Bosch Heatronic 4000 Installation & Operating Instructions Manual page 14

IDHW Mode -- - --- - - --- -- - -- -- - -- -- - - - - - -- - -- - - - -- - ---- - -- ---- -- -- --- -- -- -- - -- - -- - -- - -- -- - -- - - - - - - - -
The control has a IDHW MODE setting that selects whether
or not indirect DHW operation is active.
OFF
IDHW operation is inactive. All DHW Calls are ignored. If this
mode is selected while DHW operation is underway, all DHW
operation ceases.
ON
IDHW operation is active. All DHW Calls are responded to.
IDHW Location -- -- - --- --- - -- - - - - - -- - -- - - - - - -- - - - -- - -- - -- ---- --- ---- -- -- - -- - -- -- - -- - -- - -- -- - - - - - - - -
The control has a IDHW Location setting that selects where
the indirect DHW tank is located in the system. This setting
determines the operating sensor & affects pump operation.
NEAR
The indirect DHW tank is piped in parallel within the near boiler
piping of boiler 4. When a valid DHW Call is present, the IDHW
Pump relay turns on & boiler pump 4 turns off. The control uses
the boiler 4 outlet sensor as the operating sensor in order to
measure the boiler supply temperature supplied to the indirect
DHW tank. There are two boiler target temperatures. One for
the space heating system (Boil TARG) & one for the indirect
DHW system (IDHW TARG).
• All boilers are used for space heating requirements.
• Boiler 4 is used for indirect DHW when there is a DHW
Call.
• The dedicated indirect DHW boiler is always boiler 4, even
if there are less than four boilers.
• If boiler 4 is disabled & NEAR is selected for the IDHW Location,
the dedicated indirect DHW boiler 4 will not operate.
PRIM
The indirect DHW tank is piped in the boiler system loop. When
a valid DHW Call is present, the IDHW Pump relay turns on.
Primary Pump During IDHW --------------------------------------------------
The control has a Primary Pump during IDHW setting that
selects whether or not the primary pump is required during
indirect DHW operation.
Heatronic 4000
Near Boiler
Piped off
boiler
system loop
--------------------------------------------------
OFF
The primary pump does not turn on during indirect DHW opera-
tion. This would be typical of an indirect DHW tank piped in
parallel in the boiler system loop. It is assumed that the DHW
pump will provide adequate flow through the indirect DHW
heat exchanger & the boiler system loop.
ON
The primary pump turns on during indirect DHW operation.
This would be typical of an indirect DHW tank piped in
primary/secondary in the boiler system loop.
IDHW Priority --- --- --- --- --- --- --- -- -- --- --- - --- --- --- -- --- --- --- --- --- --- --- --- --- --- ---- --- --- ---
The control has a IDHW Priority setting that selects whether or
not priority of indirect DHW is required over the space heating
system. Indirect DHW priority stops or limits the delivery of
heat to the space heating system while the indirect DHW tank
calls for heat. This allows for quick recovery of the indirect
DHW tank.
OFF
IDHW priority is not provided. The primary pump can operate
when a Heat Call is present. Heating zones are unaffected by
indirect DHW operation.
ON
IDHW priority is provided. The primary pump shuts off for a
period of time to provide priority.
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DHW
Pump
ON
Primary
Pump OFF
DHW
Pump
ON
Primary
Pump ON
BTC461503101C | 6720810369 (2018/03)