Four ring stainless hob, 1x large; 2x medium; 1x small rings, bought 3
years ago, with a 5 year guarantee - except I couldn't find the receipt
or remember where it was bought from, just an online source.

Soon after I installed it, the large ring, then the smallest ring,
began giving problems getting them to stay lit, the valves were not
reliably holding in once lit - a bit of a lottery.

Yesterday evening, I got a roundtuit. I wasted ages, struggling to get
the entire hob out of the worktop, thinking access would be from below.
I was WRONG, what wasn't obvious was that the entire top plate cover
could be removed without disturbing the actual hob from the worktop.
Remove cast iron pan supports, the control knobs, then two screws
either side of each burner and off it came, giving full access to the
entire gubbins - the work of minutes, not the hour I had spent so far
getting the hob out.

There was nothing obviously amiss at all, so it was pointing towards
the individual gas valves being a bit iffy, or the 'thermocouples'.
Undetered, I disconnected the 'thermocouples' from the gas valves,
cleaned up the contacts and reassembled and tested. Now they all work
fine. There was some dirt from some where on the contacts, but no
obvious way for it to get in there other than during manufacture. The
base panel, pipework valves etc. were quite clean. I rested again this
morning and all still working fine, the valves hold in a fraction of a
second after lighting.

I called them 'thermocouples' because they are not like any
thermocouple I have ever seen before, hence my posting this. The sensor
ends looked like TC's, but they each had their own separate earth wire.
The TC seemed to have a a tiny tube, then at the end they had a small
plastic unit (A), with a pin which pushed into the tube end and a
spring contact where it connected to the valve. A sleave nut fitted
over the end of the tube flange, item A and tightened onto the valve. A
seemed to have 'something' inside the clear plastic tube.

What sort of 'TC' is this, for holding the valves in please? I have
heard of a system which uses a voltage generated by the gas itself
burning. Might this be one of those?

Harry Bloomfield wrote:

I called them 'thermocouples' because they are not like any
thermocouple I have ever seen before, hence my posting this.

Usually called flame failure devices, but they are thermocouples.

What sort of 'TC' is this

http://gasproducts.co.uk/catering/flame-failure-devices.html

On 03/07/2016 09:38, Harry Bloomfield wrote:
There was some dirt from some where on the contacts, but no
obvious way for it to get in there other than during manufacture.


We converted my old office into two flats. The builder supplied what I
presume were the cheapest hobs he could find. Both stopped working
because of the flame failure devices within a couple of years. I'm sure
this was a manufacturing fault similar to what you found.

We just replaced the pieces of junk.

In article ,
Harry Bloomfield wrote:
Four ring stainless hob, 1x large; 2x medium; 1x small rings, bought 3
years ago, with a 5 year guarantee - except I couldn't find the receipt
or remember where it was bought from, just an online source.

You don't need the receipt just evidence of having purchased the item.
Look at your old bank / credit card statements from around the time you
bought it and this will give evidence of the purchase and also the account
of the seller. Then look at your emails from that time as you should have
an online email receipt from the seller. Use a search engine to find the
contact details and invoke the 5 year guarantee. - sorted or perhaps not?
:-)

Alan

--


Using an ARMX6

Harry Bloomfield wrote:
Four ring stainless hob, 1x large; 2x medium; 1x small rings, bought 3
years ago, with a 5 year guarantee - except I couldn't find the receipt
or remember where it was bought from, just an online source.

Soon after I installed it, the large ring, then the smallest ring, began
giving problems getting them to stay lit, the valves were not reliably
holding in once lit - a bit of a lottery.

Yesterday evening, I got a roundtuit. I wasted ages, struggling to get
the entire hob out of the worktop, thinking access would be from below.
I was WRONG, what wasn't obvious was that the entire top plate cover
could be removed without disturbing the actual hob from the worktop.
Remove cast iron pan supports, the control knobs, then two screws either
side of each burner and off it came, giving full access to the entire
gubbins - the work of minutes, not the hour I had spent so far getting
the hob out.

There was nothing obviously amiss at all, so it was pointing towards the
individual gas valves being a bit iffy, or the 'thermocouples'.
Undetered, I disconnected the 'thermocouples' from the gas valves,
cleaned up the contacts and reassembled and tested. Now they all work
fine. There was some dirt from some where on the contacts, but no
obvious way for it to get in there other than during manufacture. The
base panel, pipework valves etc. were quite clean. I rested again this
morning and all still working fine, the valves hold in a fraction of a
second after lighting.

I called them 'thermocouples' because they are not like any thermocouple
I have ever seen before, hence my posting this. The sensor ends looked
like TC's, but they each had their own separate earth wire. The TC
seemed to have a a tiny tube, then at the end they had a small plastic
unit (A), with a pin which pushed into the tube end and a spring contact
where it connected to the valve. A sleave nut fitted over the end of the
tube flange, item A and tightened onto the valve. A seemed to have
'something' inside the clear plastic tube.

What sort of 'TC' is this, for holding the valves in please? I have
heard of a system which uses a voltage generated by the gas itself
burning. Might this be one of those?

Check that the pipe delivering gas is big enough to supply the flow
needed for that particular hob, which may be more than the previous one.

On Sunday, 3 July 2016 09:38:43 UTC+1, Harry Bloomfield wrote:
Four ring stainless hob, 1x large; 2x medium; 1x small rings, bought 3
years ago, with a 5 year guarantee - except I couldn't find the receipt
or remember where it was bought from, just an online source.

Soon after I installed it, the large ring, then the smallest ring,
began giving problems getting them to stay lit, the valves were not
reliably holding in once lit - a bit of a lottery.

Yesterday evening, I got a roundtuit. I wasted ages, struggling to get
the entire hob out of the worktop, thinking access would be from below.
I was WRONG, what wasn't obvious was that the entire top plate cover
could be removed without disturbing the actual hob from the worktop.
Remove cast iron pan supports, the control knobs, then two screws
either side of each burner and off it came, giving full access to the
entire gubbins - the work of minutes, not the hour I had spent so far
getting the hob out.

There was nothing obviously amiss at all, so it was pointing towards
the individual gas valves being a bit iffy, or the 'thermocouples'.
Undetered, I disconnected the 'thermocouples' from the gas valves,
cleaned up the contacts and reassembled and tested. Now they all work
fine. There was some dirt from some where on the contacts, but no
obvious way for it to get in there other than during manufacture. The
base panel, pipework valves etc. were quite clean. I rested again this
morning and all still working fine, the valves hold in a fraction of a
second after lighting.

I called them 'thermocouples' because they are not like any
thermocouple I have ever seen before, hence my posting this. The sensor
ends looked like TC's, but they each had their own separate earth wire.
The TC seemed to have a a tiny tube, then at the end they had a small
plastic unit (A), with a pin which pushed into the tube end and a
spring contact where it connected to the valve. A sleave nut fitted
over the end of the tube flange, item A and tightened onto the valve. A
seemed to have 'something' inside the clear plastic tube.

What sort of 'TC' is this, for holding the valves in please? I have
heard of a system which uses a voltage generated by the gas itself
burning. Might this be one of those?

Why are you asking after you went to the bother you did?
I think you will find that the thermocouples are designed so that your gas will NOT stay lit unless you reassure the stove that you mean business. It is a safety device that makes you keep your finger on the button long enough for it to believe you (seven seconds I was told.)

Alan Dawes a écrit :
You don't need the receipt just evidence of having purchased the item.
Look at your old bank / credit card statements from around the time you
bought it and this will give evidence of the purchase and also the account
of the seller. Then look at your emails from that time as you should have
an online email receipt from the seller. Use a search engine to find the
contact details and invoke the 5 year guarantee. - sorted or perhaps not?
:-)

It was a purchase made by my deceased partner, so impossible to trace
now. I oft find it easier to at least attempt to fix things myself,
than invoke warranties. In this case it was an easy fix.

F Murtz a écrit :
Check that the pipe delivering gas is big enough to supply the flow needed
for that particular hob, which may be more than the previous one.

It is more than big enough, it feeds the double oven and boiler - the
problem was evident with no other gas in use. It was simply the flame
failure system at fault.

Weatherlawyer a écrit :
Why are you asking after you went to the bother you did?
I think you will find that the thermocouples are designed so that your gas
will NOT stay lit unless you reassure the stove that you mean business. It is
a safety device that makes you keep your finger on the button long enough for
it to believe you (seven seconds I was told.)

I am well aware of their purpose, I was just puzzled by the device used
- not a TC type I have seen before (see my quote below).

'I called them 'thermocouples' because they are not like any
thermocouple I have ever seen before, hence my posting this. The sensor
ends looked like TC's, but they each had their own separate earth wire.
The TC seemed to have a a tiny tube, then at the end they had a small
plastic unit (A), with a pin which pushed into the tube end and a
spring contact where it connected to the valve. A sleave nut fitted
over the end of the tube flange, item A and tightened onto the valve. A
seemed to have 'something' inside the clear plastic tube.

What sort of 'TC' is this, for holding the valves in please? I have
heard of a system which uses a voltage generated by the gas itself
burning. Might this be one of those?'

Weatherlawyer a écrit :
It is a safety device that makes you keep your finger on the button long
enough for it to believe you (seven seconds I was told.)

They usually say hold it in for 10 seconds. The hob in my caravan only
needs a fraction of a second, as does the now fixed kitchen hob.

On Sunday, 3 July 2016 09:38:43 UTC+1, Harry Bloomfield wrote:
Four ring stainless hob, 1x large; 2x medium; 1x small rings, bought 3
years ago, with a 5 year guarantee - except I couldn't find the receipt
or remember where it was bought from, just an online source.

Soon after I installed it, the large ring, then the smallest ring,
began giving problems getting them to stay lit, the valves were not
reliably holding in once lit - a bit of a lottery.

Yesterday evening, I got a roundtuit. I wasted ages, struggling to get
the entire hob out of the worktop, thinking access would be from below.
I was WRONG, what wasn't obvious was that the entire top plate cover
could be removed without disturbing the actual hob from the worktop.
Remove cast iron pan supports, the control knobs, then two screws
either side of each burner and off it came, giving full access to the
entire gubbins - the work of minutes, not the hour I had spent so far
getting the hob out.

There was nothing obviously amiss at all, so it was pointing towards
the individual gas valves being a bit iffy, or the 'thermocouples'.
Undetered, I disconnected the 'thermocouples' from the gas valves,
cleaned up the contacts and reassembled and tested. Now they all work
fine. There was some dirt from some where on the contacts, but no
obvious way for it to get in there other than during manufacture. The
base panel, pipework valves etc. were quite clean. I rested again this
morning and all still working fine, the valves hold in a fraction of a
second after lighting.

I called them 'thermocouples' because they are not like any
thermocouple I have ever seen before, hence my posting this. The sensor
ends looked like TC's, but they each had their own separate earth wire.
The TC seemed to have a a tiny tube, then at the end they had a small
plastic unit (A), with a pin which pushed into the tube end and a
spring contact where it connected to the valve. A sleave nut fitted
over the end of the tube flange, item A and tightened onto the valve. A
seemed to have 'something' inside the clear plastic tube.

What sort of 'TC' is this, for holding the valves in please? I have
heard of a system which uses a voltage generated by the gas itself
burning. Might this be one of those?

All thermocouples generate electricity by means of a joint of dissimilar metals being heated. Usually concentric.
The tiny voltage holds a solenoid valve open.
Takes a few seconds to heat up.
Flame failure means the valve shuts.

https://en.wikipedia.org/wiki/Thermocouple