Trounleshooting Central Heating Help Needed

DTDfanBoy

I’m currently giving a friend a hand to flush his radiators and add trv’s to his system, we drained the system and flushed the radiators and have just added some f3 to the system to circulate for the week.

We’ll drain the F3 out next week when adding the TRV’s then refill, so this will be the ideal time to change the diverter valve if that’s where the problem lies.

We refilled the system today then tested it, I found that the 3 way diverter valve was not operating correctly, but my friend states that it has not operated correctly since he had a 7 day programmable thermostat/timer added to the central heating just after he purchased the property a year ago.

The system is open vented, gravity fed and fully pumped.

The diverter valve is a Drayton 3 way, operated via a Dayton relay unit RB1

The boiler is a Baxi Bermuda back boiler

The HW is controlled via a switch and tank thermostat, the CH is controlled via a switch and a 7 day electronic Siemens RDE10 thermostat/timer
　
The problem is that the 3 way valve only operates correctly when moving in the one direction, from the default HW only through to HW/CH then to CH only. If the valve is in the CH only position and the HW is turned on it will move to the HW/CH position but will not move any further regardless of whether the CH thermostat is in the on or off position. The only way of getting the valve to switch to HW only is to switch the CH off via the switch not via the thermostat/timer, it then returns to the default HW only position.

If the HW is on, with the valve in the HW only position, and the CH is then turned via the switch on as long as the CH thermostat isn’t calling for heat the valve remains on HW only.

As the problem only occurred after the RDE10 was added to the system I’ve had a look at the wiring connection diagram for it.

DTDfanBoy

The RDE10 is currently wired as follows

From boiler

RED to L Black terminated Earth terminated

From Drayton relay

Red to Q14 Black to N Earth terminated

There is also a jumper from Q11 to L


Does the wiring look ok or should be wired to Q12 for N.C valves as the diverter valve default position is closed for CH open for HW ?

If the wiring is currently OK any ideas on how to troubleshoot further ?

Any assistance greatly appreciated

ormus

whats the model number of the drayton valve?
i reckon the wiring is ar se about face. try wiring it for NC valves.

DTDfanBoy

It's a Drayton TA/M4, it has five wires running off it.

I take it you're referring to rewiring from Q14 to Q12 ?