deterioration of the windings.
Electrical tests of motor winding resistance must be performed by a qualified service
technician in accordance with the Service Instructions Manual ( Form 160.88-M1 ) because it
involves determination of power leads between the motor and the variable speed drive.
Results from these winding insulation resistance tests must be trended each interval to
determine any degradation in motor windings.
Table 96: Approximate refrigerant and water weight
Evaporator Condenser Refrigerant weight, lb (kg) Water weight, lb (kg)
EB2514
25 mm 4G
microchannel
700 (318) 1680 (762)
Note:
• The refrigerant weight is based on a maximum tube bundle.
• The water weight is the total water in the evaporator shell and for 150 psi, two-pass,
compact waterbox.
Evaporator maintenance
Maintenance of the evaporator shell is important to provide trouble-free operation of the chiller.
The water side of the tubes in the shell must be kept clean and free from scale.
The major portion of maintenance on the evaporator involves maintaining the water side of the
evaporator in a clean condition.
The use of untreated water in closed water systems and similar environments frequently results in
one or more of the following issues:
• Scale formation
• Corrosion or rusting
• Slime and algae formation
As a result, to ensure a longer and more economical life of the equipment, it is beneficial for the
user to provide for correct water treatment. To determine the condition of the water side of the
evaporator tubes, use the following guidance:
• The evaporator tubes under normal circumstances do not require cleaning. However, if the
temperature difference between the refrigerant and the chilled water increases slowly over
the operating season, it can indicate the following issues:
- The evaporator tubes are fouling
- A water bypass in the waterbox requires gasket replacement
- Refrigerant has leaked from the chiller
Chemical water treatment
The mineral content of the water circulated through evaporators varies with almost every source of
supply. As a result, it is possible that the water being used might corrode the tubes or deposit heat-
resistant scale in them. Reliable water treatment companies are available in most large cities to
supply a water treating process that can greatly reduce the corrosive and scale-forming properties
of almost any type of water.
To prevent the development of scale and corrosion and to prolong the life of evaporator tubes,
conduct a chemical analysis of the water, preferably before the system is installed. Consult a
reliable water treatment company to determine if water treatment is necessary, and if so, to
provide the correct treatment for the particular water condition.
YVAM Control Center 136