DIY not Unferfloor heating !

[Agile]

That afternoon I went to repair a combi boiler connected to an UFH system designed by the father !

The boiler was a standard 24 kW condensing ( badly installed too ) directly feeding the UFH loop.

The UFH was made of a SINGLE loop 94 m long made up of 8 mm copper tube.

The tube was neatly slotted into 10 mm plywood cut to fit where the tube was not.

The 8 mm tube was covering most of the downstairs of the larger house on 400 mm centres. It was covered with large floor tiles about600 mm square and 10 mm thick on about 6-10 mm of tile cement on top of the plywood.

Because of the length and resistance it was a full 20 minutes before the return started to feel just slightly warm. In the meantime the boiler heated for about 30 seconds and then went off because the flow was at 60 degrees and stayed off for 4-5 minutes on the anticycle delay.

I explained to the son that it was not the usual way of providing UFH and may not be very effective and would lose a lot of heat to the underfloor cavity.

Tony

 

[clf-gas]

Any rads up stairs Tony, or was it just the UFH?.

 

[Balenza]

Certainly not usual.
Good heat transfer will be acheived therefore better response and a lot quicker than a plastic pipe buried in a screed. His pipe spacings are too wide I would have thought.
Tiling would be the only option for something like this.
Many would have reservations about copper being in contact with the tile screed also.
Also the possibility for overheating the surface to uncomfortable temperatures with no temperature regulation.
Perhaps a manifold needed for something like this and split into zones for greater efficiency and some temperature regulation or a combi compatible for direct connection to UF systems with flow compensated boiler modulation.

Whats an "underfloor cavity" with reference to this system ?
Surely he has insulaion laid below the 10mm plywood .
Did the client comment on how effective it is and what the comfort levels are like or how efficient it is to run ??.

 

[breezer]

not being a plumber are you saying that as it was one huge continious run, with the pipe diameter being so small the pump could not pump it round fast enough (due to pipe diameter) so as the boiler was getting too hot it cuts out untill it cools down by which time the floor will not get that warm.

 

[gas4you]

Perhaps a manifold needed for something like this and split into zones for greater efficiency and some temperature regulation

can I believe my eyes A manifold in a UFH system Whats happened to your 'ripping people off' with a manifold and all you need is a danfoss, or whatever, valve you keep harping on about

 

[clf-gas]

Perhaps a manifold needed for something like this and split into zones for greater efficiency

Well i would never have thought it you and I agreeing on a manifold and all the expence that goes with it

Well spotted breezer

 

[Balenza]

For small areas manifolds are not needed plus they are expensive.
Wirsbo,s smallest 2 outlet manifold assembly is £110.
Their Push 12 system is ideal for small areas. Which is a pump and temperature regulation unit all built as one assembly for single loop layouts and not that expensive either at £206 for areas up to 15/sq m.

Thats not to say the FHV-R could not be used on the system that Agile is talking about. Just split the microbore pipes into smaller loops using diyed copper manifold's and return to the FHV-R.
With some ingeniuty I dont think it would be impossible.

 

[clf-gas]

You could be right in a Heath robinson sort of way, but lok at this and you may understand why manifolds are used.

Because of the length and resistance it was a full 20 minutes before the return started to feel just slightly warm. In the meantime the boiler heated for about 30 seconds and then went off because the flow was at 60 degrees and stayed off for 4-5 minutes on the anticycle delay.

 

[Balenza]

Agile stated length and resistance which is correct to do so.
But he left out "heat transfer".
On start up from cold an UF system with a boiler output rated at about 26 kw hooked up to about 300 sq meters of floor area with about
1800 m pipe buried in a screed will take about 2 hours for the boiler return to reach 50C.
Though no cyling will occur here I should point out.
Just stating my findings by the way.

 

[clf-gas]

Would agree balenza, did I just type that . A 94m run in 8mm copper, not for me. Would have split this into two zones using 12mm or one depending on floor shape in 15mm, and a 2 port mani with actuators.

 

[ChrisR]

Some of these things are there to be worked out.
Flow rate, 6m head on 100m of 8mm pipe, about 0.0025 litres/sec (off the graph, I'm extrapolating wildly)
That's around 10 Watts heat dissipation for each degree flow/return difference, so it might make 600 watts.

And it takes a bit over 20 minutes for the water to get round !