Economy 7 Water Heating Faulty

[markweatherill]

Dear Folks

My Economy 7 water heating has stopped working.
Unfortunately, when mine packed up, instead of thinking about the possible problem causes in a rational manner, i went into rabbit-caught-in-headlights mode and called in a plumber.
This company then replaced both elements and thermostats, charged me £318 and went on their merry way. I've been left with a system that still doesn't give me a tank of off-peak hot water. I've had them back around twice, but all they've done is check the pieces they installed, twice.
I've read all the posts about Economy 7 water heaters not working, but they all referred to the heating components, like thermostats, elements, the actual power supply etc.
Is it possible that the internal structure of the tank has become blocked by limescale build up, and this is somehow preventing either the lower element from heating the water effectively overnight, or, preventing the heated water from getting to the top of the tank, where it is drawn off when taps are turned on?
Regarding the elements and thermostats, i'm 100% sure they're all functioning correctly, and also that there is 240V getting to the off-peak stat.
Would be very grateful for any useful feedback before i call this plumber firm again and get them back here to finish the job they started (incidentally, they have not called me back once to check on whether i've got it going; so much for their customer care.)
Thanks,

Mark.

 

[luminaire]

Are you sure the E7 is coming on at the right time and staying on long enough to heat the tank?

 

[markweatherill]

The Economy 7 switchover does occur, currently, at just past midnight. I stayed up to witness the change on the meter. Likewise at just after 7am, the meter switches back to peak rate.

 

[crystal ball]

How is the E7 water heating controlled, is it a timeswitch (horstmann) usually located near the immersion heater

 

[markweatherill]

The E7 heating starts when the off-peak electricity comes on at just after midnight, and goes off at 7am. The actual water temperature is thermostat controlled.

 

[crystal ball]

can you describe the set up, from each immersion heater, to the switch etc or post a piccie

 

[Lectrician]

Sounds like you have a 'proper' econ7 install with two elements and no customer timer. The bottom element being controlled by the DNO's econ7 telelswitch, via an off-peak consumer unit.

The top element is used as a boost during the day, and is connect to the peak consumer unit.

As you have had both elements changed, you are also likely to have the new stats which prevent the water being heated beond 60degC. This often upsets many folk used to extra hot water! Is this possibly the issue?

You really need a spark, not a plumber to confirm everything is as it should be.

 

[nozspark]

Do you get any hot water in the morning???

IE... just the top of the cylinder!!!

It maybe that the plumber wired the top element as your "E7" and the bottom element as your "Boost"