Replacing radiators - building regulations?

[gdickin2]

Hi, I am embarking on a bit of a modernisation project and want to replace all rads in my house with newer more efficient models.
Some of this will involve replacing long singles with shorter doubles and/or relocating some of them to different walls.
To do this do I have to have a buildings inspectors ok for the work to go ahead and for an inspection once complete or am I ok to go ahead without incurring the wrath of the buildings inspector?

Cheers.

 

[seco services]

don't need a building inspector for changing or repositioning a rad.

 

[muggles]

Just make sure you get the correct size rads and you'll be fine! If I was you I'd spend some time working out what sizes will be needed with your boiler running a 60/40 or even 50/30 flow & return temperature, that way should you get a condensing boiler you'll be able to run it cooler, making it much more efficient. If you need more help doing this please ask!

 

[CharteredEngineer]

I would actually spec slightly larger radiators than you actually need on 50 flow 30 return, this is primarily for two reasons.

1. Winters appear to be getting more extreme despite global warming!
2. You can run a lower flow temperature, this is a more efficient way to heat a building and if you have a condensing machine you will get double benefit.

CE

 

[muggles]

I would actually spec slightly larger radiators than you actually need on 50 flow 30 return, this is primarily for two reasons......................

2. You can run a lower flow temperature, this is a more efficient way to heat a building and if you have a condensing machine you will get double benefit.

CE

What flow/return temps are you expecting then, 45/25? 40/20? Lower still? You'll have to have a device to pre-cool the return before it enters the boiler at this rate to keep it condensing!

 

[CharteredEngineer]

If the OP has a non condensing boiler, he or she will still get the benefit because it is more efficient to heat a large surface area at lower temperature.

If he or she has a condensing boiler the lower flow temperature will keep the boiler condensing more and thus will have double benefit.

The actual flow and return temperatures will be almost impossible to calculate based on the info the OP has provided.

If I was sizing, I would use 50/30 and then add 10-20% as a rough rule of thumb. I think this would give enough capacity for the nuclear winters we have started to have.

CE

 

[Corgigrouch]

1. Winters appear to be getting more extreme despite global warming!


CE

For the reason stated, global warming has been re branded as "Climate change"

So if it is a nice sunny day, then it is climate change, if it is cold and wet, then it is climate change..... If you tell a lie long enough and hard enough then it becomes the truth....

 

[gdickin2]

Thanks all, the boiler is a Vaillant Ecotec 837 condensing and is about 18 months old.
How do I calculate the rad sizes based on the flow/return temps you mentioned?

BTW:
"If he or she has a condensing boiler" - it's a he.

 

[muggles]

To calculate the rad sizes, first you need to know the required heat output for each room, which can be found using an online calculator if you don't have any other way.

Once you have the required output, get a radiator brochure, here's one to get you going: http://www.stelrad.com/UK/docs/compact.pdf

Scroll down to the page where outputs are quoted. This is where it gets a bit involved. These outputs are for a mean water temperature of 50ºC above room temperature, IE a 75ºC flow and a 65ºC return, with a room temperature of 20ºC. You need a mean water temperature of 30ºC above room temp (half way between 60 and 40 is 50, less the room temp of 20 = 30), so in order to find the correct radiator size you need to multiply the quoted outputs by 0.515.

To make this simpler I would simply choose a radiator off the original chart that is quoting twice the output required for each room, that'll give you a bit in hand that may be useful if it gets really really cold, as CharteredEngineer has suggested.

So, for example, if you have a room that requires 1000w to heat it, find a radiator on the chart that has a quoted output of about 2000w and you'll have a radiator the right size for the room using a 60ºC flow & 40ºC return. You'll probably find that the K2 double panel double convector radiators are generally what you'll be installing unless you have plenty of wall space for a wider P+, and it might be worth looking at rads that are 700mm high as well.


If you want to go down to a 50/30 F&R then the multiplication factor is 0.304, so roughly speaking a room requiring 1000w would now need a radiator quoted at 3000w on the chart. You'd end up with a very efficient system this way but the trade-off is monster-sized radiators, or more smaller ones.

Something else to look at, if you don't already have it, is Vaillant's VRC430 Weather Compensation system, this will also help to improve overall efficiency.


Hope this helps!