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Honeywell RP908A Series Service Data

Comfort control system. pneumatic controllers
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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
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.
Fig. 1. Typical RP908A Primary Control of Normally
Open Valve.
Rev. 6-84
5737-2
RP908A & B
PNEUMATIC CONTROLLERS
PRIMARY
CONTROLLER
Fig. 2. Typical RP908A Low Limit Control.
RP908B
The RP908B dual input Controller is applied to com-
pensating systems by using an additional compensating
signal to change the control point of the Controller (Fig.
3). Temperature, humidity, pressure, or dewpoint may
be controlled by using the appropriate sensors,
LOW LIMIT
5759-2
CONTROLLER
Form No
Commercial
MLFTAB: 111 C. 6.
Group

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  Summary of Contents for Honeywell RP908A Series

  • Page 1 RP908A & B PNEUMATIC CONTROLLERS 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.
  • Page 2: Operation

    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- SENSOR 2 mary sensor span, field adjustable. AUTHORITY: 10 to 200 percent of primary sensor span, field adjustable.
  • Page 3: Calibration Check

    CALIBRATION CHECK percent of the sensor range span and the branchline pres- RP908A sure must be within the operating range of the controlled device. If recalibration is necessary, see CALIBRA- Change the setpoint of the Controller to the existing TION. sensor temperature if the two do not already match.
  • Page 4 REMOTE CONTROL POINT 1 (and Port 2 if RP908B is used). If the reset signal on an RP908B is produced by the output of a room thermostat or pressure control, a 30-psi gage must be installed in A pressure change from 3 to 13 psi (21 to 90 kPa) in the gage Port 2.
  • Page 5 Where: Two separate parameters must be known in order to properly calibrate a reset system, Reset Schedule and TR = Throttling Range Throttling Range. Proportional Band and Authority may be calculated from these parameters RESET SCHEDULE EXAMPLE: The reset schedule is plotted by determining the out- Determine settings for a system where hot water should door air temperature at which designed maximum heat- be controlled at 180F (82C) when outdoor air...
  • Page 6 Before troubleshooting the RP908, make a visual still not working properly, refer to Fig. 8, RP908 check of the Controller to see that springs and pivots are Troubleshooting Flowchart. connected properly for the application. If the RP908 is CONTROLLER NOT CONTROLLING ADJUST PRV OR RECONNECT TO MEASURE CONTROLLED...
  • Page 7 REPAIR RP908 DISASSEMBLY PROCEDURES For replacement of the Proportional Band Adjust- ment Knob, simply unscrew from the Indicator Assembly. remove Cover (Fig. 9, Part 1). Non-CPA Models: Remove the Setpoint Knob (Fig. 9, Part 4). The Set- the Backplate, and move Controller to a bench, point Spring, Setpoint Nut, and Setpoint Screw will then come right out.
  • Page 8: Parts And Accessories

    REPLACEMENT OF RP908 WITH Table 2. Application Replacement Listing. RP920 Table 2 lists specific model numbers of the RP920 that are direct replacements for the RP908. PARTS AND ACCESSORIES PARTS LIST Refer to Figure 9, Parts 1 through 4, and Table 3 for available replacement parts for the RP908A and B Con- trollers.
  • Page 9 Table 3. RP908 Parts List. (Continued) Fig. 9 Part Number Description Ref. No. 304963-001 Washer 316165A Body Repair Assembly for RP908A-includes Items 15 through 26 Body Repair Assembly for RP908B-includes Items 14 through 26 Tube, RP908B Body, RP908A, B 3 15224 Pivot Screw (2) 303634 Spring...
  • Page 11 P O R T 2 , x2101 Fig. 9 (Part 3 of 4). RP908 Controller-Exploded View.
  • Page 12 Fig. 9 (Part 4 of 4). RP908 Controller-Exploded View. Table 4. Scaleplate Decals b ACCESSORIES Scaleplate Decals. No. 315993A: Table 4 lists the scaleplate decals that are available for the RP908. WARMER/COOLER 40 to 160F 2. Blank Orifice 316125-00606 (field installed). 15 to 85% RH 40 to 240F 3.
  • Page 13 Table 5. Gages. Part No. back corm. Scale Range Temperature For Use with Sensor 25 to 125F LP914 14000786-002 to 55C LP914 L P 9 1 4 LP914 40 to 240F L P 9 1 4 5to 115c LP914 305986 L P 9 1 4 305987 LP914...
  • Page 14 TEXAS NEW MEXICO ALABAMA MAINE OKLAHOMA FLORIDA Dallas, TX Albuquerque, NM Oklahoma Cw. OK Tulsa, OK El Paso, TX Mobile, AL MARY LAND NEW YORK Orlando, FL Houston, TX Albany, NY ALASKA OREGON Anchorage, AK MASSACHUSETTS Lubbock, TX Tampa, F Eugene, OR Buffalo, NY Boston, MA...