Drayton / Invensys 3 port valve

[polchraine]

This is my first post here after being told it was possibly the best place to ask.

I am trying to sort out a central heating problem for some relatives I am staying with. So far the plumber has been a few times and the bill is climbing and I want to try to have a reasonable discussion with him about how the problem can be solved. I think I have found out what it is.

The boiler is a Worcester Bosch oil fired with internal pump and 3 port valve. Burner works fine and circulating water gets very hot but goes the wrong way.

The problem they had was possibly linked to the 3 port valve and a new one was procured from a Worcester Bosch spares agent. The device removed was an from Appliance Components and the replacement a Drayton/Invensys ZA3/679-3.

The data sheet says that when 240V is applied and the valve head energised Port A will open. However, looking at the unit on the side where the indicator is, there is a label with A on the left and B on the right, port A is on the right and B on the left (in the casting). When 240v is applied the indicator moves to position B - contrary to the data sheet but port A opens.

The plumber has installed the valve with B for hot water and A for heating - which according to the valve labelling should be correct.

However, when system goes "live" for hot water, the indicator moves to B, port A opens and heated water flows around the heating circuit and there is only cold water from the tap. Turing off the tap causes the flow switch to break and the boiler turns off.

Questions:
Is the valve labelled incorrectly?
Will turning it around solve the problem?

 

[Softus]

Is the valve labelled incorrectly?

Either that or its assembled wrongly.

Will turning it around solve the problem?

If being labeled, or assembled, 180° wrongly is the only problem, then yes.

 

[polchraine]

By assembled wrongly do you mean the head has been rotated? If so, then no it has not, there is only one way that they can go together.

 

[Softus]

By assembled wrongly do you mean the head has been rotated? If so, then no it has not, there is only one way that they can go together.

Have you posted merely to ask me whether I meant the possible way, or the impossible way, of it being wrongly assembled?

Let's just assume that I meant the possible way, shall we?

 

[polchraine]

Apparently, the valve was installed straight out of the box - the plumber did not remove the head before installing. He applied 240v and saw where teh indicator went to and apparently installed that similarly maked end to hot water.

Is it possible that the insides could be incorrectly assembled? I have looked at the head and valve casting and there is only one way for them to go together.

Thinking it through fully, rotating the complete assembly will resolve it, but the indication of A/B will be incorrect.

 

[Softus]

Is it possible that the insides could be incorrectly assembled?

That depends on the design of the whole assembly. It's certainly possible to design a valve in such a way as to make it possible to be wrongly assembled.

Thinking it through fully, rotating the complete assembly will resolve it, but the indication of A/B will be incorrect.

In that case the use of a pencil will complete the repair.

 

[Balenza]

polchraine wrote

However, when system goes "live" for hot water, the indicator moves to B, port A opens and heated water flows around the heating circuit and there is only cold water from the tap. Turing off the tap causes the flow switch to break and the boiler turns off.

WB's Technical and specification information state the following......

Central heating mode
On a demand for central heating the diverter valve will open
and the pump will energise to circulate primary water around
the heating system. The burner will automatically light and
the radiators will heat up to the temperature set by the
heating control thermostat.

Which begs the question why is the valve being energised for HW ??.