Complicated dual tariff arrangement with four main switches.

[Selfmade]

Hi Folks

I'm used to (and understand reasonably well) simple dual tariff arrangements with two main switches (either two separate consumer units or a duplex). But I occasionally come across, and am now quoting for changing consumer units for a more complex arrangement that I don't full understand. There are four main switches, one for regular 24 hour loads (light, sockets, etc.), one for 24 hour heating, one for off-peak space heating, and one for off-peak water heating. I've seen this type of arrangement in a single duplex consumer unit, four separate consumer units, or two consumer units (one with all heating loads, one with just the 24 hour non-heating loads). So my questions are:

1. Why are the 24 hour heating and non-heating loads separate?

2. Why is the off-peak water heating load separate from the off-peak space-heating loads?

3. Is there any reason not to combine the loads onto two main switches, one with all 24 hour loads and one with all off-peak loads?

P.S. I can't remember the exact setup with the meters, but as far as I can remember, there were separate live tails to each main switch, each fed from different meter terminals, i.e. none of the main switches were fed from the same live meter terminals via a Henley block.

 

[ferg]

The Telemeter can have 3 outputs.
Storage, 24hr and hot water.

Plus normal for domestic board.

 

[littlespark]

I came across this set up the other day, so it’s not just a north of Scotland thing. (I’m south Scotland) and I do remember them being popular in the 90’s.
Scottish Power thing only I believe, and other suppliers don’t offer the same set up.

The one I saw was a MEM double row board with lighting and power on top, and the 3 heater circuits below.
Beware of borrowed neutrals in the heating side. Mine had storage heater points that had been moved to the 24hr heating side for replacements with electric radiators... but they had only moved the live conductors, not the neutrals.
3 neutral bars off the 3 mainswitches.
Works fine until one of the main switches is turned off.... then the neutral of the swapped over circuit doesn’t have a return path except through my finger!!

(Details changed for dramatic intent. Safe isolation procedures were followed, and N-E showed 240v.... no fingers were harmed in the making of this post)

 

[sunray]

My experience of this setup is the other end of the UK from Scotland, way down in Kent

 

[littlespark]

So its a little more common than you think.
Maybe other suppliers tried the same idea??
Did the suppliers not think at the time that people would use the cheap daytime heating tariff for a s
Its not too complicated if you can follow the spaghetti of cables inside the board.