Vaillant 428 - Hot water no heating.

[krazaq]

Have the following installed.

Vaillant 428 boiler
Wireless Room Stat Y6630D1007
ST9400C Programmer
L641 Cylinder stat
V4073A 3 port motorized valve
10 Way junction box

All honeywell

Wired as follows



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or

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Now call for water and everything works, but heating does not work. its calling but the boiler is not firing up.

any ideas? I know its got something to do with Room thermostat but i have wired exactly as the Programmer wiring diagram as asked. There are so many different ways.

 

[Youllneverguess]

With water AND heating on do the rads heat?

Have you confirmed that the valve is moving to the heating or heating/hot water postilion?

In heat only mode does the valve move fully across? Do you get your mains volts to the boiler?

 

[krazaq]

With water yes the rads do get hot only until the cylinder thermostat reachs 60 deg where it is set, the the boiler goes off.

Valve seems open on CH and HW.

Heat only, nothing actually happens and valve remains in the same place. the boiler does not fire up at all.

 

[Youllneverguess]

Have you wired the hot water "off" side of the clock and cylinder stat correctly?

Hot water off in clock should link to terminal two of the cylinder stat and the grey wire of the valve.

Go and double check this... don't assume you did it correctly by the diagram.

 

[krazaq]

yes that is correct.

 

[Youllneverguess]

So have you checked for the correct voltage at terminals 4, 5 and 8 of the wiring centre? You should also have 240 at the grey wire of the valve.

Also double check that all the neutral wires are correctly seated.

 

[Youllneverguess]

You have made sure the room stat is turned up? I have to ask...

 

[krazaq]

You have made sure the room stat is turned up? I have to ask...

yes room thermostat fully up and functional.

its the wiring of the Y6630D1007. I have live to 1 and Neutral to 2. A to 4 and B to 5??

But another diagram shows a live connection from L to 4....

L to 4 connection does work but then thermostat starts the boiler to come on even though the programmer says off for both heating and HW

all connections checked and seated properly. I thought with Junction box it wouold be a lot simpler. but there are too many contradicting in diagrams.

 

[Youllneverguess]

L to 4 would be for a programmable room stat eliminating the need for the timer.

What voltage do you have on terminal 7?

Not sure what you mean by contradicting diagrams? they are pretty straightforward and long established.

 

[krazaq]

ok can't check voltage right now, had enough.

ok can you help me out, tomorrow after work i will rewire the hole junction box again. i have all wires running directly to the junction box.

The following are installed

Vaillant 428 (5 Core Cable for pump over run)
Pump (3 Core Cable)
ST9400C (5 Core Cable)
Honey V4073A (5 Core Cable)
L641A Cylinder stat (3 Core Cable)
Honeywell Wireless room thermostat y6630D (4 Core Cable at the min)

Can you suggest a diagram that would fit all the above?

What i meant earlier with contradicting diagrams is that there are two different diagrams for the wireless room thermostat. one with 3 cables going to junction box and one with 4 cables going to junction box. One came with the thermostat and the other came with the programmer.

Thanks

 

[Youllneverguess]

OK, you are just confusing "contradiction" with "alternative".

Your cable types are fine (assuming 0.75mm heat resistant). I also assume you have the valve plumbed correctly - B - hot water, A - heating, AB boiler flow.

The Sundial Y-Plan diagram you have is fine. As is your room stat wiring by al accounts - otherwise you wouldn't have heating with hot water.

I will upload a handy diagram I use to teach electricians how a Y plan works... Got it from Honeywell ages ago.

I suspect you have the hot water off part of the circuit incorrect.

You should have 240V at terminal 7 with heating only selected. If not trace that link set back to their terminals.

Below is Honeywell's explanation for how it works:


In the Y plan system, when Hot Water is called for, power to the Boiler is provided directly from the cylinder thermostat, the valve is not energised. When Heating is called for, the Heating ON wire (White) is energised and the valve will motor to micro-switch #1 and stop in a mid-position.

If the Hot Water is then turned off, (either by the programmer or cylinder thermostat) the Hot Water OFF wire (Grey) is energised. If there is still a demand for Heating the valve will then motor towards the Heating Only position and switch micro-switch #2, which then puts a 240V supply onto the boiler. The orange wire only has a 240V supply from the valve when it is in the Heating Only position i.e. 240V on White & Grey wires.

When heating is satisfied, from the Heating Only position, 50 - 150V (voltage can vary according to the supply) will remain on the orange wire and the valve will continue to be energised and warm to the touch. Switching ON Hot Water or turning OFF at the mains will de-energise the valve and it will spring return back to the Hot Water Only position.

 

[Youllneverguess]

Untitled

• Youllneverguess
• 8 Sep 2011
• 1

 

[krazaq]

ok thanks will look at it tomorrow and advise if it all works. would still like to have a junction box diagram for everything i got , but however you are right, its alternatives that got me a little confused.

 

[Youllneverguess]

The only difference is the addition L and N for the transmitter. Otherwise, your substitution of A/B to 4/5 are fine.

Your problem has to be the hot water off aspect as that is what enables the valve to travel fully to heating mode.

Unless of course the valve is faulty, but I have never seen that with a new one over a decade of plumbing. In fact, i can only think of a couple of faulty heads of these valves (motors not withstanding).

 

[krazaq]

the wiring was totally correct from the start.only that the 4 cable from behind the programmer had come out. hence the programmer was not making a call for heating on and off.

Luckily i noticed this before i undone thejjunction box. now the system is working and all tests have been carried out.

The whole house is heaving with heat. How long do you suggest i test the system for?

Thanks again for all your help.