BOILER INCONSTSENTLY TURNING OFF AND ON!

[Tubbsup]

The boiler I have is a gas fired Stelrad Ideal Classic NF 60. The instruction manual with it is dated 1991. A possible important point to add is that I only use the boiler for the central heating, this means during the summer months I fire up the boiler once a month just to give the system a run.

The problem I have is this: a few days ago the boiler just fired up on its own accord, even though the room temperature had not fallen to the wall thermostat dial setting. I then moved the thermostat wall dial clock-wise and anti-clock, got the usual clicking sounds but this had no effect at all on the boiler, it just kept on working; to confirm – the wall thermostat dial had no effect on the turning on or off of the boiler.
To add, everything on the central heating system appears to be working fine, the radiators heating up well and pump running. There are 7 rads. in the house, of which only 4 are being used. All serviced by just one thermostat.

To stop the boiler I had to turn off the central heating switch, which is next to the timer, the pump and emersion heater.
Later on that day I turned this switch back on and found that the boiler DID NOT immediately fire up. This was good news. I then turned up the wall thermostat dial, got the click when it met with the room temperature and found the boiler started up. So it was now working correctly. Then, yesterday, the boiler again fired up on its own accord even though the room temperature hadn't dropped enough. I again turned the wall thermostat dial left and right and, as before, the stat had no effect in turning the boiler on or off.
I again turned off the central heating switch. Later that same day I turned it back on and as of now the system is working fine.

I have taken off the boiler casing and I'm wondering if the issue is with the boiler thermostat. There is a wire/lead going into the top left hand corner of the Heat Exchange. Is this where the stat is? And does anyone think this wire/lead/stat will need replacing? (The instruction manual I have has a diagram of a breakdown of the parts of the boiler, but the manual says it's for an Ideal Classic NF 30, whereas I have an NF 60. In the manual drawing there is no wire/lead going into the Heat Exchange – so the boiler I have is slightly different).

I would be very grateful if someone could help me with this problem as paying someone to come out and repair it will cause me an even greater problem.

Thank you

Paul

 

[TicklyT]

Is the boiler switching under the control of the hot water temperature?

You may have the hot water control switched off, but a fault in a 3-way valve (if fitted) could leave the hot water cylinder thermostat controlling the boiler.

Why choose to use an immersion heater to heat your water if you have a functioning gas boiler?

 

[kevplumb]

A possible important point to add is that I only use the boiler for the central heating,

 

[Tubbsup]

Hi Ticklyt,

Thank you for your message.

With the emersion heater/hot water cylinder:

1) Because I have some issues with the piping on the hot water side in my house, which still needs fixing, I do not use either the emersion heater or gas heated water via the boiler for my hot water needs.

2) Because the timer switch won't allow me to just set it for central heating the switch is then set for both central heating and water heating.

3) With the timer switch set on both I have set the cylinder thermostat at zero so that the water in the cylinder isn't being heated up.

With the 3 way valve you mentioned the picture I have with this message is similar to what I have. (I hope the picture comes out ok? I believe I have followed correctly the picture attachment instructions?).

Thank you again.

Untitled

• Tubbsup
• 11 Nov 2009
• 1

 

[Tubbsup]

Hi Again,

If any one has any questions, please feel free to ask?

 

[Agile]

From what you are telling us you dont have hot water pipes to the bath and basins and it would seem its been like that for ages!

Many people would find it odd that you dont deal with that as a priority.

If the boiler fires up on its own then there may be a frost stat bringing it on because its set too high?

Tony

 

[Tubbsup]

Many thanks for your reply Agile.

With hot water issue, I worry too much about the costs of repairs, and have found in time I can adequately meet what hot water needs I have through other means.

If the problem is the Frost stat, would you know where that is on a Stelrad Ideal Classic NF 60 boiler?

Also would you think that the wire/lead that is going into the top left hand corner of the heat exchange is connected to a bolier stat? Could this be the frost stat?

And is this easy to replace?

Thanks again.

 

[Agile]

A frost stat is an expernal device often looking like a room stat but sometimes with no visible dial.

The boiler stat is not your problem.

Tony

 

[kevplumb]

nf 60 dont have an intregal frost stat

if you have one its outside the boiler

 

[Tubbsup]

Thanks Agile and Kevplumb,

I am thinking I don't have an external frost stat?

Looking over the system I can find the hot water cyliner, the mains switch, the 3 way valve, the pump, the timer, the Aerjec II de-aerator, and one room/wall stat with a dial. That appears to be it.

If the problem isn't related to a frost stat what other reason could we find for the boiler inconsistenly turning on and off?

 

[Agile]

It could be a fault in the motor valve or the programmer.

Tony

 

[jackthom]

I suppose it is possible that the DHW cylinder thermostat is playing up and switching on occasionally.

 

[Tubbsup]

Thanks Jackthom, and Agile for your continued interest.

The interesting thing here for me is that both your comments about the inconsistent turning off and on of the boiler relate to devices that are away from the boiler - this could make for a cheaper repair?

3 points to comment on:

1) As I don't actually use the Hot water cylinder would it be a good idea to disconnect the stat wiring to eliminate that as a potential trouble spot?

2) Is there a way I can check whether the programmer is faulty?

3) With the 3 way motor valve: is there a way that I can check whether that is misbehaving?

Thanks again.

 

[jackthom]

if you disconnect the cylinder stat, there should be no way the programmer can cause the boiler to fire up, except of course when the room thermostat calls for CH.

 

[Tubbsup]

Many thanks for that Jackthom.

I will go ahead a disconnect the wiring for the cylinder thermostat.

Any thoughts with checking to see if a programmer or a 3 way motor valve are faulty.

Also, allow me mention what the 3 way motor valve is doing at this moment: at present the boiler is behaving itself, i.e. it is working correctly - turning on and off - in conjunction with the room/wall thermostat. The room temperature itself has not decreased to the wall/room stat reading since using it last night; with this in mind the pump is cold to the touch, as are all the surrounding pipes, including pipes in and out of the motor valve, but the casing of the motor valve itself is warm to the touch - is this ok? Also the lever on the valve is to the far left, and can be manually easily moved without resistance to the far right, where it remains until I manually return it to the far left again. Again, this is with the heating not being activated or being on for the past 12 hours or so.

Thank you.