CH problems

[st.john]

Hi, please help,
So, we recently bought a house, Essex, UK (detached bungalow about 100 m2, 1950-1960 era) in September, we have done some renovation, new flooring(laminate), new kitchen, new bathroom, changed couple windows from single to double glazing, changed one radiator in bathroom to towel rail.
All this time thermostat was set up for 18 degrees, like I said nobody lived in a house, just tradesmen and myself recently used to come in evenings to do the job, we received gas bill for nearly £700!!! (FOR WHAT???!!!)


The new central heating system was installed in 2019.11 new radiators, new pipes, and new boiler(there are paperwork for proofs etc.) Previous owner was very proud about that and told me he was boiling in the house (obviously he could lie)...
Last week we moved in, and then.....

1. The house barely reaches 18 degrees in any room, even the heating is constantly on. Thermostat is "HIVE" remote, we tried in every room it doesn't matter where it stays everywhere shows roughly the same.
2. The radiators have TRV all set on max, the flow from boiler 65C (tried and 60C - the same), rads get hot but room still very cold, tried heating all day long, no success. 1 rad in hall don't have TRV.
3. Insulation on loft 200mm, partly boarded. Double-glazed windows in every room (quite old).
4. All radiators take very long to preheat (except towel rail, I think it's 1st in line). And most of them very hot on top and warm on bottom.
5. All radiators are "designer" modern ones. Some vertical single, some doubles but horizontal. By the way, they all 5 years old but all of them rusted on the bottom and paint flicking on all of them.(this might be important detail.)
6. Smart meter shows that we use about 6–7 kWh in half an hour, then about 3 kWh and then 0, and then cycle again. 10Kwh every 1.5 hours... it's been 2000kwh for October, more that 3000kwh for November, and more that 3000kwh for December, I can't believe that's normal. In previous house we used 25 kWh a day, and 1000kwh on very cold month.
7. Boiler - Worcester Greenstar 32CDi Compact. Service have been done in September - came as all OK.
8. I've checked on boiler's settings, and it shows that return is only 5C lower than flow. So in my case, flow 65C return 60C.

Please help where I should start from to reduce bill and get house warm.

 

[Stuckinarut]

You might want to start with balancing, as you’re flow and return should ideally have a 20 degree difference. I would also check or have checked for any bypass failure and the diverter/motorised valve(s).

 

[Old Salt]

I have a bungalow (semi) built in about the same period, double glazed, 300 mm loft insulation, 8 standard radiators plus an under plinth heater and use gas for heating and hot water, combi boiler.

My place is warm with further capacity to up the trv settings etc. normally about 21 degrees and during November we used 995 kwh and December was about 1200 kwh.

 

[Justin Passing]

CHeck some radiator sizes against charts for similar types, do the calculations, see if they're big enough.
Then see if they add up to more than 24kW, if so your boiler's too small (unlikely).
If it's all calculated for a 20°C rise over outside, and outside is -3°, then it's working as designed.
The boiler obviously should go up to 82 on the flow. I know nothing of Hive thermostats so....


You DO NOT balance a system using the temperature knob on a trv, you use the lockshield valve the other end. (Unless you use the adjustment few know about inside the head of a Drayton TRV4). The rads nearest the boiler should be barely open, barely an 1/8th of a turn on the lockshield. Otherwise the boiler goes through the nearest rad , staright back to the boiler, which turns itself off because the water's hot. If that were entirely the case then farthest rads wouldn't be hot, which you say they are.
The return CAN be only only 5° under, your rads will just be emitting more heat, but it doesn't sound right. Feel the rads centre bottom edge. Are they all really that hot??
It would be more efficient if the return were cooler, but we're in the weeds now, something else is wrong.

 

[JohnD]

"detached bungalow about 100 m2, 1950-1960 era"

It would have had poor insulation when new

You have 200mm loft insulation now?

Does it have CWI?

I don't understand why you had the heating set to 18C when it was unoccupied. What dates did the £700 bill span?

Is there a hot water cylinder? What colour?

You say the radiators are hot at the top and warm at the bottom, but boiler return is 60C
The water from the bottom of the radiators returns to the boiler. Therefore it is short-circuiting somewhere. Is one of your radiators fully hot? Turn it off. Do the others heat up?