ARI Armaturen Liquid PN25 EN - Manual (Page 3)

Rev. 0040807002 0405 Page 3
Operating and installation instructions
Liquid return temperature limiter
4.0 Description
4.1 Scope of applications
Liquid return temperature limiters with temperature control are used for return control in
heating systems.
The information complies to the Pressure Equipment Directive 97/23/EC.
It is the responsibility of the machine planner to ensure compliance.
The special markings on the valve must be taken into account.
Refer to the catalogue sheet to see which materials are used in standard versions.
Please contact the supplier or the manufacturer if you have any questions.
4.2 Operating principles
(refer to Fig. 1 - Fig. 2 page 4 and Fig. 3 page 6)
Liquid return temperature limiters maintain a constant returning water temperature in a
water system; if the returning water temperature falls, the valve will open wider to allow a
greater flow into the water heater, and the reverse occurs with a rising temperature in the
return line.
When the valve is in the closed position, a snall amount of water will still flow through the
valve. This is to ensure that the valve is sensing a representative sample of water in the
system and allow rapid response to load changes.
The bi-metallic discs (Pos. 24.6) in the controller (Pos. 24) arch when heated, moving the
annular slide valve (Pos. 24.18) to the „closed“ position. Conversely, if the discs are cooled
by the process fluid, the flatten out, moving the annular slide valve towards the „open“
position.
ATTENTION !
- Refer to the data sheet for applications, limits on use and possibilities.
- Certain media require or preclude the use of special materials.
- The valves are designed for standard operating conditions. If conditions exceed
these requirements, e.g. aggressive or abrasive media, the operator should
state the higher requirements when ordering.
- Valves made from grey cast iron are not authorised for use in systems subject
to TRD 110.