Economy 7 Thermostat Question and Help?

9
Found 31st Mar
I've got a faulty thermostat on an Economy 7 tank. (Trips the circuit). The bottom thermostat which heats the tank, not the top one that heats the header of the tank (the Econ 7 booster). The cap on the thermostat says 11" but I've removed the thermostat and it only measures 7".
For context, the top one says on the cover 14" but I've not removed that one yet to see if it is/isn't.

The main question being.
Should I replace with a 7" or get an 11"?

Help appreciated as I've no hot water
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Can you not take it to a shop and ask them for one the same size? I'd assume 11 if it says 11, but I've never had to replace one.
Original Poster
MSK.1 h, 46 m ago

Can you not take it to a shop and ask them for one the same size? I'd …Can you not take it to a shop and ask them for one the same size? I'd assume 11 if it says 11, but I've never had to replace one.


That's what is confusing me. The covers say different to what is actually in the tanks
found this on google. it would appear for economy 7 tanks, there are no 7", only 11"? it could be that the 11" is the measure of the whole product and not just the element length. is the cap attached to the element or can you remove the element from the cap?

wiki.diyfaq.org.uk/ind…ers
Original Poster
mutley159 m ago

found this on google. it would appear for economy 7 tanks, there are no …found this on google. it would appear for economy 7 tanks, there are no 7", only 11"? it could be that the 11" is the measure of the whole product and not just the element length. is the cap attached to the element or can you remove the element from the cap?http://wiki.diyfaq.org.uk/index.php?title=Immersion_Heaters


The cap covers the element. Top is 14 inch and bottom cap says 11inch but they're both 7 inches.

Totally baffled.

And yeah I can remove the element. They don't measure 11 inches though
Edited by: "Wings18" 31st Mar
Wings1841 m ago

The cap covers the element. Top is 14 inch and bottom cap says 11inch but …The cap covers the element. Top is 14 inch and bottom cap says 11inch but they're both 7 inches.Totally baffled.And yeah I can remove the element. They don't measure 11 inches though


as you can remove the cap, i would buy the elements sized to what the cap states as it would appear that someone has a done a bodged job and put in smaller elements than what it should be. it states in that article that i found, that the element should be 3" to 6" smaller than the "max length physically fittable", so you could see if the tank will take 11" and 14" as stated.

i think the longer the element, the more powerful it is, so your wiring may not be good enough to cope with 11" and 14", so they reduced it to 7" as a botched job.

actually, as an afterthought, how long has the tank worked before it blew? it could be that even at the shorter length of 7", the wiring is still not good enough and so tripping rather than the thermostat being faulty. if this is the case, then disregard my comment about buying the correct length immersion heating elements as that will just make things worst!
Edited by: "mutley1" 31st Mar
Original Poster
mutley121 m ago

as you can remove the cap, i would buy the elements sized to what the cap …as you can remove the cap, i would buy the elements sized to what the cap states as it would appear that someone has a done a bodged job and put in smaller elements than what it should be. it states in that article that i found, that the element should be 3" to 6" smaller than the "max length physically fittable", so you could see if the tank will take 11" and 14" as stated.i think the longer the element, the more powerful it is, so your wiring may not be good enough to cope with 11" and 14", so they reduced it to 7" as a botched job.actually, as an afterthought, how long has the tank worked before it blew? it could be that even at the shorter length of 7", the wiring is still not good enough and so tripping rather than the thermostat being faulty. if this is the case, then disregard my comment about buying the correct length immersion heating elements as that will just make things worst!


I think the last time I had an issue was about 8 years ago. Couldn't tell you what thermostat was in there last time though.

Wiring did cross my mind when I looked at 11 inch ones today. Hmmm.
Wings1831st Mar

I think the last time I had an issue was about 8 years ago. Couldn't tell …I think the last time I had an issue was about 8 years ago. Couldn't tell you what thermostat was in there last time though.Wiring did cross my mind when I looked at 11 inch ones today. Hmmm.


so these 7 inch ones have worked for a while until now. i would err on the side of caution and buy similar ones as the longer ones may be too much for the circuitry. we have these economy 7 immersion tanks at some of our properties and the immersion heaters can trip the circuit when they burn out or they are too high powered. these sort of tanks are sometimes bodged when they are installed with the wiring not being powerful enough to take the load from the immersion heaters.

i have never replaced the immersion heaters myself, but i have heard the electricians refer to them when they replace them.
From my experience and trust me I've been there and got the t shirt. Some economy 7 boilers work on a high pressurised heat tank. By this I mean they go Up to 85 degrees and then have a mixer valve located on the top to reduce the heat by adding cold water before it gets to your tap. The reason for this is so a smaller hot water tank can be used. To do this they usually have a 11inch thermostat probe. Now these are expensive compared to a 7inch 75 degree one (can be about £45/£60 more compared to £12 For a 7inch). Also some Plumbers have no idea of this and just buy the cheepest one. Now here is the problem if they have also replaced the heating element the sleeve in which the thermostatc probe goes in may not be long enough and or have a big enough diameter. There is nothing wrong with a 75degree thermostatic probe however your hot water tank water will not last as long.
Original Poster
Thanks both. Might just get a 7 to tide me over.
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