Heating on when timer off?

[SyncroMan]

Up till now my heating has been working fine, on/off with timer, room-stat and tank-stat etc. The other day the central heating mcb tripped and after resetting the heating is constantly on even when the timer says off. Lowering the room-stat temp does still turn the heating off.

Has anyone had this situation before, and is it most likely a timer problem?

Any suggestions would be appreciated.

Cheers

 

[marcusone]

If roomstat will shut heating off then its the timer.

Sent from my HTC One X using Tapatalk 2

 

[ringer]

Yes, is most likely the timer. If you can get the same make/model then it can most likely be fitted without having to touch any wiring - they usually plug in to a backplate, and the wiring is terminated to the backplate. Just turn off the mcb before you look at replacing the timer.

 

[Darkwood]

It sounds like you had a short circuit thats cleared itself but in doing so it welded the contacts in timer permanently closed... the mcb tripped for a reason just replacing the timer may cost you again if it re-occurs until you know what was the cause of the tripping id be weary of just replacing it and forgetting about it.

 

[tamz]

Its a motorised valve

NOT.

Reading the post correctly would help.
If the stat is turning it off then it is the timer.

 

[fog]

Agree with Darkwood, what is causing, worth checking.
Had similar problem, changed timer only to burn new one out expensive, 2 valves is s plan, 1 valve is y plan, the way i tested eventually which is good tip, to prevent from blowing new timer is to link the hot water on terminal to permenant live, then turn on and off by switch fuse, then do same for central heating on terminal, on and off by switch fuse making certain you have correct fuse 3 amp gas 5 amp oil, if this works ok atleast you have proved the motorised valves are ok (i had a burnt out motorised valve which then burnt out 2 timers expensive) once you have proved the motorised valves you can then connect your new timer, the only other components are the cyclinder stat and the room stat, WHICH do go wrong albeit very rarely, also check the ten block connector these are prone to welding wires together if a component goes wrong as the wires are so close together. hope this helps

 

[fog]

Remember my post above is only a temporary fix do not run permantly with linked wires to permanant live. Thought would state that in case someone thinks thats a permanant fix .DO NOT LEAVE AS ABOVE ONLY FOR FAULT FINDING

 

[Darkwood]

Its a motorised valve

Is this a question, statement etc is it direct to OP's query or following my last post .... punctuation carries alot of weight as to your intended message!, also if you are just throwing a guess into the thread explain your reasoning for your view this will aid the OP and also may help others agree or disagree with your views.

P.S. Welcome to the forum.

 

[fog]

Of course my previous post didnt enlighten a problem with boiler as i presumed this is ok, if its working for hot water it must be external to this for the central heating not to work correctly, as the boiler doe not know if its heating up hot water or central heating its the valves that do this via the stats and timer/programmer

 

[tamz]

Is this a question, statement etc is it direct to OP's query or following my last post .... punctuation carries alot of weight as to your intended message!, also if you are just throwing a guess into the thread explain your reasoning for your view this will aid the OP and also may help others agree or disagree with your views.

P.S. Welcome to the forum.

Just a passing browse. Reading the post correctly helps of course.
If the stat wasn't turning off the heating (or boiler) it (as i'm sure you will know) is being fed from the microswitch on a valve. It could also, depending on the boiler, be feeding from there.
But it is not.

Thanks for the welcome.
Tam
(Poor plumber with hopefully only another 10 or so years more left doing this garbage)

 

[fog]

We like plumbers very good wit tamz, never heard of a poor plumber though!! ho ho

 

[tamz]

never heard of a poor plumber though!! ho ho

A bit of an urban myth but nearer the truth than we are all on 60k+

 

[mountainman]

We like plumbers very good wit tamz, never heard of a poor plumber though!! ho ho

Could say the same about sparks too!

 

[SyncroMan]

Agree with Darkwood, what is causing, worth checking.
Had similar problem, changed timer only to burn new one out expensive, 2 valves is s plan, 1 valve is y plan, the way i tested eventually which is good tip, to prevent from blowing new timer is to link the hot water on terminal to permenant live, then turn on and off by switch fuse, then do same for central heating on terminal, on and off by switch fuse making certain you have correct fuse 3 amp gas 5 amp oil, if this works ok atleast you have proved the motorised valves are ok (i had a burnt out motorised valve which then burnt out 2 timers expensive) once you have proved the motorised valves you can then connect your new timer, the only other components are the cyclinder stat and the room stat, WHICH do go wrong albeit very rarely, also check the ten block connector these are prone to welding wires together if a component goes wrong as the wires are so close together. hope this helps

Thanks for all the responses.

Before I buy a new timer, All house wiring is new and i have checked all the terminals are secure, the three way motorized valve is new and appears to be working fine i.e. goes to heating, water and mid-position. Hot water side of timer works fine, timer turns it on/off and tank-stat does the same. Boiler coming on and off as it should. When heating is in off position the pump and boiler still fire up when room-stat is high enough. The tank-stat is old but works fine, the timer is a Grasslin QE2 which is about 8 years old, and the room-stat is a tower rs and is about 8 years old.

Can a faulty timer cause the mcb to trip, or is it more likely to be another problem? Its worked fine for the last three months.

 

[oldtimer]

Why dont you turn up your room stat so it call for heating and when it does then remove the timeclock from its backplate heating goes off its the timer

 

[SyncroMan]

Why dont you turn up your room stat so it call for heating and when it does then remove the timeclock from its backplate heating goes off its the timer

Thanks, i've done that and can confirm that the heating goes off when removed. But going back to Darkwood's comments makes me wonder what caused it, and should it have tripped the mcb? There are no visual signs of damage on the timer circuit board, shouldn't the fuse in the fused connection unit have gone first?

 

[Darkwood]

Time current curves on mcb's can often beat the good old plug/spur fuse in the race to trip and like you mentioned it may have even been within the time clock itself... sometimes without knowing what caused it or seeing the evidence you just have to grit and bare it and replace the timeclock but doing so you need to enlighten the customer that a fault may still exist although its intermittent thus cant be located, then explain the risks of it doing the same again and if so the timeclock wont be replaced under warranty. Sometimes in our job faults occur which are self clearing and leave no trace..... blown capacitors are usually high on the list on the electronics boards as they can short and blown themselves apart clearing the fault and if they are only for smoothing the power supply they wont effect the function of the board but may leave it more prone to transients from the power supply; but thats another fault for another day.

It may be a good idea to check the wiring from timeclock to heater as it may be trapped, nailed damaged etc but only really need to check the 'calling for heat' flex/cable as this is the offending part of the circuit.

 

[mountainman]

In support of Darkwood, I've seen cables running in the same notches as heating pipes.
You may have an intermittent short circuit that has taken a while to appear.

 

[oldtimer]

Thanks, i've done that and can confirm that the heating goes off when removed. But going back to Darkwood's comments makes me wonder what caused it, and should it have tripped the mcb? There are no visual signs of damage on the timer circuit board, shouldn't the fuse in the fused connection unit have gone first?

Listen I dont want to shoot you down here but dont you think you are being a bit excesive ? If your mobile stops working you get another one you dont try to strip it down to understand why and we are talking about a £30-£40 time clock here and I would point out I have replaced many a time clock that was either stuck on heating 24 hours a day or would not switch on the heating either way you have proved it is the time clock at fault just replace it and get on with your life.

 

[Darkwood]

I see your point Oldtimer and yes ive replaced many a time clock myself straight swap walk away, but with regards to OP case he mentioned the circuit tripped mcb and then we've established the timer to have possibly welded contacts, i would question the competence or dedication to his/her job of any electrician who didn't at least try fault find, the thought of returning and charging the customer again after it blows next timer would not only upset the customer but wont do reputation any favours, as long as customer is kept in the loop and fully explained then their wont be any supprises if it goes again and yes sometimes you are left with the only option of replacing without sourcing the initial cause of the fault.
We are trying to help and direct the OP, im supprised with your response, you may hold a opinion of which you have posted but saying 'just replace it and get on with your life' is neither constructive or called for...