Simmerstat Life

[Johntheo5]

I have a 2008 Belling 90E cooker which uses MP-V01-SVC simmerstats, original manufacturer, Invensys.
These have a relativey short life of ~ 2/2.5 years.
I never see any complaints re this short life as this type of simmerstat must be widely used, wonder is this a fairly typical lifespan?, only 2 people in this house.
I had a Creeda Cavalier for 20 years or more cooking for a family of 5 with not one simmerstat failure.

I opened one (failed) up today, and can see that the PCB eventually wears down where the baynot strip end in the cover contacts it due to the very slight pivoting movement of the 5W heating element/bimetal strip as it opens/closes, (rises/falls) the main contacts, the element the will then heat continuously as the 5W heater stops working, until switched off.
Most of the cookers I see in Spain don't use this system, the elements have several spirals and are switched in directly by the control switch.

Look at the red arrows in the attached, if interested.

 

[FrodoOne]

I have a 2008 Belling 90E cooker which uses MP-V01-SVC simmerstats, original manufacturer, Invensys.
These have a relativey (sic) short life of ~ 2/2.5 years.

I opened one (failed) up today, and can see that the PCB eventually wears down where the baynot (sic) strip end in the cover contacts it due to the very slight pivoting movement of the 5W heating element/bimetal strip as it opens/closes, (rises/falls) the main contacts, the element the will then heat continuously as the 5W heater stops working, until switched off.
Most of the cookers I see in Spain don't use this system, the elements have several spirals and are switched in directly by the control switch.

Look at the red arrows in the attached, if interested.

Blurry photos - and convoluted question.

Those Contacts may be too weak for purpose (!)

Presumably, the 5W refers to the power used by the "Bi-Metal Strip",
NOT the "Heating Element" which it is switching.

 

[Johntheo5]

Yes, referring to the 5W (I0.8k ohm) bi metal heater.
The contacts are in perfect condition, as (tried to) explained, continuity is lost through this heating strip when one end becomes worn through due tp the baynot mechanically wearing away the PCB, therefore the main contacts remain closed and the main stove heating element(s) of ~ 1.2kW to 2.5kW will never open except the control is switched off.

 

[FrodoOne]

While there may be a PCB in that blurry photo, any details cannot be discerned.

I can discern no "bayonet strip end" in that picture - only several male "Spade" connectors - at the edges of the body of the device.

You appear to have indicated what may be a spring contact "finger" on the inside of the cover in your second photo (?)

 

[Johntheo5]

Hi Fred?

I thrust you havn't any drink taken down under?,

If you look carefully at the cover photo, again attached, you should see the arrowed baynot end and strip that shorts (when in place) the "load" terminal to the N (neutral) terminal, (permanently), when the control switch is switched on, the contacts are switched in with contacts closed and power to the main "plate" via the contacts, and also through the 5W resistor via the live, load & neutral terminals, when the bi metal strip opens the contacts then the supply volage is interrupted to both the "plate" and the bi metal strip heater so the contacts again close to repeat the cycle.

Hope that makes it easier to understand.

John.

 

[fixitflav]

Hi Fred?

I thrust you havn't any drink taken down under?,

If you look carefully at the cover photo, again attached, you should see the arrowed baynot end and strip that shorts (when in place) the "load" terminal to the N (neutral) terminal, (permanently), when the control switch is switched on, the contacts are switched in with contacts closed and power to the main "plate" via the contacts, and also through the 5W resistor via the live, load & neutral terminals, when the bi metal strip opens the contacts then the supply volage is interrupted to both the "plate" and the bi metal strip heater so the contacts again close to repeat the cycle.

Hope that makes it easier to understand.

John.

I used to play with simmerstats in the 80s and 90s, for my cooker, ma-in-law's and friend's, but they didn't have a PCB, just contacts that opened/closed with frequency determined by the setting, or stayed closed when at max. From memory, life was nowhere near as short as ~2.5 years, maybe needed adjustment after ~ 10 years. ]
According to the internet they're still available, but can't tell whether the ones shown have a PCB. Given a choice I'd get one without, always worked OK.

 

[Johntheo5]

When I say PCB I am referring to the resistance (10.8k ohm) piece/board.

I would like to see that timed? type stat.

 

[fixitflav]

When I say PCB I am referring to the resistance (10.8k ohm) piece/board.

Not Printed Circuit Board?

I would like to see that timed? type stat.

Don't understand the question. Please help!

 

[Johntheo5]

Not Printed Circuit Board?

Yes, thats how I would describe it?


Don't understand the question. Please help!

what makes the contacts opn and close, is there no bimetal strip or heating resistance?
"just contacts that opened/closed with frequency determined by the setting, or stayed closed when at max."

 

[fixitflav]

what makes the contacts opn and close, is there no bimetal strip or heating resistance?

Yes there are both. The heater warms the bimetallic strip which opens the contacts, reclose when it cools. The strip is biased by the adjustment knob which varies the contacts open and closed times. That's on the ones I remember from way back.

 

[Johntheo5]

what makes the contacts opn and close, is there no bimetal strip or heating resistance?

Yes there are both. The heater warms the bimetallic strip which opens the contacts, reclose when it cools. The strip is biased by the adjustment knob which varies the contacts open and closed times. That's on the ones I remember from way back.

Mine works exactly the same way, the weak point is where the sharp point of the metal strip in the cover is permanently in contact with the right hand side of the heater, you can see it (little white square), in the "Simmerstat Bi-metal strip" photo, when the strip is heated it springs DOWN, opens the contacts and as the other end (of the bi metal strip) is now no longer in contact with the metal piece in the cover, its circuit is broken until it cools down, to spring back up to remake the heating circuit and recloses the contacts, there is a slight movement at the sharp end which after hundreds of cycles will inevitably wear away the heating strip.
One of these simmerstats actually gave up after around 8 months, the warranty service guy kindly replaced the other frequently used one even though it was fine, I reused it years later.

 

[fixitflav]

Mine works exactly the same way, the weak point is where the sharp point of the metal strip in the cover is permanently in contact with the right hand side of the heater, you can see it (little white square), in the "Simmerstat Bi-metal strip" photo, when the strip is heated it springs DOWN, opens the contacts and as the other end (of the bi metal strip) is now no longer in contact with the metal piece in the cover, its circuit is broken until it cools down, to spring back up to remake the heating circuit and recloses the contacts, there is a slight movement at the sharp end which after hundreds of cycles will inevitably wear away the heating strip.
One of these simmerstats actually gave up after around 8 months, the warranty service guy kindly replaced the other frequently used one even though it was fine, I reused it years later.

I'm not clear what your problem is. It seems you can still get them, it's annoying if they don't last long, but not a big job to replace.

 

[FrodoOne]

Hi Fred?

I thrust you havn't any drink taken down under?,

One wonders to whom you are referring !

If you look carefully at the cover photo, again attached, you should see the arrowed baynot (sic) end and strip that shorts (when in place) the "load" terminal to the N (neutral) terminal, (permanently), when the control switch is switched on, the contacts are switched in with contacts closed and power to the main "plate" via the contacts, and also through the 5W resistor via the live, load & neutral terminals, when the bi metal strip opens the contacts then the supply volage is interrupted to both the "plate" and the bi metal strip heater so the contacts again close to repeat the cycle.

Hope that makes it easier to understand.

Well, NO!
I see "what may be a spring contact "finger" on the inside of the cover in your second photo" - as I wrote in Post #4 - and not a "bayonet end".

A "bayonet end" would be pointed.

(A Bayonet Connector is defined - in Wikipedia - as
"A bayonet connector (for electrical use) is a fastening mechanism consisting of a cylindrical male side with one or more radial pegs, and a female receptor with matching L-shaped slot(s) and with spring(s) to keep the two parts locked together. The slots are shaped like a capital letter L with serif (a short upward segment at the end of the horizontal arm); the peg slides into the vertical arm of the L, rotates across the horizontal arm, then is pushed slightly upwards into the short vertical "serif" by the spring; the connector is no longer free to rotate unless pushed down against the spring until the peg is out of the "serif".")

Of course, you may subscribe to the thoughts of Humpty Dumpty in "Through the Looking Glass" (by Lewis Carroll):-
“When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean — neither more nor less."

Shorting the "load" terminal to the N (neutral) terminal would not seem to be a "good-idea"!
I cannot understand what is meant in your single long (convoluted) sentence, quoted above.

 

[jj4091]

My recent experience with a brand new Belling oven suggests they are not particularly well made so probably all down to the old adage "you get what you pay for".

 

[Harry Bloomfield]

They work on a similar principle, to the old-fashioned car indicator flasher switch/relay. The difference being that these are adjustable, and the flasher relays, have the entire load passing through the heater element. A more modern replacement for a simmer stat, is to use a triac, to do the switching, and a timer to set the on to off ratio. I'm sure there would be something suitable, and ready-made on ebay - just a higher power version of a dimmer circuit.