Controlling storage heaters on domestic 3 phase supply

[fuzzytrifle]

I've got a domestic 3 phase supply with economy 7 and want to connect a couple of storage heaters in the garage.

I'm planning on connecting the heaters on radial circuits to a seperate consumer unit and timeswitch, but recently I've read a few artilces that mention radio teleswitches but don't know anything about them. Is it something that I'd have to ask my supplier to add to my existing meter?

Untitled

• fuzzytrifle
• 30 Mar 2013
• 1

Can anyone tell me what the small white thing (with the red dots and neutral cable) is next to the fuses?

 

[dingodeano]

Looks like a fuse.

 

[westie101]

A couple of questions first

Are you already on an off peak tariff?

Do you have existing storage heaters

 

[AdrianUK]

The white thing is a fuse. The supplier has left you a switched neutral ready to use to operate a contactor to control the feed to the storage heaters. The control switching is already incorporated into the meter.

You need to source a suitable contactor & enclosure. From a fused way in the 24hr board you feed through the contactor coil & returns its neutral to that fuse. The contactor will then be energised during the economy 7 period.

From another way in the 24 hr board you can take a suitably fused feed through one of the main contacts of the contactor & onto the storage heater. You can do likewise with the other two main contacts of the contactor. If you need more than three storage heaters then use the contactor to feed an off peak board.

 

[OwainDIYer]

The small thing is a fuse. Depending on the meter it's an output for powering the teleswitch or controlling a contactor, or an input from a teleswitch for rate changeover.

To get Economy 7 you will need to have your electricity supplier install Economy 7 metering.

That hole at the bottom of the meter box should be grommetted.

 

[Lectrician]

As above, the white fuse or link will be a switched neutral on rate change (most likely).

Your tails look like single insulated cores from an SWA?

In my experience with TP metering, the DNO will provide a pair of volt free (low current) contacts for customer switching, not just a switched neutral. It is difficult for you to use a switched neutral and comply with BS7671.

 

[AdrianUK]

In my experience with TP metering, the DNO will provide a pair of volt free (low current) contacts for customer switching, not just a switched neutral. It is difficult for you to use a switched neutral and comply with BS7671.

I agree that a switched neutral falls outside BS7671 ..... then then so does the meter install ... the DNO is not bound by BS7671. Consider the colour of the wire that the DNO has used to connect to the fuse & follow its route back to the neutral block...

The reason that this is done by using a switched neutral & not a switched live is for fraud prevention purposes.

 

[Lectrician]

I know the DNO are not bound to BS7671, but we are, which is why I made the comment. You should request a dry pair if contacts. These are often available within the meter, or they can fit a boxed contactor to their switched neutral. We can't really do that as we should not pull a live from our installation to that neutral.

 

[davelx]

I know the DNO are not bound to BS7671, but we are, which is why I made the comment. You should request a dry pair if contacts. These are often available within the meter, or they can fit a boxed contactor to their switched neutral. We can't really do that as we should not pull a live from our installation to that neutral.

It looks to me as if the meter does have dry contacts, and that one side of those contacts is linked to neutral by the thinner blue cable running from the service head N/E block to the meter.

So I would think it is simply be a matter of disconnecting that link to make the both side of those contacts available

View media item 59317

 

[Lectrician]

Yep, it certainly looks like that. Strictly speaking, the meter operator should alter that........, but hey.

 

[RF Lighting]

3 phase supplies and interfering with meter connections is certainly not DIY work.

 

[fuzzytrifle]

A couple of questions first

Are you already on an off peak tariff?

Do you have existing storage heaters

Yes, I already have economy 7, and no we don't have any storage heaters. The house is heated by a 3 phase ground source heat pump, but the garage/workshops aren't heated.

 

[fuzzytrifle]

Your tails look like single insulated cores from an SWA?

Yes, the tails are single insulated SWA that go to a switch fuse then busbar chamber.

 

[Lectrician]

Single insulated SWA? That is a cr@p install, and non compliant. Should be double insulated.

 

[fuzzytrifle]

Thank you for the replies.

I think for ease of installation and cost I'll just get heaters with built in time switches connected to their own board fed from the busbar chamber. There will only be a maximum of 3 heaters and I could always invest in contactors etc. later on.

Is the 'DNO' different to my supplier? Just wondered who I contact if I do decide to use the radio timeswitch option.