High gas bill - Vaillant 637 - UFH and Alu Rads - Help

[Sharp Point]

Secondary hot water circuits are energy thief’s, as the pump is circulating the hot water, it’s cooling the cylinder down...as water in the loop is continuously losing heat, the situation would be worse if you had little or no lagging on the pipework.

 

[Sharp Point]

And yes, the cylinder thermostat controls the boiler, you possibly may have a stuck zone valve, that is keeping the hot water on

 

[Parmsuk]

Okay, so I noticed the boiler come back on this afternoon again even though there is no heat demand or timer requirement for HW. So checking the flow pipes to each zone, only the hot water flow was hot which feeds the HW tank. I looked at the boiler stat attached to the tank and it was on 65 (max). I turned it down a bit to say 45 and I could hear the hot water value make a noise (closing??) and then followed by the boiler turning off. It never came back on since...I've turned the stat back to approx. 55C.

So it seems, that regardless of timer settings for HW (which by the way I turned off beginning of Feb to see impact of hot water supply) we have never been without hot water as the boiler keeps it to temp. I wonder if this could also be the reason it coming on middle of the night to reheat the water due to temperature drop?

 

[doitmyself]

So it seems, that regardless of timer settings for HW (which by the way I turned off beginning of Feb to see impact of hot water supply) we have never been without hot water as the boiler keeps it to temp. I wonder if this could also be the reason it coming on middle of the night to reheat the water due to temperature drop?

If you turned the HW off at the timer but the cylinder is still being heated, I would say there is definitely something wrong with the way it has been wired up.

What sort of insulation does the HW cylinder have - none, loose red jacket or fixed insulation? Modern cylinder with fixed insulation will keep hot for many hours. Our one stops heating about midnight and the water is still hot enough for a shower at 10am the next day.

60C is the recommended temperature as it kills of any legionella bacteria.

 

[Parmsuk]

If you turned the HW off at the timer but the cylinder is still being heated, I would say there is definitely something wrong with the way it has been wired up.

What sort of insulation does the HW cylinder have - none, loose red jacket or fixed insulation? Modern cylinder with fixed insulation will keep hot for many hours. Our one stops heating about midnight and the water is still hot enough for a shower at 10am the next day.

60C is the recommended temperature as it kills of any legionella bacteria.

Hi,

Its a valliant Unistore 300l unit.

 

[Parmsuk]

I turned down the thermostat on the HW tank (experiment) down to 40 degrees before I went to bed. Checking the smart meter before the heating came this morning there was no gas usage 🙂. Also observed the hot water tank temperature at 43"

So can conclude that the HW is on permanent regardless of timer settings to maintain the temperature of the HW tank. The heating will turn off after 10:30am, i'll then turn up the HW thermostat back to 60 degrees and expect it to turn back on. I'll report back....thanks once again for everyone expertise help.

 

[ShaunCorbs]

Turn it back up now please there’s a reason why it’s set at 60

 

[Parmsuk]

Turn it back up now please there’s a reason why it’s set at 60

Will do 🙂

 

[malx42]

Fork and Knife. 45000 kw hr a year! That’s a lot.

Have you just moved in? Or have you heating bills from this house or previous ones?

If it’s a complete refurb ... is it an old house? What age? Does it have solid brick walls. Did the refurb include insulation.

If you post a pic of the brickwork we can see if it’s solid or cavity walls.

My daughter had a leak in her hot water system. 2 litres a minute. So the boiler was constantly heating hot water that was leaking away under the floor. I reckon this cost her £80 a month. 3000 kwhr a month ... 36000 a year. Her boiler was constantly switching off and on.

Have you a water meter? Look at that ... see how much you use overnight. Or turn off the main water supply. The heating will still work fine, the boiler will heat up, you won’t get hot water. but can’t heat any more cold water as it’s not getting to the cylinder.

Did you say you had a smart meter? Is Gas being used all the time?

We only have our water heated once a day, for one hour. Cylinder is well insulated and it keeps hot for a long time ... we shower so don’t use that much water.

Has the bill always been that high?