Danfoss STM Safety Temperature Monitor Actuator User Guide

Prior to assembly and commissioning to avoid injury of persons and damages of the devices, it is absolutely necessary to carefully read and observe these instructions.
Necessary assembly, start-up, and maintenance work must be performed only by qualified, trained and authorized personnel.
Prior to assembly and maintenance work on the controller, the system must be:

depressurized,
cooled down,
emptied and
cleaned.

Please comply with the instructions of the system manufacturer or system operator.

Disposal instruction

This product should be dismantled and its components sorted, if possible, in various groups before recycling or disposal. Always follow the local disposal regulations.

Definition of Application

Safety temperature monitor (actuator) STM is, in combination with Danfoss valves (STM/VG(F), VGS) and Danfoss controller combinations (STM/AVT/VG(F), VGS), used for temperature control and temperature monitoring of drinking water, water and water glycol mixtures for heating and district heating systems.
The controllers STM/VG(F), VGS and STM/AVT/VG(F), VGS are:

Type-tested acc. to EN 14597 and protect against exceeding temperatures:
District heating systems acc. to DIN 4747
Heating systems acc. to EN 12828 (DIN 4751) and EN 12953‑6 (DIN 4752)
Water heating systems for drinking and industrial waters acc. to DIN 4753

The technical parameters on the product labels determine the use.

Application examples ❶
Safety temperature monitor (actuator) STM can be combined with:

VG(F) and VGS valves.
Combination pieces K2, K3, AVT actuators and valves mentioned above

Assembly

Admissible Installation Positions ➋

Safety temperature monitor (actuator)with valves
In combination with VG(F) valves:

Can be installed in any position ①.
In combination with VGS valves:
Medium temperatures up to 160 °C:
- Can be installed in any position ②.
Medium temperatures > 160 °C:
- Can be installed horizontal and in horizontal pipelines with the actuator oriented downwards ③.

Temperature sensor

The capillary tube may not be twisted or buckled. The minimum bending radius is 50 mm.
The place of installation must be chosen in a way that the temperature of the medium is directly taken without any delay. Avoid overheating of temperature sensor.
The temperature sensor must be immersed into the medium in its full length ④.
The temperature sensor may be installed in any position ⑤.

Installation Location and Installation Scheme ❸

STM/valve ①,
STM/AVT/valve flow mounting ②

Valve Installation ❹

Clean pipeline system prior to assembly.
Install a strainer in front of the controller ①. Max. mesh width:
- DN 15-25: 0,5 mm
- DN 32-50: 0,8 mm
Install temperature indicators in the system part to be controlled.
Install valve ❹
The flow direction indicated on the product label ② or on the valve ③ must be observed.
- The valve with mounted weld-on tailpieces may only be spot welded to the pipeline ④. The weld-on tailpieces may be welded only without the valve and seals! ⑤⑥
  If these instructions are not observed, high welding temperatures may destroy the seals.
- Flanges ⑦ in the pipeline must be in parallel position and sealing surfaces must be clean and without any damage.
  Tighten screws in flanges crosswise in 3 steps up to the maximum torque (50 Nm).
Caution:
Mechanical loads of the valve body by the pipelines are not permitted.

Mounting of safety temperature monitor (actuator) ❺

Before mounting the actuator, carry out Filling the system, First start-up and Leak and pressure tests, ❽❾.
Place temperature actuator at the valve ① or combination piece ② and tighten union nut with wrench SW 50. Torque 35 Nm.

Insulation ❻

Do not insulate the safety temperature monitor (actuator) and the valve as well.

Start-up ❼

Note
Valves ① VG(F) and VGS are normally opened (NO) valves.

Filling the system and Leak and pressure test should be done without mounted temperature actuator ② – valve has to be open.

Filling the system, first start-up ❽

Slowly open shut-off devices ① in the flow pipeline.
Slowly open shut-off devices ② in the return pipeline.

Leak and Pressure Tests ❾
Pressure must be gradually increased at the +/- side of the valve.

Do not test with closed valve!
Non-compliance may cause damages at the actuator or the valve.

A pressure test of the entire system must be carried out in accordance with anufacturer’s instructions.
The maximum test pressure for the valves is: 1,5 × PN

PN – see product label
Putting out of operation

Slowly close shut-off devices ① in the flow pipeline.
Slowly close shut-off devices ② in the return pipeline.

Settings ❿

Temperature Setting
The temperature setting range is indicated on product label ①.

Pre-conditions
The system must be opened and the flow of the medium guaranteed.

Procedure

Set desired set point by turning the setting adjuster ② with the delivered Allan key SW 5 ③.
You may only adjust within the marked range, see ①.
Turning to the left (couter-clockwise) increases the set point.
Turning to the right (clockwise) reduces the set point.
Observe temperature indicator.
Wait for about 3 to 5 min. until the temperature indicator shows the final value.
If the device is used as a temperature monitor, the setting adjuster ⑤ must be sealed by a sealing wire ④.

Temperature setting – AVT
(relevant only at STM/AVT/VG(F), VGS controllers) See instructions for temperature actuator AVT.

Safety function

⓫

If there is a leakage in the area of the temperature sensor ①, the capillary tube ②, or the thermostat ③, the valve is closed by a pressure spring in the safety thermostat. In this case safety temperature monitor (actuator) must be replaced.

Dimensions, Weights

⓬

Disposal instruction

Conical ext. thread acc. to EN 10226-1
Flanges PN 25, acc. to EN 1092-2

Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products already on order provided that such alterations can be made without subsequential changes being necessary eady agreed.
All trademarks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.

FAQ

Q: What are the application examples of the Safety Temperature Monitor (Actuator) STM?
A: The STM is used with Danfoss valves and controllers for temperature control in heating and district heating systems, as well as water heating systems for drinking and industrial waters.
Q: How should I dispose of the product?
A: Disassemble the product and sort its components before recycling or disposal according to localregulations.

Documents / Resources

Danfoss STM Safety Temperature Monitor Actuator [pdf] User Guide
STW871, STM-VG, STM-VGF, STM-VGS, STM-AVT-VG, STM-AVT-VGF, STM-AVT-VGS, STM Safety Temperature Monitor Actuator, STM, Safety Temperature Monitor Actuator, Temperature Monitor Actuator, Monitor Actuator, Actuator

References

User Manual

Danfoss STM Safety Temperature Monitor Actuator

Safety Notes