Running Pipes


Postby avrkris » Tue Feb 08, 2011 8:57 am

Dear Experts,

Just bought a house, half Victorian half modern extension. Moved in and the fist night i realised that the central heating is not performing well. Looks like someone fitted a modern condensing boiler to old installation. Previous owner claimed the CH is modern and showed me the boiler, I assumed this is enough of evidence, but turns up that most of the radiators have been piped in series ! ie. output from one goes to another and so on ... by the time the water reaches last bedroom it's just warm and can't heat the room anywhere above 18deg :( ... Got a little baby at home and really need to get it sorted as soon as possible.

With limited cash after buying the house I'm forced to try and do as much work as possible myself. I've spent last 3 days going through the forums looking at ways to run the new pipes to all radiators and looks like realistically plastic pipes is my best solution - yes I know 75% will say copper is better but it's middle of winter and I need to do the work in one day hence the choice.

Here is a question if any of would please help answer. I will be lifting floor boards to run the pipes but I would like to avoid any connections under floors... So the plan is to run 15mm plastic pipes from the radiators, under floors to a manifold in the corridor/airing cupboard. What I'm not sure is if I will be able to do 90deg bend under the floor (to come out of radiator). This way I would avoid any risk of pushfit connections breaking or leaking. The radiator to plastic pipe connection will use compression fittings and the only pushfit connections would be to the manifold. How realistic is my plan ?

Any other suggestions very welcome.

Kris
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Postby plastic_man77 » Tue Feb 08, 2011 9:10 pm

Sounds like you have a one pipe system, which as you say is not very good. It is possible to improve on what you have without drastic action though. If the coolest room already reaches 18 degs, you should only need to heat it another 4 degs for it to be easily comfortable.

Firstly, consider how insulated your property is? Could you install loft insulation to improve the situation? I think the current recommendation is 270mm deep. Do you have a cavity wall- which you could get insulated? These are big factors in improving how well your property heats up and maintains its temperature.

Look on this site about how to balance a heating system, or google it. Typically, the rad first on the circuit needs to have a greater resistance to flow through it than the radiator at the end of the circuit- make the adjustments by closing/opening the lockshield valve (Usually the valve with a loose fitting cap that doesn't operate the valve if you turn it- ie. you will probably need to make adjustments using a small spanner).

Open the opposite rad valve fully.

Next, if you haven't got radiator thermostats, consider fitting them. These will cause natural balancing, ie. the more efficient rads in the system will heat their respective rooms to the required temperature quicker and the thermostats willl then shut the radiator off- thus allowing the pump to force heated water to the radiators that are still open and aren't working so well. If you keep the doors to rooms closed, it will also improve your situation.

You should also consider calling a heating engineer. Have the boiler serviced and make sure it is set up to the requirements of your property. By this, I'm refering to the heating output.

While the heating engineer is there, pick his brains and ask if the rads in the cooler rooms are sized correctly.

As a DIYer, only if I had no joy with the above would I consider running more pipework.

Also, if you do end up running more pipework, don't worry about joints under your floors. Every house that has conventional heating pipes run below floors will have a number of joints. If the joints are made correctly and tested for leaks during commissioning, then there is little problem with them. Modern plastic joints are pretty reliable.
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Postby avrkris » Wed Feb 09, 2011 4:35 pm

Hi plastic_man77

Thanks for your suggestions. I've check/followed some of them already. The balancing will have no effect as all radiators are linked in series - return of the first one is supply of the next radiator. So if I balance the first radiator I starve the next of heat. I must admit the person who designed/installed this is an idiot. The pipe is only 15 mm so doesn't really carry enough water to supply the whole house with heat.

So I'm back to thinking about upgrading the pipes. The question is still valid, is it possible to use a single run of plastic pipe all the way from radiator to manifold without using any joins ?

Cheers
Kris
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Postby plastic_man77 » Thu Feb 10, 2011 10:20 pm

Balancing would have an affect on a normal one pipe system as the flow and return pipe off each rad would join the same pipe that runs in a continuous route below all rads in the circuit.

If indeed the pipe work is as you say, and there is no pipework between the inlet and outlet to a rad, then it is in series and to turn a valve off at any point in the circuit would render the system inoperable.

So in answer to your question, yes.

And as far as I'm aware, there isn't a plastic heating pipe that you can bend at a right angle that wont kink and restrict flow. You can however make a sweeping bend that is effectively 90degs.
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