Photo's and info submitted by RODALCO:








{Thanks Ray}

There's the slimy little culprit in the foreground, so slow he hasn't fled the scene of the crime yet!
This would never happen here- he would have been sautéd, stuffed with garlic butter and served with a nice bottle of merlot!

Alan

ps YUK!

Please....

There are enough craft atrocities in the USA....

Please... don't show me any more uglies.

These pictures are absolutely disturbing.

If you keep showing me such truth...

I know I can't handle it.

This is brutally scary.

If I may ask a dumb U.S.-centric question...

I've seen several references to "hot water" circuits across this forum. Does this mean what it sounds like -- that the power utility provides different service drops for hot water heaters than for other loads? Why?

Respectfully ignorant,
John

Where I grew up in the rural suburbs of Philadelphia we had a seperate meter and 30a service disconnect just for the water heater. This was commen in many neighborhoods served by PECO. It also had a tamper proof timer attached to the meter box. The idea was you paid a lower rate for electric water heat as the unit could only operate on non-peak hours.

I believe it is a similar concept, except instead of a timer signal, a pilot sgnal comes fomr the poco to switch rates, or enable a mass storage heater at off peak hours.

My chauff-eau holds 200 litres [c.50 gallons] and is a 2kw immersion-element water heater running soley on cheap rate 230VAC supply, presently about 7 centimes per kwh. Models range from 50 litres and up. I have 2 meters, the cheap rate automatically switching for all consumption in the off peak times, 1am-7am and 12pm-2pm, and times which, incidentally, I can choose within limits. During off peak only, a live [hot] signal appears from the off-peak meter and feeds to 3 breaker 'units', for want of a better description.
a] A 10A breaker to protect the signal/relay circuit. This is the lowest rated breaker now available in France, [ it used to be a 5A fuse in the old days].
b] A 16A [or as necessary] breaker to protect the immersion element circuitry.
c] The switching device itself, basically a 20A rated relay arranged so that cheap rate is only normally used for water heating, and occupying one breaker space. This has a 3-position slider switch to enable OFF/AUTO/OVERRIDE selection, the latter so you can heat water during normal rates if necessary. The slider automatically returns to the cheap rate position on getting the pilot signal, so you don't have to remember to switch back to auto from manual, which is neat.
Chauff-eaux [plural] are almost universally used here for domestic hot water generation, as it is by far and away the cheapest option. It is reliable, cheap to install, totally automatic and the insulation round the cylinder is so effective it will keep stored water hot for at least a week with no power.
And since France has 75% nuclear*/hydro generation, off peak is now cheaper than gazoil per kwh considering overall efficiencies.

Alan

* 58 nuclear reactors in 14 power stations.


[This message has been edited by Alan Belson (edited 05-03-2006).]

Gus, what you are describing is known as an "off-peak" service. It is the same service drop as the main service,, but the POCO adds an additional meter to the drop for water heaters and electric heat. This meter is either clock driven, or wireless. The idea is to turn power to these loads off at given times, to reduce deamnd on the whole system during peak hours. In return of allowing them to shut these loads off, during demand times, they in turn bill you for this use at a lower rate...


Dnk...

Dnk,
You are correct.
Power companies here limit the operation of storage Hot-water cylinders by what is known as a Ripple Control system.
Effectively all it means is, the PoCo induces a series of tones (anywhere from 500 to 1500Hz) into the supply lines to open and close a ripple relay (actually a type of impulse relay) at each customers installation, thus controlling the amount of time the load is energised.
It is generally referred to as "Night-Rate" as the supply is usually switched on at 11pm and switched off again at 7am.
Night-store heating is also controlled in this manner, except this requires an extra meter in the meterbox and an extra channel module in the ripple relay itself.

Thanks to all for the comments.

If I'm reading correctly, there is only one drop to each residence, but a PoCo-controlled relay enables power through a second meter for reduced-cost night-time loads.

This, of course, raises more questions:

1. Why not switch ALL loads to the night-time meter? Unacceptable dropouts during the transfer (which don't matter to a heater)?

2. Why then would there be a "hot water" contactor in a distribution transformer cabinet that presumably feeds multiple customers?

It's interesting to see how the rest of the world encourages load demand leveling. (Quoting comedian Eddie Izzard at a U.S. performance: "You do know there are other countries, yes?") The dual-rate meters I've seen photos of in this forum make a lot of sense to me.

Here in Southern California, I understand that some utilities offer a discount to customers who allow them to install remotely-controlled contactors that shed high-power loads (e.g., air conditioning) at peak demand times.

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:

Ray,
In your first pic of that pair that you gave me, is it my eyes, or that smoke coming out of that Xformer bay?.

Hi Mike, it's definitely no smoke. I took the photo into the light which is not ideal, some over exposure did occur.

Re the discussion of the Hotwater controls.

Generally in Auckland the hotwaters are controlled by the pilot system, which is basically a controlwire which operates at the meterbox a relay or contactor, to switch on or off hotwater, spa pools, fixed wired electrical heaters. It's used for demand control mainly over the peak periods 1700 - 1900 hrs in the winter period, sometimes early mornings on very cold days.
This extra wire is controlled from the substations, and as an extra wire via overhead or underground brought into the premises for the load management.

Also the ripple or Zellweger plant is used which provides a 1050 Hz signal superimposed over the mains and controls a ripple relay on or off.
This system is more used in the outer suburbs or rural area's because of the costs of running the extra pilot wires.

The third sytem used in Warkworth and Wellsford is the GEC Cyclo system which switches at the zero crossings where a cyclo relay detects the code and controls a load on or off.

In New Zealand we can't tap in an external grid from Australia or take advantages of time differences, like in the U.S. so it is essential that loads can be dropped off quickly. The pilot system has the advantage that the loads can be dropped immidiately in case an important generator is lost and the frequency drops below 49.7 Hz.
All the substations have an under frequency relay which can dump hotwater normally and sometimes streetlights loads in extreme circumstances to avoid having a blackout.

The two rate metering tariff was introduced in the early 1990's to provide a cheap night rate for hotwater heating and storage heating, the night rate was about 4½ cents while the day rate was around 9 cents / kWh, a little higher than the standard day rate of 8.26 cents / kWh.
Now these days it's hardly worth while anymore because greed through privatisation made the tariffs for day and night about 1 cent apart.

Control was done by quarz operated timeclocks on the meter and one for the hotwater cylinder.

These had their fair share of problems too, and made me a lot of OT for call outs for stopped clocks over the weekends.

Regards Raymond

In my area (North East USA) we also used to have two rates.

I have always heard it called "Off Peak".

The house would have one service drop with two separate identical meters, one normal and one off peak feeding a separate small panel via time clock.

I do not believe it is available now.