Zellweger off-peak
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Zellweger is the brand-name of an electric switching device used to switch off-peak electrical loads, such as off-peak hot water, on and off. Power stations transmit a ripple on the main transmission lines when off-peak rates start (often around 10pm). This ripple noise is picked up by the Zellweger, which after a random delay turns the hot water heater on. The noise is often picked up by other equipment, especially audio amplifiers and stereos and the noise can cause problems with other electrical devices. Even some telephone lines can pick up the noise.
Newer electrical meters incorporate this technology into the meter. "Time of use" meters charge electricity to the current tarrif within half an hour, giving customers incentive to run appliances such as dishwashers, pool pumps and clothes dryers during the night.
[edit] Impact
Power stations have plenty of unused capacity late at night but must keep running as they take days to shut down. Off-peak rates are used as an incentive for customers to use this surplus capacity and to reduce the amount of peak demand. This can produce cheaper power by delaying the need to build new power stations and reduce environmental impact. The random time delay in the Zellweger means that the power stations aren't hit with a huge demand when all the hot water systems turn on at the same time, rather the load is spread over a greater time period.
[edit] History in Australia
Originally time-clocks were used, however they can easily lose accurate time and are not easily adjusted for daylight saving time. Zellwegers were first introduced in Australia in 1953, however were not compliant with modern harmonic disturbance standards. The second generation was introduced in the 1970s and was more reliable.
A variety of devices can still be seen across Australia.
Zellweger ZE22/3 contain low-risk radioactive material, and must be only handled by authorised people, as breakage of the glass tube could cause a dangerous situation by releasing the radioactive material. An information sheet gives details.[citation needed]
