I've installed the piping for UHF in the conservatory and the time has now come to connect it to the boiler. Since the boiler's going to be replaced in a while that would seem to be a good time to do it - when someone's already busy buggering about with the pipes.
The system I've installed is a Hepworth unit
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intend to make the UHF a seperate circuit so it can run a different times to the house radiators, partly to reduce the load on the boiler and partly because of the time lag in heating the floor slab and partly to make it easier and more flexible to control.
The boiler will be a condenser but NOT a combi.
Will I need a bypass valve for when the UHF which is thermostatically controlled is the only device being fed?
Is there a generally accepted way of connecting this all up? I can think of several ways of doing it - a second pump with a single-way motorised valve or use the main pump and add another three-port valve etc.
Suggestions (not including "use another brand" 'cos it's under 3" of concrete)?
I don't think that there is anyone here who does much UFH. At least some of my questions on screeding didn't get answered. But you're beyond that point.
I think I'd go for a bypass valve because (and this will probably get a response) the TRV rad circuit might be valved off at the same time as the UFH is up to temp, so the boiler needs a circulation. My installation certainly has one (non-combi, condensing oil burner).
As to connecting it up, I don't know. I have a Polyplumb ZRU, and that just connects in as if it were a radiator.
No bypass required. Simply get a room stat, a separate zone controller, and couple the stat to a motorized valve that tees of the main pump circuit and wire OR the contacts on that with your other MV contacts, so that when the stat calls for heat the boiler/pump fires up.
I think the controller in that system dies not strangle the water completely, just reduce flow rate to get a constant outflow temp. Needless to say this is a shade less than ideal because if you run the boiler flat out the flow temps into the screed will be enough to possibly crack it.
Yu MIGHT want to consider better temp regulator valve. One that is in itself a bypass .
Despite their idiotic 'you don't need a room stat cos the floor will be cold when the sun shines' bit, I'd put in a stat. In MY house the sun shines on the floor and heats it anyway...that's why its insulated..
My advice would be either an independent zone, or run it 24x7 using the room stat to control it completely. Run that as I said to an MY isolation valve on teh flow sized. That takes care of everything. If te MV is off the boiler will also be off unless the other CH/HW stuff is open.
I'd probably throw away the temp regulator and fit a proper 4 port temp reducing valve. But it should be OK if you run the boiler at less than IIRC 50C outflow temp.
Note that this system is reckoned to be a floor warmer, to be used WITH rads as well. Its not a full blown UFH system (and the reason for that is few systems can cope with the massive heatloss through even triple glazed glass, without an excessive floor temp being used).
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