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Building Technologies Modular Heating Controller RMH760B CE1P3133en
HVAC Products 6 Boiler temperature control 05.02.2007
In most cases, the boiler can be hydraulically decoupled via a shutoff valve. In the case of
plant with a mixing valve for minimum limitation for the return temperature, this function is
performed by the mixing valve. If the boiler is not released, the mixing valve is driven to
the fully closed position so that the boiler will be hydraulically decoupled from the plant.
Shutoff valve for hydraulically decoupling the boiler from the system. It is possible to
configure the shutoff valve to terminals with changeover contact so that both an on and
an off contact are available.
Often, the shutoff valve is controlled “parallel“ to the boiler pump (common output), or
the boiler pump is controlled parallel to the shutoff valve, but activated only when the
shutoff valve is fully open.
T
3132S69
Y1 Y2 3
4
BuSt1
VlvShOff
BuSt1 Burner stage 1
VlvShOff Shutoff valve
If the shutoff valve and the boiler pump are controlled by different outputs, the shutoff
valve must be driven to the fully open position before the boiler pump is activated and
before the burner is switched on. Complete opening of the shutoff valve is ensured
either by the valve’s checkback signal or the selected switch-on delay for the pump.
If a checkback signal shall be delivered, input Checkb sign shutoff valve must be config-
ured for it. If a checkback signal from the shutoff valve is configured and there is no
such signal on completion of the adjusted switch-on delay time, a fault status message
will be delivered. This fault will lead to a boiler fault.
For more detailed information, refer to section
6.9 “Boiler faults”.
Main menu > Commissioning > Settings > … or
Main menu > Settings > Boiler > Fault settings > Checkb sign shutoff valve
Operating line Range Factory setting
Signal delay start 00.05…59.55 m.s 02.00 m.s
If the boiler pump is installed in the bypass, there is no need to wait for switching on
until the shutoff valve is open. In that case, the pump’s switch-on delay can be set to 0.
Main menu > Commissioning > Settings > … or
Main menu > Settings > Boiler > Operation settings
Operating line Range Factory setting
Switch-on delay pump 0…255 s 0 s
Switch-on delay burner 0…255 s 0 s
Shutoff valve (MBRT) Open / Closed Open
If both the pump’s switch-on delay and the burner’s switch-on delay are parameterized,
first the pump will be activated on completion of the pump’s switch-on delay; then, on
completion of the burner’s switch-on delay, the burner will be released.
The selected overrun time acts on both the boiler pump and the shutoff valve (for setting
the overrun time, refer to subsection
6.6.4 “Boiler shutdown”).
Normally, the shutoff valve is fully open when the boiler is released. In the case of the
maintained boiler return temperature where the boiler is always kept at the minimum
temperature, the behavior of the shutoff valve can be parameterized.
When Open is selected for the shutoff valve (maintained boiler temperature), the valve
will always be opened when the burner runs, even if there is no heat request.
Shutoff valve
Control of the shutoff
valve
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