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GENERAL

DESCRIPTION

The RP908A  and B are force balance pneumatic

amplifiers, with adjustable proportional band, for use as
Controllers in HVAC systems,

The RP908 is no longer being manufactured. There is

an RP920 model available for all RP908A and B applica-
tions. Refer to Application Replacement Listing in the
REPAIR section.

APPLICATION

RP908A

RP908A & B

PNEUMATIC CONTROLLERS

The RP908A, in conjunction with a remote sensor,

provides direct or limit control in air conditioning con-
trol systems, with or without remote control point
adjustment (CPA). It may be adjusted for either direct or

reverse acting operation. Refer to Figures 1 and 2 for
these applications.

PRIMARY LOW 

CONTROLLER CONTROLLER

5759-2

Fig. 2. Typical RP908A Low Limit Control.

RP908B

5737-2

The RP908B dual input Controller is applied to com-

pensating systems by using an additional compensating

Fig. 1. Typical RP908A  Primary Control of Normally

Open Valve.

signal to change the control point of the Controller (Fig.
3). Temperature, humidity, pressure, or dewpoint  may
be controlled by using the appropriate sensors,

Rev. 6-84

Form No

 

Commercial  

 Group

MLFTAB:   C. 6.

Содержание RP908A 1005

Страница 1: ...ioning con trol systems with or without remote control point adjustment CPA It may be adjusted for either direct or reverse acting operation Refer to Figures 1 and 2 for these applications PRIMARY LOW LIMIT CONTROLLER CONTROLLER 5759 2 Fig 2 Typical RP908A Low Limit Control RP908B 5737 2 The RP908B dual input Controller is applied to com pensating systems by using an additional compensating Fig 1 ...

Страница 2: ...duces 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 an increase 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 authori...

Страница 3: ...T percent of the sensor range span and the branchline pres sure must be within the operating range of the controlled device If recalibration is necessary see CALIBRA TION CHANGE FROM DIRECT TO REVERSE ACTING The change from direct to reverse acting is made by following the three steps listed in Figure 6 40 30 I 4 1 770 z 8 i OUTDOOR AIR TEMPERATURE IN F C 20885 Fig 5 Typical Hot Water Reset Schedu...

Страница 4: ...to the Control ler and the internal restriction is not blocked CALIBRATION USING AN ADJUSTABLE RESTRICTION 1 2 3 4 5 6 Install the proper scaleplate on the Controller if not already installed Disconnect the Port 1 sensor and connect an adjust able restriction to Port 1 Choose a setpoint and adjust the restriction until the gage in Port 1 shows this setpoint Turn the setpoint knob until the branchl...

Страница 5: ...ted 10 PB 200 x 100 5 AUTHORITY Authority indicates the amount of effect that the change in outdoor air temperature will have on the control point The formula must take into account the spans of Sensor 1 and Sensor 2 The complete formula is Authority Span S X A l m xloQ Span SI Al 2 Where TR Throttling Range AT1 Change in Hot Water Temperature AT2 Change in Outdoor Air Temperature EXAMPLE 2 3 4 5 ...

Страница 6: ...ESSARY CHECK VALVE OR DAMPER FOR CLOSEOFF LEAK OR MALFUNCTION CHECK RF 908 FOR CLOGGED RESTRICTIONS FILTERS SCREENS SENSOR I LINE AIR LEAK BAD SENSOR OR GAGE OUT OF CALIBRATION CORRECT AS NECESSARY I CHECK OPERATION CHECK BRANCH LINE PRESSURE TEST BRANCH LINE FOR LEAKS REPAIR IF NECESSARY h 1 CHECKOPERATION 1 LUBRICATE CONTROLLER PIVOT POINTS REPLACE CONTROLLER IF LIBRICATION DOESN T HELP ADJUST P...

Страница 7: ...d Adjust ment Knob simply unscrew from the Indicator Assembly Non CPA Models Remove the Setpoint Knob Fig 9 Part 4 The Set point Spring Setpoint Nut and Setpoint Screw will then come right out CPA Models a Loosen the two cross head Screws and remove the CPA Housing Fig 9 Part 4 Carefully remove the Seal while the bracket is still attached to the Body The Seal should be removed and then the Bracket...

Страница 8: ... 00767 3 15299 00767 315282 315255 315263 3 15293 00605 3 15740 00062 315284 00101 315204A 3 16205A 14002696 00 1 14004146 001 312826 315249 3 15245 315253 Table 3 RP908 Parts List Backplate RP908A Backplate RP908B Screw Backplate 3 No 6 32 x l 4 Panhead Cover RP908A without CPA Cdver RP908B without CPA Cover RP908A B with CPA Screw Cover 2 Screw Bracket 4 No 8 32 Oval Undercut Head Manifold RP908...

Страница 9: ...crew 8 32 x 1 l 16 Panhead Tension Nut Tension Screw PB Adj Upper Lever Assembly Lever Assembly RP908A Lever Assembly RP908A wit Lever Assembly RP908B h CPA Proportional Band Adjustment Knob Indicator Assembly Bias Spring Reverse Acting Spring 2 CPA Housing CPA models Screw 8 32 x l 2 Fillister Head CPA Models CPA Seal CPA Models Scaleplate Screw RP908B 8 32 x 5 16 Oval Head 3 Body Assembly RP908B...

Страница 10: ......

Страница 11: ...0 16 I I I_ _ I i PORT 2 I i PORT I lo J I w J x2101 Fig 9 Part 3 of 4 RP908 Controller Exploded View 11 75 553 1 ...

Страница 12: ...installed 3 Self rewinding Rapid Adjustment Knob 3 16479A 4 Gages Table 5 lists gages that are applicable for use with the RP908 F 20888 No 315993A Oto2OOF lOto4OC 40 to 160F WARMER COOLER 40 to 240F 15 to 85 RH 50 to 1OOF 20 to 80F 3 to 15psig 30 to 30F 0 2 to 1 O kg cm2 25 to 125F 20 to 80C 5to55C 40 to 60C 15 to 75 RH 5 to 105c 65 to 95 RH No 316005 1 to 6 in H20 D A No l 316089 25 to 1SOmm Hz0...

Страница 13: ... 1 20to 80C I LP915 305972 1 50to 1OOF 1 TP924 TP974 TP925 305973 1 lOto38C 1 TP924 TP974 TP925 Relative Humidity 14000786 005 1 15 to 85 1 HP971 14000786 003 15 to 75 1 HP971 14000786 004 1 65 to 95 I HP971 305988 Dewpoint 40 to 75F TP925A1018 305965 305615 0 to 30 psi 1 to 1 in o f WC PP9C 305616 I 0 to 2 in of WC I PP905 305617 1 to 3 in of WC PP905 305618 2to4in ofWC PP905 305624 I 50to IOOmmo...

Страница 14: ...1 3200 AR KANSAS LIttIe Rock AR 1501 6644070 IL LINOIS Chrcago North IL 1312 478 9266 CALIFORNIA Irwne CA 714 557 6392 Los Angeles CA 213 7266161 Sacramento CA 916 485 2221 San Dlego CA 714 292 5311 San Jose CA 415 957 2674 San Franc sco CA 415 957 2674 ChIcago South Lar 312 568 4200 Irlngl I Elgln IL 312 697 7880 Peona IL 1309 692 0610 INDIANA Fort Wayne IN 219 482 9654 Indianapolls IN 317 243 08...

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