In an earlier contribution to this discussion,
geoff wrote:

In message , Harry
Bloomfield writes
Following on from problems with the Danfoss HSA 3 valve actuator
earlier in the week, my heating system is now running fine using the
compatible Sunvic SD 2701, which I had in as a spare.

I have just got around to pulling the 2 year old Danfoss HSA 3 unit
apart, to see if it might be repairable for use as a spare and this
is what I found -

Internally and externally it was like new, no obvious signs of any
wear and tear at all. The motor also checks out fine. The only
problem I could find was no continuity between the centre (N/O)
contact and the common of both of the switches, when the button is
operated. The N/C contacts are fine.

It just seems a little odd that both of the micro switches have
suffered the same failure mode simultaneously. The items fitted are
SAIA rated at 250v 6amp.

The HSA really suffers from ****e microswitches


Three-port valves are horribly unreliable and are probably the single cause
of the greatest number of CH woes reported here. Maybe time to replace it
with 2 x 2-port valves and convert to S-Plan.
--
Cheers,
Roger
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