Pipe sizing on CH/Hot water system

[Johnny B]

My new house has 25 x 2.5mm Uponor MLC flow and return pipes from/to the boiler. In the loft the pipework feeds the sealed system comprising cylinder coil, upstairs radiators and downstairs underfloor heating through separate 20 x 2.25mm MLC pipes.

The radiators and coil are served by an integral pump in the Valliant condensing boiler downstairs. The underfloor heating has its own circulating pump on the manifold.

The water circulation through the radiator system is very poor, although the system has been bled and flushed, the valves checked and so on.

I am not a plumber, but the pipework in the loft concerns me. On the flow lines, the 25mm pipe is reduced to 20mm before it branches off to the heating systems and the cylinder coil. On the return from the underfloor and radiator systems the two 20mm pipes feed into a single 20mm pipe. This is then joined by the 20mm return from the cylinder it continues for a few inches at this diameter before widening to the 25mm pipe returning to the boiler.

It does not make any sense to me, but what do the professionals think?

It was all fitted by the house builder and the tradesmen he employed. I had no part in it!

 

[Toddyplumb]

Can u post some photo's

 

[fuzzy]

is it in copper?

 

[ecowarm]

Fuzzy its this pipe Uponor Multi-layer Composite Pipe Products

 

[ecowarm]

I think some pics would be good, but it does sound a bit odd?

 

[Johnny B]

The pipework is MLC 'Multi Layer Composite'; plastic pipe with an aluminium core. The unions are standard unipipe proprietory fittings.

Here are a few pictures.:

 

[Toddyplumb]

Could do with some more pictures of it overall.
I can see you have secondary circulation for hot water. If the arrows are correct the pipework is poor , the Ts are in the wrong size / place

 

[Johnny B]

Thanks for the observations.

Here is another picture:




There is not much else to see. The rest of the pipework is just the 20mm flow and return MLC pipes to the upstairs radiators, downstairs under floor system and the cylinder, with motorised valves.

Common sense tells me that the pipework in the loft has been carried out with the wrong pipe sizes, although I think (hope) that the rest of the work in the house is OK.

The flow and return to both the under floor and radiator systems are via manifolds. The pipework from them is determined by the respective manifold. 16mm MLC to each radiator and 12mm MLC in the underfloor system.

The flow and return to the cylinder are short runs of 20mm MLC.

I hope that the only problem is the pipe sizing and jointing to/from the 20mm flow and return pipes in the loft as shown in the pictures.

I am a fairly handy DIY guy, is this a job for me? Otherwise anybody know an experienced MLC guy around Cambridge/Royston?

This house has given me nothing but trouble since I bought it in 2007. Three years of fixing things like this. We were told the builder had a good reputation!

Oh, and the arrows in the previous pictures do indicate the direction of water flow.

 

[Johnny B]

One final picture of the whole area: