Honeywell V4073 3-Position Diverter Valve

[Stuthehandyman]

I have a problem with a heating system. The central heating works OK but only when the hot water is also on. When the hot water is off, the pump stops. Somebody else has changed the programmer unit and the wall thermostat but this didn't fix the problem. I think the problem is something to do with the Honeywell V4073 3-position diverter valve. I have changed the powerhead but this has still not fixed the problem! The valve moves to the fully open position but there is only about 140 volts (instead of 240 volts) coming out of the orange wire from the powerhead. How much movement should there be on the actual valve? When I turn the valve with a pair of pliers (with the powerhead removed) there is only about 15 degrees of movement (I would have perhaps expected more) but this seems to stack-up with the amount of movement of the powerhead "slot" to move the lever from one extreme to the other. Any suggestions please?

Stuart

 

[ChrisR]

You might have a gooey ball - the lump inside the wet part which closes the pipes off, They swell up and restrict the movement. 15º sounds too small. If the ball has "gone" you will be able to move the spidle over a greater arc fairly easily, with a wee spanner. It will then work ok for movement - for a while. You can get new innards kits which are much easier to change than the whole vlave, and cheaper. If the movement stops "hard" at the ends of the travel then it's OK.

But your other problem sounds like a wiring error. Normally one could blame the microswitches in the head but as you've changed it that's unlikely.

Check carefully:
http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.4 Y Plan.pdf

 

[Stuthehandyman]

Thanks for the information Chris. I've been back to the house today and discovered they had already had the complete diverter valve assembly changed about a month ago. I needn't have bothered changing the powerhead after all! However, the problem still exists. Like you, the customer thinks it is a wiring fault but I've checked just about everything and I'm convinced it's wired as per the Sundial "Y" Plan.
This is the situation with both CH and DHW selected "On":-
With cylinder stat set at Max:
Valve motors to midpoint "Open" position. (Turns anti-clockwise about 15 degrees).
Both pump and boiler run.
Power is being supplied to Terminal 8 via cylinder stat.
Voltage on Orange wire is 150V (Disconnected wire and checked)
With cylinder stat set at Min:
Valve motors to fully "Open" position. (Turns anti-clockwise a further 15 degrees).
Both pump and boiler continue to run but power (240V) is now being supplied to Terminal 8 via the Orange wire from the V4073, not the cylinder stat.

Turn power off and valve spring returns to fully closed position (Turns clockwise about 30 degrees)

Turn power back on. This is the situation with just CH selected. i.e. DHW is "Off".
Valve motors to midpoint "Open" position. (Turns anti-clockwise about 15 degrees).
Pump and boiler do NOT run.
No power to Terminal 8 from from cylinder stat (as expected) but also no power via the Orange wire! Voltage on Terminal 8 is 150V.

The customer swears that in the past it has been possible to run the central heating without the domestic hot water, and that is what the Sundial "Y" Plan says but..........

Any ideas please?

 

[ChrisR]

Turn power back on. This is the situation with just CH selected. i.e. DHW is "Off".
Valve motors to midpoint "Open" position. (Turns anti-clockwise about 15 degrees).

That's wrong - it should go right round to CH only.

FOr CH only you should have
Grey at 230v (that's "off")
White at 230v. (that's "on")

Check you have the wire from the HW OFF on the programmer.

If that's not it I'll have to get the wiring diagram out...

 

[pf_mills]

That seems strange..obvious question..

When selected to CH only are you getting 240v on terminal 4 and on terminal 5.

If/when you sort it would be interested in outcome..thanks

edit..sorry didnt see previous posting

see also http://customer.honeywell.com/Techlit/Pdf/95c-00000s/95c-10820.pdf

 

[Stuthehandyman]

Thanks for your help Chris and pf_mills.
Now that you point it out Chris, it's obvious that the valve should open the full 30 degrees (not the mid-point position as it is doing) when CH only is selected without DHW. Duh! It's the same position as when DHW is selected but the cylinder stat has opened because the water is hot enough.
Going back to the situation where CH only is selected without DHW, there is definitely 240V on Terminals 4 & 5 (and therefore on the white wire) when the room stat is set at max but I can't remember the condition of Terminal 7. i.e. The grey wire. I will check when I go back again but that is likely to be Tuesday at the earliest. Is it the 240V on Terminal 7 that should keep the valve motoring open the full 30 degrees?
I will obviously let you both know the outcome after my next visit!

 

[ChrisR]

Whenever the valve is in the mid-position or beyond, an internal microswitch connects its grey wire directly to its motor. You get mains on this wire from either the programmer's HW OFF wire, or the cyl stat's "satisfied" connection. That motors the valve across to the CH position, and holds it there (even if the call for CH ceases).

 

[Stuthehandyman]

Sorry it has taken me so long to get back to you ChrisR and pf_mills but I've just been so busy!

You were spot on ChrisR, there was no wire from HW OFF on the programmer to Terminal 7! I had to take up the floorboards on the landing yesterday and run a new cable from the terminal box in the airing cupboard to the programmer in the kitchen but now everything is working fine. I don't know how it ever worked before (there were no spare cores in the programmer box) but my customer is very pleased.

The house and heating system are about 20 years old but my customer has only been living there for about 18 months. I was the 4th person to investigate the problem and thanks to your help, we've done it!

Thanks again for all your help.

Stuart