Economy 7 immersion boiler with timer only for top element? Confused with how it's meant to work!

Vergo777

I've moved into a new rented flat and I'm trying to figure out how to set up the immersion boiler for efficient use. A few details of the setup (along with pictures): 

• Property has a Smart Meter and is currently on an Economy 7 tariff 
• There are two separate switches next to the boiler, an "Off Peak" one and an "On Peak" one
• There's a Horstmann control panel, which as far as I can make out seems to be connected only to the top element of the heater? Moreover if I disable the "On Peak" switch it cuts power to the control panel's display as well 

Now here's the parts where I'm confused 

• I initially assumed that the Horstmann panel controls both the top AND bottom element, so I enabled both the "Off Peak" and "On Peak" switches and programmed it for timed heating during Economy 7 hours. But throughout the course of the day I noticed random spikes on my smart meter display so I'm now thinking it doesn't control both? 
• After a bit more reading it seems like it's common for the bottom element of the heater to be connected to the Off Peak E7 circuit directly? i.e, if I keep the "Off Peak" switch on it should just automatically heat during the defined E7 hours? 
• Does this mean I have no control over the exact hours I can heat the bottom element? eg. if I want to have it heat for just 4 out of the 7 hours? Ideally I'd like to move to the Octopus Go tariff which is why I'm interested in being able to set exact times. 

Ultimately I'm just not sure whether the Hortsmann panel controls both elements or just the top one, and why there's two separate On Peak and Off Peak switches present? And does Economy 7 play well with Smart Meters, particularly with plans such as Octopus Go which might follow completely different off-peak hours (00:30 - 04:30)? 

If anyone with a similar setup could help with how this all works that'd be a huge help! 

• 

Sandtree

E7 works fine with smart meters, or it did with ours at least. 

To see how yours works you either have to experiment or look at the wiring. On the surface it looks like the control panel is only controlling the upper heating element and the lower heating element is simply on the fused switch but looks can be deceiving. 

Does the off peak light on the device come on during the E7 hours?

Last all electric flat we had was almost the exact opposite way round... the lower element went to a control panel that also controlled the underfloor storage heating and took input from an eternal sensor whereas the upper element was just an on/off switch.

coffeehound

Hiya.  What a muddle.

Really there's two basic set-ups for water heated by E7:  

1)  the off-peak supply is connected directly to the off-peak element (as you suggest) and the meter controls a switch to automatically turn it on and off at the right times.  
Or,
2)  you have a timer like the Horstman to control when the element is switched on, set to correspond with the off-peak times. 

The fact that you have a timer suggests that your meter does not have the facility to switch the circuit automatically.  Therefore you need to set the times carefully yourself.

Next thing is that you absolutely do not want either element switched on during the peak rate, unless absolutely necessary.  So the element that is not connected to the Horstman needs to be *Definitely Off*.  Exactly what that lower element is currently connected to is not clear at present.  You would think it is just connected to the 'on peak' switch but you say the Horstmann is also supplied from that switch.

Used properly, the Horstman would control the non-E7 element through the Boost switch and would prevent both heaters being on at the same time.  We need to establish what that lower element is controlled by.

It may well be that the both the off-peak and on-peak switches are both always live now, meaning when they are switched on, they supply power at any time of day.  Therefore if the lower element is connected to the 'off-peak' switch, and the switch is on, the element will come on at any time of day or night.  You don't want that.

The 'on-peak' switch is apparently supplying the Horstman and so by setting that to 'timed' and setting the times you want, it should switch on the element as intended.

The set up at present has the upper element controlled by the timer.  This is unusual and it would normally be the lower element that is switched on over night to give a full tank of water in the morning.  A previous tenant probably decided they didn't need a whole tank each day, and so switched over the cables so the the upper element comes on overnight to give about half a tank of hot water instead, which is reasonable if that's all that is required.  (There is a chance of Legionella contamination if the whole tank is not heated above 50-odd degrees from time to time, though.)

You may want to switch these back so that the lower element is controlled by the Horstman, if you feel you want more hot water on tap throughout the day.

greenguppie

Vergo777 said:

I've moved into a new rented flat and I'm trying to figure out how to set up the immersion boiler for efficient use. A few details of the setup (along with pictures): 

• Property has a Smart Meter and is currently on an Economy 7 tariff 
• There are two separate switches next to the boiler, an "Off Peak" one and an "On Peak" one
• There's a Horstmann control panel, which as far as I can make out seems to be connected only to the top element of the heater? Moreover if I disable the "On Peak" switch it cuts power to the control panel's display as well 

Now here's the parts where I'm confused 

• I initially assumed that the Horstmann panel controls both the top AND bottom element, so I enabled both the "Off Peak" and "On Peak" switches and programmed it for timed heating during Economy 7 hours. But throughout the course of the day I noticed random spikes on my smart meter display so I'm now thinking it doesn't control both? 
• After a bit more reading it seems like it's common for the bottom element of the heater to be connected to the Off Peak E7 circuit directly? i.e, if I keep the "Off Peak" switch on it should just automatically heat during the defined E7 hours? 
• Does this mean I have no control over the exact hours I can heat the bottom element? eg. if I want to have it heat for just 4 out of the 7 hours? Ideally I'd like to move to the Octopus Go tariff which is why I'm interested in being able to set exact times. 

Ultimately I'm just not sure whether the Hortsmann panel controls both elements or just the top one, and why there's two separate On Peak and Off Peak switches present? And does Economy 7 play well with Smart Meters, particularly with plans such as Octopus Go which might follow completely different off-peak hours (00:30 - 04:30)? 

If anyone with a similar setup could help with how this all works that'd be a huge help! 

• 

User Instructions for your model Horstmann controller
https://www.tlc-direct.co.uk/Technical/DataSheets/Horstmann/EL7_U.PDF

It should control both immersion heaters (separately)

Sorry, unable to assist with what the external switches control (if anything)
My guess is that they are isolatiion switches, probably before the controller, for each heater but you would need to have a play to confirm that.

The switches may not control anything today - perhaps a legacy from a time before the Horstmann was fitted?

The controller obviously controls the upper heater as you can see the cable.
The lower heater cable is concealed behind the wall. It maybe a bodged job and the lower heater is not controlled by the Horstmann, despite the Horstmann having the ability to do so.
More probably, the cable exits the Horstmann direct into the wall.

As for the usage spikes, this could be due to the fact the heater is thermostatically controlled even when powered.

Check the timings the heaters are timed to go on. Details in the link above.
The boost is either 1 hour or timed. In the current (recommended) setting it is 1 hour when activated.

Note that the upper boost heater should not work during the period the lower heater is powered  (assuming the Horstmann is wired correctly)

Vergo777

Thanks for all the above info folks, really useful! I played around with some combinations yesterday and came to the following conclusions

• The Horstmann control behaves incredibly weirdly. I followed the instructions on the manual to the letter, but Boost does not work - the red light comes on but I see no spike in my smart meter. 
• The ONLY thing that seems to actually result in a 3 KWh spike is flicking on the switch for "Timed Heating". But this then completely ignores the actual programme timings I've set and just registers 3KWh usage throughout, regardless of whether the "off-peak" light is on or not. 
  
• The separate "off-peak" physical switch doesn't seem to do anything. I set the Hortsmann water heater switch to "off" and left the off-peak physical switch on overnight, and my smart meter has recorded only 1.7 KW usage which suggests that no heating has kicked in. 

So basically it looks like the timing function on the Horstmann isn't working as intended, and I'm only able to control turning it off/on through physically flicking the Water Heater switch on the control panel? 

In addition I still have no idea whether the Horstmann is heating just the bottom element or the top one! Given that there's only 3KWh usage recorded at any time it's a safe assumption that both elements are never coming on? 

I'm unsure about what else I can do to test out the functionality isn't working as expected. Since I'm renting, I'm going to have to somehow show the landlord there might be a genuine issue at play, particularly since there seem to have been no complaints from the previous tenants (who might not have gone into such detail). 

coffeehound

It’s possible the lower element has failed, and instead of getting it replaced, the previous tenant swapped the connections so that the Horstmann now controls the top element. 

I think you should ask the landlord/letting agent to inspect the system and say that you suspect the lower element has failed and that the timer is not working. Also that the wrong element is connected as the Economy7 overnight heater. 

Gerry1

Don't worry about the history of the installation, you need to ensure that you have the following set up.

• The Off Peak circuit is switched by the smart meter and supplies the lower heater.  It seems that the Smart Meter Fiasco means that there aren't many smart meters that do this: you need a 5-terminal meter.  This will have two fat cables going in and THREE fat cables going out.
  
Alternatively, a control signal one or two very thin wires can go to a separate contactor unit to get the same result.  Don't settle for anything less.  A Horstmann unit can mimic the switching times but it's an inferior solution.  If the programming is wrong, if you get caught out by GMT/BST changes, if the smart meter times are varied remotely, if the timer loses its settings, any of these can make your bills rocket and you'll be none the wiser until hit by a big bill.

• The On Peak circuit is NOT switched by the smart meter and supplies the upper heater.

• There is a local timer just to ensure that the upper heater can't be left on permanently.  Best to replace the Horstmann and keep it really simple, just a knob that you rotate to get up to two hours use in the daytime (effectively a glorified Smiths kitchen 'pinger') if you've run out of hot water or have been away and left the lower heater switched off.

Ideally the On Peak and Off Peak switches should have neon indicators so that the tenant can understand what's happening and minimise the risk of an unnecessary callout.  Any such changes should be relatively inexpensive.  If the landlord is less than enthusiastic, explain that they will make the property more attractive, lessen the risks of a tenant experiencing unnecessarily high bills, reporting non-existent faults or even moving out.

Vergo777

Cheers, I'm going to speak to the landlord and try and get this sorted out. 

Just for my information, suppose the bottom element isn't working at all and it's just the top element doing all the heating - are there any potential problems with this? If left on for long enough, would the top element eventually end up heating the whole tank in a safe manner to kill off any bacteria?

Since I was planning to move away from an E7 tariff anyway, I'm almost tempted to keep life simple and just have the Horstmann/top element always on. It does have a thermostat since I've noticed previously it doesn't just keep up the 3KWh usage throughout the day and it cuts out once temperature is reached. 

If I were to do this, would there be any major cost or safety implications? I've tried to do a bit of reading but still can't figure out whether the top element is able to heat up the entire tank by itself if left on until the thermostat kicks in? 

QrizB

Vergo777 said:

Since I was planning to move away from an E7 tariff anyway, I'm almost tempted to keep life simple and just have the Horstmann/top element always on. It does have a thermostat since I've noticed previously it doesn't just keep up the 3KWh usage throughout the day and it cuts out once temperature is reached. 

If I were to do this, would there be any major cost or safety implications? I've tried to do a bit of reading but still can't figure out whether the top element is able to heat up the entire tank by itself if left on until the thermostat kicks in? 

The top element can't heat the whole tank without some sort of mixer or circulator, which is far more faff than I'd consider sensible for a domestic tank.

Leaving E7 will make your hot water twice as expensive, ish. If your flat has electric heating it will make that twice as expensive too. Full-price electricity is the most expensive mainstream heating option there is. (Gas in small bottles is more expensive but only touring caravans and the like would bother with that, on the whole.)

Swipe

Vergo777 said:

 If left on for long enough, would the top element eventually end up heating the whole tank in a safe manner to kill off any bacteria?

Don't worry about bacteria as any water you use is being heated above the required temperature and the water is also being rotated. Legionella is only really a problem in long standing water.

Gerry1

What does the flat have for room heating?  That usually determines whether E7 makes sense.  If you have storage radiators then E7 is a must.  If you have panel heaters, oil filled radiators, infra red heaters, electric fires, fan heaters, convectors etc then E7 is probably not for you because the daytime rates are likely to be even more expensive than for single rate.  Sadly, being all electric is bad news, but almost nothing is more expensive than heating at daytime rates.

I trust you registered with the existing supplier when you moved in and gave an opening meter reading that you'd taken?  Never allow anyone else to do this on your behalf.  Don't assume that the smart meter is doing its job, one of the many pitfalls of the Smart Meter Fiasco is that many have gone dumb.

Establish the kWh rates and standing charge, then consider shopping around for a better credit tariff deal starting with Citizens Advice and 'Which? Switch'.