Boiler not powerful enough?

[OnTheBenchOfDoom]

I don't really want to admit to how much of an idiot I feel having to post this so please be kind. I will hope @PigletJohn can wade in on this too as I am sure that they know about heating systmes.

We had a new boiler and all the mostly single radiators in our house replaced with new double ones by Helplink in 2016. Despite replacing our G rated piece of crap boiler that came with the house we never saw the savings we thought we would see with the new Worcester Bosch boiler.

Due to one radiator not getting hot today we go to the boiler to check the pump setting and for the first time I take notice of the sticker on the side of the boiler says it is a Greenstar 24ri. Which means it is a 24kw boiler.

We have 15 radiators in our 4 bed house, Helplink knew this as they replaced them all. Having looked a bit online the 24kw boiler is only suitable for 10 radiators. A 28-30kw boiler is recommended for 15 radiators.

I feel like an idiot because I knew they had installed a Worcester boiler but never looked at which one they had installed. Firstly is their any recourse at this late stage of the game with Helplink who are now another company, secondly are my bills are higher than expected because it is going full out to try to heat more radiators than it is designed for?

It will be fine , unless you want it on full whack all the time , with one radiator not getting hot it could be it needs bleeding or the system needs balancing.

24kW is quite a lot.

How old is your house?

I had a 30kW Heat-Only boiler in a previous house, but it was Edwardian, 5-bed, 2-bath, fair size, detached, with solid brick walls. On frosty nights the boiler ran flat out.

My current house is a bit smaller, but has cavity walls with insulation, and the calculated heat loss, at 0C outside and 20C inside, is only 12kW (plus the cylinder, for short periods). The boiler itself is 24kW, but never runs flat out, except for 20 minutes when it starts up from cold when the house has been unoccupied and everything is cold. The total volume of water in the radiators is just under 100 litres

You can calculate the nominal output of your radiators. If the total is less than your boiler, the boiler cannot deliver to its maximum. It is OK to have radiators totalling more than your boiler, because (1) they will keep the rooms at a more even temperature, and (2) if you have TRVs, it is most unlikely that they will all be running at max for long.

Combi boilers are usually bigger, around 30kW because you need a great deal of heat to supply a hot bath tap delivering 12 litres per minute. As they often run at full power they tend to be noisier. While you are running hot taps, a combi will not heat the radiators.

You can calculate the heat loss of your house if you want. I will try to find an online calculator.

Here's a heat-loss calculator. I can't find a whole-house calculator at the moment (which would be better)

if responding, I work in kW, not BTU

@PigletJohn thank you so much for the reply and the maths challenge you set me luckily I have just bought a laser tape measure so this was an easier than I thought challenge.

My house was built in 2000, it has thermalite and brick walls but no insulation within the cavity but does retain heat. We were on first name terms with British Gas due to the number of times the old boiler just stopped working and I had forgotten that we monitored the temperature when we had no heating in December.

I have 15 rads as my lounge has a french door bay window so 4 windows and the french doors plus another window so there are 2 rads in there and we converted a double garage to a playroom for the children so again 2 rads in there. It is a 4 bed detached house with a separate dining room and an extended kitchen.

If my calculations are correct then my boiler is sufficient for the house. I panicked last night. I hate being cold and we live in Yorkshire so we have more cold days than the south coast. Our boiler is set to come on when we feel it is cold, we have a Nest device thing. We didn't choose a combi after having issues with bath filling at a previous house.

You have made me quite jealous with your previous Edwardian property. Sadly there are none here when you have to be near a great secondary school. However my sister lives in a beautiful Edwardian house so I get my fix at hers.

Thank you for your help.

You do have TRVs, don't you?

And a programmable thermostat?

Good heat control will improve economy and comfort.

Cavity will insulation will cut heat loss a lot, and your house is modern enough that it should not have defective wet walls. It is not expensive.

@PigletJohn

yes to TRVs,

yes to programmable thermostat, we have Nest so it is accessible on my phone.

I am a SAHM so here all day. I am partially disabled so not incredibly active sadly but I don't ever increase the temperature of the heating up, just stick a hoodie or jumper on if I feel a bit chilly.

Cavity wall insulation isn't needed due to the thermalite block instead of breezeblocks in the construction. Those that have had insulation blown in have had issues with wind driven rain causing damp.

Our estate is quite hilly, causes great fun in winter. We are up one side of a hill and then it goes down and back up another hill. We take bets on how many goes it will take a car to try to get up the hill opposite when it has snowed. Also will the car overshoot the junction when it slides down the same hill. Great for entertaining children when schools are shut due to snow.

The point of that is to say we are quite exposed, to the wind and rain my house stands alone, no neighbours next to my house, we are offset. This and living in Yorkshire means we seem to have the heating on a fair bit. Cost is not an issue fortunately.