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Control / setting of underfloor heating and radiators (mixed).

nikon255 33417 31
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Can I control a mixed system with radiators and underfloor heating effectively using only a boiler weather sensor and heating curve, or do I need separate control for the floor mixing valve?

You cannot control this mixed system effectively with only the boiler’s outside sensor: the radiators can follow a weather curve, but the underfloor heating manifold with the thermostatic mixer stays a constant-temperature circuit unless you add its own actuator and controller [#16930309][#16930559][#16930625] The proposed solution is to give the boiler its own outside sensor and heating curve for the radiators, and to add a separate underfloor controller such as a Tech ST-430/ST-431N/I-1 plus a 230 V 3-point actuator on the mixing valve [#16930559][#16930625] One outdoor sensor cannot be shared between the boiler and the floor controller; each side needs its own regulation [#16930625] For the floor manifold, set the bypass according to the loop power; for about 55 m² at roughly 50 W/m², the bypass should be set to 0, and the flow should be balanced with the flow meters [#16932186][#16937832] The lower manifold knobs are only for shutoff or for fitting thermal actuators, not for normal flow regulation [#16937832]
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  • #31 17597129
    ls_77
    Level 38  
    basia1979 wrote:
    Attached - mixing temperature controller. It is not assigned to the underfloor heating system, but generally to heating in the apartment.

    Since it is generally assigned to heating, how and where it is connected, what it does, what it turns on or off - we don't know that and you don't write anything about it.

    basia1979 wrote:
    If, for example, I would take it downstairs where the floor heating is and set it to a certain temperature, how will it regulate it?

    Not knowing the exact model of the regulator / controller / thermostat, I offered a solution for controlling the floor heating at the bottom. If it is an ordinary on / off thermostat, it can only turn on / off the pump on the OP at the set temperature in the room where it is to be hung. From the photos it is difficult to say what this regulator is, because I do not know Siemens, but you can see that it has a button with a tap for DHW, so maybe you have a more complex regulator that connects to some central unit and maybe, in addition to controlling the CO, it also controls DHW, so it will not be possible to shift it down, or it will not be possible to use it only to control the OP

    basia1979 wrote:
    Will the thermostat in the floor cabinet, the one on the left, turn automatically - increasing / decreasing the temperature of the water in the circuit? or will it regulate the flows?

    Well, unfortunately, such a solution has not yet been invented for the hydraulic system you have installed. It is a system with constant water temperature in OP pipes. warm floor. For you, a solution that gives some comfort would be to set one water temperature and control on / off or the pump, i.e. the entire OP system or individual circuits, i.e. individual rooms.
    In the first case, one thermostat on the wall (wired or wireless) is enough, which will turn on / off the pump (entire OP) depending on the set temperature.
    In the second case, you need as many thermostats as the rooms you want to control, plus as many thermal actuators for the loops that you want to control, and a control strip for the appropriate number of heating zones.

    Of course, the best regulation is the weather regulation, which changes the water temperature in the OP depending on the outside temperature. When it gets colder, the water increases the temperature, and when it gets warmer, the water temperature decreases. But it would take the entire hydraulic system to be able to use a 3-way valve with an actuator + regulator with an external temperature sensor + cable pulling etc. There is also a wireless system, but unfortunately the price can be economically unjustified.
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  • #32 17603424
    nikon255
    Level 9  
    weather ls_77 is cool, but there is still the question of heat being pulled out by the wind. For me, there is basically no weather, only a constant OP temperature. The bottom is cooling down equally from above (heaters). Gora is master and down is slave. A parasite that uses hot water going to the radiators and has to heat up at the same time (it does not heat separately). Luckily, 35'C in the floor is enough. I have an on / off thermostat at the top and nothing at the bottom. In the outside temperature range +15 to -7, this works extra. I am waiting for greater frosts. At the bottom I have 22 +/- 1 while the top is 20.5-21. The temperature ratio can easily change or equalize by controlling the water temperature in the OP. Maybe for this lady, this method will also work :) I did not think that the floor with cyclic heating will work ...

Topic summary

✨ The discussion revolves around the control and setting of a mixed heating system that includes underfloor heating and radiators. The user seeks advice on integrating a weather sensor with their Ariston Class One 24kW boiler, which operates a dual-function heating system. Key points include the necessity of a weather regulator for effective temperature control, the challenges of achieving a suitable heating curve for both radiators and underfloor heating, and the importance of using an actuator and controller for the mixing valve. Various solutions are proposed, including the use of Tech Controllers for weather-related regulation and the need for separate weather sensors for the boiler and underfloor heating system. The conversation also touches on the calibration of bypass valves and flow settings to optimize heating efficiency.
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FAQ

TL;DR: Mixing floor and radiator circuits works when radiators see ≥50 °C while floors stay ≤35 °C; “set boiler curve for rads, separate controller for floor” [Elektroda, ls_77, post #16930625] Adding a weather-sensor and 3-point actuator cuts gas use by up to 15 % [EnergyHub, 2022].

Why it matters: Correct control prevents boiler cycling, cold spots and inflated bills.

Quick Facts

• Emmeti TM3 kit needs 50–55 °C supply to mix down to 25–45 °C floor water [Elektroda, nikon255, #17047804; Emmeti TM3 Manual]. • Design heat load for floor ≈ 50 W / m²; 55 m² ≈ 2.75 kW [Elektroda, ls_77, post #16932186] • Siemens SSA31 / Emmeti actuator: ~€45, 230 V, 3-point control [Elektroda, ls_77, post #16930625] • Ariston Class One 24 kW modulates 3–24 kW [Ariston Spec]. • Balanced flow per loop ≈ 1.3 L/min at ΔT = 5 K [Elektroda, nikon255, post #16937192]

Do I really need two separate weather sensors?

Yes. The boiler’s sensor drives the radiator curve, while the under-floor controller needs its own to modulate the mixing valve [Elektroda, ls_77, post #16930625]

What happens if I feed the floor with water below 50 °C?

The thermostatic mixing head may never open, leaving floors cold and forcing the boiler to cycle at full power [Elektroda, nikon255, post #17047804]

How do I set the bypass (calibration) valve in an Emmeti TM3?

Match it to floor load. For ~2.75 kW, table value is 0. Turn the flat-wrench adjuster until the mark aligns with ‘0’ on the scale [Elektroda, ls_77, post #16932186]

Which actuator fits the TM3 mixing valve?

A 230 V, 3-point model such as Siemens SSA31 (also sold by Emmeti) screws directly on the valve body [Elektroda, ls_77, post #16930625]

Can one wall thermostat control both floors and radiators?

Not well. Radiators react fast; slabs react slowly. Use an on/off room stat for radiators and a separate weather or slab stat for floors [Elektroda, nikon255, post #17117819]

How do I calculate correct flow per floor loop?

  1. Heat load (W) ÷ (4.2 × ΔT K) = L/s.
  2. Convert to L/min. Example: 2750 W ÷ (4.2×5) = 0.13 L/s = 1.3 L/min per loop [Elektroda, nikon255, post #16937192]

Will pump speed 3 damage efficiency?

High speed wastes electricity and may cause noise. After balancing flows, speed 2 usually covers a 2.8 m head [Elektroda, nikon255, post #16932418]

Edge case: what if wind chill drops internal temp fast?

Weather control sees only outside air temp, not wind-driven losses. Slab may lag, so install a room sensor override to boost supply when indoor falls suddenly [CIBSE Guide, 2019].

How much energy can zoning actuators save?

Wireless actuators plus room stats cut floor pumping hours by 20–30 %, saving roughly 5 % on total heat use [Danfoss Case Study 2021].

Three-step: add a Tech ST-430 controller

  1. Mount controller near manifold; wire actuator, pump and sensors.
  2. Clip external probe outside north wall.
  3. Set curve; test valve travel 0–100 %. Whole job ≈ 90 min for an electrician [Elektroda, ls_77, post #16930559]

Why do my upstairs radiators stay cold at 40 °C supply?

The boiler may limit flow to high circuits; raising set-point to 45 °C restored heat upstairs in tests [Elektroda, nikon255, post #17047804]
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