In an earlier contribution to this discussion,
wrote:

hi all, i have a danfoss hsv3 valve on my central heating that is
malfunctining... it is fine when ch is on or hw and ch is on but not
when hw only should be on...it stays in mid position. other than
draining down and fitting a new one or changing the powerhead...are
they repairable? i have some skill with a soldering iron so would be
happy to give it a go! anyone help me out with some tips?

ta!

steve

These things can occasionally get confused, and need a master reset!

The first thing to try is to remove *all* power to the thing. This means
turning off the isolator which provides power to the whole heating/hot water
system - *not* just turning off at the programmer.

With all power removed, does it return to the home (hot water only)
position? If it *does*, try using it as is for a few days - this may have
fixed it.

If it *doesn't* there is either a problem with the spring return mechanism
in the actuator, or the mechanical (wet) part of the valve is stuck. Remove
the actuator from the valve (2 screws, no need to drain down). Does the
actuator *then* return to the home position? If so, the valve is probably
stuck. You should be able to turn the spindle with your fingers or - at any
rate - with only *light* pressure, using a pair of pliers.

If the valve is stuck, you may be able to free it by rotating the spindle
back and forth. If not, it's a new valve - which *does* require a partial
drain down - unless you have strategically placed isolator valves.

HTH.

--
Cheers,
Set Square
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