Blower Status Switch; Blower Status Alarm; Filters; Dirty Filter Switch - Bard MEGA-TEC W120AP Service Instructions Manual

TABLE 5
Maximum ESP of Operation
Electric Heat Only
Model
-B0Z
-B09
-B18
-C0Z
-C09
-C18
* Unit is rated for free blow non-ducted operation with
SG-10W Supply Grille and RG-10W Return Grille.

Blower Status Switch

The unit is equipped with a differential pressure airflow
switch to monitor the blower (see Figure 23). If the
blower is turned on and the switch doesn't close to
indicate there is differential pressure between the inlet
and outlet of the blower, an alarm will be generated.
For switch settings, see Figure 23.
Differential airflow 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;
press ENTER key.
5. Reference AIrflw 1 row and Val column (see Figure
24).
FIGURE 23
Dirty Filter Switch and Blower Status Switch

Dirty Filter Switch

(Set @ 1.40)
Manual 2100-671
Page 18 of 44
Static Pressure*
.50"
.50"
.50"
.50"
.50"
.50"
Blower Status Switch
(Set @ .080)
FIGURE 24
Verifying Differential Airflow Status

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 unit is equipped with four (4) 20" x 24" x 2" MERV 8
filters (two per coil). The filters lift and slide into position
making them easy to service. The filters can be serviced
by opening the "hinged" front access panel and locking it
into position. Then lift and slide into position as needed.
Dirty Filter Switch
These units are equipped with a differential pressure
switch to indicate when the filter(s) needs to be
replaced (see Figure 23). 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 open 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 25 to aid in setting
the filter switch to operate at different percentages of
filter blockage.

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.
The threshold of this alarm is adjusted by changing the
settings on the switch (see Figure 25).