Baxi Solo 2PF

[norris108]

Hi all,

I have a Baxi Solo 2PF boiler supplying hot water & central heating via a Landis & Gyr 3 port mid-position motorised valve, part number MAV-322

Just recently, I was not getting any central heating, only hot water. The only way I am able to get central heating is to manually open the valve with a lever on the side and turn up the thermostat on the cylinder in the airing cupboard. Not an ideal solution as I'm getting scorching hot water, but at least the house is warm!

Where do I start diagnosing the problem? I'm guessing it could it be a problem with the motorised valve not opening. Is it possible to replace just the motor, which I could do myself, or do I need to replace the whole valve? In which case a plumber would be required.

I'm also a bit confused how the boiler knows to fire up to heat the water for the central heating as I don't have any room thermostats in the house only individual themostatic valves on each radiator. Could someone please explain how it works?

Another thing, I'm thinking of replacing the old Landis & Gyr mechanical timer control panel (can't find a part/model number, but from a Google search it appears to be an RWB2? A picture is attached below) with an electric version as although it's set to "twice" for both hot water and central heating it is operating as though it's set to "once". Is it as simple and removing the old control panel from the backplate on the wall and replacing it with the new one? Or do I need to also replace the backplate on the wall as well?

Any help on any/all of these matters would be greatly received.

Thanks in advance!

Mark

Untitled

• norris108
• 14 Dec 2010
• 2

Landis & Gyr Timer Control Panel

 

[45yearsagasman]

If you can expose the motor then its easy to change on most makes of valve although not sure I've seen your model.As you have no room stat the (normally)white wire will receive a signal direct from the programmer.That programmer has an industry standard back plate and most programmers will be plug in.

 

[pontered]

valve works off ch switch on clock no need for a stat

should be an easy swap for the clock, try a ACL/Drayton brand, back plate is nearly the same and may fit... if not it is easy to switch the back plates between the 2

now for the problem.....

this could be a faulty motor in the 3 way valve, easy to change, 2 small screws & 2 wires

if its not the motor they have a small pcb in them which would mean a new complete valve

however you have to check you have power down the white wire when heating is on, if not its not the valve, its an electric fault, clock or wireing??

 

[norris108]

Thanks for the propmpt replies so far.

I've just tried switching central heating to the "on" position at the control panel and hot water to the "off" position so I can test if there is power going to the motor in the valve, but as soon as I do that the boiler switches off. Is there anyway to force the boiler to fire up in central heating mode? Could this point to a problem with the control panel?

Sorry if these sounds like a daft questions, but I've not been in this house long, and this is the 1st system I've seen without a room thermostat! If I had a room thermostat I could wack it up and get the boiler to come on.

Mark

 

[sabrinaleech]

Mark (or anyone else) we have the exact same problem ... how did you rectify it?

 

[OLLIE20]

This is a simple fault, only problem is you have no concept of how your system is wired or how it works, by the sound of it, which makes it a little difficuilt.

However i will try

Turn off HW at timer, turn on CH, find your mid position diverter valve

Now find where the wiring from valve terminates (should be in a junction box of some kind)

With CH calling on programmer go across White wire (usually) and a neutral wire (blue/ black) or earth (yellow & green)

If you have 240v programmer is doing what it should be, and there is a fault with the valve

Usually in this country, we use whats called a spring return valve, which sits in the HW position as its default setting, which is why HW works as the valve doesnt realy need to move

If you're CH is coming on and its in the HW position only, c
hances are your valve is probably passing, which at this time of year wont bother you, but when it 30C outside in summer it sure will

Once youre HW stat is satisfied it will break the end switch within the valve and shut down pump + boiler, untill CYL rqs heat again

Dont worry about a room stat, all it is, is a switch, basically the power goes form CH on from clock into one side of r/s, when you turn uo r/s it makes switch other side of r/s connected to white wire (normally) on Div valve, which them motors over and brings on pump + boiler

Your CH on at timer goes straight to white wire on ZV, hope you followed all that