Danfoss 017-140266 RT 112 Low Pressure Switch 0.1-1.1 bar

RT 112 monitors very low pressures with a differential of only 0.07 to 0.16 bar

The 017-140266 is the Danfoss RT 112, the member of the RT series that covers the lowest pressure window with an adjustable differential: 0.1 to 1.1 bar. Fan pressure, burner air, filter condition and gas supply lines all move in that band, and a bellows tuned for hundreds of millibar reacts where a general purpose 0-10 bar switch would barely move. In this code the switch resets automatically and the housing is IP66, so it can sit in a duct or on a skid without an extra enclosure.

Like all RT switches it uses a single-pole change-over contact and a screwed cable entry, and the series data sheet claims high accuracy, high repeatability and the major marine approvals. The approvals printed for this code include BV, DNV, GL, LR and NKK in addition to CE and EAC.

Technical specifications

Selecting the set point and protecting the bellows

Because the working pressure is limited to 7 bar and the test pressure to 8 bar, this switch is not forgiving of surges. A compressed air line or a pump discharge can exceed 7 bar during start-up; do not connect the RT 112 there unless a damper or a throttled impulse line limits the peak at the connection. For differential-pressure duty across a filter or fan, use the dedicated RT 260A type rather than a single-port switch.

With a 0.1 to 1.1 bar scale, setting is read directly from the pointer; a cut-out at 0.4 bar with a differential of 0.1 bar gives a restart at 0.5 bar. Keep the setting at least a few hundredths of a bar from the ends of the scale, where repeatability is lower, and consider how elevation of the impulse line changes the pressure seen by a gas-filled bellows.

Fitting guidance and order checklist

Mount with the pressure connection down if possible so that condensate drains away from the bellows, use the G 3/8 sealing washer, and keep the impulse line short. The installation guide for RT 5, RT 110, RT 112, RT 116, RT 117, RT 121 and RT 200 shows the contact diagram and cable entry torque.

Before ordering, confirm medium, the need for auto or manual reset and the voltage on the contact. Other versions of the RT 112 exist with different reset functions and a 1/2 in connection under separate code numbers. Seven Star LLC is an independent supplier in Muscat and can quote 017-140266 on request.

Application checks before choosing this code

Write down what the switch must do in the system: stop a burner when air pressure is lost, raise an alarm when a supply line falls, or start equipment when pressure drops. That decides whether the change-over contact will be wired to open or close on falling pressure and whether automatic reset is acceptable, or whether the process requires an operator to reset after a trip, in which case one of the other RT 112 reset versions should be considered. Confirm that the medium is compatible with the switch according to the Danfoss data sheet, check the highest pressure the connection can see during start-up, shutdown or testing, and compare the contact load with the ratings in the table, especially for inductive loads such as contactor coils.

Installation and electrical connection

Fit the switch on a rigid support so that pipe vibration is not transmitted to it, and use the impulse line arrangement described above. If the line can contain dirt or pulsations, plan isolation and damping so the switch can be removed without shutting down the whole system. Electrical work should follow the Danfoss installation guide and local regulations: use cable suited to the contact load, seal the screwed cable entries correctly to keep the IP66 rating, and make sure protective earthing is in place where required.

Setting, testing and periodic maintenance

Adjust the range and differential with the system isolated or under controlled conditions, then verify the actual switching point with a calibrated test gauge rather than relying only on the scale. Raise and lower the pressure slowly and record the cut-out and cut-in values. Repeat this check at intervals set by the plant maintenance plan, after any work on the pressure line, and whenever the protected equipment trips without an obvious reason. During inspections, look for moisture inside the housing, damaged cable entries and signs that the setting has been disturbed, and keep a record of each test result.

Operating environment in Oman and the GCC

The RT 112 often sits on boiler skids, burner trains, HVAC plant and compressor packages that are installed outdoors or in hot plant rooms. Check that the ambient temperature at the mounting point, including heat radiated from nearby equipment and summer sun, stays inside the range in the specification table. Shade the switch where practical, keep cable entries sealed against fine dust, and in humid coastal locations watch for condensation, which is another reason to mount the pressure connection downwards. A short, regular test of the switching point is a sensible way to confirm that heat and dust have not affected performance.

Documents and quotation

We attach the Danfoss RT industrial pressure switch data sheet AI555514425055 with range tables and drawings. For related pressure and temperature controls see pressure instrumentation and ask for a quotation with quantity.