The BCP type is a series of dedicated pressure switches for
safety and pressure monitoring of steam and hot water boilers.
The BCP incorporates a single-pole changeover microswitch
where the contact position depends on the pressure in the
connection port and the range set value.
For installations, in which operation is particularly critical for
safety reason, the use of fail-safe control is recommended.
Features
Approvals
y Available as high and low pressure limiters as well as
pressure controllers
y Wide pressure range:
from low pressure BCP1 with narrow dierential to high
pressure BCP7
y The fail-safe dual bellows enable premature cut-out when
fault occurs
y DIN plug mounted on the top of control for easy electrical
wiring
y Single-pole changeover switch (SPDT), switch + alarm
CE-marked in accordance with EN 60947-4/-5
VdTŰV-Merkblatt „Druck 100”
TŰV. SDWFS/SDBFS . 15 - 335
y Direct mounting on pressure connection or wall mounting
by means of a bracket
y Versions with automatic and manual resets available
y Screw adjustments made on top of housing
y Manual reset for pressure limiters possible only by means
of tools
y Safety Integrity Level: SIL 2 according to IEC 61508:2010
CE marked in accordance with 2014/68/EU,
category IV, safety equipment, testing basis
pr EN12952-11 and EN12953-9.
Version with automatic reset cut-in again automatically when
the pressure falls to the set point minus dierential. Version
with manual reset has to be cut in manually by means of tool.
Fail-safe bellows concept
BCP 6, BCP 6H, BCP 7, and BCP 7H have a double bellows: an
operating bellows (inner) and safety bellows (outer).
17-893.11
3
2
1. Pressure connection
2. Regulating bellows
3. Safety bellows
1
Danfoss
Microswitch
BCP is a microswitch based control with DIN plug. Such design
enables easy electrical connection and makes control suitable
for operation with modern electronic systems, as PLC.
Silver/gold plated contacts
Silver/gold plated contacts are used for low currents and
middle range of current, especially in applications with PLC
or other corresponding electronic devices. Such contacts
have also signicantly lower emission of electromagnetic
noises produced on contact break. EMC (Electro Magnetic
Compatibility) is an important parameter where electronic
equipment is used. A gold plated contact has a silver layer
under the gold and can therefore also be used in the middle
range of load. The gold will disappear at loads above 0,1 A.
Note:
Ambient temperature inuence
All BCP pressure switches operate independently of changes in
ambient temperature around the switch.
Therefore the settings for cut-out pressure and dierential
stay constant unless the permissible ambient temperature is
exceeded.
When system pressure exceeds the set value, the BCP will
automatically stop the plant.
A rupture in the inner bellows cause the control cut-out
pressure to fall about 3 times less then the preset value, thus
the system stops prematurely.
A rupture in the outer bellows cause the control cut-out
pressure to fall about 3 bar under the preset value, thus
providing a fail-safe function.
In other BCP types with single bellows assembly, fail-safe
function is satised by proved 2 millions cycles mechanical life
time test.
Cut-in and cut-out pressures of the system should always be
checked with accurate pressure gauges.
Pressure settings for switches (with automatic reset)
Set the cut-out pressure on RANGE scale and dierential on
DIFF. scale. Restart pressure is equal to cut-out pressure minus
pre-set dierential value.
Pressure switches with manual reset
High pressure limiters
Set cut-out pressure on the RANGE scale. Pressure limiter can
only be manually reset by pressing reset button by means
of tools when the pressure is equal to or below the cut-out
pressure minus value of the dierential.
Pressure limiters
Limiters are devices that, on reaching a xed value interrupt
and lock out the energy supply.
Manual unlocking is required before restart.
A limiter shall be such that a single fault in any related part shall
not lead to a loss of the safety function.
Note:
If a BCP pressure controller with automatic reset is used as
limiter, lockout must be realized externally as a part of safety
logic, e.g.: by external contactors and/ or relays according to
requirements of standard prEN501156-1 for safety relevant
hardware. External closure must be interlocked, while loss of
auxiliary energy must lead to closure.
Resetting must not be automated; it has to be performed
manually.
Resetting on fault must lead to a repeated closure.
When BCP limits, is for rising or falling applications, the external
safety logic must change to fail-safe position.
Fail-safe control
A control is fail-safe if it has the capability to remain in a safe
condition or transition to a safe condition when a fault occurs.
Low pressure limiters
Set cut-out pressure on RANGE scale. Limiter can only be
reset manually by pressing (with tool) the reset button when
pressure rises to cut-out pressure plus dierential or above it.
Note:
Pressure limiters have no dierential scale. Fixed dierential
value is printed on the scale plate.
Maximum working pressure
The maximum permissible pressure for safe
functioning of the system or any of its components.
Snap function
A specic contact force is maintained in micro-switch until snap
is initiated, therefore, contact bounce cannot occur as a result,
for example, of slight vibrations before cut-out.
These design features ensure that the cut-out point of the BCP
control remains very accurate and completely independent of
the magnitude of the current load.
Set point
A predetermined value to which a control is adjusted and at
which it performs its intended function.
Dierential
The dierence between pressure cut-out and pressure cut-in.
Reset
1. Manual reset
A unit with manual reset can only be restored to operational
mode by activation of the external reset button.
Note:
If the system pressure exceeds PS/MWP then accuracy of the
control settings can be lost.
Maximum test pressure
The maximum pressure applied in strength or leakage tests on
heating systems or components thereof.
2. Automatic reset
A unit with automatic reset is restored to operational mode
automatically