Pipework for central heating system

[Jever]

Hi all,

I'm renovating a bungalow and have agreed with my plumber that I will install the radiators and pipework for the central heating system so that he can them install a new boiler.

I understand the basic logic of the pipework in that each radiator needs a feed from the boiler and a return to it but I'm puzzling on how to organise the return pipe so that the water successfully returns to the boiler.

Simple, I thought at first, start with the radiator furthest from the boiler and run past each of the other radiators branching in with a T-connection in each case.

My problem is, the boiler is situated in the middle of seven radiators and I will have to run from two different ends picking up the others as I pass by. What happens when I then have two return pipes coming from different directions meeting up under the boiler?

I guess join them together with a T-connection and then go back to the boiler. However, if I take two return flows into a T-connection that are facing eachother (and maybe one has more pressure than the other) can I be certain they will both turn the corner and go up to the boiler?

Or should I arrange it in a different way?

I hope I've explained myself clearly....let me know if I haven't!

Jever

 

[wizbongre]

Hi Jever,
I expect vastly more knowledgeable people will shortly be along to offer advice in their various, and inimitable ways, however from reading your question, I'd suggest you are in way over your head. I won't pretend to be an expert, so take the following with a pinch of salt (and maybe just focus on the last bit of advice I'll get to.)

Central Heating systems need careful consideration given to pipe runs in terms of pipe diameter, layout, etc. and should include suitably sized flow and return main lines, with branches off to each radiator. Typically these are split at least for upstairs and downstairs (probably not applicable in your case) and sometimes maybe for different parts of the house, or zones. As I understand it, generally the main lines are run in 22mm pipe and the branches to each radiator can be anything from 8mm up to 15mm - what you need should probably be calculated or at least thought about sensibly. I suspect there may be further implications depending if you are going for a combi or system boiler too, for example, as well as maybe the specific brand/model of boiler and/or any pumps required.

Your comment about one radiator return being at a different pressure to another makes no sense to me at all within the context of a central heating system.

I suggest you use the power of Google to research how to design and install central heating pipework, and maybe consider getting a qualified expert in to at least design, if not install it for you. I'm pretty sure getting the fundamentals of the system wrong with incorrect pipework will lead to no end of woe.

 

[oldbuffer]

As suggested above, you need a flow and return pair, which I call a "spine". With seven radiators, 22 mm pipework will almost certainly be ample.
Run the spine from the motorised valve location (unless combi, in which case boiler) to (almost) the site of the last radiator. It doesn't have to be straight, but can run so it passes quite close to each radiator. For each radiator, run pipes from each of flow and return to the radiator. I'd use 15 mm pipe for this. The connection of the 22 mm to 15 mm for each radiator is made with a 22 22 15 "tee". The final radiator connection might use a 22 15 reducer. Some other points to bear in mind:

1. If you have to notch joists to run the pipes, look up and obey the rules for where and how deep.
2. The pipes need to be well clipped at specified intervals. The intervals vary with type and size of pipe, plastic pipes need more clips.
3. If you have a hot water cylinder, then the return pipe from the cylinder must be the last one to to join the return pipework before that pipework joins the boiler. If you don't so this you may get radiators heating up when the hot water only is on.

 

[fixitflav]

Hi all,

I'm renovating a bungalow and have agreed with my plumber that I will install the radiators and pipework for the central heating system so that he can them install a new boiler.

I understand the basic logic of the pipework in that each radiator needs a feed from the boiler and a return to it but I'm puzzling on how to organise the return pipe so that the water successfully returns to the boiler.

Simple, I thought at first, start with the radiator furthest from the boiler and run past each of the other radiators branching in with a T-connection in each case.

My problem is, the boiler is situated in the middle of seven radiators and I will have to run from two different ends picking up the others as I pass by. What happens when I then have two return pipes coming from different directions meeting up under the boiler?

I guess join them together with a T-connection and then go back to the boiler. However, if I take two return flows into a T-connection that are facing eachother (and maybe one has more pressure than the other) can I be certain they will both turn the corner and go up to the boiler?

Or should I arrange it in a different way?

I hope I've explained myself clearly....let me know if I haven't!

Jever

Your fears about pipes coming from opposite directions are unfounded. As long as you do as oldbuffer said about any cylinder return coming in last, you'll be OK.

 

[Jever]

Hi,

Thanks guys, that's helpful.

It's a combination boiler, so luckily I won't have to worry about the tank issue.

Just to be on the safe side, I'll sketch up the system deciding the pipe diameters using this guide: https://www.diydata.com/planning/ch_design/sizing_pipes.php

and show them to the guy that's installing the boiler before I do anything.

Jever