Why do some Immersion Heaters have twin thermostats?

[scotty plumber]

Thank's in advance!

 

[Plamber]

Bottom one usually works on a timer on a cheap rate due to it being used at times when there isnt much electricity usage. the top one is usually the boost. You get these when customers have no gas and are on tariffs like economy 7 or total control.

 

[scotty plumber]

Bottom one usually works on a timer on a cheap rate due to it being used at times when there isnt much electricity usage. the top one is usually the boost. You get these when customers have no gas and are on tariffs like economy 7 or total control.

LOL! I know that, read the question again

 

[Plamber]

jeez its been a long day. never noticed that. appologies.

I always just thought it was for unvented cylinders that have normal immersion bosses.

 

[SimonJohns]

i think you will find that immersions have twin thermostats because of stats failing, one stat will be the adjustible stat and one will be a non resetting failsafe stat

this is linked back to the incident back a few years when the was a fatality because of a cylinder boiling, making the cwsc boil and the cwsc colapsing into the bedroom below

http://www.wras.co.uk/PDF_Files/Scalding%20information%20note%20Jan%2008.pdf < further reading for you

 

[TTB]

All immersion heaters supplied within the UK & NI are supplied with twin stats , one control stat and one high limit stat.
Though you may find new immersion heaters supplied with both controls, high limit and control built into one thermostat rod.

Hope it helps.

TTB

 

[Best]

Think it is compulsory to fit immersions that have the manual resettable overheat cut out. Only ones I know of are built in to the stat.
Danger of hot water replacing the cold in the cold storage tank makes you think the old method of the cylinder vent going safely through the roof wasn't a bad idea.

 

[Best]

All immersion heaters supplied within the UK & NI are supplied with twin stats , one control stat and one high limit stat.

NI is actually UK! Lol! :grin:

 

[scotty plumber]

so if one stat fails in a twin could that prevent immersion heater heating up properly??

 

[SimonJohns]

so if one stat fails in a twin could that prevent immersion heater heating up properly??

If one fails. The other will prevent it from over heating