Ma-Ter XP602 Combi Boiler Pressure Sensor – Baxi 5114748 Compatible Water Pressure Switch, 0.2–1.2 bar, Plastic Thread

Ma-Ter XP602 is a water pressure switch that monitors the water pressure in the combi boiler system; in the field it is also referred to as a combi boiler pressure sensor, pressure switch or water pressure switch. It is matched with the Baxi JJJ005114748 code on the packaging label, i.e. it is the equivalent of Baxi's water pressure switch number 5114748.

The switching range is 0.2–1.2 bar, the contact rating is 10(2) A 250 V~. The connection thread is plastic; the brass-threaded version of the same family is the Ma-Ter XP600.

What Does It Do?

When the water pressure in a closed-circuit heating system drops, operating the combi boiler is not safe: the pump may run dry, the heat exchanger may overheat. The XP602 continuously monitors the system pressure. When the pressure falls below the set value, the contact changes position; the PCB stops the burner and pump and shows a low water pressure warning on the display. When water is added to the system and the pressure returns to normal, the contact returns to its previous position and the combi boiler restarts.

Fault Symptoms

• The combi boiler gives a low pressure error even though the pressure gauge shows normal pressure (approximately 1–1.5 bar).
• The combi boiler does not ignite at all, or cuts out and restarts intermittently while running.
• There is a water leak from the threaded area of the switch.

For diagnosis, the combi boiler's electricity is switched off and the switch terminals are measured with a multimeter. If the contact does not change position while the system is pressurised, the switch is faulty.

Pressure Switch or Electronic Sensor?

The XP602 only gives an open/closed contact signal. Some combi boilers, on the other hand, use an electronic water pressure sensor (transducer) that measures the pressure continuously and reports it to the PCB as a voltage; for example the Huba 505.91572. These two parts are not fitted in place of each other. If the body of the removed part says XP602 and it has three flat faston terminals, this product is the correct part.

When Replacing

• The combi boiler's electricity is switched off; the system pressure is reduced to zero and, if necessary, the combi boiler side is drained.
• The plastic thread must not be overtightened; after the sealing gasket is seated, hand-tightening plus a measured torque is sufficient.
• Before the cable terminals are disconnected, note which terminal is connected where, and fit them to the new one in the same order.

Technical Specifications

• Brand / model: Ma-Ter XP602
• Equivalent OEM code: Baxi 5114748 (JJJ005114748)
• Product type: Water pressure switch (pressure sensor / pressure switch)
• Switching range: 0.2–1.2 bar
• Contact: 3-terminal, 10(2) A 250 V~
• Electrical connection: 6.3 mm flat faston terminal
• Maximum ambient temperature: T125
• Connection thread: Plastic