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

[Parmsuk]

Hi,

Following a full refurbishment of an house and a new build rear extension we had a brand new heating system installed. Give you an idea of what it is:

• Vaillant 637 system boiler
• 300l Water tank
• Wet UFH (floor area 15x4m) in new rear extension (family area, kitchen and dining) - used all day (1 zone). Unknown but calculated by SOLFEX from what I recall seeing by the heating engineer at the time.
• Existing Downstairs, existing upstairs each with own zone (2 zones).
• 5 bedrooms (1 guest so hardly used), 3 bathrooms.
• 17 Aluminium radiators in total 25Kw in output excluding UFH (i don't the KW what this actually is)
• Honeywell Evohome with Y87 wall stats in each zone

1 year in and our gas bill seem very high, much more than anticipated. Approx. 45,000Kw used.

I've been many forums over the past week or so and it does seem that my usage is much higher than standard (18Kw-20Kw).

The past week I've also been monitoring evohome and I can see that the UFH once up to heat even in this cold weather spell (-1 degree) it maintains a lovely 19 degrees all through the day with just the odd call every couple of hours for a bit of heat (10% or so) and switches back down to 17 through the night (i can see that it does'nt drop lower than 17.5 through the night using some logging software so no heat demand).

The downstairs zone (non UFH - 9 radiators - approx 14KW - downstairs includes bedroom 5 and ensuite) seems to be running most of the day to maintain a temp of 19.5 degrees. I've witness it "cycling" every 10 minutes or so throughout the day.

This morning, i've changed the D00 setting to 24KW, previously it was set to 37KW and see if that makes any difference.

I also took the following readings if it helps:
Flow temperature is: 75C
Return temperature is: 65C

Should I just wait and monitor our smart meter over the next couple days and see if it as any impact??

I've noticed that the max reading on smart meter shows is 22.84Kw since I've made the change to D00, however it goes down only as low to 6.8Kw.

Any other advice??? Is this to be expected??? Oversized boiler???

Thanks in advance.

 

[gmartine]

Pictures of the system would be helpful, Evo doesn't do weather comp which you should have for such a large residence especially with UFH.

 

[Rob Foster]

some gas meter readings are a good start ..tariff and supplier
..and a historical run down of the gas usage. then we can look at the system as gmartine asks
Centralheatking

 

[SJB060685]

Following

 

[Rob Foster]

Following

ok but I am out doin till later but others are just as good if not better than me at this stuff
centralheatking

 

[SJB060685]

I’m curious as to what the end result is lol.

 

[Parmsuk]

Hi,

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

My energy supplier is Tonik and Positively Green v20 tarif. 2.9p/Kw and 22.37p standard charge.

 

[Rob Foster]

Hi,

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

My energy supplier is Tonik and Positively Green v20 tarif. 2.9p/Kw and 22.37p standard charge.

how many people , and a building lifestyle is handy.
ie how many carpet rats ..wrinklies ..etc like me. ..
do you all leave the building
5 days a week or run a home office...see what I mean ?
centralheatking

 

[Parmsuk]

Three adult and 2 young children.
Occupied downstairs throughout the day. However, from 10-4pm we turn down the standard downstairs heating (radiators) to 19degrees. The extension area is where we spend most of the day (kitchen,dining room and family room) and this is heated by the wet UFH at constant 19.5degress from 6am to 8pm which takes an 2.5 hours in the morning to get the desired temp but then maintains it easily throughout the day into the evening with only a couple of times for gentle heat call.

 

[Rob Foster]

Three adult and 2 young children.
Occupied downstairs throughout the day. However, from 10-4pm we turn down the standard downstairs heating (radiators) to 19degrees. The extension area is where we spend most of the day (kitchen,dining room and family room) and this is heated by the wet UFH at constant 19.5degress from 6am to 8pm which takes an 2.5 hours in the morning to get the desired temp but then maintains it easily throughout the day into the evening with only a couple of times for gentle heat call.

ok ...wow ...so ur system is never off essentially . later We will go over it ..you must be loaded ..but hey
centralheatking

 

[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?