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.

So its off to Maplin for some replacement microswitches.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

"Harry Bloomfield" wrote in message
. uk...
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.

So its off to Maplin for some replacement microswitches.

Get the highest Amp rating you can.

In article ,
"Doctor Drivel" writes:

"Harry Bloomfield" wrote in message
. uk...
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.

So its off to Maplin for some replacement microswitches.

Get the highest Amp rating you can.

Physical size is going to be more important.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Andrew Gabriel" wrote in message
...
In article ,
"Doctor Drivel" writes:

"Harry Bloomfield" wrote in message
. uk...
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.

So its off to Maplin for some replacement microswitches.

Get the highest Amp rating you can.

Physical size is going to be more important.

To clarify. The highest amp rating that fits in. They you are.

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

easy to replace


--
geoff

In message , Doctor Drivel
writes

"Harry Bloomfield" wrote in message
.uk...
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.

So its off to Maplin for some replacement microswitches.

Get the highest Amp rating you can.


Clueless ****

--
geoff

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
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

on 23/12/2009, geoff supposed :
The HSA really suffers from ****e microswitches

That might explain it.

easy to replace

You might think so, but I am struggling to get the replacement
microswitches to actually be switched by the cams. Other than possibly
rubbish switches, the HSA seems to be more robustly built than the
Sunvic.

The cam doesn't seem to protrude out towards the switches as far as it
should, which might explain the early demise of the original switches.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Roger Mills presented the following explanation :
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.

On that point I certainly agree. The actuators barely make it out of
the guarantee period before they fail. Mine average 18 months to 2
years, which is why I now keep a spare set up ready to swap out.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Harry Bloomfield formulated on Tuesday :
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.

So its off to Maplin for some replacement microswitches.

In the interests of experiment, I have now got to the problem.

So from the top.....

The N/O contacts on both microswitches had burnt out. I picked up 2x
replacements plus 2x extra spares from Maplin yesterday, then fitted
them in place of the failed ones. Under the plastic half round plate
which holds the microswitchs, is a brass cam plate with has at its
centre a plastic hub which has the return spring wrapped around it.
After fitting new switches, the N/O ones were still not making
reliably.

I drilled a small hole in the half round plate, one directly above the
operating button of each switch, so I could see what was happening.
What I found was that the brass cam ring is just barely low enough to
catch the switch buttons - they are not able to reliably push them in.
Usually the cams are riding over the edge of the buttons. To hit the
buttons square on, the brass cam plate needs to be about 1.5mm lower.
The new microswitches are physically identical to the old ones, so I
strongly suspect that the N/O contact were burnt out as a direct result
of the poor alignment between the cam and microswitch operating
buttons.

My next trick will be to skim 1.5mm off the bottom of the hub and make
a 1.5mm thick washer to get the cam to properly align with the
switches. My lathe is tied up with another project at the moment, so
this will have to wait a while.

You would though think, that manufacturers might spot these simple
problems in the early design stages.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk