is a 24kw boiler big enough for a 3 bed house??

CrazyRed

BristolS wrote: »

Have you tried not having the hot tap fully open?
A lower flow will mean hotter water. Also insulating the hot water pipe will reduce the heat lost from the boiler to the tap

Hi, and thanks for your reply. Yes, I have tried not having the tap on so fully but this particular boiler "modulates" and, closing the tap down also seems to 'turn down' the boiler (you can hear a difference in the noise it's making when you do this) so the temperature remains fairly constant!

There is a brief period, once the tap's been open, where the water comes through lovely and hot, but after a few seconds it goes back to being luke-ish warm. I say lukewarm, but in reality, that's probably around 40-45C whereas I used to have the old tank on 55C minimum, with 65C being used for a couple of days each month to 'sterilise' the tank and pipes.

The bathroom hot tap is directly above the boiler - there's less than 2 metres of pipe between it and the boiler so I don't think that insulating said pipe would do a lot of good, but thank-you for your suggestion.

southcoastrgi

If it's a combi i personally wouldn't fit anything less than a 28kw

PaulBowen

Not sure to be honest, I guess the best thing to do is ring some heating engineers and ask them. If they're any good they'll let you know without wanting to talk figures. After all, you're only asking for free advice, right ?

It's like when I moved house, there was a 10 yr old boiler in and I wasn't sure if it was up to the job. I called some local firms and independent firms and most of them tried to quote figures or offer to come out for a fee ?!?! In the end, just before I'd given up I decided to try one last time - when I spoke to stl heating they were able to explain that the boiler was actually ok for my home and that was it - no hassle, no figures. So yeah try some local guys and see what they say.

bobsmum

PaulBowen wrote: »

....
In the end, just before I'd given up I decided to try one last time - when I spoke to XXXXX they were able to explain that the boiler was actually ok for my home and that was it - no hassle, no figures. So yeah try some local guys and see what they say.

Despite some helpful advice, you are still spamming for this company on numerous boiler threads - do you work for them???

Seronera

Like most people of knowledge on here have said, where combis are concerned I rarely if ever specify a 24kW boiler for 3 bed houses as the litre/min hot water production is at the limit of acceptability and once the HW heat exchanger gets even slightly congested...as it will...the hot water performance tails off quite rapidly. Putting a 28 or 30 kw combi in builds in a small degree of redundant capacity to ensure that the hot water performance remains acceptably good.

If you work in the industry fixing these things you find a disproportionate number of complaints about poor hot water come from people with 24 kW combis.

If its not a combi being considered then none of this applies of course as you need to do a heat calculation based on the capacity of radiators and hot water cylinder and the building construction heat losses. With combis the high rating needed for hot water production usually more than covers the heating requirement... almost certainly so for a three bed. The boiler will modulate its way to the correct requirement for heating unless it is vastly oversized.

techguy81

We live in an average-sized 4-bed semi with 13 rads, bathroom with electric shower and separate shower room, also electric.

The boiler is a 15-year-old Worcester Bosch 24CDi combi, and until it started packing up recently, we noticed no problems whatsoever with hot water and central heating. I'm a big fan of my daily baths, sometimes taking two per day, and the boiler has always given sterling service.

We've had a few quotes from different firms for a replacement, and the difference in opinion is surprising. Two of the firms quoted for 28kW and 30kW replacements, one of them left it at 24kW. There is easily a £200 - £300 jump the higher you go.

I was told that should we ever wish to upgrade to boiler-fed showers, we'd definitiely need a bigger boiler. However, changing the showers had never crossed our minds previously, and it will be some time before we're in a position to upgrade, so we've opted for the 24kW.

I must admit, reading some of the comments on the 'net and doing the estimates on the size calculator websites leaves me feeling a bit worried. But on the other hand, the old boiler has been installed 15 years with no complaints, so surely a like-for-like replacement will suffice?

thescouselander

We've just changed our boiler for a combi and I was concerned about the rate of hot water production as my previous experience of combis was not good. I measured the amount of water per minute our mains could deliver and specced the boiler to be able to heat that amount of water so we ended up with a 36 kw model - I'm very happy with my decision.

My parents have a 24 kw combi and I can only describe its performance as unsatisfactory.