Strange behaviour with Salus EP200 controller

13 Jan 2010
Reaction score
United Kingdom
Hello all

Apologies in advance for being long winded but the problem is complicated, I think.

Our system is fully-pumped, boiler is Potterton Kingfisher MF.

We had a new 3-way valve (Salus MV322) and a Salus EP200 fitted before Christmas. Thermostat is wireless, I can't remember the model. When we bought the house, the controls were for a gravity-fed system and CH wouldn't work without the HW thermostat set to 70deg, costing a fortune. Cylinder thermostat was working OK so wasn't replaced.

The problem is, if we ask for just CH (either manual "on", override button or timed) the heating works OK. Same if just HW is selected. However, if BOTH CH and HW were selected, we would only get HW. For instance if:

CH - 6pm-10pm timed
HW - 7pm-8pm timed

then the CH would work from 6pm-7pm, then the HW would start up but the radiators start cooling down. When HW goes to off, the CH does not start back up even though programmed to. The +1hr button on the heating channel is still lit, i.e. commanding heat via the timed setting, and the room thermostat is showing 17 deg, flashing for command heat and set point is 20 deg, but boiler not firing.

The only way to get the heating to come back on after HW has been on, is to turn the CH channel to "off," which moves the motorized valve lever from middle to left, and then after a few seconds, switch the CH channel back to Auto (motorized valve goes back to mid position) at which point the boiler will fire immediately.

Obviously I'm going to get the plumber back to get it fixed but I wondered if anyone has an idea what could possibly be wrong in case he argues with me.

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The outcome was that eventually, after 18 weeks, the plumber admitted the motorized valve was faulty and replaced it. The heating and hot water worked correctly from then on.


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