CH turning on by itself problem

[mcm]

was asked about a central heating problem the other day but as not done much of this was not sure.

I was told that the central heating would come on by itself even if the programmer was switched to the off position. The heating would come on in the night on its own but on the programmer says its off, the timer works ok on the programer as tested the the on off times, was thinking it could be the valve sticking does this sound right?

The programmer is a drayton tempus six

 

[invisable]

is the boiler located where it can get cold does it have a froststat or a pipe stat installed ? (it could have a internal frost stat on the boiler).
sound like the boiler is coming on at night when the temperature drops to stop pipes freezing.

 

[i=p/u]

sounds good to me, cause this overides ..... but not to clued up either

 

[mcm]

is the boiler located where it can get cold does it have a froststat or a pipe stat installed ? (it could have a internal frost stat on the boiler).
sound like the boiler is coming on at night when the temperature drops to stop pipes freezing.

no the boiler is in the kitchen would'nt of thought it would get that cold. someone said about the valve could be sticking that at night it was moving causing it to come on. think its more than the programmer at fault but not sure.

 

[invisable]

What type of system is it does it have 2 valves (s plan) or one valve (y plan) the vavle could be sticking usally when a valve sticks it would just stay open or closed to let the heat through eg. heating would get hot when hot water is callling.

 

[UNG]

What make is the boiler. A lot of boilers have built in frost protection that activates when the temperature drops it normally kicks the pump in first at around 5° or 6° C and fires the boiler at 2° C

 

[mechelec]

Has the system got a room stat that is incorrectly wired ie in parallel with the programmer and has just been turned down low.
It could be the programmer that has a sticking relay and not switching off, but usually they fail open circuit not short.
Not sure how a sticking valve would cause the boiler to fire.

 

[chris murphy]

What make is the boiler. A lot of boilers have built in frost protection that activates when the temperature drops it normally kicks the pump in first at around 5° or 6° C and fires the boiler at 2° C

"Hello mcm",

I am a Heating Engineer - What UNG stated here could be the case - If the Boiler Frost Protection is operating the Heating should NOT actually run / Heat Up to `Normal` / Hot Temperatures - but the Boiler would Fire Up and the Pump should run and distribute a small amount of Heat around the System - then the Boiler would Go Off until the Frost Protection turned it on again If the Temperature within the Boiler dropped to actuate the Frost Thermostat.



I have noted outside Temperatures here in the London Suburbs of as Low as Minus 6 Degrees C during the early part of this Week - and Boiler Frost Protection turns on the Boiler at a Higher Temperature than this - usually approximately as UNG stated, there have also been some quite Cold Nights earlier in the Month.

Remember that the Cold Air is entering into the Boiler via the Flue - both the Air Intake and the Combustion Products exit - any Wind in the direction of the Boiler Flue will cause this to be more prevalent - Temperatures of much less Cold than I mentioned should actuate the Boiler Frost Protection.

The People in the Home would obviously be thinking that the Heating is `On` - But the Boiler Frost Protection should not actually Heat Up the Home - just Protect the Boiler from Freezing.

Perhaps the Heating is On during the Day normally - or this situation might have occurred during Cold Days also.

If the Members of the Household are out all Day and the Frost Protection had operated during a Cold Day it would usually Not be detectable because not enough Heat should have circulated around the Heating System for anyone coming in to notice.

But It is very likely that People who are Out all Day will have the Heating Set to come On a couple of Hours before they get Home - so they would definitely NOT know whether the Boiler Frost Protection had operated during the Day.

I can only suggest that on a Cold Night someone stays up and actually `Witnesses` the Boiler Fire Up - it should not run for a Long Period - after which it will Turn Off again - this is how the Boiler Frost Protection works.

BUT If the Heating System gets Hot - as normal it would be unlikely to be the Frost Protection - unless that is not Turning Off when it should after Warming the Boiler - then there is a Problem somewhere else.


Chris

 

[mcm]

hi chris

they said the heating was coming on during the night and it was very warm.

like i described I set the times on the programmer to see if they come on and off as they should and it does. Do you think as its getting warm when its ment to be off that it could be a faulty programmer? they say when it comes on in the night the programmer shows it being off any thoughts.

thanks

 

[chris murphy]

hi chris

they said the heating was coming on during the night and it was very warm.

like i described I set the times on the programmer to see if they come on and off as they should and it does. Do you think as its getting warm when its ment to be off that it could be a faulty programmer? they say when it comes on in the night the programmer shows it being off any thoughts.

thanks

"Hello mcm",

I have never come across a Programmer that caused this to happen - in the last 40 Years that I have been a Heating Installer / Engineer.

Especially as You mentioned that when the Boiler / Heating is On the Programmer shows that it is Off - But I would be interested to see if any of the Electrical Professionals on here do know whether this could ever happen regarding an `Internal Malfunction` of the Programmer - ?

When this happens do You happen to know whether the People in the Home decide to Turn Off the Boiler ? - How have they said that the Heating goes Off - Or does it then continue when the Programmer Setting comes to the Morning `On` Time ?


THIS is very unlikely But:


I am wondering if the Boiler Frost Protection Thermostat is Turning On the Boiler and instead of allowing it to just Fire for a short period of time to `Warm` the Boiler [and as a result of that the surrounding Pipework] - it is not Turning Off the Boiler after a small rise in the Temperature but is allowing it to run for a much longer period of time - ?

That would be a Very Strange situation because at what point would the Frost Protection Thermostat then `Turn Off` the Boiler ?

IF the situation with the Heating Turning On is caused by the Boiler Frost Protection Thermostat and the Boiler is then continuing to Run into the Morning `On` Period as determined by the Programmer because the Frost Thermostat is NOT Turning the Boiler Off when it should perhaps then the Frost Thermostat is being `Overridden` by the Operation of the Programmer / Switched `On` and then the Boiler / Heating System works correctly until the operation of the Frost Protection Thermostat again - ??


I would strongly advise that You contact the Boiler Manufacturer Technical Helpline to ask whether this CAN Happen as they would obviously know more about the `Internal Components and Electrical System` than We could ever `Diagnose` on here.

All of the Well Known Boiler Manufacturers have good Technical Helplines - although obviously they are run to be used by mainly Heating Installers / Engineers. - I would suggest that they will probably advise You that this should be looked at by a Boiler Servicing Engineer - You should obviously not speak as if You would be doing any work to the Boiler.

If that is the case You should definitely advise the People in the Home to arrange for an Engineer who actually works for the Boiler Manufacturer to Inspect / Test the Boiler - NOT an Independent Boiler Engineer - If only because the Manufacturers Engineer would have the Facility to Change the Frost Protection Thermostat straight away if He suspects that is causing the Problem - NOT `Have to Order the Stat`.

Obviously whether the Boiler is being Turned On by the Frost Protection Thermostat or the Programmer the Boiler [Heat] Thermostat governs the `Firing` of the Burners [Room Thermostat should not operate with Frost Protection] - SO even IF the fault is the Frost Thermostat causing the Boiler to be Turned On during the Night - the Boiler Thermostat [Heat Setting] will cause the Burners to be Turned On / Off.

I mention this in case anyone reading the Posts wonders why the Boiler does not just `Keep Firing` if turned on by the [Faulty ?] Frost Protection Thermostat.


I cannot think of any other cause of what You described - I hope to see a couple of opinions about the possibility of the Programmer Malfunctioning and causing this - ?


"Sorry" - that I cannot give You a Definitive Answer to this - In My experience it is a Unique Situation ! - as I have not encountered this - although a Boiler Service Engineer MAY have ?


Regards,


Chris