Thermocouple gone after 5 months!

[staithes14]

Back in May I had problems with the Glowworm Fuelsaver 30 - pilot wouldn't stay lit. After advice from this forum I had a new thermocouple fitted which cured the problem.

Started using the CH again a few days ago and it's been OK but now the problem is repeating itself. The pilot lights OK and is a good strong flame, but goes out soon as I release the knob.

As it's the same problem in every way, i'm assuming the thermocouple's gone again but how likely or common is it for a new one to go so soon? It was just a cheap universal from Plumco.

 

[PEDANTICVINDICTIVEMAN]

Might not be t/couple this time, could be gas valve, you ain't gonna know till
man comes and check it for you, if your lucky it will be the cheap t/couple.

 

[StevenJames125]

could be a few things - all gas related though

try holding the button in for a longer periold and releasing the button very very slowly

 

[Agile]

To get an idea of the cause of the problem the voltage in circuit would need to be measured.

However, the thermocouple is a safety device and should not be the subject of DIY investigation/repairs.

I get the impression that not many RGIs are experienced at electronic measumements on TCs.

Tony

 

[StevenJames125]

Agile is right - thermocouple's can always fluctuate when they are starting to fail - but you need to check the mVoltage at the GV end

 

[spraggo]

You say that you have a good strong pilot flame?. This flame should be strong enough to cause the thermocouple to glow a dull red, If it is glowing bright red then it will eventually melt it. The pilot flame is adjustable at the gas valve.

 

[onlyfitidealboilers]

it may be in thew wrong place. flame should only touch the tip.

 

[boabcelt]

If I recall correctly, the fuelsaver has an overheat stat which interrupts the pilot. Check this hasn't happened.

 

[Agile]

If I recall correctly, the fuelsaver has an overheat stat which interrupts the pilot. Check this hasn't happened.[/quote]

So you think the OP should start doing his own gas work?

 

[kevplumb]

if there is an interrupter inline with the thermocouple and it has failed it has failed safe

what the flying has that got to do with gas

plenty of boilers didn't have an overheat stat before the adoption of sealed systems

did the OP say he had a sealed system

i think not

So you think the OP should start doing his own gas work?

no i think you should start leaving the bottle alone

 

[Agile]

An o/h stat in seriew with a thermocouple is a safety device controlling gas combustion.

One of the most common faults with these is that they develop higher resistance contacts however measuring their performance needs to be checked by a very competent engineer who understands how it needs to be done.

Tony

 

[StevenJames125]

Interesting - how do they develop higher resistance contacts Agile?

 

[kevplumb]

oooh don't ask your not a highly qualified engineer

orr a waffle merchant

 

[staithes14]

Steady on lads, no fighting over an old boiler!

After refusing to work all day, I decided to have one last go last night. Held the button in for over a minute, and it worked! Pilot stayed on all night and at present, is still on. I don't want to spend money on it, as we're getting a combo boiler in the new year, so fingers crossed it will limp along until then.

 

[Agile]

Interesting - how do they develop higher resistance contacts Agile?

Oxidisation of the contact surface.