New Build CH System Sizing

[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 ??????

 

[Bronze_tap]

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

Dear Chris.
Basically I want that guy to have a nice LOW temperature system, so that condensing boiler operates at the peak efficiency, and it also can be heated by the air/grouind source heat pump, without any futher radiators upgrades. -> So house is at 20 even when the rads are just warm (~40)...

The condensing boiler manual states, that you need to uprate your's rads ~2 times with the NORMAL (non-condensing) boiler to achieve peak efficiency. In this case those radiators are UNDERSIZED even for the normal non-condensing system - so another 1.5-2X timer uprate is needed.

In the end we need 2X*2X = 4X or so uprate.

PS: also do check the quality and quantity of the insulation, because ~78% of builder fraud is the quality and quantity of the insulation... In the UK I would also add "and radiator (under-)sizing"... Get the pro with FLIR to take some thermal pics of your's house when there is 0 or so outside.

When Uprating it is important to keep the ratio of radiator's sizes to actual rooms heat demand. - so it would simlify ballancing task.

PPS: My own room had one 1000x600 rad mounted 40 cm above the floor when I've moved in, and no insulation behind it in the 2m wide bay window. With LL consent I've put 2cm of the polystyrene insulation behind it (solid wall), lined it with paper/foil, added another 600x600 rad with the new TRV and inhibitor filling point on top corner, lowered it down to 12-13cm above the floor, and cold floor drafts problem fixed. Also I've got way wider dynamic range of the temps control in the room, using the TRV. And way cheaper than the 300-400KWh of electricity used up before by the oil filled rad...

BTW: When the landlady bought that house in 2006, there was a 1000x600 single convector rad on the internal wall, with no loft or bay window top insulation. No room thermostat, only vintage randal ticking timeswith. No wonders her's son had nearly frozen ones upon a time in the that room. 😀

 

[chris watkins]

Well thank you Bronze_tap for being so honest & admitting that you do not carry out any heatloss calculations (& so many so called engineer also do not), all of what you have posted may or may not be true regarding builders but in this case that will be the builders fault, without some sort of proof i.e. heat loss / design calculations, this can not be proved.

P.S If you are going to quote for a job against me with rads 4 times bigger than the ones I have sized, you are not going to win many jobs?

 

[Ray Stafford]

P.S If you are going to quote for a job against me with rads 4 times bigger than the ones I have sized, you are not going to win many jobs?

Speaking as a radiator salesman, I think its an excellent plan. 😉

 

[chris watkins]

I bet you do Ray but then if I am not wining any jobs your not getting any sales !!!!!

 

[Ray Stafford]

I bet you do Ray but then if I am not wining any jobs your not getting any sales !!!!!

We'll just have to convince everyone that Bronzetap is right. These rads won't sell themselves!

 

[Bronze_tap]

Well thank you Bronze_tap for being so honest & admitting that you do not carry out any heatloss calculations
P.S If you are going to quote for a job against me with rads 4 times bigger than the ones I have sized, you are not going to win many jobs?

It was just sort of estimate using my experience with practical British rad sizing guidelines 🙂

In my case I'm just a DIY-er, not a pro (despite using water cooling for my server). So that's a hobby... The task is not to win as many jobs as possible, but to enjoy the process and the results in the time free from my main work. An make sure your's friend/colleagues are happy with results too. 90% of them represent 1% of British users, so not an average chaps...

And physicists/chemists usually don't need much explanation what a thermal gradient is or efficiency coefficient is, or what would happen to a modern boiler with plastic bits in a few years time, if you always run it 75+ degrees flow temperature...

PS: But I've not seen anyone saying/complaining that his rad with TRv (or at least tap) was too big so far. 😀 Why?

And some pro would give customer 2 or more quotes - one for a proper job, and one for a cheapest one... and try explaining what the diff is. Or just quote for the labour w/o rads - and show them the suggested ones to get. The only problem may bee if the custards never lived before in the property with correctly sized rads or UFH.

 

[chris watkins]

It was just sort of estimate using my experience with practical British rad sizing guidelines 🙂

In my case I'm just a DIY-er, not a pro (despite using water cooling for my server). So that's a hobby... The task is not to win as many jobs as possible, but to enjoy the process and the results in the time free from my main work. An make sure your's friend/colleagues are happy with results too. 90% of them represent 1% of British users, so not an average chaps...

And physicists/chemists usually don't need much explanation what a thermal gradient is or efficiency coefficient is, or what would happen to a modern boiler with plastic bits in a few years time, if you always run it 75+ degrees flow temperature...

PS: But I've not seen anyone saying/complaining that his rad with TRv (or at least tap) was too big so far. 😀 Why?

And some pro would give customer 2 or more quotes - one for a proper job, and one for a cheapest one... and try explaining what the diff is. Or just quote for the labour w/o rads - and show them the suggested ones to get. The only problem may bee if the custards never lived before in the property with correctly sized rads or UFH.

Again, I would thank you for your input but the OP would probably not, I have read through the above post a couple of times & with all due respect I can not understand it or what it is you are getting at ?
All I will say is that I do not play at this but earn my living at it, so for a lot of my life it has been all about winning jobs, as far as providing quotes, I give only one & that is the correct one. Priced & sized correctly, can I humbly suggest that you leave the art of rad sizing to the experts on here.

 

[Howsie]

I think you'll find most of us on here only quote for a proper job, not a (yeehaa) cheapest one.