Product Overview
This document provides installation guidance for Danfoss pressure switches, specifically models RT 5, RT 110, RT 112, RT 116, RT 117, RT 121, and RT 200. It covers essential data, fitting instructions, setting procedures, and practical examples for proper installation and operation.
Technical Data
Pressure Switch Types
The following pressure switch types are covered: RT 5, RT 110, RT 112, RT 117, RT 121, RT 200, RT 116.
Maximum Test Pressure
- RT 110, RT 112, RT 121: 8 bar
- RT 5, RT 116, RT 200: 25 bar
- RT 117: 47 bar
Operating Temperature Limits
The pressure connection of the control should not exceed 100 °C. For high plant temperatures, a water-filled tube loop (e.g., a 10 mm Cu tube) can be used as a temperature lock.
The pressure switch itself has an operating temperature range from -50 °C to +70 °C (for RT 5) or +100 °C (for other models).
Fitting Instructions
A Pg13.5 cable gland is supplied separately with the pressure switch. To ensure the enclosure's ingress protection rating (IP66 for automatic reset units, IP54 for external reset units), this gland must be assembled as shown in Figure 2. If the cable gland is not used with a cable, a metal blanking plug should be fitted instead.
To mitigate strong pressure pulsations, a damping coil (as shown in Figure 3 or Figure 4) is often sufficient.
Ensure the pressure control is positioned to avoid exposure to frost in water systems; it can operate on an air cushion for example.
Setting the Pressure Switch
The pressure controller is set by rotating the knob (labeled '5' in Figure 1), while observing the main scale (labeled '9' in Figure 1).
The differential pressure is adjusted by rotating the differential adjusting nut (labeled '19' in Figure 1). The correct setting for the differential nut is determined using the nomogram shown in Figure 6, which provides a value (e.g., '7' as per the example in Figure 7).
The maximum operating pressure is the sum of the set pressure and the differential.
Setting Example
Scenario:
This section illustrates setting the pressure switch for an oil-fired steam boiler application using an RT 116 model. Desired control pressure: Maximum 9 bar, Minimum 8.2 bar. This results in a differential of 0.8 bar (9 - 8.2 = 0.8 bar).
Steps:
- Connect the oil burner to terminals 1-2 of the pressure switch.
- Set the pressure switch to 8.2 bar by rotating the knob (5).
- Adjust the differential adjusting nut (19) to the value indicated by the nomogram in Figure 6 (e.g., setting '7' as shown in Figure 7).
Diagram Descriptions
Figure 1: Pressure Switch Components
Illustrates the main components of the pressure switch, including the setting knob (5), main scale (9), and differential adjusting nut (19).
Figure 2: Cable Gland Assembly
Shows the correct method for assembling the Pg13.5 cable gland to the pressure switch enclosure for IP rating compliance.
Figure 3 & 4: Damping Coils
Depicts examples of damping coils used to reduce pressure pulsations.
Figure 5: Temperature Limits
Indicates the maximum and minimum operating temperatures for the pressure connection, showing limits such as max. 70°C, min. -50°C, and max. 100°C.
Figure 6: Differential Nomogram
A nomogram used to determine the correct setting for the differential adjusting nut based on desired pressure ranges.
Figure 7: Differential Setting Example
Demonstrates how to read the nomogram from Figure 6 to find the specific value (e.g., '7') for the differential adjusting nut.
