Danfoss MP 55 oil differential pressure switch

The Danfoss MP 55 is an oil differential pressure switch: it protects compressors with an oil pump against insufficient lubricating oil pressure. It compares the oil pump pressure (OIL connection) with the suction pressure in the crankcase (LP connection). If this difference does not reach the set value at start-up, or falls during operation, its time relay stops the compressor once the release time has elapsed.

The five versions

All versions: adjustable differential 0.3 to 4.5 bar, LP side range −1 to 12 bar, 1/4″ male flare connections, DIN 8906. On request: MP 55 60 s with operating lamp (060B017891), MP 55 45 s with 1 m capillary tubes and 1/4″ ODF solder ends (060B013391), and MP 55A for ammonia R717.

Operation

• Two separate circuits: a safety circuit (contacts T1-T2, which start the timer) and an operating circuit (L-M) for the compressor.
• Alarm: terminal S can drive a fault lamp or alarm.
• Manual reset with the button, after about 2 minutes, once the cause of the fault has been found.
• Test: a test device inside the housing lets you check that the compressor stops after commissioning.
• Release time: choose it according to the compressor manufacturer, to give the pump time to build up pressure at start-up. The version without relay is used with an external time relay.

Specifications

• Differential adjustable from 0.3 to 4.5 bar with a setting disc, read on an internal scale; contact differential 0.2 bar. The factory setting is stamped on the front plate.
• Pressures: maximum working pressure 17 bar, test pressure 22 bar.
• Control voltage: 230 V or 115 V, AC or DC (−15% / +10%).
• Temperatures: ambient −40 to 60 °C; bellows 100 °C max.
• Wiring: Pg 13.5 cable entry for 6 to 14 mm cable, at the front of the unit; IP20 enclosure.
• Refrigerants: R22, R134a, R404A, R407A, R407C, R407F, R422B, R422D, R448A, R449A, R450A, R452A, R507A and R513A (HCFC and non-flammable HFC).

See also our Danfoss pressure switches KP 1 (low pressure), KP 5 (high pressure) and KP 15 (dual LP/HP).

Afric Froid, your Danfoss supplier

Afric Froid supplies Danfoss pressure switches and thermostats, installs them and provides after-sales service in Tunisia, Algeria, Senegal and Ivory Coast. Tell us the compressor and the release time you need: we will choose the right model and send you a quote.