Technical Datasheet

HYDRONIC RADIATOR BALANCING

Rt40

Rev: 3 09/07/2018

OverviewReturn Temperature Limiters have been designed to combat

problems where despite accurate flow control and correct

balancing, the system may still suffer from elevated return

temperatures. Problems typically arise in bathrooms where

towel rails are installed.

Towel rails usually only provide a small amount of heat which is

often supplementary to another heat source such as a radiator or

under-floor heating circuit. Despite being a heat emitter, a towel

rail does not give the same level of convective heat output as a

radiator. Furthermore, towels placed over the rails will effectively

insulate the rail surfaces thereby further reducing heat output

and raising return temperatures. Neither TRVs or PITRVs will be

effective in controlling this rise in return temperature as they

can only respond to the sensed room temperature.

In these cases, return temperature limiting valves (RTLVs) can

be used. A simple lockshield valve is installed on the radiator

inlet and the RTLV is installed on the outlet side.

The valve is settable between 20-50 °C and gradually closes if

the return water temperature exceeds the set value. Hence, return

temperature is maintained under all conditions.

Return Temperature Limiting Valve for Towel Rails

HYDRONIC RADIATOR BALANCING

Technical DatasheetTechnical Datasheet Rt40

OrderingReturn Temperature Limiting Valve for Towel Rails. Available in chrome or nickel finish.

Type Finish DescriptionTemp. range °C Xp = 2K

Rt40 AngleChrome 15 mm flow selectable angle valve body and thermostatic sensor.

15 mm fittings. Allen key for fixing sensor10 - 60

Nickel

Rt40 StraightChrome 15 mm flow selectable straight valve body, lockshield valve, thermostatic sensor.

15 mm fittings. Allen key for fixing sensor10 - 60

Nickel

Principle

Flow

Return

Flow

Return

All Danfoss radiator thermostats are manufactured in factories, assessed and certified by BSI (British Standard Institution)

against ISO 9000 and ISO 14001, and are approved to the European standard EN 215.

Quality

Technical Data

Thermostatic Sensor FinishMax Working Pressure (Bar)

Max Differential Pressure (Bar)

Test Pressure (Bar)

Max Water Temperature (ºC)

Return temperature limiter sensorAll white

10 0.6 16 120All chrome

Valve Body FinishKV Range at

XP = 0.5 - 2.0 KMax Working Pressure (Bar)

Max Differential Pressure (Bar)

Test Pressure (Bar)

Max Water Temperature (ºC)

Rt40 AngleChrome

0.55 10 0.6 16 120Nickel

Rt40 StraightChrome

0.55 10 0.6 16 120Nickel

Rt40 Angle Rt40 Straight

027

HYDRONIC RADIATOR BALANCING

Technical DatasheetTechnical Datasheet Rt40Valve Setting

Commissioning the valve

The Rt40 valve is unidirectional with a flow direction

selection feature.

• The Rt40 should be placed on the outlet (return) and the

lockshield valve should be installed on the inlet (flow).

• Establish the flow direction through the valve using these

diagrams, turning the setting ring as necessary to ensure

that water flow through the valve is always in the correct

direction and the risk of water hammer is eliminated.

SettingRt40 Lockshield Valve

Setting of max. water flow:

• Close the valve by means of a 6 mm Allen key

• Regulate the water flow by opening the valve

6 mm

HYDRONIC RADIATOR BALANCING

Technical DatasheetTechnical Datasheet Rt40Fitting the Sensor

1. Remove cap from valve and turn sensor to

2. Press the sensor firmly onto the valve.

Sensor horizontal: ensuring that the scale pointer is at top.

Sensor vertical: ensuring that the scale pointer is at the front.

3. Whilst holding the sensor firmly on the valve secure

connection by tightening the Allen screw using the

enclosed key.

4. Set desired room temperature.

Removing the Sensor Loosen the Allen screw (3). The sensor can now be separated

from the valve.

Sensor

Pressure pin

Gland seal

Revolver setting knob

Spindle

Bi-directional valve cone

Revolver

Valve body

Design - Rt40Valve bodies are manufactured from brass with chrome

or nickel plating. The spindle in the gland seal is of

chrominium steel and works in a lifetime lubricated

o-ring. The complete gland assembly can be replaced

without draining down the system.

Materials in contact with water

Valve body and other metal parts Brass

Valve body surface Nickel/Chrome plated

Flow-limiter PPS

O-ring EPDM

Valve cone NBR

Pressure pin and spring Chrome steel

Regulator Brass/EPDM

HYDRONIC RADIATOR BALANCING

Technical DatasheetTechnical Datasheet Rt40Design - Rt40 Lockshield Valve

Materials in contact with water - RLV-CX

Valve body and other metal parts Ms 58

O-ring EPDM

Rt401. Gland seal2. O-Ring3. Pressure pin4. Seal5. Regulation spring6. Setting dial7. Valve body8. kv-nozzle

Cover

Guide sleeve

Shut-o� cone

Valve body Union nut Tailpiece

Dimensions - Rt40 (Nickel or Chrome) Dimensions - Rt40 Lockshield Valve

10 20 30 40 50 60 °C

0 I< 1 2 3 4 >I

Closing temperature

Setting the Temperature

SAV (UK) Limited, Scandia House, Boundary Road, Woking, Surrey GU21 5BX

Phone: 01483 771910 Email: info@sav-systems.com

Web: www.sav-systems.com LinkedIn: www.linkedin.com/company/sav-systems

Technical DatasheetTechnical Datasheet Rt40Capacities - Rt40 (Nickel or Chrome)

Capacities - Rt40 Lockshield Valve

Capacity with P-band between 0.5K and 3K

Turns from Closed Valve

RLV-D 15 Angle RLV-D 15 Straight Tolerance

l/h Kv value l/h Kv value

1/4 36 0.11 62 0.20 ± 20%

1/2 58 0.18 118 0.37 ± 20%

3/4 78 0.25 164 0.52 ± 20%

1 94 0.30 211 0.67 ± 20%

1 1/2 126 0.40 262 0.83 ± 10%

2 159 0.50 286 0.91 ± 10%

2 1/2 201 0.64 323 1.02 ± 10%

3 254 0.80 357 1.13 ± 10%

3 1/2 306 0.97 378 1.20 ± 10%

4 365 1.16 401 1.27 ± 10%

4 1/2 422 1.34 415 1.31 ± 10%

5 482 1.53 427 1.35 ± 10%

Max 631 2.00 436 1.38 ± 10%