Economy 7? Combination cylinder?

[SJRSJR]

Hello

Hoping for some pointers as it's been a while since I've had to deal with electric immersion heaters.

I need to replace an old heating cylinder and water tank in a ground floor one-bedroom rental flat. It's all in a cupboard and it's currently got a pump attached.

One plumber suggested an unvented system to do away with the pump and get more space. Another suggested a like-for-like replacement.

It's an electric-only flat (not a new build). I could do with improving its EPC rating (currently E) and the assessor who did it told me Economy 7 would be the best bet, and I could always add storage heaters down the line . It's obviously had it in the past because it's got an Economy 7 meter although everything is on the standard tariff.

I've looked online and an wondering whether an Economy 7 combination cylinder be the way forward? Any reason why the plumbers didn't suggest it? Thanks.

 

[stem]

It sounds from your post that you don't currently have an Economy 7 electricity supply available. So, unless you specifically asked them to include it, that will likely be why they haven't offered it, and instead just offered direct replacements.

Both vented and unvented cylinders are available with the provision for dual electric elements. The bottom element usually heats the whole cylinder on the 'off peak' rate, then should you happen to run out of hot water the top element can be switched on anytime as required as a boost. However, it doesn't usually provide a great deal of water that would be enough for a bath.

Usually there are two separate electricity supplies one for each immersion heater, an 'off peak' supply and a permanent one, so additional wiring would be required to provide the second supply, meaning that the plumber may also engage the services of an electrician, which he probably wouldn't do if it was just a straight swap for the existing cylinder.

Alternatively, it's entirely possible to just have one immersion heater fitted that heats the whole cylinder and that can be used with both on and off peak tariffs.

 

[SJRSJR]

Thank you stem. If it happens that there's only one electric supply, am I any worse off getting an Economy 7 cylinder even if can't be used for now - does it mean you would just have to heat up the whole cylinder on the peak tariff? What I want to avoid is tearing the flat apart for new wiring now, I'd rather do it in between tenants.

Alternatively, it's entirely possible to just have one immersion heater fitted that heats the whole cylinder and that can be used with both on and off peak tariffs.

Would you mind pointing me to the type of cylinder that does that - is it just a standard cylinder and it's down to the time of day that the demand is made i.e. from the supplier's end, rather than separate wiring.

 

[Madrab]

Firstly you need to find out what the cold mains dynamic flow & pressure is, this is to ensure that an unvented cylinder could be a viable option.

Is the current setup in a cupboard in the middle of the flat? If so then need to understand if there is suitable access to a drain or to outside, as the unvented cylinder safety devices will need this.

 

[SJRSJR]

Thans Madrab. The mains pressure is good although I take your point about checking it properly. I presume that's important if I have a un-vented cylinder?

Yes, the tank/cylinder is in a cupboard in the kitchen, which backs on to the bathroom. Currently the overflow of the water storage tank tees into the sink waste pipe on its way out.

 

[ericmark]

I was under the impression that electric water heating was expensive. I was told to use oil or gas rather than electric. However, when I fitted solar panels had an iboost+ fitted which records how much it uses, typically 2.5 kWh per week, less than a £1 a week, hardly worth worrying about.

However, if part of other items, maybe. I went from a single tariff to an EV tariff, which increased the day rate, for me with batteries so at least 6 kWh used overnight in the 5 hours of off-peak well worthwhile, and most days the solar does the daytime demand, but unless one sets the washing machine, tumble drier, and dishwasher to run overnight it may work out more expensive to single rate.

In a three-story house, we do not hear machines running overnight, in a flat that may be not the case. My 5 hours is at 8.95p per kWh but for 7 hours likely more expensive. Once I accepted the EV tariff I was locked in for 12 months unless I pay a £75 exist charge, so one does need to be careful.

 

[Madrab]

Thans Madrab. The mains pressure is good although I take your point about checking it properly. I presume that's important if I have a un-vented cylinder?

Yes - there is a min that constitutes a good working spec for an unvented, that is used in a house with say 2 bathrooms and maybe 4 or 5 outlets - 2.5bar @ 20L/min dynamic. Given it's a flat with I presume only 2 HW outlets and one or 2 cold then you could probably get away with lower flow and pressure figures but I wouldn't go much lower than 15L/Min@ 2 bar dynamic.

As long as there is an outlet that could cater for a potential boiling water discharge ( plastic pipe that can cope with high temps) then that's ideal.

 

[SJRSJR]

I went from a single tariff to an EV tariff

Hadn't even heard of EV tariff but I guess you need an electric car or, if they don't do checks, you need enough running overnight to offset the increased day rate.

 

[flameport]

Would you mind pointing me to the type of cylinder that does that - is it just a standard cylinder and it's down to the time of day that the demand is made

It's a standard cylinder with one element, and connected via a controller which connects the single element to either the off peak or day supply depending on what is available at the time.
Such as https://www.cef.co.uk/catalogue/products/4968610-bx2000-water-heating-boost-controller

 

[SJRSJR]

Ah thanks. So first I'd better establish if the Economy 7 wiring is still there. But even if it's not, rather than get a specific Economy 7 cylinder, once the wiring gets sorted a standard one could be adapted down the line with this controller. Sounds good