Extending heating system

[josh 10]

Hi. My first post and I am not a professionel just a retired engineer and a keen diyer so please bear with me if I get some terminology wrong.
We are in the process of adding an extension to our house. Two floors. I am going to need to extend the heating system and am wondering what I should be looking out for. We will be using a professional to do the work but I like to understand what they will be talking about.
I have done some plumbing over the years, moving pipes, replacing bathrooms but I am not up to date with current regs and this is a fairly large job. We will be needing to add two or three radiators to a fully pumped sealed system which is about ten years old. Would anybody care to offer an opinion as to what I might expect to have to change. Mainly I am interested to have an idea as to whether adding radiators to the system will need more than just some pipework. For instance we have, in the existing system, two radiators just the other side of a convenient wall, one upstairs and one down, would it be possible to tee off the feed and return on these and go through the wall and then add a radiator the other side.
This for starters, if I am being an idiot I am sure someone will tell me but any comments and advice would be appreciated. I do understand I will probably need to give more details before anybody can comment.
Thanks in advance.
josh.

 

[chris watkins]

Wellcome Josh 10
Having rads installed back to back from a single flow & return is common place so this will not be a problem.
In simple terms the heating pipes have a heat carrying capacity depending on system designed temperature difference between the flow & return.
If you have a 10year old gas boiler it should have been designed to run with a 20deg C delta T. in which case 15mm will be able to supply 11000 Watts & 22mm up to 23000W, it is therefore possible to back work the existing rads & adding the new to ensure that no pipework leg exceeds these amounts all things being equal there should be enough water flow when rads have been balanced to provide the correct heat for all of them.

 

[Scott_D]

It depends on the pipe size and number of radiators supplied by that pipe
10mm for one radiators & 15mm for 2/3 radiators as a rough guide

You may need additional expansion to cope with the extra water content

 

[josh 10]

Wellcome Josh 10
Having rads installed back to back from a single flow & return is common place so this will not be a problem.
In simple terms the heating pipes have a heat carrying capacity depending on system designed temperature difference between the flow & return.
If you have a 10year old gas boiler it should have been designed to run with a 20deg C delta T. in which case 15mm will be able to supply 11000 Watts & 22mm up to 23000W, it is therefore possible to back work the existing rads & adding the new to ensure that no pipework leg exceeds these amounts all things being equal there should be enough water flow when rads have been balanced to provide the correct heat for all of them.

Hi Chris. Thanks for the super quick response. From what you say, dependant on certain parameters we should be able to add a couple of radiators with out too much of a problem. I take it '20deg C delta T' are the regs the boiler should have been built to. This gives me something to discuss with the engineer when he or she comes.
Thanks again.
josh.
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It depends on the pipe size and number of radiators supplied by that pipe
10mm for one radiators & 15mm for 2/3 radiators as a rough guide

You may need additional expansion to cope with the extra water content

scott d. Thanks for your response. That makes sense to me the bigger the supply pipe the more radiators it can cope with. The circuit here is all 15mm. Some copper. some plastic. I don't know at the moment if we have more than one circuit. Perhaps one for ground floor and a separate one for the upper floor.
Anyway, thanks again.
josh.

 

[chris watkins]

Not regs but if condensing then design but the system has to be sized accordingly, so rads selected to giver the required amount of heat with (normally) boiler set to 70deg C flow if heating a cylinder for hot water as well.

 

[josh 10]

Not regs but if condensing then design but the system has to be sized accordingly, so rads selected to giver the required amount of heat with (normally) boiler set to 70deg C flow if heating a cylinder for hot water as well.

Thanks Chris.
I think design was what I meant to say, not regs. It's the regs that control the design.
josh.

 

[Scott_D]

What boiler do you have?
How many radiators?

 

[josh 10]

What boiler do you have?
How many radiators?

Boiler Gloworm 30HXi. Radiators 13+3 towel rads. Hot water tank. Santon Premier unvented indirect cylinder. 210ltrs.
Hope this helps.
Look forward to hearing from you.
josh

 

[Scott_D]

Do you have a heating expansion vessel (probably red)

 

[josh 10]

Yes that's the one I use to bring the system up to pressure. If it's of use I run the system at 1bar.
I also have a grey one. Not sure what it does. I really should investigate.

 

[Stigster]

The grey vessels are usually for potable water on the unvented cylinder although the colours for potable/heating system only cannot be relied on 100%. I have made the mistake of telling a customer some joker fitted a heating type vessel on their unvented cylinder but on closer inspection it was indeed marked as suitable for potable use.

It's also possible that your expansion vessel was determined to be undersized and they added a second one in addition to the first for the heating system.

 

[centralheatking]

If you put a sketch plan of the existing layout and the new bit in another colour indicating current pipe od...15mm or 22mm we might be able to suggest some short cuts and nifty ideas we have used
centralheatking