Banging Honeywell V4073a mid position valve when HW demand

[MANDATE]

D_Hailsham!
You say if just the CH is on, port A of the valve will be held open by the motor. When CH is satisfied, Port A is still be held open; but there is only 50-100v on the orange wire.

As I understand it, when CH is satisfied the room stat cuts off the supply to the white wire. It's this white wire that leads direct to the orange through the second micro switch, so how can there be any voltage on the orange when HW and CH are satisfied or not on?
If my understanding is wrong I'd welcome an explanation.
I agree the grey is still live and holds the valve CH only position.

 

[simond]

My understanding of the Honeywell valve is that in mid position the motor supply is partially rectified ie: half wave.

The circuit employed leaks down the orange wire as a 100v low current signal and has in the past caused problems with boilers that use electronic, rather than relay sensing on their 'switched live' inputs.

For instance, the earlier Bosch 28CDi system boiler (not the current model) used to need a capacitor fitted on the switched live to avoid it being triggered on by the 100v signal. This is because in Germany it was fitted with an internal divertor and insufficient testing was done with UK common wiring systems.

As far as I know, Honeywell have not published their actual internal wiring diagrams for the three port, other than the external installer instructions.

 

[Gasguru]

AFAIR the motor is simply stalled in the mid position by half wave rectifying the mains (hence the rectifier), however there is also a resistor to that feeds a little AC to the motor winding to prevent it being magnetised.

 

[taxexile]

i had same noise when valve moving between ports whilst pumping.
honeywell valve will slam shut at times sending vibrations through out house pipes.
something to do with pump over running,ie pump under independent control from boiler.
had a suprima 60l on honeywell system.
just exchanged the complete valve for an acl 3 port valve and now silent for 3 years or so.
something to do with acl valve uses a paddle and honeywell a ball.

 

[D_Hailsham]

I too have read the explanation about rectifiers etc, but all I know is what Honeywell give in their FAQ How a Mid-position Valve Works, which can be read HERE

It is interesting that they refer to the grey wire as the HW OFF wire.

As to rectifiers, diodes etc, they don't say a word. Presumably think it is too "technical" for the average reader

 

[giblets]

Brother-in-law (who is visiting shortly) used to work for the techie side of HW. I will try & get an internal wiring diagram from him for posting here if anyone's interested.

 

[taxexile]

simond you are very correct regarding honeywell 3 port valves and early worcester greenstar system boilers.worcester supplied an addendum,stating if an external 3 port valve is used it must not be a honeywell as the heating will stay on whilst no call for it.
danfoss.drayton probaly have much lower or zero voltages whilst in heating off situation.

 

[MANDATE]

D-Hailsham! I have no problem understanding the grey wire being referred to as HW OFF wire, cause that is where it is fed from along with the satisfied terminal of the cylinder stat.

When the valve is in mid position held by the 'rectified voltage' there is a back feed through micro switch No1 making the grey the same voltage.

The bit I don't get is how can the orange wire have any voltage if both HW and CH are off. I know in this situation the grey is still live and it may or may not be energising the motor, depending which of the two sides was the last to be switched off.

I see what it says on the page referred to, but is that from an official honeywell site or someones interpretation, cause it makes the statement but does not explain it.

 

[MANDATE]

I think I may have found what I was looking for.
Have seen explanation of the resistor for de magnetizing purposes as pointed out by Gasguru. Dont know if that applies to all valves or just honeywell.
I am reasonabley happy with that, so I'll be able to sleep tonight.

 

[giblets]

Brother-in-law has just advised to fit a 0.1mfd capacitor between the switched live & neutral on the boilers that say "do not use a HW valve"

 

[D_Hailsham]

I see what it says on the page referred to, but is that from an official honeywell site or someones interpretation, cause it makes the statement but does not explain it.

If you look at the URL of the site I quoted, you will see that it the official Honeywell site.

I know they don't explain how it works, but that's typical of Honeywell.

 

[MANDATE]

The picture is somewhat clearer now!.
I now have two descriptions of 'How the mid position 3 port valve work'.
One was extracted from a thread by 'curious'. Quite a good detailed description of each stage. But only voltage on orange wire was either 240 or nil. Also no connection between grey and orange wires.

Last description appears to be the same except for a 270K resistor bridging across from orange to a point in the diode/resistor rectifier which is fed from the grey wire, which is the only live wire when HW and CH are both off.

I don't know if all valves have this resistor fitted or not, but at least I now know how and why there is a connection between grey and orange. which is something I didn't know before.

 

[D_Hailsham]

I have just found the patent granted to ACL in 1978 to a spring return mid-position valve. It ran out in 1991 because they failed to pay the renewal fee!

If anyone wants to read a detailed explanation as to how it works it is here:

ACL Mid Position Patent

I don't know if is the same as current MPVs as the ACL version requires a wire from the CH OFF as well as CH ON. Maybe Honeywell, or one of the others, came up with another way of doing it.

 

[giblets]

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.

 

[chrishutt]

The internal workings of the mid-position valve have been explored in detail here, back in 2004. It was all discussed again about a year ago, here, but some of the links contained in these links aren't working. I'll see if I can fix them.