Heating / Hot Water Help

[Jack Baker]

Hi All,

I am having an issue with me Heating & Hot Water at home.
I pretty sure that it is my Controller (Honeywell ST699) but would just like some advice before I go ahead and change the unit.

I use the controller on the 'Twice' Function, On at 6am, off at 12pm, on at 5pm, and off at 10pm.
These times I use for both the hot water and the central heating.
However over the last week my wife has noticed that the heating isn't coming on nor do we have hot water. The controller says its on but its not.

I have since been rectifying the issue by turning both the hot water and the heating off and then back on again. Sometimes I get the red LED on the controller but I cant hear the internal switch make, so I repeat turning it on and off until I hear the contact make and sure enough the boiler fires up and we then have heating/hot water.
Could it be a dirty contact or something?

Any advise would be appreciated.

Jack

 

[omega015]

Does either LED switch on when you manually set heating or hot water to the constant setting? Assuming the display is still showing the time and allowing you to change the time settings etc..?

 

[chris1982]

We have a Honeywell controller (might be the same as yours) and I noticed that the switch is very pedantic. If you don't shift it exactly on "twice", it might be constantly on or constantly off. I don't know whether with age it wears out more and the problem becomes more severe.

 

[stem]

It is difficult to say without testing the unit electrically. The Honeywell ST699 is basically just two switches, one for heating, and one for hot water. Both of which normally (but not always depending upon your heating system) will be responsible for operating the boiler. If so it would be odd that both fail at the same time!

Does your system allow you to have the central heating on without the hot water also being on? or does switching the heating on start the hot water as well?

In some systems the boiler is operated by small switch inside a motorised valve (or valves) and not directly from the programmer, although to confuse matters, the motorised valves are operated by the programmer.

Do you have any of these?

Untitled

• stem
• 26 Mar 2010
• 6

or one of these?

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• stem
• 1 Apr 2010
• 8

 

[Jack Baker]

Thanks for your replies.

Omega - Yes the LED comes on and off when I switch manually.
Chris - Thanks I will take that into account.
Stem - Yes we have one of those valves. It is functioning as I can hear it opening and closing on demand from the controller.

 

[stem]

Stem - Yes we have one of those valves. It is functioning as I can hear it opening and closing on demand from the controller.

Is the valve functioning when the fault is present? (ie you have no heating) If so, then the programmer is not at fault. It will have switched on the heating on OK and sent a live (via the room thermostat-if fitted) to the to the motorised valve which instructs it to move to the heating required position.

 

[omega015]

Thanks for confirming Jack. When setting either hot water or heating on the constant setting and the LED is on, do you actually have hot water and/or heating? Does the LED come on every single time when setting it to constant? or is that temperamental like the twice function? I am just trying to work out if its the timer/schedule function or something else.

 

[Jack Baker]

I can rule the Thermostat out as I 100% know that works.

Scenario:
Controller is set to twice for both Hot Water & Heating.
Within the time frames for the controller to be outputting, the LEDs are on but the Boiler is not nor is the pump.

I then have to turn the switches off and then back on. I hear a click along with the LEDs.
I then have to turn the temperature knob on my boiler to off and then back on again.
Then I hear the boiler fire up.
I suppose I could test the output of the controller by measuring the voltage going into the boiler?

 

[stem]

I suppose I could test the output of the controller by measuring the voltage going into the boiler?

That would be a good start, if the boiler isn't running and it is receiving 230v from the controls that would indicate that the boiler is at fault. If it isn't getting 230v then the controls would be the problem.

 

[Jack Baker]

I will try this tonight and post back the results.
Thanks for you help.
Appreciated.