ETSA Off peak (OUT OF CONTROL) load

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ETSA Off peak (OUT OF CONTROL) load

Postby Andrew_electrix » Sat Dec 03, 2011 10:43 am

Hi All,
Just had our meter changed over for the solar power system which i'm in the process of installing...

As we are in SA there is no time-of-use metering for residential customers, off peak power (J tarriff) is specifically for water heating, heat bank space heaters ect
Previously there were 2x disc meters with a time clock on the off peak (J-tariff) meter and i had adjusted the time clock to heat between 3AM and 6AM in the morning. As our slow combustion wood heater helps heat the hot water service earlier in the evening and i didn't want the HWS switched on before the fire had burnt down and contributed the maximium heat gain.

The new electronic import/export meter ETSA YA4928 controls the off peak load internally with it's real time clock, which is set when the meter is programmed for 11PM to 7AM every day.

HOWEVER - here's the key point

The meter is STUCK on standard time NOT daylight saving time!!
in other words the meter is running 1 hour slow, meaning in reality the off peak load switches on from 12AM to 8AM.
So here's what happened the first night after the new meter was installed:

1. The off peak load switched on at 12AM and heated the HWS for approx 2 hours until the thermostat switched off at 65deg.

2. We wake up at about 6:30-7AM, jump in the shower.

3. Cold water hits the thermostat in the HWS.

4. The HWS then carries on heating for the next 1-1.5 hours until 8AM until the meter switches off.

5. The HWS looses at least some that energy gained in the next 16 hours due the standing heat loss.

6. ENERGY ($$$) WASTED!!

The whole point of the controlled load is to reduce the demand on the grid at peak times but by 8AM during daylight saving in summer, everyone in the whole of Adelaide is start there working day and using peak power.
Hence the stupidity of the situation is ovbious...

The solution??

Install the original time clock in line with the HWS and set from 3AM - 6AM,

An inspection note found behind one of the disc meters stated that they was orginally installed on 25/06/1965!!
An excert from the rear of the inspection note reads as follows:

"The first inspection shall not be charged for, but any further inspection rendered necessary by the installation failing to pass the first one, a charge of 10s. will be made, and such a charge shall be paid to the trust before the installation is connected."
(10s being shillings, not dollars and cents)

time clock_RS.jpg
time clock internals

The original time clock is a mechanical work of art, it use a very small amount of power and has a clockwork spring backup to ensure it keeps time during a power failure.
The switch contacts inside look like they are made of and alloy with quite a high pecentage of silver and are arranged with a sliding leaf spring to ensure they snap closed which minimises contact bounce, acring and ultimately contact wear. (I filed the contacts flat to keep things happy, but probably would have been fine anyway)

I have to admit i'm quite sentimental for old school equipement and engineering.
I'm guessing ETSA are just binning these old meters and time clocks as they doing the upgrades, which is a crying shame if you ask me...
Good luck to anyone expecting the plastic garbage that gets pumped out (from you know where) these days to last 46 years and still be able to go for another 46 years.
Sometimes the simple things (done well) in life are often the best.

For those in SA wanting to do the same, there are DIN rail timer's that can be mounted in the switch board to do the same thing (via the plastic route), see the following link:
http://www.schnap.com.au/timers/
Actually i just ordered one of these for a friend who has a solar installation and has a massive gravity feed HWS, and can't seem to reduce his bill...

Andrew
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Re: ETSA Off peak (OUT OF CONTROL) load

Postby Smurf1976 » Sat Dec 03, 2011 11:50 am

I understand what you are saying and follow your logic :D BUT:

1. Times are set with the objective of smoothing the overall load profile. That is, the aim is to decrease the peak load and increase the minimum load compared to what would exist with no off-peak rates.

2. Due to point 1 above, the logical approach is to have the off-peak switched on throughout the minimum load period and heat water relatively slowly over this period. Also relevant are issues about peak current flow in the wiring for individual customers, or in the local distribution system in areas with a high usage of off-peak (in Vic there is actually a small power station which was built for purpose of meeting the peak demand in a part of the state where off-peak usage is very high and peak demand is literally at 1am for this reason).

3. Complicating this are heat pump water heaters, which tend to heat more slowly (especially during very cold weather) than their resistive counterparts.

Now, what all that means is that in practice there's nothing overly wrong with 11pm - 7am as an off-peak time. This is the time of actual off-peak conditions so there's no reason not to have the off-peak supply on at those times. The old electric HWS only really needed 6 hours but 8 is needed for storage space heaters and longer hours are always better where heat pump HWS are involved.

As for the daylight savings issue there is no electricity authority anywhere in Australia to my knowledge that adjusts timeswitches for daylight savings. In NSW and Qld with the remote switching they can obviously do it, but certainly it's not done in the other states or at least not that I've ever heard of.

Peak demand in SA (and in all states except NSW and Tas) is during Summer afternoons around 3pm (give or take a bit) with a secondary peak during Winter evenings about 6:15 pm. 7 - 8am in the morning is nowhere near the peak therefore not a problem.

SA is in fact one of the peakiest electricity systems in the world with average demand only about 40% of the peak. At the other end of the scale, Tas and Qld have average loads that are in the order of 70 - 75% of the peak. The high proportion of major industrial load in those states accounts for much of the explanation, along with the very enthusiastic use of off-peak tariffs for all sorts of things (not just water heating etc) in Qld.

NSW - Summer and Winter peaks are of comparable magnitude whereas elsewhere Summer is a larger peak than Winter.

Tas - Peak is a bit after 8am in Winter with a secondary peak around 6pm in Winter. There's no such thing as a peak in Summer, with a typical daily maximum demand in January being about the same as the off-peak demand would be in Winter. This is due to the high usage of electric heating and low usage of cooling devices due to the climate plus, in the case of heating, very limited use of mains gas in the state.

All that said, there's nothing wrong with fitting your own timer to shorten the hours or alternatively asking if ETSA will program the new meter for shorter hours. But they set the meter as they do because that's what suits the system and works for most customers.
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Re: ETSA Off peak (OUT OF CONTROL) load

Postby Tracker » Fri Dec 09, 2011 7:35 am

Andrew_electrix wrote:..... there are DIN rail timer's that can be mounted in the switch board to do the same thing (via the plastic route), see the following link:
http://www.schnap.com.au/timers/


I was about to order similar switches from the manufacturer in China, but at $30 for local purchase, the hastle of dealing with China was not worth it..

I picked up two timers and they seem very functional and easily useable.. They have an electrically-isolated change-over relay output, so they are very versatile in usage.
I will be using them for my Alternative Energy Peak supply circuit.
...
.
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Re: ETSA Off peak (OUT OF CONTROL) load

Postby Andrew_electrix » Fri Dec 09, 2011 11:23 pm

HI Tracker,
Your comments on heat pump HWS are fair enough, longer is definitley better...

However if we has a solar HWS the timing of the boost is even more important.
As the absolute last thing you would want would be for the HWS to heat in the morning afer showers ect and deny the sun the opportunity to heat the water though the day.

The timer i ordered arrived on wednesday and i installed it last night at my wife's uncle's place
Which is small favour for the 3x saturaday afternoons he spent heloing to fixing the airconditioning on our 4WD (the company he works for services the A/C units on the busses in Adelaide)
Last quater his bill for off peak hotwater was 1089kWh, given their family is only 4 people and not withstanding his two daughter, it did seem a little over the top!!
I had a look inside the timer before we installed it and it has a lithium CR series coin backup battery, also the relay is substantially sized so looks like it really would last for a good number of years
We set the timer to the same time as the meter, non daylight saving and programmed the HWS to turn on from 2-5AM (which is 3-6AM daylight saving time), whis should be plenty of time for the tank to heat and the thermostat switch off.
Hopefully this should generate some savings...

I not copalign
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