Sticky 2-port valve

[mdrandall]

I have a Danfoss HPA2 which has a sticky microswitch. It often stays closed energising the pump even though the valve itself has returned to the off position

A light tap on the actutor body will sometimes free up the switch.

Is the microswitch a serviceable item (like the motor) as it seems the cheapest HPA2 replacement is around £50 by the time post and VAT are added?

 

[martinwinlow]

I appreciate this is a rather late reply but others may find it useful and a serious money saver.

Like you, I discovered my switch was stuck on in the central heating circuit causing the boiler (and therefore boiler pump) to continuously run. Apart from the noise and waste of power and oil, as the valve was not open, the pump is working away against itself - can't be good.

In the actuator head (not the metal valve body), both the microswitch and the 'synchron' motor are easily replaceable. The motor can be had on ebay for around £6 (search for 'synchron motor'). You will need cut the old motor off and then crimp the new ones to the new motor. Crimps are normally supplied with the motor but ideally need a proper crimping tool - but careful use of ordinary pliers or pipe grips would do. Or just use a pair of mains connectors. Or better still, twist together the wire connections, solder them and then use the crimp on connector to insulate them.

The microswitch (a 'sub-miniature plunger' 240V AC SPDT 5A type) is very common and available from Radio Spares (amongst many other places) - order code 472-8162 for £1.73. Requires soldering in. This is the 10A version - clearly the normal 5A one isn't up to the job as mine only lasted 5 years. Perhaps that is normal and the whole thing is just a cynical ploy to keep over-paid plumbers in work. The 10A version should last the life of the boiler.

The other alternative is to just replace the actuator head - 2 x 5mm screws secure the head to the valve body. New actuators are on ebay for around £25.

MW