3 port motorised valve should move 90 degrees or 180 degrees?

9 Jan 2023
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United Kingdom
Following a faulty actuator on a Sunvic 3 port value SDMV2304, I was advised that a compatible replacement actuator is the Danfoss HSA3 (also backed up by http://www.seered.co.uk/sunvic_low_res_catalogue.pdf - see page 18).

However the Danfoss HSA3 only seems moves the spindle through 90 degrees:
  • HW only - 9 o clock
  • HW & CH – 7.30
  • CH only – 6 o clock
The problem being the Sunvic valves appear to requires a 180 degrees turn of the spindle to move from HW to CH (I have a spare sunvic valve so can see inside)

So I am confused how these are compatible :
a) Am I unlucky to have picked up a faulty HSA3 – should it move through 180 degrees?
b) Do I need a different valve body that operates with 90 degrees turn ?

Many thanks for any advice…
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a) Unlikely but not impossible.
b) The SDMV2304 is a Motor On Motor Off (MOMO) valve. The HSA 3 is a spring return. The two are not directly compatible. If you change the whole valve (body as well as actuator) and alter the wiring as necessary you should be able to use a Danfoss valve. The whole valve is probably an HS3. I cannot identify which body goes with the HSA3 to create an HS3.
thanks makes sense.
Don't suppose you know of a suitable MoMo activator to replace the sunvic (save draining the system and replacing the valve)?
1. I'm afraid I don't. As far as I'm aware, Sunvic are the only major manufacturer of MOMO valves.
2. Have a look as http://www.seered.co.uk/sunvic.htm for thoughts on, and repairs to, Sunvic valves.
3. If it were me I'd bite the bullet and replace with a normal spring return valve. My favourite are Honeywell, but some seem to think their quality is not what it once was.
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thanks makes sense.
Don't suppose you know of a suitable MoMo activator to replace the sunvic (save draining the system and replacing the valve)?

The valve body/mechanisms are completely different, so valve body has to be matched with the actuator.

Electrically, there is no difference between the Sunvic spring return and the MOMO, they are a straight swap.

I originally had the very unreliable spring return Sunvic installed, and I found the actuator so unreliable, that I was looking at devising my own actuator, until I found there was a MOMO version. The MOMO version appears to be mechanically much more robust, despite being more electrically complex, and so far I have had zero failures.

The MOMO rotates in only one direction, only moving when it needs to move to a new position. Unlike the spring return, the motor is only powered when the valve needs to change position. The spring-return has the motor under power constantly, in any position other than the HW only position.

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