Economy 7 - Hot water not working

avoidtheupsidedownbottles

Heely said:

Thanks. Could that be why the water heater switch does not come on off peak?
Could that be why when tested, the t-stat had no Voltage?

Maybe, depending on where you were measuring.  

If your neighbour is happy to move the thermostat from the top (Boost) heater and fit it in the bottom Economy7 heater, that will show whether it's all working OK.

Talldave

There should have been 240V on the input, even if the output was off because the thermostat was satisfied.  It's also worth checking the safety limiter is reset, otherwise it's not going to call for heat. 

It looks like another £30 to spend to get the correct TSR model and to get back to where you started - possibly - if it's not the thermostat at fault.  You can measure the resistance of the heating element with a multimeter to see if it's open circuit (dead) or reading around 20 ohms (OK). It's convenient having two elements as you can compare readings between the two, although they may not have identical resistances if they're of different wattage ratings.

avoidtheupsidedownbottles

Talldave said:

There should have been 240V on the input, even if the output was off because the thermostat was satisfied.  It's also worth checking the safety limiter is reset, otherwise it's not going to call for heat.  

Thing is, if they were just measuring across the t-stat terminals when it was closed 'on', they wouldn't have registered a voltage.  Easier to just swap out the stat and see if it works IMO.

From the light not working during off-peak though, it does sound like there could be a fault upstream and the stat may be a distraction.  In that case, if Heely still has the original TSR stat, it might be okay to refit, which would save buying another.  The scorching to a terminal could have been a loose connection.  A few unknowns still...

thorganby

avoidtheupsidedownbottles said:

Talldave said:

There should have been 240V on the input, even if the output was off because the thermostat was satisfied.  It's also worth checking the safety limiter is reset, otherwise it's not going to call for heat.  

Thing is, if they were just measuring across the t-stat terminals when it was closed 'on', they wouldn't have registered a voltage......................

Seriously!

You really should not be posting advice about things that you clearly don't understand.

Where exactly do you think that the voltage goes then?

There has to be voltage present across the element to generate heat.

The blind leading the blind is not helpful and simply adds more confusion to an already very confused thread.

avoidtheupsidedownbottles

thorganby said:

avoidtheupsidedownbottles said:

Talldave said:

There should have been 240V on the input, even if the output was off because the thermostat was satisfied.  It's also worth checking the safety limiter is reset, otherwise it's not going to call for heat.  

Thing is, if they were just measuring across the t-stat terminals when it was closed 'on', they wouldn't have registered a voltage......................

Seriously!

You really should not be posting advice about things that you clearly don't understand.

Where exactly do you think that the voltage goes then?

There has to be voltage present across the element to generate heat.

The blind leading the blind is not helpful and simply adds more confusion to an already very confused thread.

If you read my post again, you'll see it says "if they were just measuring across the t-stat terminals when it was closed 'on' ".  The thermostat switches the live to the element.  Therefore, when it is closed and conducting, there is little or no voltage difference present between its terminals.  Hence why I was steering away from relying on readings taken by the householder.

Gerry1

thorganby said:

avoidtheupsidedownbottles said:

Thing is, if they were just measuring across the t-stat terminals when it was closed 'on', they wouldn't have registered a voltage......................

Seriously!

You really should not be posting advice about things that you clearly don't understand.

Where exactly do you think that the voltage goes then?

There has to be voltage present across the element to generate heat.

The blind leading the blind is not helpful and simply adds more confusion to an already very confused thread.

The key word here is 'across'.  If the thermostat is calling for heat, there will indeed be no voltage across the thermostat terminals, although both the input and output terminals will then be live w.r.t earth.

Whether it's physically easy to measure the voltage at the output point is another matter.

thorganby

avoidtheupsidedownbottles said:

thorganby said:

avoidtheupsidedownbottles said:

Talldave said:

There should have been 240V on the input, even if the output was off because the thermostat was satisfied.  It's also worth checking the safety limiter is reset, otherwise it's not going to call for heat.  

Thing is, if they were just measuring across the t-stat terminals when it was closed 'on', they wouldn't have registered a voltage......................

Seriously!

You really should not be posting advice about things that you clearly don't understand.

Where exactly do you think that the voltage goes then?

There has to be voltage present across the element to generate heat.

The blind leading the blind is not helpful and simply adds more confusion to an already very confused thread.

If you read my post again, you'll see it says "if they were just measuring across the t-stat terminals when it was closed 'on' ".  The thermostat switches the live to the element.  Therefore, when it is closed and conducting, there is little or no voltage difference present between its terminals.  Hence why I was steering away from relying on readings taken by the householder.

Stop digging yourself deeper into a hole!

You are wrong.



The voltage was checked across stat terminal A & B and there will be a voltage present regardless of the stat being open or closed.

You will see that terminals 1 & 2 are provided for connection of an optional lamp and this is connected directly across the element.

The stat only has 4 terminals A & B and 1 & 2 and voltage will normally be present across A & B and between 1 & 2 when there is voltage across the element i.e. stat calling for heat.

 If what you state was true "little or no voltage" would be present at the consumer unit affecting all circuits.

avoidtheupsidedownbottles

thorganby said:Stop digging yourself deeper into a hole!

You are wrong.

It is unusual for a stat to switch both poles, the majority switch only the phase.  Since I was advising to not trust voltmeter measurements, my mistake was not an issue.  I correctly identified that the wrong stat had been fitted, and that it probably had a different measurement range from the original.  I am now suggesting the OP uses a stat of known provenence from the other heater to eliminate the stat as the source of the problem.  Sound troubleshooting procedure, so hardly 'the blind leading the blind.'

tim_p

Where does the element connect?

Heely

avoidtheupsidedownbottles said:

Heely said:

avoidtheupsidedownbottles said:

The original t-stat was a Cotherm TSR with max setting of 160º C.  Replacement 'stat is a TSE with maximum of 70 as above.  Might account for the confusion with settings.  
Or the heater element may be knackered as well . .

Both Original and Replacement T-stats are Megaflow TSE

If you look at your photo of the old one it says TSR on it.  

I suggest setting the thermostat midway between 4 and 5 and that should give you about 60 degree water.

Thanks @avoidtheupsidedownbottles. I took your advice and set the t-stat between 4 and 5. Had a lovely hot shower