b. Set the setpoint knob to the percent of span,
temperature, or humidity that corresponds to the
input pressure. The BLP should be 8 psi (55
kPa). If it is not correct, go to Step 10.
8. RP920B and D:
a.
Plot the reset schedule to determine the
corresponding compensation and primary
sensor values.
b.
Convert the reset schedule value to pressure
(See APPENDIX A) and adjust the air supplies
to those pressures. For an RP920D, the BLP
should be 8 psi (55 kPa). For an RP920B, the
expected BLP depends on which point on the
reset schedule is being simulated. If BLP is not
within 1 psi of the control point pressure, go to
Step 10. Exact control point pressure can be
established for each application by constructing
a chart similar to that shown in Figure 4 and
referencing
APPENDIX
A.
If it is not correct, go
to Step 10.
9.
a, Move the setpoint knob until the BLP is 8 psi (55
kPa). Slowly increase the setpoint adjustment
one division The BLP should decrease
proportionally if the controller is direct acting or
increase proportionally if the controller is
reverse acting.
b,
Slowly decrease the setpoint one division. The
BLP should change proportionally in the
opposite direction of Step 9a,
c.
For CPA models, repeat Steps 9a and 9b
substituting the CPA knob for the setpoint knob.
d.
If the controller works properly, go to Step 11. If
the controller works properly, but is out of
calibration, go to Step 10.
To calibrate the controller:
a.
Adjust the setpoint knob until the correct BLP is
indicated on the gage.
b. Remove the setpoint knob. Replace it at the
correct setting without changing the BLP
Return to Step 9.
11.
Connect the tubing and make settings according to
the job drawings.
NOTE: On the RP920C and D, replace fitting in the
integral module with the seal screw. Be sure the O
ring is sealed
EXAMPLE:
The hot water temperature is reset from 100 to 200F as the
outdoor temperature goes from 60 to -l0F. The range of
the primary sensor is 40 to 240F and the compensation
sensor is -40 to 16OF, Additional settings taken from the
job drawings are:
Compensation startpoint = 60F (or 50 percent).
Compensation is negative.
Authority setting = 157 percent.
Throttling range =
Proportional Band = 5 percent.
Setpoint = 1OOF (or 30 percent).
1 8 0
1 6 0
k - z
@
1 4 0
100
13 PSI (90
THROTTLING RANGE
3 PSI (21
-10
0
10
60 70
OUTDOOR AIR TEMPERATURE
(COMPENSATION SENSOR)
DIRECT ACTING
(21 TO 90
RANGE
220
200
1 8 0
1 4 0
13 PSI (90
I
100
THROTTLING RANGE
3 PSI (21
-10
0
20 30 40 50 60 70
OUTDOOR AIR TEMPERATURE
(COMPENSATION SENSOR)
DIRECT ACTING
TO 13-PSI (21 TO 90
THROTTLING RANGE
c3337
Fig. 4.
and D Reset Schedule,
Select (Fig. 4) any compensation sensor value (outdoor
temperature) within the compensation range, in this case
32F. Construct a line vertically to the control point line and
then horizontally to the left side. The hot water temperature
must be 140F to meet the reset schedule.
From APPENDIX A the input pressures are:
Port 3 (primary) 9 psi (62
Port 5 (compensation) = 7.3 psi (50.3 kPa).
The BLP should be 8 psi (55 kPa) for RP920D, or 9 psi (62
kPa) for RP920B
NOTE:
Previous discussion and illustration assumes 3 to
13 psi (21 to 90 kPa) operating range. However,
the controller may be calibrated to match the
spring range of the actuator (e.g., 4 to 11 psi). The
expected BLP at the
would then be the
center of the actuator spring range (e.g., 7.5 psi).
6
