Hot water only when heating is on...?

[NorthernChap]

Hi all,

Got an issue and I'm a bit stuck so found this forum and looks like plenty of knowledgeable people on here so fingers crossed!

Our hot water is only working when the central heating is on, and in this current weather that is a bit of an issue when there are five of us stuck at home and I have to set it to 25 degrees to have a shower!

The system is a Glowworm 30 HXi boiler, British Gas UP1 controller. In the airing cupboard there is a hot water cylinder with a thermostat, and two pipes going into it - one has two blue boxes on which I believe are motorised valves (one next to the hot pipe, the other further along). Tried giving those a tap in case stuck but no dice. There is also an immersion heater, which I don't believe has ever worked and is switched off at the consumer panel.

So, trying to work out why we don't get any hot water - the controller is set to timed for HW, but even if I put it on constant on, the boiler doesn't fire up. If I put the heating on, boiler comes on as expected and both radiators and HW work fine.

Any advice? I'm leaning towards the controller being faulty but any way I can confirm that? I'm happy doing a bit of electrical stuff so any way to bypass the controller to test the rest of the system for HW perhaps? Or any other thoughts?

Cheers!

Jimmy

 

[terryplumb]

More likely to be the motorised valves micro switch ,the valve that controls the domestic hot water.
Does your hot water get a lot hotter than it used to ,when all was working well ?

 

[NorthernChap]

It did earlier, but then my other half had the heating on full blast so who knows...

So if that valve doesn't actuate, the boiler won't kick in? I saw something elsewhere about testing the brown wire at the valve for 240v with a multimeter, is that the one immediately before the cylinder, on the hot pipe? Worth a try?

It's a BGMVSP-2 by the way if that helps. There's that one next to the cylinder, and another one further off in the pipework which I guess is for CH.

 

[terryplumb]

Can you post pics of pipework around cylinder , particularly the motorised valves ,the valve that controls the flow of water into the cylinders coil will be on a pipe that goes directly to the cylinder. Electrical testing would be done at the wiring centre.

 

[NorthernChap]

Sure - here you go, excuse the mucky airing cupboard, the flash reveals all it seems!

 

[terryplumb]

Cheers . Obvious which valve is for the cylinder !! The brown wire brings voltage to the valves motor ,motor turns a spindle ( shaft basically) that opens the port allowing water to flow thru the brass body into the cylinder. The spindle also triggers a micro switch ,which has a seperate voltage supply, and allows voltage to flow through the orange wire to the boiler and pump. The valve is getting voltage on the brown as it is opening and you are getting hot water. If it wasn't the valves default position is closed, under spring pressure, and you would not get hot water . So I suspect the micro switch is not being made / or is goosed.

 

[NorthernChap]

Ah OK, that's really helpful - thanks! I guess tomorrow I will cut the power and see if I can open it up and find anything obvious. If not then maybe bridging the switch wires as a temporary test to see if the boiler starts up (just to confirm diagnosis, I wouldn't leave it like that!) - I'll update the thread when I know more, thanks again!

 

[dilalio]

They are common parts to fail, due to the amount of work they do over their lifetime.
Order a new actuator and replace.

 

[NorthernChap]

Got a new actuator from Screwfix for £55, easy swap over with the power off - problem solved. Thanks for the help, really appreciated and saved me a load of hassle!