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.
tia