New Economy 7 storage heaters and their supply.

Apologies if this has been answered before but I did look in the forum and although similar questions have been asked I think this is a new one so any advice or information would be very much appreciated…

I have an old (approx 30 year) Creda warm air storage heater in my flat which is not quite upto the job in the depths of winter. As such I am looking at installing a couple of new storage heaters thereby still taking advantage of the E7 supply I have.

My question is with regard to supplying these new storage heaters as I already have a fused CU which supplies the whole flat from the 1 set of tails at the prepayment meter although there is also a smaller cable from this meter which I believe is the teleswitch which activates the Creda storage heater at midnight which then draws from the existing CU and then also powers the warm air fan on demand the next day.

As I am looking at installing 3 new storage heaters, please can anyone tell me how I should supply these. I believe I should install either a dual fed CU or separate CU (I was looking at upgrading the old one to MCBs anyway) which will supply the storage heaters from midnight. My question is, should this new CU be fed from separate tails from the meter or use the existing set of tails and utilise the timeswitch to activate the other half of a split CU via a contactor.

I have rung and asked my supplier (NPower) 8 times now and cannot get a word of sense from them, so any help and advice from the good people on this forum would be much appreciated.

Many Thanks,

Brixnmorta.

A picture of your supply will help.

Yes, we like pictures!

Are you able to identify which fuse supplies your current storage heater?

The usual way (that I have seen at least) is to have each storage heater run on its own circuit from a 15A fuse (16A breaker)

These are then supplied either from a separate CU or from a dual tariff CU, which has a separate bank for the storage heaters and is powered only during the cheap rate hours.

Where there is a combo storage heater with a fan the fan side is normally run from the normal circuit so that it will work at any time.

If you are replacing the consumer unit before July you should be able to use a split load dual tariff board, but after that (and possibly might be the best option now) two consumer units may be a more sensible way to go - one covering your normal power/lighting with RCD protection as appropriate, to replace your old board, and a separate board to supply the new heaters - one circuit per heater unless they are very low power.

Many thanks Dartlec and Securespark for you input and your interest, (which is far more than I have had from NPower after my 8 calls !).

I will supply pictures as soon as possible but I work away from home at the moment so it will may be a little while before I can get them but please bear with me as any help or advice is very much appreciated.


Yes I do know that each of the new storage heaters should be on its own radial circuit (which shouldn’t be an issue) it is just the switching and supply of the E7 that is the issue at the moment.


I have only been in the flat a couple of months so this is my understanding of the existing system…

I have a prepayment meter with one set of 25mm tails feeding the main CU and a small set of tails (approx 4mm) feeding a single fused unit. I believe this small set of tails from the meter is the timeswitch which goes live at midnight and therefore tells the existing Creda warm air storage heater to start drawing power from the 45A fuse in the main CU. This supply is also used the next day to power the fan (as you rightly said Dartlec).

The advantage of this system is that all of the supply drops onto the cheap rate at midnight which should be handy for doing the washing and I am looking at getting a Horstmann Economy 7 Quartz Controller to supply the immersion on the off peak rate as well.


So my question is how should I best supply the new storage heaters to work off the E7 supply at midnight onwards. I believe my 2 possible options are:

1. A dual fed CU utilising the existing tails which will feed all of the existing supplies and also the other side of the CU but via some form of contactor which would be switched by the existing timeswitch supply and thereby only power up after midnight, and obviously the new wall mounted storage heaters would be connected to this side.
I am not sure if such a contactor exists, if this way of utilising the E7 supply is ok or if this is complaint with IEE regs.

2.A dual fed or 2 CUs with the normal day rate on 1 and E7 on the other, fed via 2 sets of 25mm tails from the meter. My issue with this idea is that I need NPower to supply another set of tails from the prepayment meter to the new CU for the E7 side… As I haven’t had any sense out of them upto press I don’t rate my chances of getting this done…. Unless someone can advise otherwise ?

Many apologies for this second long post but I am trying to explain without pictures… and they do paint a thousand words as they say !


One other question I have is with regard to your post Dartlec when you said I can use a split load CU before July but will need 2 separate CUs after July… Is there a change to the regs or something I do not know about ?



Thanks for reading.

Brixnmorta said:

I have a prepayment meter with one set of 25mm tails feeding the main CU and a small set of tails (approx 4mm) feeding a single fused unit. I believe this small set of tails from the meter is the timeswitch which goes live at midnight and therefore tells the existing Creda warm air storage heater to start drawing power from the 45A fuse in the main CU. This supply is also used the next day to power the fan (as you rightly said Dartlec).

Click to expand...

That sounds about right to me

The advantage of this system is that all of the supply drops onto the cheap rate at midnight which should be handy for doing the washing and I am looking at getting a Horstmann Economy 7 Quartz Controller to supply the immersion on the off peak rate as well.

Click to expand...

These days, generally most E7 supplies are cheap rate for all power during the cheap rate, normally use a dual rate meter, which also contains a contactor which energises a second set of tails at cheap rate, on older system involved a separate white meter for the heating load and only this was charged at cheap rate, but these days a dual rate meter is the norm

Normally E7 setups have two immersion heaters, one being fed from the same place as the storage heaters

So my question is how should I best supply the new storage heaters to work off the E7 supply at midnight onwards. I believe my 2 possible options are:

1. A dual fed CU utilising the existing tails which will feed all of the existing supplies and also the other side of the CU but via some form of contactor which would be switched by the existing timeswitch supply and thereby only power up after midnight, and obviously the new wall mounted storage heaters would be connected to this side.

Click to expand...

Storage heaters are normally fed from a second CU, which is fed from a second set of tails (or a special dual rate unit which combines both in one box), no reason you couldn't use either of these in conjuction with a suitably rated contactor

2.A dual fed or 2 CUs with the normal day rate on 1 and E7 on the other, fed via 2 sets of 25mm tails from the meter. My issue with this idea is that I need NPower to supply another set of tails from the prepayment meter to the new CU for the E7 side… As I haven’t had any sense out of them upto press I don’t rate my chances of getting this done…. Unless someone can advise otherwise ?

Click to expand...

That would be the normal way, yes, but as to getting sense out of Npower, I don't know! could speak to central networks (lincs DNO), but they probably need a work order from npower?


The other option if you can't get a second set of switched tails provided, instead of a big contactor for everything, a small one for each heating circuit, which are fed from a CU connected to the main tails

One other question I have is with regard to your post Dartlec when you said I can use a split load CU before July but will need 2 separate CUs after July… Is there a change to the regs or something I do not know about ?

Click to expand...

at the end of june BS7671:2008 properly replaces BS7671:2001(2004), and rquires RCD protection for unprotected cables in walls of domestic houses (thats about the measure of it, if you want the exact requirements, just ask!), this means that just about every circuit needs RCD protection, so a split board that only provides it to half doesn't cut it anymore

Anyhow, where abouts in Lincolnshire are you? and not interested in some S/H storage heaters are you? (I know someone who is being messed around by a buyer on ebay, and so has somewhat of an obstructed hallway at the momment... )

Brixnmorta said:

One other question I have is with regard to your post Dartlec when you said I can use a split load CU before July but will need 2 separate CUs after July… Is there a change to the regs or something I do not know about ?

Click to expand...

That was a slight simplification...

The new Wiring regulations BS7671:2008 come into effect on 1st July. (You can actually choose between the previous and new editions at the moment but from that date the old ones become obselete)

One of the things the new regulations will require is that most circuits in a domestic property will have to be RCD protected. Up till now, it is has generally only been required on sockets and outdoor equipment (again I'm simplifying).

That means that while currently 'split load boards' can be considered to comply with the regulations (though not by everyone), from July 1st they almost certainly will not.

While you don't have to bring existing installations up to the new standard, if you install a new consumer unit, that WILL have to comply.

There will be a number of ways you could do that. You could use RCBOs (in conjunction with a split load board or not), you could use multiple RCD incomers.

I haven't looked to see if the manufacturers have come up with 17th edition compliant dual tariff boards yet, but they may do so - though they will be quite wide and sometimes two smaller CUs are easier to fit physically.

EDIT: BAH, too slow

Brixnmorta said:

I have a prepayment meter with one set of 25mm tails feeding the main CU and a small set of tails (approx 4mm) feeding a single fused unit.

Click to expand...

Hmm, does that unit actually contain an accessible fuse? If so what size? Is it linked to the CU at all? Most timeswitches I've seen don't have fuses that are user accessible.

It sounds almost as if the overnight part of the storage heater may be run directly from those 4mm tails through this fused unit, which could be the timed output?

If so you will likely need a new meter. You will probably find your best bet is to send a letter to NPower rather than phone. They *should* then pass it on to the DNO, who are the ones who actually do such work. However, you can rarely if ever talk directly to the DNO in my experience.

How big is the storage heater? 45A sounds a lot for a single storage heater

The way I read it was that he has a one way CU for the single SH in the property, but we'll find out for sure when the pix are posted.

Normaly in a E7 metering setup, the 25mm DI mains tails come from the service head & go to a dual rate meter. From the meter the 25mm DI Neutral tail goes to a service block, & then from the block 1 25mm DI Neutral tail goes off to the Peak CU & 1 25mm DI Neutral tail goes off to the Off Peak CU. From the meter the 25mm DI Live tail goes to a service block, & then from the block 1 25mm DI Live tail goes to the Peak CU, & then from the block 1 25mm DI Live tail goes to the Live input of the Radio Teleswitch. Also from the Live service block, & from the Neutral block a 16mm? tail goes to the Radio teleswitch (To supply the timer?). From the Live Output of the Radio Teleswitch a 25mm DI tail goes off to the Off Peak CU (This tail is only live when the Teleswitch turns on at 23.30). Also from the Radio Teleswitch a 16mm? Live tail goes to the Dual Rate meter (This is to switch the meter between the Peak & Off Peak Counters).

DI stands for Double Insulated

The Radio Teleswitch turns on at 23.30 & off at 06.30

The Pictures below are of the E7 setup at my Dad's flat, which is in Bexley.


A E7 Setup:



Meter wiring:



The Off Peak Heating CU:



The Peak CU:

Hi Guys,

Many thanks for your input, I feel incredibly humble that you have taken the time to read my posts, think about the issue and then make the effort to submit your thoughts in an attempt to help me, it really is much appreciated.

I am on the case with the pictures and have asked the old fella to pop down and take some to clarify my description.

In answer to your posts…

Adam_151
The other option if you can't get a second set of switched tails provided, instead of a big contactor for everything, a small one for each heating circuit, which are fed from a CU connected to the main tails

Click to expand...

At this stage I am certainly thinking a contactor is the way to go (can anyone recommend any ?) although I do like your point Adam_151 and think several small contactors would be better for redundancy, as if the one big contactor goes then that’s all the E7 heating out the window but several small contactors would prevent that possibility. Do you know any makes that would do the job ?

I’m definitely interested in buying some storage heaters (once I get the supply sorted) although I was looking at these nice slim line and very efficient Dimplex ones as I have heard very good reports on them. You can mail me direct on [email protected] and my location is on the Lincolnshire East Coast Riviera if you are anywhere near…. (Cleethorpes).

Dartlec
I haven't looked to see if the manufacturers have come up with 17th edition compliant dual tariff boards yet, but they may do so - though they will be quite wide and sometimes two smaller CUs are easier to fit physically.

Click to expand...

Dartlec, Many thanks for the explanation on the new regs and your point of the 2 CUs with regard to fixing, I think I am becoming enlightened.

Dartlec
Hmm, does that unit actually contain an accessible fuse? If so what size? Is it linked to the CU at all? Most timeswitches I've seen don't have fuses that are user accessible.

It sounds almost as if the overnight part of the storage heater may be run directly from those 4mm tails through this fused unit, which could be the timed output?

Click to expand...

The single fused unit (which is separate to the main CU – pictures to follow ASAP) is fed from the prepayment meter via the 4mm’ tails and then out of this unit from a 5A fuse on 2.5mm t+e to the Creda storage unit. I understand your thoughts on that this may be feeding the unit through the night, but I figured the 5A fuse is no way big enough for such a load and my suspicion is that the Creda unit is being fed from the 45A fuse in the night (via 6mm t+e) and this then also powers the fan and gives boost heating through the day. I have asked the old fells to turn the main CU off and just leave the small (one way) 5A unit on, therefore if the unit heats up we know it’s the main source of the load and if not it must be the timeswitched supply.

Dartlec
How big is the storage heater? 45A sounds a lot for a single storage heater

Click to expand...

Its big, I mean mammoth, approximate hxwxd dimensions are 6x2x2ft, and it blows warm in into 3 rooms of my 1 bed flat, I will try and get a picture of that also.

Securespark
The way I read it was that he has a one way CU for the single SH in the property, but we'll find out for sure when the pix are posted.

Click to expand...

There are definitely 2 feeds for the existing Creda warm air storage heater (I traced them in the loft), 1 feed from the 5A unit (which I think is the timeswitch as it has no voltage on it during the day, though I haven't checked at night as yet) and 1 feed from the 45A fuse in the main CU.


Many thanks for your explanation and pictures mdbalson, fortunately for me the existing system at my flat is quite a bit simpler although since seeing your pictures on the teleswitch I am questioning my theory on the 4mm tails being E7 switching but. I will get the pictures of it posted as soon as I can.


Many thanks to all for your help and advice, pictures to follow...

Brixnmorta.