Return flow temperature maintenance with thermal control valve DN 20

(3⁄4") / DN 25 (1")

Application range

• Heating installations with return flow temperature maintenance for solid

fuel boilers, wood-fired and stove heating systems

The pump sets for the return flow temperature maintenance are

groups of fittings for pumps that can be isolated. They consist of:

• High-efficiency pump

• Control valve with an opening temperature of 50, 55 or 60°C

• 1 thermometer ball valve with a red dial thermometer integrated in the

handle, can be pulled off

• 2 thermometer ball valves with a blue dial thermometer integrated in

the handle, can be pulled off

• Connections DN 20: 3⁄4" int. thread

• Connections DN 25: 1" int. thread

Thermal control valve with automatic bypass

1. The thermal valve shuts off the connection to the buffer tank as long as

the water in the boiler circuit is colder than the opening temperature of

the thermal control valve. The pump circulates the water via the bypass,

the small quantity of water in the boiler circuit can now heat up quickly.

2. When the boiler circuit reaches the opening temperature of the control

valve, the valve reduces the bypass flow rate and opens the buffer tank

circuit. The cold water from the buffer tank return is mixed with the hot

boiler circuit water in the control valve. This leads to an increase of the

return temperature in the boiler circuit to the desired level and avoids

condensation in the boiler.

3. When the buffer tank return temperature is higher than the opening

temperature, the control valve completely shuts off the bypass. Thus,

the water from the buffer tank flows directly into the boiler circuit.

Please note:

If the boiler output is controlled by the boiler temperature, the boiler

must heat up 20 K above the opening temperature of the return flow

temperature maintenance. Otherwise, the boiler might reduce the output

even before the thermal control valve is completely open.

Mounting versions 1 and 2:

Separate assembly of the group of fittings in the flow and return.

This version permits an easy isolation of the heat generator without

further shut-off valves. Consider the position of the safety group before

mounting.

Additionally required:

• 1 x gasket: DN 20 item no. 2057, DN 25 item no. 2157 1 x screw-in fitting:

DN 20 item no. 2053, DN 25 item no. 2153 1 x pump fitting: DN 20 item

no. 2049, DN 25 item no. 2149

D

N

2

0

Temperatures t

BY

= bypass t

KR

= boiler return

t

PR

= return of the buffer tank t

FIX

= opening

temperature

01/2020 • Printed in Germany

190

PAW GmbH & Co. KG • 31789 Hameln • Germany • Phone: +49-5151-9856-0 • Fax: +49-5151-9856-98 • info@paw.eu • www.paw.eu