1. Introduction and Overview
The Johnson Controls P70AA-118C is a robust pressure control designed for commercial refrigeration and air conditioning applications. Its primary functions include high pressure cut-out control, head-pressure control, and condenser fan cycling. This control is compatible with most common non-corrosive refrigerants and can also be utilized in other non-corrosive fluid applications. It features a single-pole, single-throw (SPST) switch configuration and is designed for a pressure range of 100 to 400 psi.
Figure 1: Johnson Controls P70AA-118C control unit, packaging, and mounting bracket.
Figure 2: The P70AA-118C control unit and its dedicated mounting bracket.
2. Key Features
- All-steel case and cover: Provides long-lasting, rugged protection for internal components, ensuring durability in demanding environments.
- Sight-set calibrated pressure adjustment: Features a visible pressure scale that is fully adjustable through the range without requiring removal of the cover (on NEMA 1 enclosure models), simplifying setup.
- Manual reset lockout option: Offers a trip-free lockout mechanism that prevents overriding or resetting until the pressure returns to the specified safe level, enhancing system safety.
- Variety of available pressure connection styles: Allows for greater flexibility during mounting and adaptation of pressure connections to various field application requirements.
Figure 3: Close-up of the control's front panel, showing the pressure adjustment scale and differential settings.
3. Specifications
| Specification | Value |
|---|---|
| Model Number | P70AA-118C |
| Brand | Johnson Controls |
| Pressure Range | 100 to 400 psi |
| Capillary Length | 36 inches |
| Flare Nut Size | 1/4 inch |
| Switch Type | Single-Pole, Single-Throw (SPST) |
| Material | Steel |
| Item Weight | 1.49 Pounds |
| Product Dimensions | 10.25 x 2.75 x 4.37 inches |
| Display Type | Analogue |
| Manufacturer | Johnson Controls |
| Date First Available | October 11, 2012 |
Figure 4: Detailed product label from the packaging, showing specifications including pressure range, differential, and capillary length.
4. Installation
Installation of the P70AA-118C control should be performed by a qualified HVAC technician or electrician in accordance with all local and national electrical codes. Ensure the power supply to the system is disconnected before beginning any installation work.
4.1 Mounting
Mount the control unit in a location that is easily accessible for adjustments and maintenance, yet protected from physical damage and excessive vibration. Use the provided mounting bracket and appropriate fasteners to secure the unit firmly.
Figure 5: Underside view of the P70AA-118C control unit, showing mounting points and electrical conduit entry.
4.2 Capillary Tube Connection
Carefully route the 36-inch capillary tube to the desired pressure sensing point. Avoid sharp bends or kinks that could damage the tube. Connect the 1/4 inch flare nut to the system's pressure port, ensuring a tight, leak-free seal. Do not overtighten.
Figure 6: Angled view of the P70AA-118C control, highlighting the capillary tube connection.
Figure 7: Detail of the capillary tube and 1/4 inch flare nut connection.
4.3 Electrical Wiring
Refer to the wiring diagram provided with the control unit or the system's specific schematics. Connect the electrical wiring to the appropriate terminals within the control's enclosure. Ensure all connections are secure and properly insulated. The P70AA-118C is a single-pole, single-throw (SPST) control.
5. Operating Instructions
Once installed and wired, the P70AA-118C control can be adjusted to the desired operating parameters. The control features a sight-set calibrated pressure adjustment for easy setting.
5.1 Setting Pressure Range
The control allows for adjustment of both the cut-out (high pressure limit) and the differential (the difference between cut-in and cut-out pressures). Use a flat-head screwdriver to adjust the set points visible through the window on the front panel. The scale indicates the pressure in PSI.
5.2 Manual Reset Lockout
If the control is equipped with a manual reset lockout, it will trip and lock the system off if the pressure exceeds a critical threshold. To reset, the pressure must return to a safe level, and then the manual reset button must be pressed. This feature prevents automatic restarts under unsafe conditions.
6. Maintenance
Regular maintenance ensures the longevity and reliable operation of your Johnson Controls P70AA-118C unit. Perform the following checks periodically:
- Visual Inspection: Check the control unit, capillary tube, and electrical connections for any signs of wear, corrosion, or damage.
- Cleanliness: Keep the control unit clean and free from dust, dirt, and debris, which can affect performance.
- Connection Integrity: Ensure all electrical and pressure connections remain tight and secure.
- Functionality Check: Periodically verify that the control is cycling the fan or cutting out at the set pressure points as expected.
7. Troubleshooting
If you encounter issues with your P70AA-118C control, consider the following common troubleshooting steps. For complex issues, always consult a qualified technician.
- Control Not Cycling Fan:
- Verify power supply to the control.
- Check pressure settings; ensure they are within the system's operating range and the control's capabilities.
- Inspect capillary tube for kinks or leaks.
- Check electrical connections for looseness or corrosion.
- Inaccurate Pressure Readings:
- Ensure the capillary tube is properly connected and not damaged.
- Verify the system's actual pressure with a calibrated gauge.
- Control Trips Frequently:
- Check for system overpressure conditions.
- Review the set pressure and differential settings.
- If equipped, ensure the manual reset lockout is not being triggered by transient pressure spikes.
8. Warranty and Support
For detailed warranty information, please refer to the official documentation provided by Johnson Controls at the time of purchase or visit the Johnson Controls official website. Support for the P70AA-118C control can be obtained through authorized distributors or by contacting Johnson Controls customer service directly.
Figure 8: Product packaging label displaying the model number P70AA-118C and barcode (UCC/EAN Code 128: 1078502829326).
Figure 9: Manufacturing origin label on the control unit, indicating 'ASSEMBLED IN MEXICO'.
