Repeated fault with mid position valves

[PeteH]

Can anyone help with a frustrating problem?

A few weeks after new boiler/time controller fitted September 2004 - Gloworm 40FF - had problem with HW not heated; that program warmed rads only. Plumber came back, diagnosed old mid position valve as faulty and replaced it. He had difficulty with electrics and notably advised that their sparky had wired old one in incorrectly.

Everything OK again for a few weeks, until problem in question - namely one very loud bang from the (new) valve (and pipe feeding it from boiler) only when HW program ran - not CH (although HW program still heats HW cylinder OK). Many calls to company that fitted it (and Trading Standards) later, they diagnosed that new valve was faulty and eventually replaced it 1/4/05.

Everything OK until this weekend - woken up at 5:30 a.m. when HW program started, by sound like a gun going off I can't believe it - checked next day and same fault has developed again!! I am wondering if any problem with wiring at controller end of circuit? I listened to valve (from cold when boiler off a few hours). When HW program starts, I could hear spring in it move, but not until pump started. Once spring reached position it banged. On CH program I can hear spring move but the pump doesn't start until its finished. Is this correct or should there be delay in the pump switching on for both programs? The sparky that originally wired this when the boiler was fitted (who was supposed to arrive at lunchtime) couldn't be ar**d to arrive until 5:00 p.m and the engineers didn't check what he was doing, because they were just leaving It seems very unlikely that two new valves have both failed.

Can anyone help with advice pleeeeaaase? I think the valve is a Honeywell V4073 and system is Y plan open vented. I have checked both loft tanks have water in and tried turning boiler output down a bit, without effect. It seems strange it's happened same time of year, could the coldness of water in feed pipe from boiler be making it bang when it's first heated?

Thanks guys.

 

[Agile]

The pump and boiler should be started only when the valve has reached the required position.

It does sound as if it has been wired wrongly to me. There is further evidence that the "plumber" was unable to wire it up himself. In that case I would not expect him to have the skils to check it either.

Its also possible that the valve has been plumbed in wrongly. The noise is probably caused by the valve closing in the direction of the pump flow with the pump running.

In my view you need a competent heating engineer who can wire and fault find on electrical control systems. Few electricians are able to deal with heating controls either.

Tony Glazier

 

[ChrisR]

NB on a 4073 the starting position may be CH only or HW only, so the valve may or may not move when a demand is made. If it was at CH only but the system was off, then a call on HW would bring the pump straight on as the motor starts to spring-unwind back to the HW position. Other situations would be different so there's no single behaviour re delays.

If the pipework's loose you can get a noise "dang?!" in the pipes when a waterway is closed off by the valve - a possibility?

 

[PIPERPETE]

you will need the 5 wire wiring diagram and a tester to rewire it correctly, the motorised valve should switch the boiler and the pump on.