Should I go from two elements to one with new tank?

[briony10]

Hello,

I have been reading through old threads and phoned my electricity supplier etc. till my head spun but still don't know what to do. The tank for my immersion heater is leaking and needs replacing (it's cracked, the element has already been replaced). The current copper tank has two elements, a top one for 'topping up' and a lower one for off-peak electricity.

Years ago when the lower, off peak element broke, we carried on using the top element. For some reason it was not replaced (I didn't live here then).

Today the plumber was going to replace the tank with a smaller tank with one element, connected to the peak electricity meter. He says a smaller tank will be better, there is no reason for a massive tank.

I then wondered why not get a tank with two elements and he said he will have to try and order it. He thinks a tank with two elements is a bad idea, because of the large size of the tank. He is a very good plumber btw, and I probably annoyed him by being indecisive.

I am on a very old Southern Electric tarrif: 'General Domestic and Off-Peak Fx'. . Peak units are 12.06p, off peak are 9.01p. I called Southern Electric who told me that the two ancient meters both run at the same time, unlike Economy 7. I have been confused all this time as I thought the off peak meter was controlled by a timer to turn it on overnight.

Basically I need to decide which type of tank to get, can anyone advise me please? I don't know if it is better to have a small tank (a bit cheaper to buy?) or a large one. Also, if the immersion heats all night, won't that water be cold by the following evening.

Edit: also, I live alone and only use the water for washing up etc., there is a seperate electric shower. I only used to have the top immersion element on for short times for washing up, knowing that it's expensive. However when I move there could be a whole family here again.

Thanks.

 

[Lectrician]

I would go for one with two elements if it was me, it makes much more sence, especially as you are not on an "economy 7" tarrif.

The bottom one would be used on your 9p a unit supply, and the top one as a boost on your 12p a unit supply. This is how it is intended to be done.

 

[plugwash]

Please post pictures of your meter setup.

It sounds to me like you have a setup with two completely independent meters. The off-peak meter which measures electricity consumed by equipment on the off-peak supply and for which the power is only switche on at night and the regular meter which measures supply from the regular CU. So you only get the off-peak rate on electricity from the off-peak supply.

This differs from the modern "economy 7" setup where all electricity used at off-peak times is charged at the off-peak rate regardless of which CU you take it from.

If you do want a single immersion tank on your present metering setup my advice would be to wire it via a supply changeover switch. That way you can run it from the off-peak supply at night and switch it to the regular supply if you need a top-up in the daytime.

 

[briony10]

Thanks for the help, I have just taken some photos. The meters are a mystery, I do have to take two readings though. I asked the electrician to explain how it works to me but he was a bit vague. I'm sure he said the whole lot goes off peak, not just the storage heaters/immersion heater, but now I am told that is wrong.

It's an interesting suggestion to have a supply changeover switch. I am not certain what times are off-peak though. Would I switch it myself or is it automatic? Is there any disadvantage compared to the current wiring (one tank, two elements with separate wires)?

Can I check something? How do I know whether it is cheaper to heat a large tank on an off-peak rate or a smaller tank on peak rate?

 

[briony10]

Sorry to reply to my own thread again but I have to give the plumber an answer.

Is a supply changeover switch something a plumber can fit? If so, what size tank is recommended?

Thanks very much for all the help so far and any other suggestions

 

[plugwash]

That does indeed look very much like an old style off-peak system where peak and off-peak supplies were completely seperate.

A supply changeover switch is a switch that switches between two supplies. Fitting one between your new single immersion heater and the two immersion heater supplies you have (peak and off-peak) should not be too difficult.

http://www.tlc-direct.co.uk/Products/KMT338212I.html is an example of such a switch.

 

[briony10]

Thanks, I assume the idea is to allow me to get a smaller tank?

 

[flameport]

If you want to keep the day/night tariff arrangement, then get one of these:
http://www.tlc-direct.co.uk/Products/HOBX2000.html
which will automatically use the cheaper electricity at night, and can be used for an additional boost during the day if required. Can be used with one or two elements.

The only minor advantage of two elements is that you can still get hot water if one of them breaks - but two elements would mean a larger size cylinder, which will cost more to heat.

Do you actually need the cheaper rate - do you have storage heaters?

 

[briony10]

Yes, I have got storage heaters and a wood-burner, the whole set-up is extremely expensive to run but there is no gas supply to the door at the moment. One day I hope to install central heating after getting the gas supply installed to the house. At the moment it would be too expensive.

Now I look at the rates, I am not sure if I wouldn't be better off on Economy 7.

 

[flameport]

For storage heaters you will need 2 rates, however those prices you are paying are rubbish.
You should see what other tariffs are available, as you can certainly get the night rate for a lot less than 9p (6p or less is easily achievable). However on some tariffs the day rate is a lot more that usual, so your choice will depend on how much electricity is used on both of the meters.

You don't need any new meters or equipment - it's simply a case of contacting your supplier (or another one) and changing what you are paying.

 

[briony10]

Thanks Flameport, you are right. This tarrif was chosen because there has always been someone working from home during the daytime, using electricity. The 'day rate' goes up so much to compensat for the 'night rate'...

Given that the two elements had completely different wiring to two separate meters, is it going to be a big job to replace the current wiring with the boost control switch just suggested (http://www.tlc-direct.co.uk/Products/HOBX2000.html)? Is it basically the same thing as the supply changeover switch?

I am still confused...the final option is to finally install central heating.

 

[briony10]

Just to summarise (got to call the plumber)...the best option seems to be a smaller tank with a Horstmann digital controller to switch between the two rates?

Any recommendations on tank size, the one now is very approx. 160cm tall/ 65 inches?

 

[flameport]

Given that the two elements had completely different wiring to two separate meters, is it going to be a big job to replace the current wiring with the boost control switch just suggested (http://www.tlc-direct.co.uk/Products/HOBX2000.html)?

No - very easy to install. It requires 2 seperate sets of wiring in (normal and the timer off peak / night supply) which is what you already have, and then it's just a flex to one or two immersion heaters.

 

[phatboy]

The size of cylinder depends on how much water you need, and your water system!

I'm guessing you don't have a pressurised system, so if you have 1 bathroom, I would get a tank about 160litres, if you have 2 maybe 180litres

 

[Lectrician]

The timer Flameport shows can't be used with your tarrif and metering arrangements.

In my opinion I would always go for two elements - even if you only opted to use one (initially).

The size of the tank means little to how you power your element(s). If you had a huge tank, the element would still heat the same quantity of water (with in reason), as hot water rises and sits at the top of the tank ready to be drawn off.

I would go for two elements, and if this meant a slightly larger tank, I would not worry.

Down this way, out in the non gas served rural areas, small(ish) tanks with two elements are very common place.