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Siemens Building Technologies Basic Documentation RVA47.320 CE1P2379E
HVAC Products Description of the OEM settings 15.07.2002
6.8 Minimum temperature differential at the
pressureless header
• Detection of a too high flow rate on the heat generation side.
Avoiding excessive return temperatures.
An excessive flow rate on the heat generation side and the resulting increase of the
return temperature is quickly detected and, if necessary, offset by shutting down one of
the BMUs.
1. Press the line selection buttons to select line 60OEM.
2. Press the + / - buttons to set the minimum temperature differential.
Setting range Unit Factory setting
0...20 K (°C) 4
The minimum temperature differential at the pressureless header prevents the return
temperature from exceeding a certain level.
The setting is only active when running time strategy 2 or 3 is selected (see page 35).
With running time strategy 1, the function is inactive.
When the return temperature rises to a level which is half a switching differential (
MTS/2) below the flow temperature (point a), the selected running time strategy 2 or 3
is switched over to running time strategy 1. This means that one of the BMUs is shut
down as soon as possible.
If the return temperature moves away from the flow temperature by one full switching
differential MTS (point b), changeover is cancelled again. This means that running time
strategy 1 switches back to the previous running time strategy 2 or 3.
[°C]
t
LZS2/3
LZS1
t
RL
t
VL
MTS
2379Z27
a
b
=
=
t
VL
Cascade flow temperature (B10)
t
RL
Cascade return temperature (B70)
MTS Minimum temperature differential at the pressureless header
LZS1-3 Running time strategy 1 - 3
a / b Changeover points of running time strategy
Benefit
Description
Setting
Effect
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