CH turning on by itself problem

[chris murphy]

First of al I take it is a domestic system where you have hot water storage tank and central heating yes ? plus you say it comes on itself so when does it come on ie low outside temp or internal thermostat so you need to find out how it is wired then as a test turn off the timer / programmer and then turn up the room stat if the boiler kicks in the the stat should be wired in series with the programmer I hear about frost stats but this is usally found on commercial systems ie schools office blocks etc

"Hello oldtimer",


Most Boilers from the well known Manufacturers that were made in certainly the last 10 to 15 Years have Built In Frost Protection Thermostats.


Regards,

Chris

 

[sambotc]

Hi chris,

It is possible, but as you say it would only raise the temperature to 20 odd degrees and the heating wouldn't be belting out as the op has described. As a heating engineer myself I would take a punt on the clock first but if the valve has jammed in the open position through sludge or corrosion then it will supply 230v to the boiler and pump. The valves have a permanent live supply, a switched live and a live supply to the boiler plus N and E ( hence 5 cores) so it is possible for the live supply to bypass the call of the clock if it malfunctions. I would have though that the customer would have also noticed the heating being on all the time. If you turn the room stat off you will cut the supply from timer ( assuming it's wired in series like most stats are on domestic heating) therefore eliminating the clock from the equation. If that solves it then the clock must be at fault, if not then you can look further into where the valve and essentially boiler and pump are getting a supply from.

 

[Guest111]

hi Chris on some sytems there is a permanent live to the junction box and I have had them were a 2 or 3 port valve has gone fault and this causes boiler to fire,was common on y plan when I did contracting for BG power to box is there at all times unless fcu turned off,hope this makes sense.phil

 

[chris murphy]

Hi chris,

It is possible, but as you say it would only raise the temperature to 20 odd degrees and the heating wouldn't be belting out as the op has described. As a heating engineer myself I would take a punt on the clock first but if the valve has jammed in the open position through sludge or corrosion then it will supply 230v to the boiler and pump. The valves have a permanent live supply, a switched live and a live supply to the boiler plus N and E ( hence 5 cores) so it is possible for the live supply to bypass the call of the clock if it malfunctions. I would have though that the customer would have also noticed the heating being on all the time. If you turn the room stat off you will cut the supply from timer ( assuming it's wired in series like most stats are on domestic heating) therefore eliminating the clock from the equation. If that solves it then the clock must be at fault, if not then you can look further into where the valve and essentially boiler and pump are getting a supply from.

"Hello Again sambotc",


I can see what You are stating - But - as You wrote the Heating System would then be ON all of the Time - If a Stuck Zone Valve can `Bypass the Programmer` regarding supplying a Live Feed to the Boiler and Pump.


Regards,

Chris

 

[chris murphy]

hi Chris on some sytems there is a permanent live to the junction box and I have had them were a 2 or 3 port valve has gone fault and this causes boiler to fire,was common on y plan when I did contracting for BG power to box is there at all times unless fcu turned off,hope this makes sense.phil

"Hello phil",

I believe that most Heating Wiring that is done using a Wiring Centre type connection Box has the Power Supply wired directly into the Wiring Box - From either an FCU or from a Three Pin Plug - ?

How does the Power get from this supply TO the Zone Valve without the `Involvement` of the Programmer and Thermostats - If the Programmer is in an OFF Setting ?

And how could a Zone Valve where the Heating has been OFF then supply Power to Turn On the Heating / Boiler & Pump in the middle of the Night - presumeably long after any ON Setting on the Programmer ?

I am genuinely interested in these points.


Regards,


Chris

 

[sambotc]

Chris,

The system is wired so that power from the programmer goes through a stat (water or heating) then to the valve. This actuates the motor to spin across to open which closes a microswitch, the microswitch turns the boiler/pump on, not the programmer. That is for a zone valve, a three port works differently but a similar principle. As the valve has a permanent live connection, it is possible for the valve to remain open and feed power to the boiler without a feed from the programmer.

 

[chris murphy]

Chris,

The system is wired so that power from the programmer goes through a stat (water or heating) then to the valve. This actuates the motor to spin across to open which closes a microswitch, the microswitch turns the boiler/pump on, not the programmer. That is for a zone valve, a three port works differently but a similar principle. As the valve has a permanent live connection, it is possible for the valve to remain open and feed power to the boiler without a feed from the programmer.

"Hello sambotc",

I hope that You are not getting annoyed / frustrated about My Questions ? - I am wondering this because of your `Details` about the Sequence that operates a Heating System - which I do know.


BUT - What motivated You to decide not to reply to this - from My last reply to You:





I can see what You are stating - But - as You wrote the Heating System would then be ON all of the Time - If a Stuck Zone Valve can `Bypass the Programmer` regarding supplying a Live Feed to the Boiler and Pump.


Regards,

Chris

 

[sambotc]

Hi chris,

No not annoyed at all, if it cam across like that I can only apologize. I'm actually on my mobile phone hence the bad grammar and blocks of text! I hope I explained it ok, as coming from the heating trade myself I appreciate it may not work how you had imagined?

I'm not quite sure what you mean on the above question that I missed, I thought I had explained that in the previous post or the power for boiler comes from the valve rather than programmer? If that's not what you were asking I'm sorry, maybe I am getting the wrong end of the stick.

I have to be honest I can't think of a time where I have come across a valve which jams the heating on, but as a live source is available in the valve it is possible, I can only presume it is not that common due to the internal design of the valve itself??

 

[chris murphy]

"Hello sambotc",


I just wanted to ask IF I was agravating You in some way with My Questions / Comments - As I definitely do NOT want to do that.


I was asking IF the Zone Valve was `Stuck` in the Open Position where the Microswitch would supply Power to the Boiler / Heating System - would that not mean that the Heating would be ON - Constantly ?

And as I mentioned in My Post to phil - The Boiler / Heating System in this particular Problem comes ON unexpectedly / at Night - How could a Zone Valve where the Heating has been OFF then supply Power to Turn On the Heating / Boiler & Pump in the middle of the Night - presumeably long after any ON Setting on the Programmer ?

I mention the Programmer again ONLY to indicate that the Heating would have been OFF for a period of Time before it `Comes On` at Night / Unexpected Times.

Just to add - I definitely know the Sequence that operates a Heating System Controls - and I have done for many Years.


Regards,

Chris

 

[sambotc]

Yeah it would mean it would be on all the time and as I say I haven't come across that personally myself, normally the valve will jan and allow water to pass or the motor will stop operating and the boiler won't fire.

I think we went a little bit off topic so I was not strictly relating this all to the above issue. Without a little more detail I think it would be hard to try and identify the issue on this particular problem.

Sam