There are several devices being sold now to variably control the power to a 3 kW immersion heater element depending on how much power is being exported.
The only way that I can imagine these achieve that is by using a triac switch.
It will work but will generate an odd current waveform on the supply which will come from the inverter but buffered by the grid.
Can anyone confirm they use a triac?
Has anyone had any problems resulting from the waveform?
Tony
Low Wattage Immersion Heater
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Quote from LJ
"I simply cannot see the point of a low power electric immersion heater. All that would mean is that it would take commensurately longer to achieve the same temperature.
The only thing that can affect energy consumption in an electric immersion heater is insulation". Quote ends.
In general, with an ample supply of grid electricity there is nothing to be gained by use of a low wattage immersion heater.
No saving in use of 1KW for 3 hours instead of 3KW for one hour.
However use of such a heater as a dump load from say a wind turbine can be most effective.
If only a restricted mains supply is available, then a low loading water heater can help. There are still some domestic supplies of only 40 amps.
Use of a standard 3KW element would leave only 27 amps for other loads which is very limiting. Changing to a 750 watt element would leave about 37 amps available, a considerable improvement.
"I simply cannot see the point of a low power electric immersion heater. All that would mean is that it would take commensurately longer to achieve the same temperature.
The only thing that can affect energy consumption in an electric immersion heater is insulation". Quote ends.
In general, with an ample supply of grid electricity there is nothing to be gained by use of a low wattage immersion heater.
No saving in use of 1KW for 3 hours instead of 3KW for one hour.
However use of such a heater as a dump load from say a wind turbine can be most effective.
If only a restricted mains supply is available, then a low loading water heater can help. There are still some domestic supplies of only 40 amps.
Use of a standard 3KW element would leave only 27 amps for other loads which is very limiting. Changing to a 750 watt element would leave about 37 amps available, a considerable improvement.
"Installers and owners of emergency diesels must assume that they will have to run for a week or more"
For people on off grid systems, the higher end MTTP controllers (Outback, Morningstar etc) have a low power relay which can be controlled using voltage set points, time etc. In the spring I'm going to install a relay which will give a timed or voltage controlled pulse of immersion heater so that we can make use of all the lovely photons that we miss out on at the moment because our batteries are in float by 10am.