Banging Honeywell V4073a mid position valve when HW demand

[D_Hailsham]

As Honeywell were actually selling their V4073A valves in 1976 I would imagine that the ACL method of operation is somewhat different. The HW valve was advertised as a "proportional" type.

Thanks for the date. I have been trying to find a Honeywell Patent but been unable.

One thing I have noticed in many of the descriptions is that many refer to 240v on the orange wire. The orange wire is an output wire and only has 240v if the White wire and the Grey Wire both have 240v. In this case the orange wire is supplying 240v to the boiler.

In all other cases, the only reason there is 240v on the orange wire is that, in the standard Y-plan configuration, the orange wire is connected to the same terminal as the Call terminal of the HW thermostat. If the orange wire was disconnected you would not find 240v on it.

 

[robsinglehurst]

Quite a bit of time has passed since I originally posted, but after finding a very good description of the internal wiring / workings of the valve here I have fitted a on-delay timer relay between the call for heat terminal on the cylinder stat and the input to the boiler (boiler controls pump itself). There was room for this in the connection box.
Have this set to approx 15 seconds and now the valve is pulled back by the spring and comes to rest before the boiler fires up and the pump starts. No more banging!
I think the reason for the banging might be that the pump is only about 200mm (pipelength) away from the AB port of the valve, I'm guessing if it were further away then it would have worked fine. The on-delay timer relay was about £15, much cheaper than a drain-down and a new valve.

--Rob