Boiler for electric-only flat

AngelaDub · 2 June 2017 at 10:50AM

Thanks Robin9 for answering. We own the flat so would be happy to replace the old cylinder with a modern one if it were to save electricity.

We are doing a test: Currently the cylinder heating is on a timer and only heats between 2am and 5am to take advantage of the Economy7 tariff. In the morning the water is piping hot and this evening I will check if it is still hot enough. We have access to our meter so I can work out how much this costs us to run the heating of the cylinder for 3 hours a day only.

If the water is not hot enough this evening, would it be better to improve the lagging on the current old cylinder or to replace with a modern cyclinder. Isn't the current cylinder really big for just two people, especially seeing as our showers are electric showers and don't use the cylinder water.

Thanks again for all your help!

AngelaDub · 2 June 2017 at 10:51AM

@Richie-from-the-Boro I'm sorry but that is the link provided by the image hosting site, please use @molerat's link, they appear to work.

Having seen the photo - is this cylinder really old? It's covered with cotton wool wrapped in red plastic which we could definitely improve, but should we rather buy a new modern cylinder with insulation?

lstar337 · 2 June 2017 at 12:08PM

You either need to sort out the lagging on that tank (as it is woeful), or get a new tank.

You need one with built in insulation.

Something like this: https://www.kingspanenviro.com/range/fortic-combination-copper-cylinders

They are very efficient, and will store hot water with minimal losses. Your tank is pretty pathetic by modern standards, but if you can get a good jacket on it it will help for a lower cost.

lstar337 · 2 June 2017 at 12:13PM

AngelaDub wrote: »

Isn't the current cylinder really big for just two people, especially seeing as our showers are electric showers and don't use the cylinder water.

If you think it's too big then it is. It's yours, so you know what water you need.

With a proper E7 tank you have two elements. One sits at the bottom and heats the whole tank using E7 electric overnight. The other sits near the top and heats just a little water quickly for other small tasks. The upper element is often used 'on-demand' and therefore on higher rate electric.

AngelaDub · 2 June 2017 at 1:28PM

@lstar337 Thanks very much for explaining this. I'll have a look tonight to see if I can figure out if our tank is of this type. Do you have any advice on how to work out if it has two elements? The cable with the timer definitely goes into the bottom half of the tank, but I haven't investigated the top.

molerat · 2 June 2017 at 2:21PM

The other problem you have with that tank is the low head (from the header tank on top of it) meaning low water pressure, not very good if you want a mains shower - in fact you probably can't run a shower from it at all. A new unvented cylinder would give you a better pressure - is your cold water pressure good ?

AngelaDub · 2 June 2017 at 4:45PM

@molerat The hot water pressure is terrible, especially in the kitchen! The cold water pressure is good.

We would love higher hot water pressure - can the unvented cylinder still work to take advantage of Economy7 and be on a timer switch, etc. ?

coffeehound · 2 June 2017 at 5:50PM

That cylinder is probably from the 1970s or early '80s. (Make sure that you get the scrap value of the copper!)

Yes a 'direct' unvented cylinder is one heated by electric element(s). Either the time-switch in your meter if you have one, or a simple separate timer can be used to control when the E7 heater element is switched on.

Have a look at online cylinder size calculators and check with your plumber what size you need. Probably something like a 210 litre would be enough. Since modern cylinders tend to be tall and narrow, hopefully the new one will fit in your existing cupboard. There are a few external accessories to fit in the cupboard as well.

You might need a larger bore cold water inlet pipe to feed the combination of hot water cylinder and showers being used at the same time.

Richie-from-the-Boro · 2 June 2017 at 8:59PM

Your immersion heater is :

- under or uninsulated
- about 150 litres old school
- with a matching sized cold only header tank
- and a mix of copper & PE-X Pipe

I assume the heating element are / is on the LHS of the cylinder as viewed [which we can't see] and would expect to :

- x2 heating elements both top & bottom
- x2 sets of wiring going to those top & bottom heating elements
- x1 water controller

"Occasionally we might want to have a bath" is going to need a 150 litre minimum unless you want to sit in 2" of water, the general rule is the max size you can get into the space. A proper PartL cylinder will double the insulation value and half the loss of heat into the house from the cylinder. Your water pressure will always be very poor, you would need that weight of water with the shower on the floor below to get any real shower pressure benefit. An average 1700 x 700mm bath is going to be about 100 litres @ 40°C with a 50/50% hot cold fill coming out the cylinder @ 60°C. A power shower 120 litres and an ordinary shower about half that volume.

average 1700 x 700mm

coffeehound · 3 June 2017 at 8:16AM

I believe these showers contain an internal pump which would indicate either they are being fed from a header tank, or that the mains pressure is low..

Boiler for electric-only flat

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