New Build CH System Sizing

[mitchsub]

Just wondered if anybody could offer any advice please..

We bought a 5 bed new build back in august last year and have recently snagged the heating system for being too cold and underpowered. We first thought that maybe the insulation had been missed out until I measured the radiators which all seem way too small.

Bedroom 1 4.26mx 3.54m 600mm x 600mm Single Convector 2123 BTU

I have confronted to developer who has eventually given me the heating schematic from the heating consultants that they use.

Problem is the heating system has been designed to be run 24hrs a day which is probably why we are having these problems. I have the heating currently switching on around 2hrs before we get in at night and the same before we get up in the morning. This means however that the rooms take ages to heat up from cold and the upstairs rooms only get warm when all the doors are open. I constantly leave the main bathroom door open as if not the room will not get over 16c.

We recently went to France for 4 days so turned the heating down a bit – we got back in at 7pm and is was 10c in the house when we when to bed 4.5 hrs later the house was at 13.5c – this with the heating on full blast.

It all seems at odds though with what has been fitted control wise as each radiator has a TRV on it and there are two 24/7programmers – one for each floor, so the heating can be used very economically.

Could I ask please..

1. Do developers have any say over what the heating consultants specify to fit ? for example it would probably suit a retired couple who are at home all day

2. Should I really be running the system 24hrs a day ?

3. Is it common to fit a 15kW boiler to a 5 bed house ?

I certainly will be pushing to have some of the radiators replaced with larger units, but now realise to fit these the boiler will have to be replaced as well L

Would be interested on the forums thoughts

Thanks

Mitch

 

[Howsie]

Welcome Mitch.

If I were you I'd get an independent opinion. 15kw sounds small but there are many factors involved. For instance, we fitted a 17kw in a large three story 6 bedroom house and its fine.

 

[AWheating]

what is the exact system details? eg. boiler?, cylinder? renewables? etc.....

if the system has not been designed to a suitable/current standards then your entitled to have the problem sorted. maybe try and get the drawings up for use to look at?

 

[tamz]

The method of calculating heatloss has changed in the past few years as houses are built with much more insulation than they once were and there is now an argument that it is cheaper to keep your heating on 24hrs a day than time it.
This method of calculation can give you a kind of idea [DLMURL]http://www.energysavingtrust.org.uk/content/download/2654/62295/version/1/file/CE54_Domestic+heating+sizing+method.pdf[/DLMURL] but if the system was designed by a consultant their calculations would be much more in depth.

You may find this interesting as it suggests what a blind man could see.
[DLMURL="http://www.lolo.ac.uk/project/view/project/56"]London - Loughborough Centre for doctoral research in energy demand[/DLMURL]

 

[Meady]

You think your heating is bad, we're working on a site at the moment that is using underfloor heating - with a twist

the thing is they are only putting the underfloor heating on the ground floor, so upstairs only has the towel rail in the bathroom for heating.

i personally can't see it working due to the fact that as soon as someone closes the bedroom door upstairs then no beat is going to get in the room.

not as bad though as another site our mate was on where they were told they couldn't have the front door open for more than 30 seconds or the underfloor heating wouldn't cope with heating the house 🙂

 

[Howsie]

That can't be right!

 

[tamz]

You get a free fleece, a beanie and pair of long johns with every new house :smile:

 

[Howsie]

And a winters supply of ReadyBrek.

 

[jrmurray]

Surely each room should be calculated on the size then they can work out how many btw's/kw's are required to get the correctly sized rad? How can someone tell you that you have to have your heating on full time? I would go and get some advice from the NHBC they should help you sort it out and the contractors have to do what they say.

 

[plumber0808]

If its a new build built by one of the large company's they pass the details onto a heating manufacturer eg myson. Who will spec the job radiator, cylinder and boiler size, they do this because the builder will then use their products.
i would expect this is done using the latest methods and will be correct.

Might be stating the obvious but it is not unknown, have you got the trvs turned up?

 

[mitchsub]

Hi Guys - many thanks for the replys

Yes, the heating has been speced by Myson but fitted by an independant plumber. The radiators fitted are the Quinn roll top type which have a slightly higher BTU than the Myson ones quoted.

TRV's in the bebrooms are set to 4 but they never shut off

I could post the drawings, but all they give is the size and type of radiator fitted to each room - no actual working out

The boiler is a Ideal Logic 15 and there is a Gledhill water cylinder in the 2nd floor airing cupboard.

I'm annoyed as the system seems to have been designed to "top up" rather than "heat up" and to leave the system on all day seems a waste of energy.

Crazy thing is that I have speced bigger radiators and boiler myself and it would have made £250 difference to the equipment cost !

I will contact the NHBC and see what they say

thanks again

Mitch

 

[Meady]

You times £250 though by the amount of houses they build And it soon adds up to a lot of money

 

[REDSAW]

ideal boiler and quinn rads!.

probably want renewing in a couple of years anyway!

it was not supposed to have secondary heating was it and forgot to install it?

 

[plumber0808]

I don't think a 15kw boiler would be sufficient for a 5 bed house with unvented cylinder.
the boiler might not be sized correctly and will not cope on full demand. What size boiler did myson specify compared to what is fitted?
they have used myson but have changed it because of cost as myson would have spec a baxi or potterton as their all part of the same company and not a logic.
the rads I would say are sized correctly I have seen a myson spec before and out of curiosity I worked the house out myself and it was not far off the same.

 

[Howsie]

No mention of an unvented cylinder though.

 

[mitchsub]

Boiler specified on the Myson spec is a Baxi Megaflow System 15HE

 

[josh]

Is the boiler stat turned up?

 

[snowhead]

Does the boiler run continuously when on ( no cycling on and off) and are the radiators all hot when on?

 

[jrmurray]

Well ive got an ideal logic 18 system and a gledhill cylinder and ive got a four bed house so i think the boiler maybe a bit to small for your property and its worh asking NHBC as the contractors have changed the original spec so it may not be up to the job and they may have to sort it out.

 

[jrmurray]

Has the boiler got a weather compensation kit on it? As this changes what heat you have in the rads? Not many people understand how they work so they think there heating isnt work correctly.