Ferroli optima 701 rads heating up when DHW on.

12 May 2019
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United Kingdom
Have a ferroli optima 701 old but been ok apart from the odd temp sensor and o'rings. But when dhw on rads are warming up. I know theres no diverter valve on it so how is it controlled and what are possible issues if any one can help i'd be very grateful. Would it be the modureg?
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The pump is supposed to stop when hot water is called for, if the pump is running in hot water mode it normally means the heat exchanger is overheating, needs to be descaled probably.
Last edited:
Thanks for the reply. Think I'll try swapping out thermostats first probably the cheapest option. Would ou agree?
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Yeah just jumped in without thinking a bit went down line of overtemp cut off being faulty not why it's overheating

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