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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> Economy 7 Storage Heaters https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1241080699 Message started by Mikecork on Apr 30^th, 2009, 9:38am

Title: Economy 7 Storage Heaters
Post by Mikecork on Apr 30^th, 2009, 9:38am

I have an apartment which has Economy 7 storage heaters installed. There isn't a storage heater in the bedroom (only an electrical on-demand heater), is it possible to replace this with another Economy 7 storage heater by wiring it back to the Economy 7 RCB in the consumer unit? There are two 2.4Kw heaters in the lounge and a 1.7Kw in the hall at present. I would plan to install a 1.7Kw in the bedroom.

Thanks in advance for any help

Title: Re: Economy 7 Storage Heaters
Post by Zambezi on Apr 30^th, 2009, 10:05am

Can you give us some more details about the board feeding the other night storage heaters (NSH)? What turns the other NSH on and off (can be the E7 unit or it can be by timers)? What rating is the heater currently in your bedroom?

Title: Re: Economy 7 Storage Heaters
Post by Mikecork on Apr 30^th, 2009, 10:27am

I will have to check the capacity of the current heater and get back to you later. The Economy 7 is connected back to the central electrical cupboard for the whole block of apartments and is switched by the energy provider. In the consumer unit there is an RCB allocated for Econ 7 storage heaters.

Title: Re: Economy 7 Storage Heaters
Post by Lectrician on Apr 30^th, 2009, 10:59am

I assume you have two fuseboards. One for your usually electrical circuits, and one for your off-peak Econ 7 circuits.

If you currently have three storage rads you are likely to have 3 MCB's or fuses in the off-peak consumer unit feeding these.

There is a chance your heater in the bedroom is on it's own circuit from the 'normal' consumer unit. If this is the case, you could easily swap that circuit from one consumer unit to the other. If this is not the case you will need to run a new circuit from your off-peak consumer unit to your bedroom.

The only niggling thing with altering this is the RCD protection to buried cables. I would hazard a guess that your storage heaters do not have 30mA RCD protection (just like the majority of other homes). However, since the 17th edition of the regulations, any cables buried at a depth of less than 2" in a wall require RCD protection unless certain other criteria is met. So, if you do alter or install a new circuit, that single circuit will require RCD protection to comply to the 17th edition. A stupid reg, and one that causes issues with nearly every job we go to!

Title: Re: Economy 7 Storage Heaters
Post by Mikecork on Apr 30^th, 2009, 4:32pm

Thanks for the valuable information provided to date i appreciate the inputs. The current on-demand heater in the bedroom at the moment is 1Kw.

Title: Re: Economy 7 Storage Heaters
Post by Y3 on Apr 30^th, 2009, 6:08pm

Lectrician wrote on Apr 30^th, 2009, 10:59am:

So, if you do alter or install a new circuit, that single circuit will require RCD protection to comply to the 17th edition.

if he has to install a new circuit for this heater, then he can do so in surface trunking to avoid the rcd. chances are the night store cu wont take todays rcbo's.

Title: Re: Economy 7 Storage Heaters
Post by Lectrician on Apr 30^th, 2009, 7:09pm

An RCBO is not the only way to provide 30mA RCD protection ;-)

Title: Re: Economy 7 Storage Heaters
Post by Y3 on Apr 30^th, 2009, 7:27pm

No its not, the only other way i can think of is to put an rcd enclosure in before the off peak cu, but that wouldnt comply with 17 ed in the way that all the heaters would be affected by a single fault from just one heater, meaning all source of heat lost in one go. Is there a different way lec?

Title: Re: Economy 7 Storage Heaters
Post by Y3 on Apr 30^th, 2009, 9:18pm

wrote on Apr 30^th, 2009, 6:08pm:

Lectrician wrote on Apr 30^th, 2009, 10:59am:

So, if you do alter or install a new circuit, that single circuit will require RCD protection to comply to the 17th edition.

if he has to install a new circuit for this heater, then he can do so in surface trunking to avoid the rcd. chances are the night store cu wont take todays rcbo's.

I jumped the gun when i assumed that the cu for the night store would be old, its just that the majority of the ones i come across are, but this might not be the case with this scenario. An rcbo could well be used depending on the cu.

Title: Re: Economy 7 Storage Heaters
Post by Lectrician on Apr 30^th, 2009, 9:26pm

wrote on Apr 30^th, 2009, 7:27pm:

How about an RCD in a seperate two mod enclosure AFTER the MCB or fuse in the CU? As was often done to RCD protect sockets circuits when altering installs under the 16th ;-)

Title: Re: Economy 7 Storage Heaters
Post by Y3 on May 1^st, 2009, 7:05am

Ahh yes, turn it into a sub-main, should of thought of that.

Title: Re: Economy 7 Storage Heaters
Post by Lectrician on May 1^st, 2009, 7:45am

wrote on May 1^st, 2009, 7:05am:

Ahh yes, turn it into a sub-main, should of thought of that.

ehh?

No, I mean put an RCD in the cable between the CU and storage rad. This is usually done beside the CU - remove the cable from the CU, place it into the RCD. Then a new piece of cable from inside CU to the RCD.

This used to be done regularly when a customer did not want a new CU and you where fitting sockets etc.

Title: Re: Economy 7 Storage Heaters
Post by kamog on May 19^th, 2009, 7:04am

I was thinking of adding 2 x 1.7kW storage heaters in bedroom’s in my daughter’s house and totted up the wattage of the existing 4 downstairs storage heaters plus immersion heater. Divide by 230 volts to get amps = 55.2.

Noticed no seals on anything in meter cupboard!!!! – so pulled main fuse: 60A. Taking advantage of that removed a meter tail and found it’s 7/1.70 (Have micrometer to measure unsquashed core strand)

The meter is a modern digital, says 80A

The existing storage heater consumer unit is 4-way and is full. There is room to add another 2-way cu and feed it from the tails to the 4-way via tail connector blocks but it seems to me I have to get the fuse uprated and maybe meter and tails as well.

It’s quite likely the washing m/c will be timed to come on soon after off-peak is available, unlikely but possible a late night supper in the cooker could add to the load.

I think I need some advice on loading, maybe others will be interested in this aspect..

One more query re earthing the 2-way cu (if the loading doesn’t make the extra heaters impossible): There is room to run an earth cable from the 4-way to the 2-way but I notice that earth wire for each existing cu and a water bonding all run independently back to the earth clamp on the underground cable, each having crimped tag. Is this now the only way of making earth connections – in other installations I have often seen only one earth wire running round all cu’s and occasionally use of an uninsulated earth connector block.