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LG Therma V DHW settings

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I have a 14kW LG Therma V ASHP installed just over a year ago.  I also have solar thermal for hot water installed at the same time.  I’m looking to optimise how the two systems work together, as at the moment if the hot water falls below 40C (early morning showers, overnight dishwasher etc), then the ASHP kicks in.  That seems sub-optimal when a bit later in the day (assuming it’s sunny) the solar thermal will heat the water for free.  I’d like to schedule the hot water control to only use the ASHP to heat the water if by say 5pm it still needs heating, but not to come on before then. The ASHP central heating function is controlled by Nest, but the hot water seems to be automated only by the Therma controller - can this be over-ridden? 

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My hot water is off overnight then comes on at 6:30 at 50 C for showers.  At 10:00 I drop the required temperature to 40 C and keep it there until 16:00 when it is set back up to 50 C.  In both cases the "hysteresis" is set to 5 C so the water is not heated until it drops more than 5 C below the set temperature.  All this is done using the scheduling function of my Therma V controller; you can choose your own times and values to suit 


If you wanted to wire-in another controller for DHW you would need a mains voltage to logic converter; somebody on this forum has done this.  The main benefit of using another controller is that the Therma V controller does not have a 'Holiday' function and you need to delete (or modify) all programs in order to stop the DHW heating when away.  


At this time of year I use spare electricity from my solar PV to heat the water via my immersion heater.  This is set to cut-out at about 72 C so on a sunny day I get enough hot water to last quite a while. 

Edited by ReedRichards
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