I wonder if anyone can advise me on some questions that I cannot find
mentioned anywhere on the web for an simple wet UFH project.

I have just laid a 7-loop underfloor heating pipe system in my (very well
insulated) small 3 floored 3 bed family Victorian house.

I intend to use a combi-condensing boiler, and run the boiler flow heating
pipe first to two directly in-line conventional radiators. Then return that
flow to the input manifold for the 4 underfloor heating loops for the
wooden upper floors. (FYI – I have used old thin aluminium offset printing plates as spreader plates wrapped around the pipes!)

The upper floors' return manifold will then go to the input manifold of the
concrete ground floor 3 heating loops. This ground floor return
manifold will then return to back to the boiler!

I figure the radiators will initially lower the water temperature down for
the wooden floor input manifold. Then this lowered return water will go
into the concrete floor input manifold, which will then return to the
boiler at a very cool temperature. Thus making a very efficient condensing
system! (If not very tepid)

To save costs (and as an experiment!) am intending to construct the two sets of
manifolds with 22mm push-fit copper tee pipes (with 15mm reducers) and locate it under the ground floor staircase in cupboard, about 4m from the boiler using 22mm insulated copper pipes.

I will balance each loop with gate valves (or any ideas?) on the
return manifolds, using temporary temperature gauges clamped onto each return pipe to get even return temps. I will put stopcocks on the input valves for isolation purposes.

I intend to only use the in-built boiler pump to circulate the heating, and
use the in-built boiler water temperature thermostat and timer to
control the room heating temperature.

I can will make allowances to retro- fit TRVs in each room if the room on the upper floor loops only If heating is uneven. But I intend to have the heating on in all rooms constantly from November to April

Q.1. Do I need to put in any Automatic Airbleed Valves on the upper storey
loops, (If so where should the AAV be positioned -Just before the return pipe goes vertically down to the manifold to catch the air?)Or does the UFH water have enough pressure force the bubbles down to the ground floor manifold AAVs.

Q.2. Do I put AAV’s on BOTH the inlet AND return manifolds, or just returns?

Q3. Is this idea workable? If so can anyone recommend a decent boiler with a tough enough pump!?

On Wed, 23 Feb 2011 04:59:29 -0800, Mick wrote:

I figure the radiators will initially lower the water temperature down
for the wooden floor input manifold. Then this lowered return water will
go into the concrete floor input manifold, which will then return to the
boiler at a very cool temperature. Thus making a very efficient
condensing system! (If not very tepid)

Might work well enough to get away with but if you do fit TRVs to any of
the rads that'll upset the balance of the system so I'd suspect it
wouldn't work too well in practice. But by all means have a play and see
if it's good enough to get away with.

To save costs (and as an experiment!) am intending to construct the two sets of
manifolds with 22mm push-fit copper tee pipes (with 15mm reducers) and
locate it under the ground floor staircase in cupboard, about 4m from
the boiler using 22mm insulated copper pipes.

Speedfit is your friend. Cuprofit etc are just poncy versions which may
look better (eye of the beholder) but probably more expensive and harder
to demount if/when you want to play around.

I will balance each loop with gate valves (or any ideas?) on the
return manifolds, using temporary temperature gauges clamped onto each
return pipe to get even return temps. I will put stopcocks on the input
valves for isolation purposes.

Gate valves are good for balancing, lever valves good for isolation.

I intend to only use the in-built boiler pump to circulate the heating, and
use the in-built boiler water temperature thermostat and timer to
control the room heating temperature.

I can will make allowances to retro- fit TRVs in each room if the room on
the upper floor loops only If heating is uneven. But I intend to have
the heating on in all rooms constantly from November to April

The inefficiency inherent in having rads blasting away hotter than
necessary in order to keep your UFH running well could negate any
improvements in economy and comfort from having UFH and your desired low
return temps.


Q.1. Do I need to put in any Automatic Airbleed Valves on the upper storey
loops, (If so where should the AAV be positioned -Just before the return
pipe goes vertically down to the manifold to catch the air?)Or does the
UFH water have enough pressure force the bubbles down to the ground
floor manifold AAVs.

That's a separate issue. If you have rads at the top of the system you can
bleed from them, but any high points in pipework may need bleed valves -
automatic or otherwise.

Q.2. Do I put AAVs on BOTH the inlet AND return manifolds, or just
returns?

Q3. Is this idea workable? If so can anyone recommend a decent boiler
with a tough enough pump!?

Shouldn't be any more demanding on the pump than a conventional system. I
like Worcester Bosch boilers.

I suggest you look at the wiki articles on UFH and also check out my
article on it on http://yaph.co.uk/ufh for an example of a DIY-able
low-cost manifold. Personally I'd go straight for that sort of system for
your UFH. You may find you need different temperatures for the screed-laid
parts of the system and those using spreader plates so don't try to run
them all off one TMV+pump setup (or knock it up with Speedfit so you can
change it around again easily).


--
John Stumbles -- http://yaph.co.uk

Thesaurus: extinct reptile noted for its wide vocabulary.