Reznor DV Operation Manual (for units built before August 2003) - Manual (Page 20)

Form O-DV/RDF/ADF, P/N 148385, Page 19
FIGURE 35 -
Photohelic
Pressure
Sensor,
P/N 159893
Photohelic Pressure
Switch
(automatic
building pressure sensor)
Description/Function: The photohelic pressure switch is a phototransister re-
lay operated positive pressure switch used in makeup air applications to auto-
matically control building pressure. It maintains a selected positive pressure
setpoint by changing the amount of outside air being introduced to the build-
ing through a modulating outside air damper. As more pressure is required in
the building, the switch activates the damper motor driving the outside air
damper towards the full open position (causing the bypass return air damper to
go toward the closed position). Conversely, as less pressure is required, the
switch drives the outside air damper in the opposite direction.
Service: Clean the tubing and the screened ends of the pressure tap vents.
If the interior of the switch is protected from dust, dirt, corrosive gases and
fluids, years of trouble-free service may be expected. Zero adjustment should
be checked and reset occasionally to maintain accuracy; follow the
manufacturer's instructions included with the switch.
There are no field-repairable parts in this switch. If the switch should require
repair, contact either the system or the switch manufacturer concerning switch
replacement or repair.
FIGURE 34 -
Pressure Null
Switch, P/N 88052
Function: The damper motor automatically actuates the return air, bypass,
and/or discharge dampers in response to an electrical control device. The damper
motor is direct-coupled to the dampers so there is no damper linkage to adjust.
Service: There is no service required on these motors other than external clean-
ing. If the motors need replaced, replace with an identical damper motor.
Function: The potentiometer is a manually set switch that operates either the
discharge damper (Option AR19) or the return air damper (Option AR22) pro-
viding a mixture of return and outside air. It is a remotely located switch that
requires manual adjustment.
Service: If the potentiometer does not function properly, replace it with an
identical switch.
Pressure Null Switch
(automatic building
pressure sensor)
FIGURE 33 -
Potentiometer,
P/N 16110
Damper Motor
Potentiometer
FIGURE 32 -
Damper Motor
Description/Function: The pressure null switch is a diaphragm operated dif-
ferential pressure switch used in makeup air applications to automatically con-
trol building pressure. It maintains a selected positive or negative pressure
setpoint by changing the amount of outside air being introduced to the build-
ing through modulating outside air damper. As more pressure is required in the
building, the pressure null switch activates the damper motor driving the out-
side air damper towards the full open position (causing the bypass return air
damper to go toward the closed position). Conversely, as less pressure is re-
quired, the switch drives the outside air damper in the opposite direction.
Service: Clean the tubing and the screened ends of the pressure tap vents. Be
sure that the switch is installed with the diaphragm in a vertical plane and that
the pressure taps are sheltered from the wind. For further service, follow the
manufacturer's instructions included with the switch.
16. Dirty Filter Switch
FIGURE 36
- Dirty Filter
Pressure
Switch,
P/N 105507
Location: Switch is located in the main electrical box (See FIGURE 9); sen-
sor tubes run to either side of the filter rack; indicator light is on the remote
console.
Function: The dirty filter switch is a pressure switch that activates an indicator
light on the remote console when the filters need cleaned or replaced (See
Service Section, Paragraph 2). This switch is only on systems with an optional
console that includes a dirty filter light. The pressure switch is set during in-