10.5kw Shower and Storage Heaters?

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dandare1980

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Hi,

I would be grateful for some advice regarding a potential electrical upgrade which I intend to get completed this summer when we have our kitchen and bathroom refurbished. I will engage the services of an electrician nearer the time, but wanted to explore some possibilities to help with planning the works.

A bit of context first - The property is a small ex-council 3 bed semi built in 1937 and most electrics appear to be from the 80s. Everything is set up around economy 7 (no option for gas). Heating is delivered via 7 storage heaters, hot water comes from a cylinder with immersion element and the kitchen has a free standing electric cooker.

EON upgraded us to a smart meter when we moved in and fitted a separate non-adjustable time switch which activates the storage heaters via their own consumer units (2 in total).
The economy 7 night rate is active for 7 hours between 1:30 and 8:30 am in the summer, and 12:30 and 7:30 am in the winter.

The storage heaters collectively draw as much as 13.6 kw at peak. The 3 kw immersion is on a timer and generally used between 5:30 and 7.30 am, then a short boost 5:00 to 6:00 pm.
We don’t have a shower and would really like to fit a 10.5 kw unit when we upgrade the bathroom. This is where I have concerns – although our supply is rated at 100 amp, would I be in an overload situation if I was to shower when the storage heaters and immersion are all going together?

This is a likely as we are all up and getting ready before the storage heaters switch off. Worst case scenario would be the storage heaters, immersion, hob plate and kettle are all going while the shower is active (other than these items we have very few other power demands).

I understand that principles of diversity may apply. In practice, when the storage heater circuits are first activated there is likely to be a big draw, but as we’re all in bed, by the time morning comes and we want to use the shower etc. most heaters will be up to temperature and only drawing intermittent power through thermostatic control. Of course, none of this is an issue in summer.

Should I instead consider a less power hungry 8.5 kw shower or do away with the idea and opt for better stored water and a pump (not preferred)?

Our current collection of consumer units (4) is a total mess so I will be getting quotes to have the lot upgraded. I am hoping it will be no more than 2 units, one for storage heaters the other for everything else.

I wanted to consider RCBOs instead of a dual RCD setup, but the cost may be prohibitive. I have thought about only applying the RCBOs to the main board, leaving the storage heaters protected by a single RCD. I have often seen showers on their own consumer unit but assume this wouldn’t be necessary with an appropriately sized consumer unit.

The electrician will need to install it to meet regulations so I may have no say on this point anyway.

Any advice or recommendations will be gladly received.

Regards,

Daniel.

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You’ve got a lot  to think about ...

re the shower, ignoring the suppliers fuse, what size is the cable! You can’t simply fit a more powerful model

Re the fuseboard rcbos is the way to go .... and I would advise against a single rcd board for the heaters, as 1 fault will mean no heat at all

best you get 2 or 3 sparks round to take a look and offer an opinion .... find them from recommendation too

 
Last edited by a moderator:
Hi Murdoch,

There's currently no shower at all, so the wiring run will be new and appropriate for the chosen rating of shower - I'm just trying to workout if the electric shower's a no go alongside storage heaters so I can look into alternatives.

Good point about the RCD on the storage heaters - RCBOs it is then - just very expensive for the number I'll be needing 😐.

 
Hi Murdoch,

There's currently no shower at all, so the wiring run will be new and appropriate for the chosen rating of shower - I'm just trying to workout if the electric shower's a no go alongside storage heaters so I can look into alternatives.

Good point about the RCD on the storage heaters - RCBOs it is then - just very expensive for the number I'll be needing 😐.




Not necessarily - just get sparks to give you pricing for the job.

Where in the UK are you?

 
RCBOs cost abit more, but are worth every penny.

By the time you get up early in the morning, the storage heaters should be more or less fully heated up, so won't be drawing full current.

 
Thanks Binky, I can see the sense of choosing RCBOs over the older style set ups.

I've dug out the power monitor display from when the smart meter was installed and if the battery can hold for more than 5 minutes I'll see what's being drawn tomorrow morning before the economy 7 tarrif switches over.

 
7 storage heaters is a LOT for a 3 bedroom semi.  

I would get all your consumer units updated as already advised and part of that process will be testing of the instalation.

I would not be worried by 13KW of heaters and a 10 KW shower. By the time you shower in the morning the heaters will mostly be up to temperature and will have switched off.  Diversity is your friend.  Plenty of houses have just this arrangement.

But as an alternative thought, electric showers are pretty rubbish.  How about a decent sized unvented hot water tank?  That will be heated by the immersion heater and will deliver mains pressure hot water, and a thermostatic mixer shower will give you the daddy of showers, and you would never want to go back to an electric shower again.

 
Thanks for the advice Dave.

We have storage heaters in the 3 bedrooms, one in the hallway downstairs, one in the living room, one in the kitchen and a small one in the bathroom.

A better hot water cylinder - thermal store or unvented - is possibly worth another look.

We have no shower at all currently so even an electric shower would be a great improvement 🙂.

 
Given that electricity is the most expensive form of heating there is, HUGELY expensive compared to gas, why not just get gas central heating. be MILES cheaper i would have thought..

john..
works.

A bit of context first - The property is a small ex-council 3 bed semi built in 1937 and most electrics appear to be from the 80s. Everything is set up around economy 7 (no option for gas). Heating is delivered via 7 storage heaters, hot water comes from a cylinder with immersion element and the kitchen has a free standing electric cooker.

??

 
Given that electricity is the most expensive form of heating there is, HUGELY expensive compared to gas, why not just get gas central heating. be MILES cheaper i would have thought..

john..


Hi John,

Unfortunately there is no mains gas where I live, so it's oil or electric for the mainstream choices.

Despite the lack of immediate temperature control with storage heaters, we've found them to be a very reliable solution to heating our house. They also have practically no servicing costs.

In a typical year we use around 11,000 Kw on the night rate, which at our current 6.05 pence per Kw you're looking at £665.50 for the year (heating only).

Any savings made from installing an alternative system would take years to pay back and we're not likely to be here long enough to benefit from it unfortunately.

Regards,

Daniel.
 

 
Update.

I think for simplicity I'll press ahead with an 8.5 Kw shower, just to give me a few more amps of wriggle room.

I've contacted Western Power and they're happy to send someone out to check the main fuse is rated at 100 amp (fingers crossed).

I'm also contacting my supplier EDF to see if they can rid me of the smart meter - it hasn't been "smart" since 2015 when I changed provider. The setup with an external heating contactor is both messy and very noisy when it operates. The previous Landis + Gyr meter had an internal contactor and relay for the storage heaters which was silent in operation and much less cluttered.

The shower priority devices are quite interesting, but hopefully an added cost I can avoid by choosing a lower rated shower.

I want to stick with an instantaneous shower device Vs a stored solution, as it will require some fairly extensive tank upgrades otherwise.

I'm getting the consumer units upgraded and as the shower is no more than 5 metres from this location the cost for installation shouldn't be too bad. If I opt for an unvented cylinder or bigger tank and pump, it's going to cost considerably more.

Out of interest I observed the wattage draw when I got up this morning at 5.30 am via my smart meter's half-broken wireless screen. The storage heaters were active and the immersion had just come on timer. The draw ranged from around 2 Kw to 8 Kw peak, but the higher loads were only present for several minutes at a time.

I'm hoping the electrician will be happy to fit all general circuits including the shower onto a 100 amp consumer unit with RCBOs. The storage heaters can be consolidated onto another 100 amp unit, but I might request a split dual RCD board to keep costs down - hopefully with a mix of heaters on each protected run so if a fault condition occurs in the middle of the night I won't lose all the heaters.

Hopefully this approach won't see the Henley blocks, meter, contactor or main fuse overloaded - not for any considerable amount of time anyway.

Daniel.

 
Might I suggest that you speak to our SBS Dave who provides RCBOs and units at a reasonable price? Can’t imagine for the few circuits you have that it’ll cost a fortune? 

 
I'm also contacting my supplier EDF to see if they can rid me of the smart meter - it hasn't been "smart" since 2015 when I changed provider. The setup with an external heating contactor is both messy and very noisy when it operates. The previous Landis + Gyr meter had an internal contactor and relay for the storage heaters which was silent in operation and much less cluttered.
 
I would be interested to hear how you get on with that and if they do swap it out.

 
Given that electricity is the most expensive form of heating there is, HUGELY expensive compared to gas, why not just get gas central heating. be MILES cheaper i would have thought..

john..


This is point that seems to be ignored with the latest carbon neutral, eco, green, campaigns to ban all gas boilers and fit electric boilers instead, How much is that going to cost the typical family household on average usage?

Doc H 

 
This is point that seems to be ignored with the latest carbon neutral, eco, green, campaigns to ban all gas boilers and fit electric boilers instead, How much is that going to cost the typical family household on average usage?

Doc H 
Totally agree, the electric boiler is the most bizarre invention know to man.

Electric heating makes sense if, as we have done, you do it by using a heat pump, that then brings the cost of electric heating down to being comparable to mains gas.

 
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