electrics - domestic distribution board wiring

[dave]

at the economy wiring on house distribution panel - can't understand the setup here. There seems to be TWO live conductors going to the Vener Timer (ERD

2BPS). One would be enough to take the load. Both live conductors come form a Henley block which itself is fed from the economy meter. The (strange) thing is, only _one_ of those conductors has a red tie on it to indicate live (I presume) - although they are tied together along the way. Can't find any info on the ERD 2BPS Vener time itself - maybe could work out what's what then. Any ideas? tvm

[Mike Humphrey]

Could you take a picture showing more of the installation - the meter and CU in particular? There are a lot of wires that I can't see where they go. If there's a meter and separate timer, then one wire should connect back to the meter for rate switching - possibly the second "live"? If that is the case, though, it should go to the meter not the Henley block.

Mike

[Andy Wade]

It would if you could expand the field of view to include the supplier's cut-out, the meter(s) and consumer units, etc., etc.

However for that type of 2-rate set-up the connections to the time switch are as follows:

- line (usually via 5 or 6 A fuse) from cut-out, this if for the timer motor or electronics only;

- neutral from cut-out, return for above circuit;

- switched control wire to meter - this controls which register of the meter is active and is o/c for normal (day) rate. To select night rate a contact in the time switch connects this wire to neutral;

- (optional, only relevant if a switched supply is required for storage heaters) heavy-current switch contacts for switched supply - line from meter and switched line to the Economy 7 consumer unit.

HTH

[dave]

Thanks. More pics would be even more confusing believe me. :) The rest of the wiring is all standard and as expected. Here's a schematic of the econ in entirity. (is not E7 but an older tariff - forgotten what it's called).

two beefy cables to the meter are my question really. One would easily carry the load of all the storage heaters. The 2nd L could be to drive the timer electrics as you say and whoever installed it just put in a beefy cable. Strange though that the timer itself can accomodate such a large cable

- for that purpose.

btw It's all working fine and has done for years.

[Andy Wade]

Just "off peak" in those days, pre E7. There's an afternoon boost period but, unlike the modern Economy 10 tariffs, off peak rates apply to the storage heater (and bottom immersion heater) circuits only.

There's no control line shown from the time switch to the meter, so the latter must be single-rate, for the off-peak usage only, as determined by the time switch. (If the meter were 2-rate a separate time-switch wouldn't be required.)

One to provide the switched power feed and one for the motor, as I said.

It does seem odd in two respects, compared to my previous experience of such things:

- the motor feed is normally taken off before the meter, since the former is part of the supplier's equipment and you shouldn't pay for its consumption, tiny though that might be;

- there is usually a ~5 A fuse in the motor feed, typically a single moulded fuse carrier mounted on the meter board.

[Mike Humphrey]

If it's a digital meter it will almost certainly do the timing for the rate change internally, so this timer is only controlling the storage heaters. Presumably there's another CU for the other electrics, but that must be connected to the meter somewhere - is there another set of Henley blocks? There are several other large wires that look like meter tails appearing from behind the board and going off the bottom of the picture. I would guess that the timer has two live inputs, one drives the timer mechanism and the other is switched to form the live output for the storage heaters. It seems an odd set-up - presumably as the timer has seals on it's the supplier's timer, but it seems odd using an electromechanical timer with a digital meter.

Mike

[Dave Liquorice]

That is what we have and the clockwork in the time switch is knackerd so our "off peak" seven hours drifts through the day in response to power cuts...

Our time switch has seperate L & N feeds for the clock, L and Sw L for the heaters, and a sense connection to the meter.

[Graham.]

;

fuse carrier mounted on the meter board.

Do does that mean he's got a little synchronous motor hanging off the incoming mains protected by only by 100A boards fuse? (very scary). Or will the timer have a fuse built in, which would account for meter-tails cable on both live in terminals?

[Andy Wade]

We don't know whether it's a single- or 2-rate meter. The installation appears to pre-date E7, so it originally might have had two separate electromechanical meters - one for normal rate, feeding the main CU and the other for timed off-peak.

When the early off-peak tariff was superseded by 'white meter' (later called E7) the usual arrangement (IME) was a 2-rate meter where the drive from the disc was switched to one or the other mechanical register by an internal solenoid, controlled from the auxiliary contact of the time-switch. Older off-peak installations weren't changed though, unless the consumer asked to convert to E7.

Later on electronic 2-rate meters incorporated both the time control (using either an ordinary quartz crystal timer or a Radio Teleswitch) and the contactor for the switched supply, so the separate time switch became obsolete.

I'm guessing that dave's installation is the earlier type and the separate meters have both been replaced with two single-rate electronic ones, retaining the time switch. As you say it would be very odd to have an electronic 2-rate meter and a separate time-switch, especially as there seems to be no control wire to synchronise the metering rate and the switched supply.

Just wait until we get multi-rate smart meters and seasonal time-of-day domestic tariffs...

[dave]

fuse carrier mounted on the meter board.

mains protected by

No he hasn't - internal fuse can be seen in timer window - so not scary.

cable on both live in terminals?

yes

[dave]

Well I _think_ it's still reliny on the mech timer as when it goes clunk on/off so do the heaters.

Yes exactly that.

There is a separate meter, CU (the lot) - the only common point is at the incoming. I should have made that clear. The Econ circuit is a world of it;s own :-)

Yes it seems so.

yes.

but it seems odd using

The digital meter replaced the mechanical meter several years ago. I wondered why the two fat cables even then - the installer chap was puzzling over it for some time I was told but had gone bfore I had chance to ask about it.

[dave]

Single.

yes exactly that.

Yes - we only have one digital meter (for single rate econ) - the other mechanical one was replace by a newer mechanical one a few years back!

Thanks for all the info folks - sorry I didn't know the correct terms re tariff/2 rate etc. in the first place.

[Mike Humphrey]

As there's a separate meter, there isn't a rate change to time. Everything on this meter is cheap rate whatever the time of day - but the sealed timer stops you using it when you're not supposed to. The other meter will be peak rate all the time - so unlike Economy 7 you will still get charged peak rate at night.

Mike

[Andy Wade]

But there was nothing to stop you wiring a few sockets from the off-peak CU, and people often did that to maximise their off-peak use for the sake of a bit of un- and re-plugging. That's why the old off-peak tariffs gave way to 'white meter' and E7, just as separate lighting and power tariffs disappeared after the war.