Hi. I have a new kitchen with wet underfloor heating. I have installed 2 zones, controlled by 2 port valves. The underfloor heating is a pretty simple install, just one zone with a mixer and pump. Its not wired in yet. I want to wire it up so that it it as efficient as possible.
As far as I can tell I have basically got an S plan system, but instead of one of the water circuits being a hot water cylinder, the second circuit is my UFH. I've a combi boiler, so the pump is integral to my boiler.
I've made the attached wiring plan and schematic.
The thing that is bugging me is that the mixer valve only takes water at about 30oC into the floor. The heating circuit going to the mixer valve is about 5m of 22mm pipe, so holds a fairly large "reservoir" of hot water. I would need to have the boiler output set fairly high so that my radiators are hot. So potentially this "reservoir of water would be circulating at 60-70C until the boilers internal stat cuts out.
Once the floor is heating up the mixer valve should only be taking a bit of water out of the central heating at 60-70C. The boiler can probably get this entire circuit of water hot in a couple of minutes. Once this pipework is hot, I don't really want the boiler running continuously if its not needed. Obviously if the return to the boiler reaches temp then the boiler will shut off, but there is a big differential between when the boiler return being hot will cause the boiler to shut off (I'd guess a few C below the set point) and the temperature the mixer valve needs the water in this loop of the heating to be experiencing (probably only 40C).
So - if anyone is following this. Can I / Should I add another stat at the mixer valve or boiler return, which will shut off the boiler if there is enough heat in the UFH "loop" of the central heating. This is the bit with the ?????'s in the plan above.
I feel that I should add this extra stat in order to cut the duty cycle of the boiler when heating UFH only. However, if I do, where do I position it. Is there a danger that the UFH mixer valve and pump will "suck" the hot water out of the loop immediately adjacent to the mixer, but not consume the hot water in the rest of the 5m of 22mm pipework. Do I need some kind of overrun pump in the central heating pipework to continue to circulate water in this loop of pipework.
I have searched around, and while I can see a lot of "off the shelf" controllers that seem to claim they will run things, they don't seem to be the most efficient method. I'm not sure uf I have over complicated this or under complicated it, by thinking too much.
Any advice gratefully received!
As far as I can tell I have basically got an S plan system, but instead of one of the water circuits being a hot water cylinder, the second circuit is my UFH. I've a combi boiler, so the pump is integral to my boiler.
I've made the attached wiring plan and schematic.
The thing that is bugging me is that the mixer valve only takes water at about 30oC into the floor. The heating circuit going to the mixer valve is about 5m of 22mm pipe, so holds a fairly large "reservoir" of hot water. I would need to have the boiler output set fairly high so that my radiators are hot. So potentially this "reservoir of water would be circulating at 60-70C until the boilers internal stat cuts out.
Once the floor is heating up the mixer valve should only be taking a bit of water out of the central heating at 60-70C. The boiler can probably get this entire circuit of water hot in a couple of minutes. Once this pipework is hot, I don't really want the boiler running continuously if its not needed. Obviously if the return to the boiler reaches temp then the boiler will shut off, but there is a big differential between when the boiler return being hot will cause the boiler to shut off (I'd guess a few C below the set point) and the temperature the mixer valve needs the water in this loop of the heating to be experiencing (probably only 40C).
So - if anyone is following this. Can I / Should I add another stat at the mixer valve or boiler return, which will shut off the boiler if there is enough heat in the UFH "loop" of the central heating. This is the bit with the ?????'s in the plan above.
I feel that I should add this extra stat in order to cut the duty cycle of the boiler when heating UFH only. However, if I do, where do I position it. Is there a danger that the UFH mixer valve and pump will "suck" the hot water out of the loop immediately adjacent to the mixer, but not consume the hot water in the rest of the 5m of 22mm pipework. Do I need some kind of overrun pump in the central heating pipework to continue to circulate water in this loop of pipework.
I have searched around, and while I can see a lot of "off the shelf" controllers that seem to claim they will run things, they don't seem to be the most efficient method. I'm not sure uf I have over complicated this or under complicated it, by thinking too much.
Any advice gratefully received!