Wiring on my heating controls (Boiler keeps firing)

[jackthemac]

Hi.

I have a DANESMOOR 26/32 with a Horstmann 425 Diadem programmer.

I have a thermostat on the boiler only and even with both the ch/hw switched off on the programmer It still keeps firing up every so often unless you turn the stat right down.

Dont realy want it keeping itself on if Im out all day wasting oil so there must be a simple soloution to do with the wiring to make the boiler turn off when the programmer is off.


I could probably do it my self with a little guidance.

Thanks

Shaun

 

[Lectrician]

Is there any zone valves? The microswitches inside these can stick which will keep the boiler firing.

 

[jackthemac]

The boiler stops firing when the thermostat is turned right down/off.

Thats why I thought it may have just been wired up with a permanent live from the programmer when it was first installed.

I will go check for micro switches.

 

[jackthemac]

Just took some pics, hopefully this will help.

 

[jackthemac]

could a spark look at the wiring diagram in relation to my pics as it doesnt look the same.

http://www.horstmann.co.uk/downloads/ElectronicDocuments/Central-Heating/425-InstallationGuide.pdf

 

[jackthemac]

This is what I can make of it.

Seems like the programmer has not been wired to turn the boiler on and off when its switched to the off position.

Can someone confirm and advise on how to correct this. I have a rough idea but would be good to get an second opinion.

thanks

 

[EFLImpudence]

I have a thermostat on the boiler only and even with both the ch/hw switched off on the programmer It still keeps firing up every so often unless you turn the stat right down.

misread

 

[ericmark]

There are many ways to wire a boiler and much depends on what software the boiler has within it. Some boilers are very clever and they monitor how long it ran last time.

The idea is if the water returns hot within x second then increase the time before it fires next. If however it takes y seconds before its hot then reduce the time before next time it fires.

This system relies on correct installation. Which normally means a pressure bypass valve and thermostatic radiator valves on every radiator.

However the old system required one radiator not to have a thermostatic radiator valve and not all plumbers are up to date as to what is required.

If a small radiator has no valve it may work OK but if the radiator without a thermostatic valve is just a little too big then the whole system fails.

Teaching plumbers (i.e. in the main not got the skills required to be electricians) how a modern system works seems to have fallen on deaf ears. As a result there are many systems which are not installed as the manufacturer instructed.

As with many trades only if all else fails are instructions read.

So although the problem may well be with a faulty valve or incorrect wiring it can also be down to poor plumbing.

So what you need to do is work out which trade has let you down. I am sure I could read the installation instructions for your boiler but to be honest I have not the time.

But first question must be is it a condensating boiler and if it is are there TRV on every radiator.

 

[jackthemac]

Hmmm thanks for the reply but think you are over complicating matters. (with respect )

The boiler functions fine, I just want it to work correct with the programmer.

It is quite clear to me (not a spark) that the programmer wiring has been wired to make the boiler stay on permanently unless otherwise turned down on the boiler itself. All I want to do is wire the permanent live through the correct terminals in the programmer so when the boiler can go off with the timer.

 

[ericmark]

But that is the point the boiler should run unless the return water is hot. OK a time switch may turn it off when not in the house but one has to be very careful not to upset the boilers inbuilt computer by adding extras.

 

[jackthemac]

I dont want the boiler firing up all the time wasting oil when Im not using it.

Thats just silly.

Right now I am turning the thermostat right down when Im not using it to prevent this. All I want is the programmer to do this for me.

 

[EFLImpudence]

If there is no room thermostat a boiler will keep firing when on.

However it should not fire when the programmer is turned off.

I cannot make out the wiring from the pictures but if you have the diagram for the timer, zone valve and system used (diagrams on google) it can be rewired from scratch.

Can we have a picture of the valve? or do you know if it is a mid-position one or are there two?
Is there a room thermostat?

 

[Lectrician]

Is there any valves, or just the pump in the picture?

Is the pump just pumping the radiators? Not the water? Is there a second pump for the water?

It does look like it is wired incorrectly.

Your timeclock is only a single channel version, and so is only switching the pump. This is in effect wired correctly.

You need to get yourself a two channel timeclock, and alter the wiring accordingly. If there is only the pump and boiler, it sounds like a typical gravity system, and so set the timeclock to "gravity" on the switch on the back, the HW output would power the boiler, and the CH output would power the pump. When you turn the CH on, the water will also be turned on (thats what the gravity switch does), and when you turn the HW on, just the boiler will fire.

Eric is over complicating things IMO too.

 

[jackthemac]

Hi thanks for the replys.

Its gravity fed hot water with a combi h/w tank so does this mean there is no other pump?

The pressure isnt good I know that much.

Just away to work but will go over these posts in more detail this afternoon,

thanks again.

 

[Lectrician]

Certainly sounds like you have gravity hot water to the cylinder and pumped central heating.

If it was me, I would get one of these (easy to use):
http://www.screwfix.com/p/drayton-lp522-mk4-programmer/20673

And wire it as below, making sure you set the commisioning switch to GRAVITY: