WB heatlave not responding to stat requests - otherwise working

[HandyAndy20390]

Worcester heatslave 15/19 (est 20 yr old)

Not responding to stat requests - otherwise working in all other respects

new stat tested, has worked for a time, then stops responding so intermittent issue


Adjusting the heating level dial will still fire it up & it will finish its run till up to adjusted temp


Am I to suspect a PCB / component issue ?

Any suggestions much appreciated, thanks

 

[Harry Bloomfield]

Not responding to stat requests - otherwise working in all other respects

new stat tested, has worked for a time, then stops responding so intermittent issue

What sort of stat? If a wireless one, is it within range/how are the batteries?

 

[denso13]

Any suggestions much appreciated, thanks

Are you able to test the stat is actually calling for heat?

 

[HandyAndy20390]

Hi thanks for your quick responses

I went and got a honeywell style super basic 3 wire analogue dial one

I have a multimeter so i guess i'll test for an output

Between now and then if any other ideas come to mind - by all means fire away !

 

[CountryFan]

How does it respond? Check for the neutral wire connection and check if live and switched the wrong way around

 

[ericmark]

Most boilers, heat pumps, etc, do not like fast cycling, so most thermostats have something to stop it. Be it a little resistor which heats up the thermostat when turned on, or some electronic part, there is normally something which results in a delay, while not affecting the temperature. Also, years ago before the condensing boiler, we had thermostats which used a mark/space ratio to gradually reduce the heat output to try and reduce the hysteresis.

Oil boilers need longer to start and finish, so many thermostats have a setting, mine is clearly set for oil and use of radiators, and this changes the minium burn times and restart delay, it will depend on thermostat make and model Nest Gen 3 shown here.

So step one, is what you're experiencing a fault? Or is it a feature? I did have a problem with this thermostat, where it would lose wireless connection with the base, and fail to turn heating off, the base

did have lights on it, so it was plain to see the thermostat was the problem. More expensive models will auto turn off if no signal every ½ hour.

Start point, is read the instructions, and see what it is designed to do. And if you can put a link to instructions it saves us also hunting for them.

 

[HandyAndy20390]

Hi all - thanks for your responses

I was away for the weekend but can now confirm the switched line is going live (240v)


To further clarify – this is a long standing setup which has been working fine
so particulars with stats have now been safely ruled out with having tried a brand new basic model


There is still an occasional response to the stat calls from the boiler so leaves me to think the
controller is blocking at times for which ever reason

the boiler had been left for a few days responding to defrost setting requests from the stat (>12C)
so means it then ran for an extended period once returning home

I have looked at the heating pump, both to see if it has ceased/needed bleeding – I feel those can now be ruled out

so this leaves the other elements governed by the controller, can anyone suggest tests that would confirm the component that is returning an error to the controller ?


Many thanks to anyone who can offer advice

 

[CountryFan]

Are there any motorised valves fitted, or does the boiler have one?

 

[HandyAndy20390]

The closest candidate I can see would be this

 

[Exedon]

That's the flow switch
The 3 port diverter valve sits above the pump
Grey plastic head .
Which model heatslave? (Not the output)
They have made quite a number!
Has yours got green plastic on front panel?

 

[HandyAndy20390]

Ah yes, thanks for that I see it now

the model is as above + OSO
Version: ANE

Green dials & switch but without the screen I've seen on others - Hope this helps


Is there a test I can do with the diverter valve?

 

[CountryFan]

Is there a test I can do with the diverter valve?

Ideally voltage tests to ensure it’s receiving voltage, but I’d suspect the microswitch inside.

 

[Exedon]

You need the instalation instructions they are available on line if you don't have them.
The 3 port valve are known to fail you must use correct replacement.
That old model uses relays that are also known to fail.
You need a multimeter and boiler instalation manual and follow the flow chart.