Diagnostic Lights; Low Water Flow - Unitrol 8400 Manual

UNITROL MODEL 8400, 8401, 8406, 8450, 8451, 8456

DIAGNOSTIC LIGHTS

See page 14 for location of diagnostic lights in this section.

LOW WATER FLOW:

Each module has a separate WATER FLOW switch located in their own enclosures. These are
switches on a T with a gray junction box on top. The switch for the main module is marked FS1,
and the switch for the remote module is marked FS2.
WHY THE LOW WATER FLOW SAFETY SWITCHES ARE
If the water flowing through the evaporators (chilling component) of
either refrigeration system is too low, the water deep in that evaporator
can easily reach temperatures below freezing.
When this happens, the evaporator can eventually crack from the
expanding ice. This will cause a break between the water system and the
refrigeration Freon system destroying the evaporator.
When this happens, the Freon will blow out of the system through the
water tank, and water will enter the refrigeration section. Permanent
damage can easily occur to the compressor at this point.
DO NOT DEFEAT THE WATER FLOW SAFETY SWITCH!
When one of the red LOW WATER FAULT lights glow, the compressor for that module will not
operate even if the tank temperature is higher than the SV value, but the water pump will
continue operation. It can be caused by several conditions:
1. The water pump is not operating correctly. This can be caused by
a. A motor failure on the pump
b. An internal broken pump impeller
c. A 3Ø pump motor operating in the incorrect rotation
d. The water passages on the equipment being chilled are too small, or a shut-off valve
is closed in the outside system.
2. A foreign object has been sucked into the water pump intake port (bulkhead at bottom of
tank).
3. The Y-strainer installed on the RETURN line is clogged. While the pump is running, open the
flush valve on the Y-strainer and flush out the screen strainer.
4. A problem with the MOTOR STARTER contactor K1.
TROUBLE SHOOTING
IMPORTANT
15