Ideal FF260 Thermistor stuck in boiler, how do I remove it?

[chrisrnuttall]

Hello

My Ideal FF260 has been boiling the water in the hot water loop recently, it does it every month or so, and the rest of the time it works perfectly. Today I removed the PCB and found black carbon deposits inside the clear housing of one of the relays so I am going to change that since I think it could be sticking closed and causing the problem.

I also want to change the thermistor, but it wont come out of its hole in the front of the heat exchanger block, I suspect that it has glued itself in due to a small amount of white paste on and around it. It is either a Boss white type sealant, or it is a thermal paste which has gone hard. I have already removed the metal locking cover disc by the way.

I have tried pulling and jiggling on the cable, I have tried a bit of WD40 down to hole to soften the paste, and I have tried pushing a bit of copper wire down the side of the cable to try to break the adhesion. Nothing will budge it.

Does anyone have a good trick for getting it out of its hole?

Lastly, is this a blind hole? I think it must be but I am not 100% sure. If it is, and push comes to shove could I give the thermistor a good hard pull with pliers and if it breaks can I then use a drill bit to clean the remnants out of the hole. Or will I risk getting bits of crud inside the heat exchanger?

Thanks

Chris

 

[Agile]

On that model the casing which you have to remove to access the PCB and the NTC sensor is also the combustion chamber cover which a DIYer should not be opening!

In that case I should not be advising you about what you want to do.

As far as I am aware the sensor is just a push fit into its hole. Seems very unlikely the sensor is at fault. In any case it can be monitored at the PCB end.

Ton y

 

[chrisrnuttall]

Thank Tony

The thermistor is reading 200 Ohms at the pcb end with the boiler cold, I haven't tried reading it as the boiler cools from hot yet though, but the 200 ohm reading suggests it is not broken to me. I just wanted to swap it out whilst I was working on the boiler.

I think it should be a loose push fit too, but it is firmly stuck in place. Has anyone seen this happen before?

I was aware that I shouldn't work on the gas parts since I am not certified, but didn't realise I wasn't even allowed to remove the cover. I'm not a total amateur however being head interdisciplinary engineer at a design / manufacturing company.

thanks

Chris

 

[45yearsagasman]

Has anyone seen this happen before?

Yep, seen it a few times and they're a pig of a job to get out. Best left to a pro.

 

[chrisrnuttall]

Right then, I'll change the pcb relay and see if that cures the intermittent boiling.

Thanks for the help

 

[Dan Robinson]

Not speaking of the OP as such; but it's funny how many people, when told they are working on something they shouldn't, all of a sudden have a tenuous link to a career on "engineering", and that their chosen field of course makes them able to work to gas appliances.

And at the same time demonstrate all the engineering abilities of the tea-boy. That wazzock from network rail springs to mind.

 

[chrisrnuttall]

Just wanted to re-assure Tony that I will not be blowing myself up based on any advice given here. I am a qualified mech engineer with sixteen years diverse hands-on experience, not Reg Prescott!

With the OP in mind, does anyone know why a thermistor should become glued into its aperture in the exchanger front?

Thanks

 

[ianmcd]

The white paste that you refer to is heat sink paste and I have seen it going hard and jamming the thermistor in, can be a job and a half to get out so if its ok I would leave it in, if you do have to get it out try and get the heat exchanger as hot as possible and it will make it easier to get the thermistor out

 

[chrisrnuttall]

Excellent. Thanks very much!

 

[Agile]

I have an Ideal Classic NF60 and I measured the NTC sensor this evening and it was 10 K.

It can be measured on the plug at the PCB end ( as this tests the leads as well ).

Few boiler NTCs would only be 200 ohms. I wonder if you correctly measured it though. Odd no one else commented on it.

Tony

 

[chrisrnuttall]

I was using my horrible £10 non-auto ranging Homebase meter. I'll get the Fluke on it and test it properly asap.

Thanks for that.

 

[chrisrnuttall]

My Fluke reads 10.77K with the boiler cold. Think I'll throw the other meter in the bin! It was a get-out-of-trouble purchase a few years ago.

 

[Boilerman2]

I'm a Qualified Mechanical engineer in the Combustion field - don't make me competent to work on my Car, re-wire my House, etc etc,
I have just spent upward of £2k getting my house hold electrics sorted properly by a pro who can certify his work

thats what life in Brittain is about these days, if you don't like it move overseas such as France whre they don't seem to give a damn about Euro this and Euro that!!

Rant over!!