Operation; Specifications; Maintenance - Honeywell RP908A Series Service Data

DISCHARGE
Fig. 3. Typical RP908B Application.

SPECIFICATIONS

MODELS: See Table 1.
Table 1. RP908A and B Model Listing.
Single
Single Input
Model Input Limit
RP908A 1005 X
RP908A 1013 X
RP908A 1021 X
RP908A 1039 X
RP908A 1047 X
RP908A 1054 X
RP908A 1042 1
I
RP908B 1003 I
I
RP908B 1011 I
RP908B 1029 I
RP908B 1037 I

MAINTENANCE

EQUIPMENT REQUIRED
cant for pivots and plungers in units with CPA.
in system).
GENERAL
The only preventive maintenance necessary is an
annual visual check for leaks, loose fittings, etc, and an
operational and calibration check.
75-553 1
Q
SENSOR 2
D.A.
J
5 7 6 0 - 2
With
Calibration
Dual With With
Input Cover CPA Knob
X X
X X X
X
X X
X
X
X
X
I
I I
I
SUPPLY AIR PRESSURE: 18 psi (124 kPa) nominal.
MAXIMUM SAFE AIR PRESSURE: 25 psi (172 kPa).
AMBIENT TEMPERATURE LIMITS: 40 to 120F (4 to
9OC).
PROPORTIONAL BAND: 2-1/2 to 40 percent of pri-
mary sensor span, field adjustable.
AUTHORITY: 10 to 200 percent of primary sensor span,
field adjustable.
REMOTE CPA: -t 10 percent of sensor span.

OPERATION

RP908A
When used in a heating system with the Controller set
for direct action, a drop in temperature at the sensor
lowers the branchline pressure, opening the valve to
increase the flow of heating medium to the coil (Fig. 1). If
the CPA model is used, an increase in air pressure on the
CPA port raises the setpoint of the Controller and a
decrease lowers it.
Used as a low limit Controller, the RP908B reduces
branchline pressure from the primary Controller, open-
ing a heating valve to maintain discharge temperature at
setpoint (Fig. 2).
RP908B
Operation is similar to RP908A. However,
in outdoor temperature causes the compensating (out-
door) sensor to reset the control point of the Controller
to raise the branch line pressure (Fig. 3). The resulting
change in branch line is dependent on the authority set-
ting on the Controller.
OPERATIONAL CHECK
Check main air pressure for 18 psi (124 kPa) at Con-
troller. For models with manual CPA adjustment, move
CPA switch up and down and observe the action of the
Controller. If the system' does not have CPA, the sen-
sor(s) may be disconnected and the port plugged so that
pressure may be slowly built up, causing the Controller to
operate from one extreme position to the other. Bleeding
this pressure slowly causes the Controller to operate in
the opposite direction. The main lever should move
smoothly, and the branchline pressure should change
gradually in the proper direction.
2
increase
an