Ideal classic nf 40 sealed system boiler with megaflow tank

[southseapirate1]

Ideal classic nf 40 sealed system boiler with megaflow tank
Hi,
i'm a DIYer

I have a ideal classic nf 40 sealed system boiler with a megaflow tank fitted upstairs. the problem I have is even though there is no demand from the timer clock for heating or hot water the pump fitted on top of the boiler is constanly running thats even if the main switch on the boiler is in the off position. If I turn on the main switch on the boiler the boiler will fire up even without the timer clock demanding heating or hot water. I have tried disconnecting main components separatley to see if that the problem i.e thermostat, air press switch over heat thermostat but as I'm not too sure I'm really stuck. i'd be very grateful if anyone could help with a little direction.

Have been in the house about six months and it hasn't done this before. Doing a bit of research could it be the pump thermostat over ride switch. The pump may still think there is hot water in the system so to safe guard boiler its moving it around unitl it gets cooler. The water in the heating system and hot water is cold though.

Thanks

 

[spraggo]

The pump over run switch on the boiler is stuck open.

 

[southseapirate1]

Thank you for your diagnose I'm most grateful. Can I fix the problem or do I need a spare part? do you by chance no where it's located within the boiler?

Thanks

 

[spraggo]

Thanks[/quote]
You will need to replace it with new, I do not have the details of this boiler at hand but, they are usually identified as being the size of say a gents wrist watch with three wires attached around the side with spade connectors and a thin copper wire extending from its centre leading to a phial inserted into the water section of the boiler

 

[southseapirate1]

Found it and the temp probe goes into the heat exchanger. I will look at changing it.
Funny thing is the pumps has now stopped.

 

[southseapirate1]

Put it all back togehter again but now the pump is ruuning again. Trying to think if i'd turned power off at the fuse spur and mistakingly thouhgt pump had stopped by it's self. But can confirm pump is on and bolier is not fired up so will change thermostat as kindly suggested. Many thanks for you help. I will let you know if it cures it.

 

[spraggo]

Found it and the temp probe goes into the heat exchanger. I will look at changing it.
Funny thing is the pumps has now stopped.

Yes, sometimes a slight bump in the vicinity of this switch will open it, as explained it was stuck open. But I think you will find that this problem will re occur.

 

[southseapirate1]

Kindly asking one more question. In the manual booklet it states the part ive identified that needs replaceing from your guidance is called a overheat thermostat. Just checking it's the same thing. It's def a thermosat that goes into the left hand side of the heat exchanger.

 

[spraggo]

Kindly asking one more question. In the manual booklet it states the part ive identified that needs replaceing from your guidance is called a overheat thermostat. Just checking it's the same thing. It's def a thermosat that goes into the left hand side of the heat exchanger.

No its not the same thing, the over heat stat has only two wires attached to it.

 

[southseapirate1]

oh right good job I asked. Looking at the heat exchanger there seems to be a sensing line going into it at the top left hand corner. It looks like wires wrapped to protect it from heat. They make there way back to the PCB. The other entry into the heat exchanger looks like a temp probe, looks like a capilary tube that runs back to a wrist watch size circlular thermostat which in turn has wires running back to the PCB, i would you say thats that it??

 

[Razor900]

I'd stop playing with the boiler and check the external controls

 

[spraggo]

oh right good job I asked. Looking at the heat exchanger there seems to be a sensing line going into it at the top left hand corner. It looks like wires wrapped to protect it from heat. They make there way back to the PCB. The other entry into the heat exchanger looks like a temp probe, looks like a capilary tube that runs back to a wrist watch size circlular thermostat which in turn has wires running back to the PCB, i would you say thats that it??

If it has three wires connected to it, yes. The three wires are, permanent live in, switched live in and live to pump out. All 240v.

 

[southseapirate1]

External controls ??? just checking which ones ?

 

[southseapirate1]

Thanks Spraggo will confirm with your valubale advice. Really appreciate your guidance.

 

[spraggo]

Thanks Spraggo will confirm with your valubale advice. Really appreciate your guidance.

No problem, let me know if my diagnosis was right or wrong. If right press the thanks button.