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

[Murdoch]

These temperatures you mention, how did you t take the reading?

 

[Parmsuk]

These temperatures you mention, how did you t take the reading?

The flow temps are from the boiler directly and the room temp are taken from the Honeywell Single Zone Thermostat (Y87RF) placed in each zone.

 

[Murdoch]

The flow temps are from the boiler directly and the room temp are taken from the Honeywell Single Zone Thermostat (Y87RF) placed in each zone.

Maybe get an old fashioned mercury thermometer and get the actual room temp ....

 

[sammathias]

So you technically have the heating on alday every day???

25kw known for rads
KW for ufh needs to be known
KW for 300l invented cylinder (5kw...others can correct me)

So without knowing the output of the ufh. You still need 30kw output on the boiler unless the timings for hot water to come on where different schedules to heating

By rating the output on the boiler to 24kw I think you said it's just not going to heat the house effectively.

 

[Sharp Point]

What’s the insulation levels in the walls/floors , how many square meters of glass in the day room?

 

[ShaunCorbs]

Sounds about right if your in the house all day

 

[gmartine]

Bet no LLH.

 

[Chuck]

Smart Meter readings for month of Jan as follows: 1st jan: 4220 and 31st 4936. 716m3 of gas...converted to KW: 8074.

That's roughly twice the volume of gas that I would have guessed based on your description the house and usage patterns. I'm assuming you're in England not the North Pole, of course.

The two areas I'd scrutinise carefully are:

Firstly, the UFH, in particular what's the specification for the construction of the floor? If there isn't enough insulation under it, or there is two much insulation on top of it, UFH can be a really money-pit.

Secondly, the hot water. How much do you use per day and how is it programmed? Have you got a hot water leak somewhere?

Unless your house is essentially uninisulated or you leave all the windows open the whole time, the amount of gas you are using if it were all dissipated as heating would be baking you all alive. This is why I'm suspcious about the hot water. You might be pouring money down the drain, literally.

There is always the possibility that the meter is faulty and is over-reading. Also, are you sure that your meter is not also supplying a neighbour?

Once you done some basic checks, I suggest you get a heating engineer to do an energy consumption and loss calculation for your house to see how much it should be costing you. They'll also be able to check, approximately, that the consumption rate indicated by the meter matches the rate expected when the boiler is working.

I'm probably repeating stuff others have already because I got interrupted for several hours while typing this answer.

 

[gmartine]

Let's just assume your newly refurbished house is reasonably well insulated and your UFH meets the latests building regs.
Your boiler still won't be able to provide the necessary flow rates at delta T20 to your system without a low loss header or other means of hydraulic seperation, that's why I suspect your boiler flow temps are so high (inefficient) and as a consequence you're burning more gas than you should be.

 

[sammathias]

Or could just have a gas leak