Bolier comes on despite timer being off

[martinjjones]

I have an Icos HE15 boiler that occasionally comes on when the timer is set to off. It doesn't happen all the time.

There is a timer system that allows HW and CH to be separately switched but I can't set separate times. It is set to come on in the morning and the evening but off during normal daylight hours and at night. I have occasionally noticed that the pump is running and that the boiler occasionally fires during the day and the night when the timer is set to off. the boiler indicates a C (a call for heat) when the timer is off. The radiators stay off so I think its a call from the hot water tank.

I think there are two separate motorised values, one on the water water tank feed and one on the central heating. They are different types. I have tested the one on the hot water system and the lever can be moved but always springs back.

When it occurred the other day, turning off and on the main elec supply to the boiler and the timer did not removed the call for heat until I turned it off for at least 20 mins.

I don't believe I have a frost stat anywhere ( the boiler is in the utility room) and I don't think there is one integral to the boiler

What is likely to be wrong?
Broken timer calling for heat even when off?
boiler fault?
Motorised valve staying open and calling for heat?

It doesn't happen all the time so its not a permanent fault ( I think).

Ideas?

 

[plumbplumb]

Sounds like either of the motorised valves.
Just because the radiators are not staying on it doesn't mean the ch valve can be eliminated if the microswitch is sticking inside the valve

 

[Whitespirit66]

If you're handy with a multimeter, next time it happens, see if there is 240V from either of the orange wires coming out of the valves. Make sure that the hw and ch are off at the programmer. The grey wire into the valve is permanently live, so be careful.

If orange is live, then it's a valve fault.

 

[martinjjones]

Ok, thought that would be simple but.....


Taken the cover off the motorised valves and the terminals are difficult to get to. There is a small cover on it and no obvious place to connect the negative probe. Taken the cover off the junction box too and all orange wires go to one terminal. Could i put the multi meter onto that too. Happy that i touch one probe onto that terminal but where would i then connect the other probe; just leave it free or connect to the earth terminal?

 

[martinjjones]

And to add a little test. When i turn the room thermostat up the valve on the ch system does make a noise. Same when i turn up the thermostat on the central heating tank. Does that suggest at the moment both are working? Or since its intermittent does that not tell me anything (timer was set to one when i did that test)

 

[Whitespirit66]

You can put the probe on the terminal where the two orange wires go to. The negative probe will go to neutral terminal on block, that comes from main feed via fused spur.

This test needs to be done when the boiler is firing when it shouldn't, and ch and hw are off at programmer. It will tell you if one of the microswitches in a valve is faulty. You will then have to seperate them out to prove which one.

I don't think that your second test proves anything.

 

[martinjjones]

Untitled

• martinjjones
• 5 Feb 2013
• 2

This is what the junction box looks like. Which one is the neutral in this context. Happy to rewire to seperate out the orange wires for the valves. The system is working at the moment so will need to wait untill the fault appear again to see if its the valve.

 

[matt1e]

Untitled

• martinjjones
• 5 Feb 2013
• 2

This is what the junction box looks like. Which one is the neutral in this context.

The one at the top

 

[martinjjones]

Well the system has not played up so far this week. However I separated out the two orange motor valve leads and the single grey wire that they connect to. Since i think this is an s plan wiring i would have thought that there would be two wires, one for the pump and one for the boiler but there if only one that appears to go into the floor(to the boiler?). With the mains on and the timer set to off then both orange wires have zero volts and the single grey one has 240v on it. It doesn't makes sense to me. I would have thought that would also be zero unless the heating/water is actually on since i though the boiler got its 240 input from one of these orange cables. So have i got a different problem or a different wiring system?