Valsir mixing kit - TECHNIC AL CHARACTERISTICS OF THE COMPONENTS H

TECHNIC AL CHARACTERISTICS OF THE COMPONENTS H

3.5 Valsir mixing kit

The function of the mixing kit is to mix the hot water coming from the boiler with the return water from the circuits in order to have a constant supply temperature. The kit is supplied with a three-speed circulation pump for the “secondary” circuit, thus making the Valsir mixing kit very versatile and applicable to all types of systems, be they small or big. The kit is fixed point but it can be converted to variable point by motorizing the three-way valve.

3.5.1 V-MIX02 fixed point mixing kit

Figure 3.5.1 V-MIX02 fixed point mixing kit.

Figure 3.5.2 Components of V-MIX02 fixed point mixing kit.

D₁ L

D₁

I H

➃ ➄

➅

➆

➇

➂

➁

➀

The V-MIX02 fixed point mixing kit is the most compact solution equipped with essential components only.

➀ Thermostatic valve for adjustment of flow on inlet to the mixing kit.

➁ Thermostatic head with liquid sensor. The temperature probe is inserted in the special pocket and actuates the head which regulates the inlet flow to the system in relation to the temperature set by means of the graduated knob.

➂ Circulation pump. Three-speed circulation pump corresponding to three different heads of 4 m, 5 m, and 6 m. It is this characteristics that makes the mixing kit suitable for all systems sizes.

➃ Pocket for probe of the thermostatic head.

➄ Thermometer on flow side to the circuits.

➅ Pre-calibrated safety by-pass. The by-pass keeps the fluid in circulation even when all the heating circuits are closed (e.g. when the rooms have reached the set temperature.

➆ No-return valve, this valve prevents an undesired return of flow in particular employment conditions.

➇ Flow-check valve on outlet of mixing kit.

TECHNICAL CHARACTERISTICS OF THE COMPONENTS

3

The characteristic curves of the V-MIX02 mixing kit are indicated in the following diagrams; they are determined considering an operating temperature of the radiant system between 30°C and 45°C with a temperature difference of 8°C and feed temperatures from the boiler of 70°C, 60°C and 50°C.

Figure 3.5.3 Characteristic curves of the V-MIX02 mixing kit with temperature from the boiler at 70°C.

0 Water flow [l/h]

Residual head [mbar]

Velocity 1

Velocity 2

Velocity 3 Temperature boiler side 70°C Temperature system side 30÷45°C Temperature difference on system side 8°C

500 1000 1500 2000

V-MIX02 mixer with circulator Wilo RS 15/6-3

Figure 3.5.4 Characteristics of the V-MIX02 mixing kit with feed temperature from the boiler at 60°C.

0 Water flow [l/h]

Residual head [mbar]

Velocity 1

Velocity 2 Velocity 3 Temperature boiler side 60°C Temperature system side 30÷45°C Temperature difference on system side 8°C

500 1000 1500 2000

V-MIX02 mixer with circulator Wilo RS 15/6-3

Figure 3.5.5 Characteristic curves of the V-MIX02 mixing kit with feed temperature from the boiler at 50°C.

500 600

Temperature boiler side 50°C Temperature system side 30÷45°C Temperature difference on system side 8°C V-MIX02 mixer with circulator

Wilo RS 15/6-3

TECHNICAL CHARACTERISTICS OF THE COMPONENTS

3 3.5.2 V-MIX01 fixed point and variable point mixing kit

Figure 3.5.6 V-MIX01 mixing kit in fixed point version. Figure 3.5.7 V-MIX01 mixing kit in variable point version.

Figure 3.5.8 Components of the V-MIX01 mixing kit.

D₁ D2D2

D₁

I H

➄

➃

➁

➂

➅

➆

➇

➈ ➆

➀

The V-MIX01 mixing kit can be supplied in the fixed point version or else as variable point for combination with a climatic control unit.

This is a kit complete with all the necessary accessories such as safety thermostat, adjustable by-pass and thermometers on the flow and on the return.

➀ 3-way valve. This device mixes the flow water with the return water from the system. It can be controlled by a thermostatic head to create a fixed point system or by an electric motor to create a variable point system.

➁ Thermostatic head with liquid sensor for the creation of a fixed point system (V-MIX01/PF). The temperature probe is inserted in a pocket and actuates the head that regulates the inlet flow to the system in relation to the temperature set with the graduated knob.

➂ Electric motor, instead of the thermostatic head for the creation of a variable point system (V-MIX01/PV).

➃ Circulation pump. It is a three-speed circulation pump correpsonding to three different heads of 4 m, 5 m, and 6 m. It is this characteristic that makes the mixing kit suitable for all systems sizes.

➄ Pocket for the probe of the thermostatic head.

➅ Safety thermostat. The safety thermostat actuates the pump motor and stops it when the temperature detected on the supply circuit is greater than the limit set.

➆ Thermometer both on the flow to the circuits and on the return.

➇ Adjustable safety by-pass. The by-pass keeps the fluid in circulation even when all the heating circuits are closed (e.g. when the rooms have reached the set temperature).

➈ No-return valve, this valve prevents an undesired return of flow in particular employment conditions.

TECHNICAL CHARACTERISTICS OF THE COMPONENTS

3

The characteristic curves of the V-MIX01 mixing kit are indicated in the following diagrams; they are determined by considering an operating temperature of the radiant system between 30°C and 45°C with a temperature difference of 8°C and feed temperatures from the boiler of 70°C, 60°C and 50°C.

Figure 3.5.9 Characteristic curves of the V-MIX01 mixing valve with temperature from the boiler at 70°C.

0 500 1000 1500 2000 2500

Water flow [l/h]

Residual head [mbar]

Velocity 1

Velocity 2

Velocity 3 Temperature boiler side 70°C Temperature system side 30÷45°C Temperature difference on system side 8°C V-MIX01 mixer with circulator

Wilo RS 15/6-3

Figure 3.5.10 Characteristic curves of the V-MIX01 mixing valve with temperature from the boiler at 60°C.

0 Water flow [l/h]

Residual head [mbar]

Velocity 1

Velocity 2

Velocity 3

500 1000 1500 2000 2500

Temperature boiler side 60°C Temperature system side 30÷45°C Temperature difference on system side 8°C V-MIX01 mixer with circulator

Wilo RS 15/6-3

Figure 3.5.11 Characteristic curves of the V-MIX01 mixing valve with temperature from the boiler at 50°C.

500

600 Temperature boiler side 50°C

Temperature system side 30÷45°C Temperature difference on system side 8°C V-MIX01 mixer with circulator

Wilo RS 15/6-3

TECHNICAL CHARACTERISTICS OF THE COMPONENTS

3 3.5.3 Theory: adjustment of the mixing kit

In the layout in Figure 3.5.12 the following are indicated with:

ms the flow in the secondary circuit, m_p the flow in the primary circuit,

mx the recirculation flow in the secondary circuit,

T_p,m the temperature of the supply fluid in the primary circuit, T_s,m the temperature of the supply fluid in the secondary circuit,

T_r the return temperature, that is the same in the primary and the secondary circuit and is given by:

Figure 3.5.12 Flow in the Valsir mixing kit.

m_p, T_p,m m_p, T_r

m_s, T_r m_s, T_s,m

m_s, T_s,m

m_x T_r

T_r =

i=1n i=1

∑ mi · Tr,i

∑ T_r,i

[3.5.1]

pondered average based on the flow of the return temperatures of the heating circuits n.

By applying the mass balance to the three-way valve, we have:

m_x = m_s - m_p [3.5.2]

Whereas the energy balance applied to the three-way valve is:

c_p · m_s · (T_s,m - T_o) - c_p · m_p · (T_p,m - T_o) - c_p · m_x ·(T_r - T_o) = 0 [3.5.3]

By simplifying the two relations we obtain:

m_s · T_s,m - m_p · T_p,m + m_s ·T_r - m_p · T_r = 0 [3.5.4]

m_s · (T_s,m - T_r) = m_p · (T_p,m - T_r) [3.5.5]

and hence

(Ts,m - Tr) (T_p,m - T_r)

mp = ms · [3.5.6]

With this last formula we can calculate the flow the boiler must supply the heating system with and using the diagram shown in Figure 3.5.3 it is possible to determine the correct positioning of the three-way valve.

TECHNICAL CHARACTERISTICS OF THE COMPONENTS

3 3.5.4 Practice: adjustment of the mixing kit

In order to further clarify the use of the formulas shown previously, reference is made to the example in the chapter “Dimensioning of floor heating systems in accordance with the standard UNI EN 1264”, the results of which are shown in the following table.

Table 3.5.1 Data of a floor heating system example.

N. Room Spacing p [cm] T_m T_r m

[°C] [°C] [l/s]

1 Bedroom 15 46 29.5 0.0154

2 Living room 22.5 46 33.5 0.0277

3 Kitchen 15 46 28.0 0.0121

4 Bathroom 15 46 35.0 0.0137

0.0689

In document FLOOR HEATING VALSIR.pdf (Page 73-78)