How exactly does my hot water tank work?

[pooksahib]

I wonder if someone would be so kind as to give me some information on my hot water system and the Horstmann 'Electrisaver' which I have inherited? The house I am now in was built in 1993 and the Electrisaver does not have a model number on it. It simply says Electrisaver Electronic Timer and has two buttons – Start and Cancel. Further down the wall is another switch connected to the hot water tank but it is a simple 'on/off' (like a lightswitch).

Electricity is supplied by Scottish and Southern Energy on their Total Heating Total Control tariff whereby there are two meters – a normal one and one for cheaper, overnight electricity (the night storage heaters are 'charged' in this way.)

What I would like to know is:
Is the water likely being heated on the cheaper, overnight meter?
How do I properly use the Start and Cancel buttons on the Electrisaver?
Is the other switch simply an 'on demand' method of heating the water?
If so, should it's normal position be 'off'?

(I suspect the second switch should indeed be 'off' if the primary heating is via the Electrisaver switch. At the moment, it's 'on' and the water is always very hot. Mogget (on another thread) kindly informed me about vent pipes and it may be that the cause of an intermittent drip from the overflow is steam going up the vent, into the cold tank and condensing on the way out via the overflow. Does that make sense?)

My thanks in anticipation of your assistance.

 

[kevindgas]

What I would like to know is:
Is the water likely being heated on the cheaper, overnight meter?

bottom element yes top no

How do I properly use the Start and Cancel buttons on the Electrisaver?
Is the other switch simply an 'on demand' method of heating the water?
If so, should it's normal position be 'off'?

yes

.

start /cancel can't remember how this works but i think it maybe a timed overide but don't quote me

 

[JohnD]

Horstmann still make a popular "Economy 7" type immersion controller. Maybe your old one works in a similar way

The way the new one works is that normally it heats the water during the overnight cheap period, but it has an override "boost" knob that you operate if you run out of water during the day (at full-price electricity)

So the override should normally be off to save money

the current one starts the daytime override heating with a timer, so that it will turn itself off even if you forget to, and it will return to overnight heating only unless you manually override it again. IIRC it lights a "boost" neon when you are on manual override.

Since your has a start and stop button maybe you have to turn off the override when you have enough hot water.

The new one also has on Off/Timed button so you can turn it completely off e.g. when you go on hols.

If you look at the electricity meter you will be able to see when it is drawing current.

The new Horstmann controller is pretty expensive, I have an idea it retails at £60 or so, so I hope your old one is working well.

 

[pooksahib]

Many thanks, Kevin and John. I now have a clearer understanding of what's going on. The version of the Electrisaver which I have is clearly very basic – you have to press 'stop' as, unlike newer versions, there is no facility to boost for 30 mins/1 hr/2 hrs etc.

Perhaps a stupid question, but how does the Electrisaver know to activate at night? As I said, it just has the Start and Cancel buttons (which we now know are for boosting). The faceplate says on it 'Electronic Timer' – who programmed it??

Here's a further question, if I may. I'm sure the tank in my old house had a wee temperature control dial. There's nothing similar on this tank. If I believe the water is too hot, how would I reduce the cut-off temperature?

Thanks again.

 

[JohnD]

but how does the Electrisaver know to activate at night? .

It probably doesn't. On older Economy 7 installations the electricity meter(s) incorporate a switch which turns on the supply to storage and water heaters during the night. In this case you usually have a separate Consumer Unit for those items, which has no power during the day.

If you post some photos of your electricity meter(s) and consumer unit(s) and the wires between them, we may be able to identify what kind of installation you have

Here's a further question, if I may. I'm sure the tank in my old house had a wee temperature control dial. There's nothing similar on this tank. If I believe the water is too hot, how would I reduce the cut-off temperature?

You probably have a hot-water cylinder with one or two immersion heaters in it. These have a thermostat under the plastic cap. Post some pics and we may recognise it. Don't take the cap off yet as you have to turn off all power first for safety.

 

[pooksahib]

You're very kind. Here a few pictures as requested although the Electrisaver switch is a tad inaccessible. There's not much to see on it anyway bar the Start/Cancel buttons and a wee light which comes on when you press the former.




I suppose what I'm looking for confirmation of is:

Is the water being heated at off-peak (overnight) rate?
Is the normal position for the 'ordinary' switch (immersion) "Off"?
If I think the water is too hot, can I reduce the temperature cut-off myself?
If the water IS too hot, could it be sending steam up the vent pipe into the cold water tank which then condenses in the overflow pipe? (There's been an intermittent drip from the overflow lately.)

Given that there are two of those plastic caps, the tank must have two immersion heaters. yes? One controlled by the Electrisaver (by pressing 'Start') and one controlled by the 'normal' power supply? If I needed a boost, which would be the best one to use - the Electrisaver since it's closer to the top of the tank? (I understand that taps draw hot water from the top..)

Once again, my sincere thanks for your assistance.

 

[JohnD]

I can't see the connections, but you have a Teleswitch which turns the off-peak meter on and off at appropriate times, (it can be adjusted by a radio signal from SSE) and I see it has a boost button which (I expect) turns on the storage heaters and deep immersion, if you need to, during the day.

the normal arrangement is that the off-peak supply is turned on and off by a timer at the meter, and it goes to a separate consumer unit (which ought to be labelled "Off Peak" and yes, the off-peak supply is normally run to the lower immersion heater, to heat the entire tank, whereas the full-price supply just goes to the upper immersion heater to top up a small amount.

there will be a thermostat under each of the plastic caps on the immersion heaters. Identify the CU for each, and preferably turn off the main switch, or switch off the individual MCB, and test for dead before touching anything under the plastic cap. It is possible for old thermostats to go wrong and get too hot, but they are easily replaceable (no water comes out when you change them as they are in a sealed compartment) but you should be able to see the adjuster easily when you remove the cap.

yours looks like a neat and modern installation. It would benefit from more labelling of the consumer units and of each MCB to show what it does. One way is to get a roll of white vinyl tape and a permanent marking pen, with a bit of practice and a ruler you can make up quite a neat strip of labels by sticking the tape to the kitchen table, and peel it off and stick it to the (clean) CU. It is surpringly difficult to write neatly on a CU when it is fixed to the wall. You can stick the tape above the MCBs if you don't want to go over the maker's label strip.

Two other things you can usefully do:

Look at a recent electricity bill to make sure you are on a tariff that charges cheap rate for the off-peak heating (it is possible to be charged full-price for it all, even if you have an off-peak meter), and look at the meter readings to see how they work.

Also, look at the meters during the night to see what hours the off-peak comes on, and, when you are on off-peak, plug in a tumble-drier or something into an ordinary socket, and see if it sends the meter going for off-peak or full-price (there are different ways of doing it; sometimes only the storage heating is charged at off-peak prices, and sometimes all electricity that is used during the night period (which is a bit better). It looks to me like in your case, only supplies from the off-peak CU will be charged at off-peak rates.

 

[pooksahib]

John, I don't know what to say. Thanks so much for spending all that time on me. This should be my final set of queries though:-

...and I see it has a boost button which (I expect) turns on the storage heaters and deep immersion, if you need to, during the day.

So I can press that red button on the meter myself? Is the blue button beside it (marked 'display') a 'stop boost' perchance? Not that I reckon I'll ever need this kind of boost but nice to know how things work. Actually, I'm pretty sure that S&SE make daily boosts to the heaters during colder days. And EVERY day at 8pm something happens as the lights dim slightly. I must find out what that's about...

the off-peak supply is turned on and off by a timer at the meter, and it goes to a separate consumer unit (which ought to be labelled "Off Peak")

Is there a simple explanation as to why I have 3 CU's (I just have too many MCB's to fit in, for example)?

your installation would benefit from more labelling of the consumer units and of each MCB to show what it does.

Actually, it's fine. You can't see it in the photos but each MCB has a description in pencil (where there isn't a proper sticker). As you maybe noticed, there's an MCB on the top CU marked 'water heater'. The MCB's beside it are all for the night storage heaters so this is obviously the 'Off Peak' CU. The bottom right CU has an MCB marked 'water heater boost' which would confirm that you have to pay top dollar for a boost.

Look at a recent electricity bill to make sure you are on a tariff that charges cheap rate for the off-peak heating

That's long since been checked!!

Thanks again my friend.

 

[JohnD]

I don't know about the buttons on the meters. If you phone SSE they might be able to send you an instruction leaflet. A display button is more likely to show you units used under different tariffs. The boost might be for a limited period.


3 CUs:

one is off peak

one has an RCD (test this regularly) so I would expect to be used for socket outlets (RCD protected sockets has been the rule for quite a few years)

one has no RCD so I would expect it to be lights, maybe also freezer and cooker

rules about RCDs changed recently but you are not obliged to retrospectively fit RCDs to all circuits in existing houses.

 

[pooksahib]

Hello John. You're quite correct about which items appear on each CU.

It turns out I was wrong in my idea that the lower of the two switches connected to the tank should be in the 'off' position (as confirmed by Kevin in his reply to my original post). A day with luke warm water proved that. I was confusing this set-up with my previous one where the immersion was a secondary source of heat (the primary source being the gas boiler). But this is an all-electric house so the cable leading to the lower of the two elements MUST be the primary heat source meaning the switch at the wall should be 'on'. And the MCB for this switch is on the Off-Peak CU. Simple when you think it through but I'd have struggled without all the invaluable help I've had on this thread.

Sincere thanks once again.