Basic Documentation

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Siemens Modular Heating Controller RMH760B CE1P3133en
Building Technologies 10 DHW heating 2017-09-29
Maximum limitation of the return temperature during DHW heating will be deactivated.
Maximum limitation of the return temperature is constant during the time the legionella
function is active, that is, independent of the outside temperature. This limitation too will
be activated only when a valid value has been set. If the value is invalid ("---"), there
will be no limitation during the time the legionella function is active.
10.8.3 Frost protection functions
Frost protection for the DHW storage tank is ensured in all operating modes and is
activated as soon as one of the 2 storage tank sensors acquires a temperature below
5 °C.
A temperature request will then be sent to the heat source, and the storage tank heated
up until both storage tank temperatures have reached 5 °C (plus the adjusted switching
differential) thereby exceeding 6 °C, independent of the operating mode.
Frost protection for the storage tank is started when the plant operation selector is set
to "Off" and / or in summer operation the storage tank is charged via the electric
immersion heater.
With plant types DHW 2 through DHW 5, the flow temperature is monitored also.
If it falls below 5 °C, the primary pump will be activated with plant type DHW 2, and the
secondary pump with all the other plant types. When the temperature exceeds 6 °C, the
pump will be switched off again.
During the time frost protection for the flow is active, no heat request is sent to the heat
source.
10.8.4 Pulse limitation
DHW heating can handle pulses for limiting the output or the volumetric flow.
Prerequisite for pulse limitation is a DHW plant type with mixing valve, that is, DHW 2,
DHW 3, DHW 4, or DHW 6.
The pulses are delivered via the meter inputs of function block "Meter". For more
detailed information about this function block, refer to chapter 12 "Function block
meter".
After one or several meter inputs have been configured, pulse limitation can be set up.
Main menu > Commissioning > Settings > … or
Main menu > Settings > DHW > Limitations > Pulse limitation
Operating line
Factory setting
Meter input
---
Type of limitation
Absolute
Limit value
75 pulses/min
Integral action time Tn
60 min
The meter input is an input of function block "Meter" and used for the limitation of
pulses. Only inputs configured to a terminal can be selected for pulse limitation.
2 limitation choices are available:
Absolute: Limitation will be activated when the limit value is crossed
Scaled: The limit value is fixed at 75 pulses/min. The limit value can be set, but this
has no effect. If less than 5 pulses/min are received, fault status message No signal
meter 1 (or …2) will be delivered. Heat meters with a scaled output deliver
120 pulses/min if there is no supply of heat or no volumetric flow. Together with pulse
limitation, this prevents hydraulic creep.
Return temperature
limitation during the
time the legionella
function is active
Frost protection for
the storage tank
Frost protection for
the flow
Meter inputs
Settings
Meter input
Type of limitation