ECN Forum Forums Photo Discussion Forums Violation Photo Forum Wiring Horrors

AFAIK the PoCos want their cheap rate electricity only to be used for defined appliances.
Usually that's night storage heating and hot water heaters here. At night the relay closes a big contactor, the storage heaters and boiler start charging. In the morning the control shuts off again and that has to be enough for the day. Some night storage heaters offer day-tariff auxiliary heating too, but generally it just gets cold in the evening. One more reason why I hate night storage heating, aside of the huge, ugly bulky heaters and the cost. Gas and oil are just a lot cheaper than electricity here.

I had an apartment in Arizona (SRP service area) where the meter recorded usage in two well defined time slots. Something like 9AM to 9PM weekdays was one time slot, and the nights and weekends another time slot. The POCO charged me 16 cents/KWh for the weekday daytime usage, and 4 cents for nights and weekends. They didn't know nor car what I used it for.

Ray,
Could you send me a pic of that whole enclosure?.
As it is now?.
Cheers,
Mike.

John,

We've had cheap-rate power at night in the U.K. for many years, installed primarily for electric storage heating.

There is only a single service drop, but the older installations had two completely separate meters. One was the normal meter feeding a distribution panel for all the regular house circuits, providing 24-hour power billed at the standard rate at all times.

The second meter fed a separate panel via a contactor, the latter being controlled by a simple timeswitch in the earlier days (PoCo-owned and sealed). This second distribution panel then fed the storage heaters so that they would be charged overnight.

This system became known as the "White meter" tariff, simply because the second meter was actually in a white casing instead of black to provide easy identification.

Electric water heating could be wired various ways. If there was only a single element, then it was generally wired onto the normal panel so that it could be used at any time of day. Dual-element cylinders were also fairly common. The main, lower element was run from the "white meter" panel to provide a full cylinder of hot water overnight. The upper, smaller element was then run from the standard-rate panel so that a boost could be applied at any time.

Gradually, the white-meter system gave way to the "Economy 7" tariff. Instead of providing cheap-rate power only to selected heating appliances, Economy 7 uses a single dual-tariff meter so that the whole house switches to the cheaper rate at night (the "7" part of name referring to the fact that the cheap rate runs for 7 hours per night, generally midnight to 7 a.m. in winter, 1 a.m. to 8 a.m. in summer).

There is still a PoCo-provided contactor so that a separate panel can be used to feed storage heaters, but water heater wiring is generally just taken from the regular panel and a separate (customer-owned) timeswtich can then be used to run it during the cheap-rate night hours.

By the way, there's no drop-out on the 24-hour circuits at switchover times, as the control line from the timeswitch to the dual-tariff meter just causes a small solenoid to switch the mechanical drive to the second set of dials (or performs the equivalent signaling function on the newer electronic meters).

The mechanical PoCo timeswitches have gradually given way to contactors controlled by radio signaling, and there are also extra tariffs available in some places such as Economy 10, which is basically Economy 7 but with the addition of another cheaper period during mid-afternoon, handy for boosting storage heaters and replenishing the hot-water supply for the evening.

The utilities have traditionally imposed a higher quarterly "standing charge" for the cheap-rate options, but in recent years this has started to change. My PoCo, for example, recently increased the per-unit rates but completely abandoned the standing charge.


[This message has been edited by pauluk (edited 05-05-2006).]

From Alan Belson:



[This message has been edited by pauluk (edited 05-05-2006).]

Compare this:



This is my own meter box in my place.
To the left is the General Rate meter, next to that is the Ripple Relay.
To the right is the Hot Water Meter (Also known as the Night Rate meter).

Paul and Trumpy,

That's great info, thank you. Returning to the photo that started all this: I'm guessing that the blue box marked "H-W" is indeed for some hot water (night rate) function, but it's low-level -- perhaps sending commands to contactors on the served premises, rather than switching actual loads.

Here in Southern California, natural gas is the logical choice for water and space heating, being maybe 1/3 the cost of electric heating. The future costs are far from certain, though...

Thanks again,
John

Maybe not so high as a 3:1 ratio, but gas has generally been cheaper to run here as well. Given the wildly rising prices of both gas and electric recently though, it's anybody's guess how it will be in a few years' time.

Here is a typical Austrian setup. (the freakin' ugly mess of hot wires sticking out is a different story). The top meter is a 10(60)A digital 3ph meter, the bottom left a 10(40)A standard 3ph meter. In the middle you can see the receiver for the radio signal (Rundsteuerempfaenger) and the bottom right meter is a simple 10(30)A single phase meter for the night tariff. It's only for a 100l 1,7 kW water heater in the basement.

The picture was taken last year in a 2-family-house that had been converted to offices, split and then joined again, now used by an architect who also owns the house.
Hence the once five meters. One is for the common rooms (the smaller one) and the big digital meter now controls most of the house. When the PoCo disconnected the two meters a few years ago they left a _real_ ugly mess! They wrapped the phases with tape, wrapped a lead seal around the ends and left the neutral bare...

The panel itself dates from 1996 and looks mostly ok (from the outside, never dared to open it since I was only there to plan a photovoltaics system for the guy), aside of the fact it's real full.



{Message edited to add image to ECN server.}

[This message has been edited by Trumpy (edited 05-24-2006).]

From RODALCO: