Can someone explain how these storage heaters were wired via the contactor?

[ManchesterKirchoff]

Been round to a house to quote to replace some storage heaters for new panel heaters and came across a strange (to me at least) way of wiring the old storage heaters via a contactor in the board, as usually I see their own off peak consumer unit which powers up at night via economy 7.

From the pictures it seems the busbar for each row ends at the last breaker and there is no space to move any of the circuits away from the contactor to the main switch side and it MAY need a board change as a result. I have admitted to him as I’m an apprentice with limited experience of this type of wiring arrangement I would be out of my depth to consider doing such work.

I thought originally the three breakers next to the contractor fed the FCU’s for the storage heaters but when looking at the circuit ref’s they are on the middle shelf and there is also 4 heaters (so what do the breakers next to the contactor do and where do the supply and load for these come and go)?

I was pretty hesitant to leave the job after seeing inside the board so I didn’t stay long but I would like to understand what’s actually going on so that once I’m qualified I could actually feel confident going into a job like this.

One thing to note for any help is I tested to see if any of the FCU’s were live. (The three storage heaters were dead) but circuit 5 listed as “bedroom right” was actually a panel heater- this was live at 230v until the breaker was switched off so this surely must have not been running through the contactor.

Cheers in advance for any help!

 

[Avo Mk8]

A change from the old separate cu for off-peak electricity to 'whole house' switchover for meters, and then since 2018 environmental legislation to require heaters to incorporate energy saving tech, including a thermostat and timer/ programmer, have meant wiring requirements have changed a lot over time. That board is surely from the earlier days, mid-sixties or maybe '70's ??

I think panel heaters are normally wired to a 24hr supply (as opposed to older storage heaters). Panel heaters work on the principle of radiating the heat directly at you, which makes you feel warmer than just heating the air. Most people want the warmth during the day, so the panels heat during the day. Modern ones have built in thermostats, timers, 'open window' detection etc, and often remote/wi-fi control.

So I don't think your potential customer's contactors will be required in the future. And that is why you found the one panel heater to have a 24hr supply.

But I'm not the best person to comment on the intracies of that board!

 

[ManchesterKirchoff]

So I don't think your potential customer's contactors will be required in the future. And that is why you found the one panel heater to have a 24hr supply.

Cheers for this, this was about the only conclusion I actually managed to make myself. Was hoping to move breakers about in the board so they would all be on a 24hr supply but doesn’t appear to be possible and no longer as simple a job as I thought it would be

 

[snowhead]

There have been multiple configurations of Off Peak / E.7 over the years ranging from DNO switched Off Peak C.U feeding storage / water heating to Dual Rate E.7 meters with no Off Peak switching provided by the DNO for customer use only for switching the meter over.

On the pictured C.U,

Bottom row,, Main Switch (Supplier feed into bottom) Top busbar feeding 4 adjacent MCB AND Red feed to row above. (live 24hr)

Middle row,, Red feed from bottom row into top of 8 MCBs and Busbar. (live 24hr)

Top row,, 4 pole contactor plus 3 single relays.

The contactor will be fed from either a separate customers timeswitch or a fused timed feed supplied by the DNO (nowadays Supplier) near the meter.

The Storage heater circuits will be connected to the contactor and relays, which will be fed from some of the MCBs (labelling not clear).

All MCBs are on 24hr so if your scrapping some or all of the Storage heaters and Off peak water heating, disconnect the feed from MCB to contactor or relay and connect panel heater direct to MCB instead.

If your scrapping all Off peak, the contactor and relays can be removed BUT find, make safe and disconnect the timed supply first.

 

[Mike Johnson]

Thirteen module three tier board, power in at the top by bus bar and supply at the bottom, French by any chance?

 

[freddo]

That board is surely from the earlier days, mid-sixties or maybe '70's ??

I was thinking early 90s ?

 

[ipf]

MG multi 9 came in mid 70's.
Not sure with that Eaton contactor, though. 80's early 90's, I'd guess.

 

[freddo]

MG multi 9 came in mid 70's.
Not sure with that Eaton contactor, though. 80's early 90's, I'd guess.

Oh wow 1974 according to their website for multi 9! I had no idea they could be that old!

 

[ManchesterKirchoff]

Thirteen module three tier board, power in at the top by bus bar and supply at the bottom, French by any chance?

I’ve tried googling the brand and I can’t find anything on them, got to be an obsolete board. It’s more the contactor/3 relays at the top I’m struggling to get my head round, no doubt there’s logic behind it but I wouldn’t know why or even how to properly get rid of them for the customer as the storage heaters are being replaced for panel ones which need a 24hr supply

 

[loz2754]

All the information you need is in the post above by @snowhead.
You just need to follow the wiring to work out how achieve your aim.

 

[ipf]

You've googled the brand....was there a brand name on it?
It may be bespoke, made up by a contractor, perhaps, with different makes of components. There was quite a bit of it at the time, especially involving off peak systems.

 

[oscar21]

That is an electra Tech board, I think they were fitted when Norweb etc still used to do installs. The three things next to the contactor are actually single pole contactors with a 24V coil, originally there would have been more where the Eaton contactor is and that will be a replacement for when the electra tech stuff stopped working. The eaton contactor must have a timer somewhere external to control it.

The original contactors were controlled by an external basic computer/controller with a keypad mounted in the property somehwere, there is normally an adaptable box next to the mains unit with the brainbox inside it and a 24V transformer sat inside the mains unit, looks like it used to be to the left of the main switch.

All the MCB's are live 24hrs and their output is fed via the various contactors to the heaters and immersions. There was a later verison of electra Tech that used wireless and you could fit an adaptor round a socket or spur etc that switched it on and off remotely, only ever seen a couple of versions of those knocking about and neither worked.

I found this thread from a few years ago with a couple of extra picutres.

Electra Tech Replacement

Hello, This controller below needs replacing, can anyone shed any light on a replacement model as it seems the company has gone bust. Thank you.

www.electriciansforums.net

PS The one I adapted the other month was in Middlewich, it looks remarkably similar to your pictures.

 

[ipf]

Seems they used to be installed by Norweb/Manweb back in the 80's.
From what I've read, the best thing to do is replace them. It seems you can retro fit any make of gear, judging from photos.

 

[davesparks]

Thirteen module three tier board, power in at the top by bus bar and supply at the bottom, French by any chance?

It's Merlin Gerin kit so yes, of course it's French, they are a French company.

 

[davesparks]

I’ve tried googling the brand and I can’t find anything on them, got to be an obsolete board.

Merlin Gerin is now owned by Schneider and was/is the manufacturer of some of the best off-the-shelf switchgear you can get.

 

[freddo]

Merlin Gerin is now owned by Schneider and was/is the manufacturer of some of the best off-the-shelf switchgear you can get.

I really like the new PON boards, it's nice the single phase boards are now side hinged instead of bottom hinged too. I hate that they moved the earth terminals to the top though, having 3 layers of terminals in the larger boards is a nightmare.

 

[Mike Johnson]

Strange that France has standardised on thirteen module boards and Germany have standardised on twelve module boards, must be a germanic thing about being orderly/symmetrical.

 

[Mike Johnson]

It's Merlin Gerin kit so yes, of course it's French, they are a French company.

Did not know that France extends as far as Manchester.

 

[nicebutdim]

Did not know that France extends as far as Manchester.

Part of Guy Verhofstadt's cunning plan.

 

[ManchesterKirchoff]

There have been multiple configurations of Off Peak / E.7 over the years ranging from DNO switched Off Peak C.U feeding storage / water heating to Dual Rate E.7 meters with no Off Peak switching provided by the DNO for customer use only for switching the meter over.

On the pictured C.U,

Bottom row,, Main Switch (Supplier feed into bottom) Top busbar feeding 4 adjacent MCB AND Red feed to row above. (live 24hr)

Middle row,, Red feed from bottom row into top of 8 MCBs and Busbar. (live 24hr)

Top row,, 4 pole contactor plus 3 single relays.

The contactor will be fed from either a separate customers timeswitch or a fused timed feed supplied by the DNO (nowadays Supplier) near the meter.

The Storage heater circuits will be connected to the contactor and relays, which will be fed from some of the MCBs (labelling not clear).

All MCBs are on 24hr so if your scrapping some or all of the Storage heaters and Off peak water heating, disconnect the feed from MCB to contactor or relay and connect panel heater direct to MCB instead.

If you’re scrapping all Off peak, the contactor and relays can be removed BUT find, make safe and disconnect the timed supply first.

You’ve explained it brilliantly- I have seen storage heaters powered via a contactor before which makes sense when having only the one consumer unit, but I still don’t understand the role of the relays in this configuration- Why are they there when it could just be the contactor, with the load of the contactor supplying the power to the MCB’s during E7 hours?