possible actuator fault

[coldwetnclueless]

Hi
Any help with the following would be very much appreciated.
The basic problem is that when the hot water is on (at the programmer and demanded by the tank thermostat) then if the central heating switches on it cannot be switched off.

I have a siemens RWB9 programmer
Two Danfoss HPA2 valves
A wickes room thermostat
A British gas CS1 tank thermostat
And a v. old BAXI boiler

If the hot water is off (at either the programmer or the thermostat) then I can switch the central heating on at the programmer and then when the room thermostat is turned on I can see that the CH valve opens (the manual override bar moves freely) when the room thermostat is turned off I can then see that the CH valve closes (the manual override bar now requires force to move it)

If the hot water is on and demanded the HW valve opens and if the HW thermostat is turned down the valve then closes.

I.E. everything seems to work fine.
However if the HW valve is open then it is not possible to close the CH valve except by turning off the demand for the HW

I thought this was a problem with the programmer so I have replaced it with a Drayton unit but the problem still persists.

The problem could be wiring (and we have only recently noticed it) or could it be a problem with one of the valve actuators.

I have tried to match the wiring to the Honeywell guide listed in other posts and my system would seem to match the Sundial S plan (with a two wire thermostat) although it is not obvious whether my wiring matches the S plan wiring

Is it worth swapping the wiring for the two actuators to see if the problem reverses? Or is the system behaving normally

Many thanks for any help you can provide

 

[gas4you]

It certainly at first sight, appears to be a wiring problem.

If you want a copy of the Honeywell wiring guide, e-mail me from my profile and I will send you it.

 

[coldwetnclueless]

Thanks for the quick reply.
I have a copy of the honeywell guide from the website and it would seem that the only difference in my wiring is that the actuators' grey and brown wires are connected together (and connected to the appropriate thermostat) rather than the grey being connected to the live from the controller. (I have no live from the controller or any live connections in the wiring centre). I can see that this could mean that the actuators are possibly being held at live but I don't understand why this would result in the HW keeping the CH valve open.
Thanks again

 

[giblets]

The grey wire on both valves must be fed from a permanent live and not be connected to the brown wire. The orange wire on both valves is used to power the pump & boiler. The brown wire is connected to the relevant stat. Sounds like someone has tried to do the job cheaply by not using another cable (perm live) and has used the wrong coloured wires to operate the pump/boiler.

 

[swbjackson]

If you follow the wiring diagram through you will see that wired like that the power will backfeed through the switch and hold the valve in the open position.

 

[coldwetnclueless]

Thankyou all for your replies - looks like I have a rewire job on my hands. I will need to get some 4 core + earth and see if I can pull it through the existing channels from the programmer.
Thanks again for your help

 

[D_Hailsham]

If you follow the wiring diagram through you will see that wired like that the power will backfeed through the switch and hold the valve in the open position.

If you mean backfeed through the auxiliary switch in the valve, then I don't follow you.

The OP said:

the actuators' grey and brown wires are connected together (and connected to the appropriate thermostat)

When a thermostat's contacts are closed, power will be supplied to both brown and grey wires, so the valve will open, aux switch closes, and power is then supplied to the orange wire. When the thermostat's contacts open, power no longer gets to either grey or brown wire, so the valve closes closed, aux switch opens, and power no longer gets to the orange wire.

 

[coldwetnclueless]

Hi
If I understand what you are saying correctly then it would seem that the "shortcut" of making use of the fact that HW and HTG are live when the programmer switches CH and HW on. So while it might not be nice or proper to do so it is ok to connect the actuator's grey and brown to the thermostat "output" i.e. actuator's grey and brown connected to the thermostat's C (or 3) with the thermostat's 1 connected to the programmers HW or HTG.

If this is the case then I can only conclude that the HTG is being kept open when the HW is on due to the presence of a live on the orange due to the live on the orange of the HW i.e. an internal short in the HTG actuator resulting in the orange holding the grey live.

Or have I completely misunderstood?

Thanks

 

[D_Hailsham]

Hi
If I understand what you are saying correctly then it would seem that the "shortcut" of making use of the fact that HW and HTG are live when the programmer switches CH and HW on. So while it might not be nice or proper to do so it is ok to connect the actuator's grey and brown to the thermostat "output" i.e. actuator's grey and brown connected to the thermostat's C (or 3) with the thermostat's 1 connected to the programmers HW or HTG.

If this is the case then I can only conclude that the HTG is being kept open when the HW is on due to the presence of a live on the orange due to the live on the orange of the HW i.e. an internal short in the HTG actuator resulting in the orange holding the grey live.

Not sure who you are asking but I agree with your conclusion.

You said earlier, "I have no live from the controller or any live connections in the wiring centre." I presume this means that power is fed direct to the boiler, which then supplies the programmer. The only power to the wiring centre comes from either the CH ON or the HW ON terminals of the programmer. Is this correct?

Presumably the programmer is in or close to the boiler and the valves and wiring centre are some distance away.

Have you tried following the fault finding info in the Honeywell Wiring Guide - it may be a bit difficult as it assumes you have power to the wiring centre. Alternatively try disconnecting one grey wire at a time and check what happens.