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.

 

[DirksPlumbing]

Is heating round the clock wasting energy? I would not think so. First of all I have been able to cut the gas usage in my old house (pre1800) by 1 cbm a day by keeping it going rather timing pretty restrictive.

It is quite understandable if you bear in mind that heating your house to a comfortable temperature is a fixed target. It will not come closer just by reducing times.

Lets stress the good old car analogies: You are driving from Liverpool to London. Would you in order to save fuel put your foot down through the sheet metal in order to safe fuel? Would you honestly believe that if you made the run in half the time that you have used half the fuel? Why on earth do people believe that this is the case on a static combustion engine (aka boiler)?

The aim is actually an as comfortable temperature as possible at as low system temperatures as possible. How do you get this by cutting times?

 

[chris watkins]

You need to request a copy of the heat loss calculations for the property these should have been held on file for this job. Without them you cannot tell what the design parameters of your house are against the boiler & rad's installed, for instants what 'U' values have been used for the structure, whether an allowance (typically +15%) for intermittent heating (turning it on or off), what the deign outside - inside & flow/return temperatures have been used. As you can see the process can be a little complex, as has perviously been suggested I would employ the services of a good heating engineer or a consultant if the house builder will not come across with the designs.

Unless it was made very clear on the documentation / users guide when you purchased the house that the heating had to be left on 24/7 during the winter, then most would consider the heating system not fit for purpose if it can not raise the room temperature by 5 deg in say an hour or two & then hold it at 21 deg C when the outside temp is at -3 deg C.

 

[lame plumber]

go talk to buildings control, they should have copies of everything as they had approved the plans/specs.

 

[Bronze_tap]

Just wondered if anybody could offer any advice please..
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.
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

Man...
Looks like "Developers" (Robes) had done you on the radiator size (for arround 1k on the whole house)... 600x600 Single convector :grin::grin::grin::grin::grin::grin::grin::grin: for a WHOLE bedroom???

Did it say "Supercritical steam boiler required" anywhere in the specifications? :grin: It should have said for such rads sizes... (All through I'm not sure you want your rads to be @100-200 degrees :grin: and 10 bars+ preassure).

In this case tripple/quadruple the rads size. You probably Will not have to upgrade the boiler if you upgrade all rads (unless there is no insulation).
It is normal for the modern boiler to trickle at around 5-6KW for the whole 3 bedroom house - so 15 should be enough for properly insulated 5 bed one...

for the bedroom I would put something like 1400x600 Double Convector, and site it under the window... Also go for diagonal connections if possible.

PS: Myself I've got one 1000x600 double convector and an 600x600 double convector sitting under my window with diagonal connection (rad Tops/bottoms linked) for 15 sqm.

 

[chris watkins]

Man...
Looks like "Developers" (Robes) had done you on the radiator size (for arround 1k on the whole house)... 600x600 Single convector :grin::grin::grin::grin::grin::grin::grin::grin: for a WHOLE bedroom???

Did it say "Supercritical steam boiler required" anywhere in the specifications? :grin: It should have said for such rads sizes... (All through I'm not sure you want your rads to be @100-200 degrees :grin: and 10 bars+ preassure).

In this case tripple/quadruple the rads size. You probably Will not have to upgrade the boiler if you upgrade all rads (unless there is no insulation).
It is normal for the modern boiler to trickle at around 5-6KW for the whole 3 bedroom house - so 15 should be enough for properly insulated 5 bed one...

for the bedroom I would put something like 1400x600 Double Convector, and site it under the window... Also go for diagonal connections if possible.

PS: Myself I've got one 1000x600 double convector and an 600x600 double convector sitting under my window with diagonal connection (rad Tops/bottoms linked) for 15 sqm.

Perhaps Bronze you can enlighten us as to how you arrive at these rad sizes of yours ??????