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Andrew Smith
Andrew Smith, Home Appliance Technician
Category: Appliance
Satisfied Customers: 3757
Experience:  Gas cooker specialist
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HSV3 / HSA3 combination. Water gets too hot when central heating

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HSV3 / HSA3 combination. Water gets too hot when central heating is on - suspect 3-way valve may be in mid position heating water with radiators. What position should the actuator be in for a) No demand, b) hot water only demand, c) central heating demand, d) both hot water and central heating demand? The actuator only seems to move through 90 degs. Is that right?

XXXXX XXXXX : No demand it will be in the closed position and the pump and boiler off
XXXXX XXXXX : hot water only it will be in the closed position with the pump and boiler on
XXXXX XXXXX : Heating only it will be in the fully open position with the pump and boiler on
XXXXX XXXXX : heating and hot water on it will be in a mid position with the pump and boiler on
XXXXX XXXXX : If you are getting hot water when the heating only is on then like you I suspect the 3 port valve, it is possible to take the head off and lube the spindle with WD40 and
XXXXX XXXXX : give it a wiggle back and forth to see if you can free it yourself
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Customer: replied 3 years ago.

Thank you for that. Having done some tests looking at the spindle with the actuator temporarily removed and comparing with your notes I now think the valve is working correctly. This is confirmed by feeling the outlet pipes from the valve getting hot with the boiler and pump running and with different demands set. I now suspect the programmer / timer (Danfoss FP715) which seems to turn itself off with a blank screen from time to time and when it comes on again all the times need resetting. I am still not sure how this would make the hot water so hot. The other suspect could be the water thermostat on the cylinder. Any views on this?

well done!

The timer should have a back up battery that holds the display until the power is reinstated. If it does not then you should replace the timer so it does.