Manual 2100-749
Page
21 of 68
FIGURE 30
Dirty Filter Switch and Filter Indicator Light
SCREW TO
REMOVE COVER
COVER
TUBE LOCATED IN
AIRSTREAM AFTER FILTER
MIS-3952
INDICATOR ARROW
ADJUSTMENT
ADJUSTMENT
KNOB
FILTER LIGHT
* See Figure 28 for dirty
filter switch settings
Blower Status Alarm
When the blower is on for 45 seconds and no airflow
is detected by the airflow switch, the compressor
and heating operations will be disabled. The system
will wait 5 minutes before trying again. After three
consecutive no airflow events, the system will generate
an alarm and lockout requiring a user reset.
Filters
The filters can be serviced by opening the "hinged" front
access panel and locking it into position. They sit upon
a removal tray by pushing or pulling them in place. This
also improves access to back filters without having to
reach inside the unit. There are six (6) MERV 8 filters
(three per coil), each measuring 16" x 25" x 2".
Dirty Filter Switch
These units are equipped with a differential pressure
switch to indicate when the filter(s) needs to be
replaced (see Figure 28). The dirty filter switch
measures the pressure difference across the filter
through silicone tubing routed to the blower and
evaporator areas of the unit.
The switch circuit consists of a
normally closed
filter pressure switch. The switch will open when the
pressure differential goes above the setting indicated
on the dial. When the pressure difference returns below
the setting on the dial, the switch will close.
Adjustment of dirty filter switch may be necessary to
ensure proper operation. See Figure 30 to aid in setting
the filter switch to operate at different percentages of
filter blockage.
Filter switch status can be viewed by:
1. Press MENU key to go to the Main Menu screen.
2. Press UP or DOWN keys and ENTER key to enter
TECHNICIAN password 1313.
3. Press UP or DOWN keys to scroll to
I/O Config
;
press ENTER key.
4. Press UP or DOWN keys to scroll to
Digital Inputs
C1-1
(Filter 1) or
Digital Inputs C1-2
(Filter 2);
press ENTER key.
5. Reference
Filter 1
or
Filter 2
row and
Val
column
(see Figure 29).
Dirty Filter Alarm
The wall-mount unit is equipped with a differential
pressure switch input to the controller. When the switch
indicates a dirty filter, the controller will generate an
alarm. The alarm will latch once triggered requiring a
technician to acknowledge the alarm after replacing
filters. Additionally, an indicator light will be turned on
with the alarm and turned off when the alarm clears.