Faulty water cylinder thermostat?

[stem]

It's possible I suppose, but if the feed and expansion tanks are in use, it raises the question as to why has an expansion vessel been fitted?

 

[Mojo12345]

I have a pump in the bathroom tommorow I’ll try all the hot water taps again and see if the boiler fires up, are expansion vessels only used for combi boilers?

 

[denso13]

I’ll try all the hot water taps again and see if the boiler fires up

It won't straight away, only if the cylinder stat is calling for heat. You don't have a combi.

 

[Hugh Jaleak]

Looking at the pictures, the system appears to have been converted, (badly) to a sealed system. The cold supply to the F&E cistern has been cut and capped, (at the wrong end...), and the former vent and cold feed on the cylinder primaries have also been capped.

However, the air vent has been fitted on the return, so I am now wondering if there is one massive airlock in the cylinder coil which is causing the issue..... Mojo, can you run the HW, and tell us if the 2 pipes going into the side of the cylinder, one above the other, (where it says 'Med duty'), are showing any signs of getting hot?

 

[Mojo12345]

Ok I will try and go in the loft tomorrow thanks for the advice and help

 

[Mojo12345]

Just so I’m sure I’ll check the pipes that go into the green tank for warmth, also I will check the cylinder thermostat which I have set to 65 so it should click around 65 is that correct? Last week when I checked it it was at maximum but when I adjusted it it was clicking at 35 ?? Thanks

 

[EFLImpudence]

It will click at whatever temperature the water is at the time.

Think about it.

 

[Mojo12345]

I understand the thermostat clicks at the temperature the water cylinder is at I just wanted to confirm the temperature the hot water cylinder should’ve at when the hot water has been running for an hour, should it be between 60-65 ?

 

[Hugh Jaleak]

If the system isn't working correctly, the boiler could be technically 'ON' all day, but if it isn't putting any heat into the cylinder, the contents of the cylinder wont heat up. You need to check those primaries are circulating first.

 

[stem]

You don't have a combi.

That's interesting, for my personal enlightenment, could you explain what this control is for then please?

 

[Hugh Jaleak]

That's interesting, for my personal enlightenment, could you explain what this control is for then please?

From the user manual "Optional maximum hot water temperature control available only when additional optional accessories are fitted (VR 65, VRT 360, VRC 400)."

 

[stem]

So what is this dial actually controlling?

 

[Hugh Jaleak]

I believe, if using full Vaillant controls, it allows remote adjustment of cylinder temperature, i.e. rather than adjust the cylinder stat, the user can adjust HW temperature at the boiler. With the OP's setup it may not be connected to anything so will have no effect.

 

[denso13]

That's interesting, for my personal enlightenment, could you explain what this control is for then please?

As Hugh mentions, it depends on the external controls.

 

[ianmcd]

You have an s plan system not a combi boiler, as already said the HW control on the boiler is only used with additional Valliant controls, @stem if you look at the pic of the boiler it only has a gas supply at the bottom and a flow and return at the top, tells you it is not a combi, agree the HW temp control is confusing