CH turning on by itself problem

brooky25 said:

Hi, Been to a job today with exactly the same kind of symptoms. Boiler firing up in the middle of the night when programmer is turned off but the pump is not running so pipes are banging because of heat waking the customer up. Thought it was a problem with frost stat as this is what plumber said to me. This is a s plan system but boiler is in garage, side of boiler is a 15 amp switch and frost stat. Also there is a pipe stat above boiler. Cannot understand why it would have a pipe stat as I thought boiler would have a built in overheat stat and frost stat. When I turned up the pipe stat from 20 c to 40 c the boiler fan fired up ? So basically when pipe stat falls below 20 c it fires up the boiler. Back of frost has a perm live into terminal 3 which should be sw feed back up the yellow in my book? this has confused me all afternoon and hopefully I have now sorted problem by removing the pipe stat. I thought that the pipe stat would be for overheat not call or am i wrong.
Any advice would be great to clear my head up
thanks

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"Hello brooky25",


I am a Heating Engineer - the reason for the Pipe Thermostat being fitted in conjunction with the Frost Thermostat is because the Boiler only needs to Fire occasionally for Short Periods of Time during Cold Temperatures to Stop it from Freezing - the Boiler does NOT need to Fire until the Boiler Thermostat Setting is reached.

The Pipe Thermostat is fitted so that the Boiler only Fires to remove the Immediate `Threat` of Freezing - So it does not need the Boiler to reach a High Temperature such as would be on the Boiler Thermostat Setting.

However from what You described it sounds like it was NOT wired Correctly - it should only be operating in conjunction with the Frost Thermostat - and I am assuming that it was not Cold enough when You were doing this to have caused the Frost Thermostat to be in Operation [?].


I would advise You to refit the Pipe Thermostat as the Combination of a Frost Thermostat and a Pipe Thermostat IS the Correct Method of providing Frost Protection for the Boiler in this instance.


Regards,


Chris

Many thanks for the advice Chris, I do believe you are right iv'e been thinking about this all night. I am going to go back and sort the problem. The trouble is new tennants have only been in property 3 weeks and previous tennants have moved to Aus, so I don't know how long the problem has been there or who has messed with it. Need to start from beginning with this as in my head there should be sl,n,e going to boiler from orange on valves to call for heat and perm l,n going to frost stat then sw out of frost stat through pipe stat back to call on boiler. Am I correct ?

P.s Sorry for hijacking this thread

brooky25 said:

Many thanks for the advice Chris, I do believe you are right iv'e been thinking about this all night. I am going to go back and sort the problem. The trouble is new tennants have only been in property 3 weeks and previous tennants have moved to Aus, so I don't know how long the problem has been there or who has messed with it. Need to start from beginning with this as in my head there should be sl,n,e going to boiler from orange on valves to call for heat and perm l,n going to frost stat then sw out of frost stat through pipe stat back to call on boiler. Am I correct ?

P.s Sorry for hijacking this thread

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"Hello brooky25",


Sorry if this is Disappointing - But I will have to `Bow` to Your Electrical Knowledge / Any wiring Diagrams that You can find online / on Here - as I cannot remember How a Frost Thermostat and Pipe Thermostat should be wired.


In the Past My Heating Systems have usually been wired by a Qualified and [about last 6 - 7 Years] Registered Electrician - as it was always required by the Client that ALL Electrical Works were Tested and Certified by an NICEIC Registered Electrician / Electrical Company.


Although I do know how to Wire Up various Heating Systems `S Plan` etc. - the addition of a Frost Thermostat and a Pipe Thermostat would always require Me to be able to read the Wiring Diagram / Wiring Details.

Could I suggest that You go onto the Honeywell website where I am fairly confident that You will be able to find the Wiring Diagram for a Heating System which includes a Frost Thermostat and a Pipe Thermostat - as these Two Stats should always be used in conjunction with each other.


IF You have Time I am sure that some of the Extremely Helpful Electricians / Electrical Engineers on here will be able to perhaps Post a Diagram for these Thermostats to be wired to an `S Plan` System.


Regards,


Chris


EDIT - I have found and Attached a Screenshot from the Honeywell website regarding Frost Protection Thermostats - I hope that it will be Helpful in Identifying the Wires and where they are connected.


Chris

Thank you very much for your help Chris, after your explanation of why pipe stats are needed I have found out what the problem is. Thinking back to how its been wired ( altered ), they have wired both stats in parallel not series and I think pipe stat is on flow not return. After a quick search I now fully understand how the system works and how it should be wired. Someone has definatly altered the circuit, most prob plumber. This is what has thrown me. I am a Niceic registered electrician but these heating systems I rarely come across. All will be wired as it should be and I will post the outcome. I always seem to get jobs that others have tried and failed at to rectify. Thanks for helping me get it clear in my head it seems so simple now. (Must have had a blonde moment)
Thanks again
Lesson learnt, Never listen to a plumber who does not know how the system works

brooky25 said:

Thank you very much for your help Chris, after your explanation of why pipe stats are needed I have found out what the problem is. Thinking back to how its been wired ( altered ), they have wired both stats in parallel not series and I think pipe stat is on flow not return. After a quick search I now fully understand how the system works and how it should be wired. Someone has definatly altered the circuit, most prob plumber. This is what has thrown me. I am a Niceic registered electrician but these heating systems I rarely come across. All will be wired as it should be and I will post the outcome. I always seem to get jobs that others have tried and failed at to rectify. Thanks for helping me get it clear in my head it seems so simple now. (Must have had a blonde moment)
Thanks again
Lesson learnt, Never listen to a plumber who does not know how the system works

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"Hello brooky25",


I Edited My last Post to Attach a Small Wiring Diagram from the Honeywell website - From the Frost Thermostat section - this shows the Wires from the Frost Thermostat and Pipe Thermostat - and where they are connected to in various Wiring Plans.


I expect that you have already worked out what goes where or found a `Full` Wiring Diagram - BUT - Just in case this Helps You or others - I was Pleased to Post it.


Regards,


Chris

Yes Chris, Worked it out and your diagram confirms this. Thanks for your time and advice its much appreciated
regards
Mick

brooky25 said:

Yes Chris, Worked it out and your diagram confirms this. Thanks for your time and advice its much appreciated
regards
Mick

Click to expand...

"Hello Mick",


Its been a pleasure to be of Help - I realise that it was just the description of why the Pipe Thermostat is required that was of Help - as I would never try to advise an Electrician on Electrical Wiring.


"Thanks" for showing that You appreciated My small amount of `Help`.


Regards,


Chris