Y-Plan - 3 Port Valve - cannot have CH on by itself?

[minirock]

Hi All,

Wonder if you can help.

Had a Danfoss 3 port Mid position valve replaced last year on my Y-Plan CH and HW system, the Plumber replaced it with a piece of rubbish, Altech 3 Port motorised valve.
The reason we had it replaced was the old valve body had got stuck in the mid position and trying to make it move caused it to leak.

Anyway, a plumber came and and replaced it with the Altech.
Problem is, we cannot now just turn on the CH as we could before with the old Valve, the HW has to be on too otherwise the Boiler and Pump do not fire. I did question the plumber on this when he was leaving, but he said this was how it was supposed to be, as the CH circuit doesn't power the Pump and Boiler on its own. I trusted what he said, as he was the professional.
He has since gone AWOL, and cannot find him!

I have examined the wiring diagrams, and have determined it is wired correctly. And from what I understand the Orange cable coming from the 3-port valve should fire the Pump / boiler once the Valve has moved into the CH only position. The valve is moving and can see it and hear it once in place.
The only way is to leave the HW on constantly, until the HW stat is satisfied, then the CH works on its own as such. But would prefer just to have the HW timed so it is just heating for a couple hours of the day.

Is it just a faulty valve? Or will this model just not do it?

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[ukrobj]

Untitled

• ukrobj
• 14 May 2012
• 9

might help you. If you can follow that and its wired correctly then the valve is at fault.

 

[minirock]

Hi,

Thanks for reply.

I have a similar diagram, and think I no what the problem is, I do not have a HW off live running too the Grey cable of the 3 -Port Valve / HW satisfied.
Would that make sense?

 

[seco services]

You need a hw off wire from programmer to the grey connection block.
Should be 3 wires in the grey connection block.

Stat satisfied
Hw off
Grey from mot valve.

 

[minirock]

Hi,

Yes I think that is what it is, how would it of worked with the Old valve, or couldn't of it?

My programmer is an old Honey well type, looks similar to this, but older looking!! Would it have the HW off live as an option?

http://www.honeywelluk.com/products/Time-Controls/Wired/ST799/

 

[ukrobj]

Should have, they still sell the st799's, can always separate the timer from its housing and check it.

 

[MANDATE]

There are two parts to the valve. The valve itself with spindle and the actuator head.
If the actuator head is moving the valve fully across to CH only ie from HW to mid position and then on from mid position to CH.
It proves the valve and valve spindle is not the problem.
Nor are the wires that provide the power to do the driving. IE the white to drive valve over first half and the grey to drive valve over last half.
Its during the last half that a micro switch is triggered and allows power out of the valves orange wire to operate the boiler/pump.
When valve set to HW only, the power to operate boiler/pump goes through the cylinder stat. Same applies for HW and CH together.
The wire to boiler/pump must be joined to the orange as there will be no other source of power if HW is off.
I would say your problem is like one I had and that is the related micro switch is at fault.
It is either not breaking contact on one set of contacts or failing to make contact on the other set of contacts, but whichever it is it is not allowing power out from the valves orange wire.

 

[MANDATE]

My reply was based on your statement that the wiring was correct, but if the HW OFF wire is missing valve cannot move to CH only without having HW on and satisfied.

 

[minirock]

Thanks all.

Will check tomorrow.

But from memory can only see two cables coming from programmer, guessing one is HW On and other is CH ON.

Will confirm whether the Grey / HW Off is missing.

 

[minirock]

Hi,

Just to confirm there is no HW off running to the GREY cable of the 3 port valve.

I have took the front off the programmer,and the HW off (terminal 7) of old Honeywell ST699B is empty.

Assuming all i need to do is run a link from there to the Grey cable of the 3 port valve?

Thanks!!

 

[picasso]

The missing off from the programmer can be done with a relay in the wiring centre if its not possible to get a cable to the programmer.

 

[gaswizzard]

How did the original valve function correctly when 'HW OFF' at progammer not connected/empty?

 

[minirock]

Hi All,

gaswizard, i am not sure how it worked without the HW off connected before!
Maybe it didn't and I was mistaken!

I added the HW off today, and all is well.
I can now fire up Central Heating, Hot water or Both!


Thanks for all the help.

 

[MANDATE]

The motor plays no active part in the HW operation.
The valve/motor is supposed to be in the rest position which is HW.
The motor is only used to drive the valve away from HW to mid position and CH position. When it's not needed and power is removed it unwinds back to HW position.
The valve/motor could get stuck at CH which means the HW port would be closed, but this would not stop boiler from lighting.
The electrical operation for HW is fairly simple,
Power from the programmers HW ON terminal goes to the cylinder stat, then across the stats contacts, from there it goes to boiler/pump.
When set temperature is reached contacts open and boiler stops.
If HW does not work then I'd be looking for fault between programmer and output terminal of cylinder stat.
Note! there are two output terminals on the stat and two sets of contacts. one set closed and other set open, so when cylinder stat operates it cuts power to boiler,diverts power from other terminal to the grey wire of the valve. If the CH was also on the valve would have been in mid position and it would require this diverted power to drive the valve forward from mid position to CH only position. During this movement a microswitch in the actuator head would be triggered allowing power out from the valves orange wire and this would re-power the boiler/pump