No CH without HW being on

[walderslade]

I'm about ready to throw in the towel.

Last week, woke up to a puddle downstairs, and found the pump had failed. No problem, and whilst I was fixing that, I figured i'd deal with the dodgy motorised valve.

And thats where my problems began.

Replaced, pump (now Wilo smart pump), and mid position valve (now Siemens SFCMV322). Found wiring to be a rats nest, and emergency plumber looked at it, said needed tracing back and left.

Traced back wiring, and reworked to match the instructions that came with the CMV322.

Could get HW, or HW+CH, but CH on own just fires pump, not boiler.

Today, have changed room stat (now Siemens RAA20), and cylinder stat (now Danfoss ATC), and the programmer (now Centaur C27)

I still can only get HW, HW+CH - CH on own just fires the pump still

Boiler is a Glow Worm Ultimate, and uses pump overrun.

Any ideas?

 

[picasso]

Is the pump wired into and controlled by the boiler ?

 

[MANDATE]

My thoughts are.
If the valve is moving to the CH position and boiler does not fire up then the second micro switch in the actuator head is faulty and not allowing power out through the orange wire.
If the valve only moves to mid position and will not go further, then that could be due to the first micro switch. But it could be due to no power on the grey wire before it passes through the micro switch.
Power on the grey comes from one of two sources depending on circumstances.
If HW is on and becomes satisfied, the cylinder stat diverts the power to the grey wire. (cylinder stat is a two way switch) The wire from cyl stat to grey may have poor connection.
If HW is not on then the grey cannot receive power from cyl stat, so there is a additional source which is a wire direct from the programmers HW OFF terminal. Again this wire may have poor connection or wired into wrong terminal in terminal box.( It has been known for this wire to be missing)
So first thing I suppose is to check if the grey is live under the two conditions. If it a new mid position valve its more likely to be a wiring fault.
Not only must you make sure that the wires are in the correct terminals, make sure they are not pushed in too far so the terminal screw comes on the wires insulation (no contact = no power)

 

[walderslade]

Thanks for that Mandate,

Between my orginal post, and now, I have moved all the connections in the Junction board twice. Once remaking all connections into the same connector block, the second moving into a new "chunkier" block.

Same outcome.

What I did notice, is that when I turn off the power completely, the valve seems to spool back.

Also, in running the multimeter over things, I came across a situation where I had 110V at grey (Room stat call, HW satisfied I think it was)

 

[easyas123Viessmann]

How many wires from your programmer?

 

[MANDATE]

The valve operates over two halves.
The motor gets its power from the white wire for the first half. This power is dropped at mid point and it picks up power again from the grey (if its live) and then continues to CH only.
In this position the motor is up against a stop as long as the power remains.
If the heating becomes satisfied the room stat cuts off the white wire supply so it no longer allows power out of the orange, but it does not affect the grey so the motor remains energised. Of course if you remove all power the motor unwinds due to the return spring so it drops back to the HW position which is the rest position.
A initial check with power back on but HW and CH both off the grey should be live and to me it should be 230v

 

[picasso]

The pump should be controlled by the boiler for pump over run so how can you have the pump only when the ch is called for ? if the pump isint wired to the boiler it sounds like you have miswired somewhere.

 

[walderslade]

The pump should be controlled by the boiler for pump over run so how can you have the pump only when the ch is called for ? if the pump isint wired to the boiler it sounds like you have miswired somewhere.

All i've done is to take a system that's been here at least 10 years (cos I've been here and the comment from the heating engineer (needs wiring tracing), and started from there.

I get pump and boiler no problem for HW, but no boiler for CH, only pump.

 

[walderslade]

How many wires from your programmer?

3 - 1, 3 & 4 from the programmer

 

[walderslade]

The valve operates over two halves.
The motor gets its power from the white wire for the first half. This power is dropped at mid point and it picks up power again from the grey (if its live) and then continues to CH only.
In this position the motor is up against a stop as long as the power remains.
If the heating becomes satisfied the room stat cuts off the white wire supply so it no longer allows power out of the orange, but it does not affect the grey so the motor remains energised. Of course if you remove all power the motor unwinds due to the return spring so it drops back to the HW position which is the rest position.
A initial check with power back on but HW and CH both off the grey should be live and to me it should be 230v

Could it be a fault in the actuator head on the valve then? As its not a fortnight old yet then that can be exchanged easily enough

 

[easyas123Viessmann]

Should be neutral, live, ch call, hw say, and hw call from programmer. the hw say is often missing.

 

[easyas123Viessmann]

A new valve is unlikely to be faulty. Look at the Honeywell y plan wiring guide from their Web site. Follow it closely from start to finish.use a new wiring centre if the wires are a mess. A pro should do this job in less than one hour. Approx £90. It's an interesting challenge though.

 

[dave18]

Hi Walderslade,

This is interesting, I went to look at a system a while back in one of the newer areas of Walderslade, with the same problems, found that the "hot water off" had not been connected between the programmer and the 3 port valve, The cable was installed but had not been connected at either end.

The cable had not become disconnected as the un used cables had been neatly coiled up in the back box.

From what you say I think there are more problems than this wire not connected. You say that if CH only is selected only the pump starts.The point is the pump and boiler do not know or care if the HW, HW/CH or CH only selected all they know is heat is required or heat is not required. its the 3port valve that decides, with the aid of the clock & stats where the heat goes.

The boiler and pump should come on together unless the water in the system is up to boiler stat temp, in which case the boiler will switch off leaving the pump running, when the system temp drops the boiler will fire again.

Looking at the wiring diagram for this boiler there is no pump over run with this boiler the pump is just wired to the switch live connection to the boiler.

If you wish I could sort it out for you after a short visit to find the extent of the problem.

David at Lordswood

 

[joe-90]

A new valve is unlikely to be faulty. Look at the Honeywell y plan wiring guide from their Web site. Follow it closely from start to finish.use a new wiring centre if the wires are a mess. A pro should do this job in less than one hour. Approx £90. It's an interesting challenge though.

Ninety quid? A heart surgeon charges less.

 

[easyas123Viessmann]

Any one can do heart surgery. quality heating engineers are harder to find.