Heating - final planning...

At long last the kitchen extension gets underway: builders have started
on the outside, and next weekend the old combi gets swapped out in
preparation for the underfloor heating installation.
Existing boiler is an Ocean Style FF - somehow it's managed to keep
going for the last year. New one will be an Ideal Isar 30HE
(physical size was a primary consideration).
House at moment has one zone, no TRVs anywhere, mechanical room stat and
a mechanical timer.
UFH will go down in the kitchen, and as the bathroom is directly above
the boiler position I'll probably fit it up there as well when I get
round to sorting that room out. The rest of the heating will be left
as-is (except for fitting TRVs) on a single zone. Uponor MLCP will be
used & Uponor controls - this company has been fantastically helpful
during the design phase.
If I've understood everything correctly, extending the UFH to the
bathroom will be straightforwards: pipe up, fit control, drop pipe down
to manifold in kitchen, fit the actuator heads and job done. Only
proviso is that it has to have the same installation details i.e.
couldn't have solid screed downstairs and heat diffuser plates upstairs
as the running temperature would need to be different, but this isn't a
problem as I'll be using solid between-joist insulation & screed in the
kitchen & can do the same with the bathroom.
Anyway, question is more about controls.
UFH has its own set of controls and I'd like this to run as its own
zone. With the actuator heads fitted & appropriate room stats it
handles sub-zoning itself.
However, to have the UFH & rad circuits running independently, by my
understanding I will need to fit a zone valve in the rad circuit,
otherwise every time the UFH issues call-to-heat then the combi pump
will fire up, internal valve switch to heating circuit & it will end up
pumping through the rad circuit as well. This essentially makes this an
S-Plan system (according to the Wiki etc). Is this correct?
Second thing is that we want a decent programmable stat. Any
recommendations? The existing room stat is mounted downstairs in the
hallway - pretty much the last place to heat up, so that's ok. There is
wiring for it already installed, so I could easily reuse that so
wireless isn't necessarily required.
As there are essentially two programmable stats now (the UFH & the rad
circuit) in the control loop then my understanding is that the combi
does not need the timer option - again, is this correct?
Not sure what other things I need to consider - splitting the house into
two zones might have been nice but it would add unneccessary
complications and expense to a project that is already complicated and
expensive enough. House not really of a size to warrant it anyway.
Still, it's good to be underway at last. Already discovered the source
of the musty smell in the kitchen: breached soil stack below ground
level (and must have been that way for many years). fingers crossed
that all goes smoothly from now on.
Reply to
Yup, you need a two port valve per zone... if the UFH system effectively containers it own zoning, then you will need one extra for the heating circuit. That way you can have one or the other or both on at any given time. The call for heat to the boiler being the logical "or" of the demands from the zones.
Centaurstat 7 seems to work well for me. If you house is particularly slow to heat up, then there may be some advantage to an optimising stat that can learn the characteristics of the house and automatically adjust the heating start times to arrive at the requested temperatures closer to the start times of each stat period. Personally I have never found the need since the house can get to temperature in 10 mins anyway.
Yup. The timing elements are built into the stats. In effect you never turn the heating off - it just responds to the demands of the prog stats.
Much depends on the pipe layout as to how easy it would be to retrofit another zone. Its easy to do from the outset, but can be a PITA to go back later.
One other thing you will need is a bypass pipe and valve. Since you will now have the potential situation where (for example) the UFH is off, and the CH is running. The stat then signals it is satisfied and the CH zone closes. The boiler however will want to overrun for a short while so as circulate the water for a bit, and not allow it to cool too much in the primary HE. With both zones off there is not path for this to happen. Hence the bypass is in effect a third zone, with a spring loaded valve. When either of the real zones are open, the lack of flow pressure on the spring valve keeps the bypass closed. Once all the other valves close the full force of the pump is now focussed on the bypass and this opens, allowing the boiler pump to still circulate water.
Good luck!
Reply to
John Rumm
In article , snipped-for-privacy@nowhere.null says...
Ta - that's validated the conclusion I had come to.
Will have a look at Centaurstat 7 then. After initial setup is it easy enough to control? I'll have to explain the thing to Mrs S & she's a complete technophobe (I think an etch-a-sketch had two too many knobs on it as far as she was concerned...)
Hmmm, yes. That might be one needing rather more tuits than available currently. Back burner then.
Oops, yes! I hadn't completely overlooked this, just slipped my mind when posting thats all. One for the checklist though.
Thanks! Today's challenge.... next door's rainwater drainage utilises our sewer connection... running slap bang down the middle of where the strip foundations should be. Aaaagh.
Reply to
Once setup there is probably not much to control. There are + and - buttons that let you tweak the desired temperature up or down. The effect of this lasts until you tweak again, or the next time period is reached at which point it goes to the programmed setting for that period.
To be honest, after a little fiddling after setup the first time I have not found the need to touch it at all really. So it ought to be SWMBO friendly.
(you can download the manual from screwfix)
Reply to
John Rumm

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