SRL Service Manual
Revision 00
July 2007
Page 41 of 56
10.2.3 Low dewpoint (Alarm)
What it means: Temperature sensor B1 (dew point temperature) registers a temperature below
28.4
o
F (-2
o
C) for 3 minutes or more.
What it does:
Cuts power to compressor contactor & alarm contacts. Turns dryer OFF. Turns on
Warning Light & blinks “Ld” on the digital display.
Possible Causes & Remedies:
1)
Hot Gas Bypass Valve is miscalibrated
, causing it to allow pressure in the
evaporator to go too low, causing the temperature to go below 28.4
o
F (-2
o
C).
Remedy – Adjust the Hot Gas Bypass Valve as outlined in Section 12.
2)
Low ambient temperature
is causing excessive cooling of the refrigerant in the
condenser.
T
he dryer may be installed outdoors, in an unheated room, or near a
vent. This cause can be confirmed by checking the condensation pressure with a
gauge. It will stay below 261 psig and the fan never comes on.
Remedy – Increase the ambient temperature in the room or duct the air for the
condenser from a warmer source. Alternately, you can partially cover the
condenser coils in order to reduce the air flow across them, thereby reducing the
cooling effect.
3) A
defective fan pressure switch
is causing the condenser fan to stay on all the
time causing excessive cooling of the refrigerant.
Remedy – Replace the defective component.
4) The
dewpoint temperature sensor (B1) is miscalibrated
, causing a low reading.
This can be confirmed by using a temperature gun to check the temperature at the
location of the dew point probe, and comparing it to what the probe is reading.
Remedy – Replace the defective component.
To Reset:
Find the cause of the alarm and fix the problem.
Press ALARM RESET to clear alarm. Power restored to alarm relay, Warning Light
goes off. Dryer remains OFF. Display clears.
Press ON/OFF to restart dryer.
Notes:
Alarm can only be cleared if the dew point temperature is above 28.4
o
F (-2
o
C).
The low dew point alarm is possible whether the dryer is ON, or in Remote Off
Mode – as long as there is power to the controller.
