BC 3000 Controller - Spirax Sarco
Installation and
Maintenance Instructions
AB Issue 3
Hazards to be considered when installing/using/maintaining Spirax Sarco products
1. Access
Ensure safe access and if necessary a safe
working platform before attempting to work on
the product. Arrange suitable lifting gear if
2. Lighting
Ensure adequate lighting, particularly where
detailed or intricate work is required e.g. electrical
3. Hazardous liquids or gases in the pipeline
Consider what is in the pipeline or what may
have been in the pipeline at some previous
time. Consider; flammable materials, substances
hazardous to health, extremes of temperature .
4. Hazardous environment around the product
Consider; explosion risk areas, lack of oxygen
(e.g. tanks, pits), dangerous gases, extremes of
temperature, hot surfaces, fire hazard (e.g.
during welding), excessive noise, moving
5. The system
Consider the effect on the complete system of
the work proposed. Will any proposed action
(e.g. closing isolating valves, electrical isolation)
put any other part of the system or any other
workers at risk? Dangers might include isolation
of vents or protective devices or the rendering
ineffective of controls or alarms. Ensure isolation
valves are turned on and off in a gradual way to
avoid system shocks.
6. Pressure systems
Ensure that any pressure is isolated and safely
vented to atmospheric pressure. Consider
double isolation (double block and bleed) and
the locking and/or labelling of valves shut. Do
not assume the system is de-pressurised even
when the pressure gauge indicates zero.
7. Temperature
Allow time for temperature to normalise after
isolation to avoid the danger of burns.
8. Tools and consumables
Before starting work ensure that you have
suitable tools and/or consumables available. Use
only genuine Spirax Sarco replacement parts.
9. Protective clothing
Consider whether any protective clothing is
required to protect against the hazards of, for
example, chemicals, high/low temperature,
noise, falling objects, dangers to eyes/face.
10. Permits to work
All work must be carried out or be supervised by
a suitably competent person.
Where a formal permit to work system is in force
it must be complied with. Where there is no
such system, it is recommended that a
responsible person knows what work is going
on and where necessary arrange to have an
assistant whose primary responsibility is safety.
Post warning notices if necessary.
11. Electrical work
Before starting work study the wiring diagram
and wiring instructions and note any special
requirements. Consider particularly;
mains supply voltage and phase, local mains
isolation, fuse requirements, earthing, special
cables, cable entries/cable glands,
electrical screening.
12. Commissioning
After installation or maintenance ensure that
the system is fully functioning. Carry out tests
on any alarms or protective devices.
13. Disposal
Unwanted equipment should be disposed of in
a safe manner.
NOTE: The products supplied by Spirax
Sarco Ltd are classified as components and
are not affected by the Machinery Directive
Customers and stockists are reminded that under UK and EC Health, Safety and
Environmental Law, when returning products to Spirax Sarco they must provide information
on any hazards and the precautions to be taken due to contamination residues or mechanical
damage which may present a Health, Safety or Enviromental risk.
This information must be provided in writing, including Health and Safety data sheets
relating to any substances indentified as hazardous.
Installation &
Setting up the Controller
Fault Finding
Printed in U.K.
В© Copyright 1995
BC 3000 Controller
The BC 3000 controller continuously monitors,
displays, and controls the level of total dissolved
solids (TDS) in steam boilers or other water
The controller is used with a probe which senses
water conductivity (closely related to TDS).
The BCS 3 system described here has the probe
mounted directly in the boiler.
Another system, the BCS 2, provides blowdown
control for coil boilers.
This has a probe which senses the feedwater
The BC 3000 can also be used for monitoring
the conductivity of condensate.
These systems are described in separate
Control of the blowdown is normally achieved
by means of an electrically actuated valve which
opens when the TDS rises above the set level
and closes when the TDS returns to normal.
An adjustable high TDS alarm with relay output
and an isolated 0-20 or 4-20mA output are
included as standard.
Some versions of the BC 3000 are available
with a В‘self-cleaningВ’, or probe conditioning circuit
(Patent Applied For) which allows the system to
operate where less than ideal feedwater
treatment is causing some boiler scaling to occur.
A label on the controller defines the range and
calibration units.
A Pt 100 temperature probe is also available to
compensate the conductivity measurement for
boilers where the working pressure varies, for
coil boiler feed tanks, or for condensate systems.
The controller is protected to IP65, and can be
wall-mounted or installed adjacent to the boiler
control panel in a position where it does not
receive excessive radiation from hot surfaces.
Maximum ambient temperature 55В°C.
For outdoor applications install inside a
weatherproof enclosure.
Controller mounting is by one В‘keyholeВ’ slot on
the back and two screw slots at the sides of the
terminal compartment. Eleven cable entry
В‘knockoutsВ’ are provided, six on the controller
base and five at the rear of the terminal
Provision is made for the fitting of security seals
to the controller door and terminal compartment
cover. A lock can also be supplied for fitting to
the door catch.
BCV 30
Blowdown Valve
Blowdown to heat recovery
system or blowdown vessel
Sample Cooler
SC 20 (optional)
A typical installation
Wiring - BCS 3 System
Wiring Diagram - 4 terminal TDS probe
1. TDS probe wiring
The probe requires a 4 core screened cable
connection. A suitable cable is Pirelli FP 200 or
Delta Crompton Firetuf OHLS, 1mmВІ. Whilst pairs
of conductors are linked at the probe, the four
wire connection compensates for voltage drop
along the cable. Connect the screen only as
shown; do not connect at the probe. Maximum
cable length 100m.
Internal Links
BC 3000
terminal block
5. Control relay
The control relay is also volt-free and goes to
the high position when the TDS is above the
control set point. When the controller is switched
off the relay goes to the low TDS position.
Remember to link a live supply into terminal 17.
To ensure the blowdown valve closes on boiler
shut-down, this supply may be taken from a
separate source which is live only when the
boiler is on.
Caution: Mains supplies must be on the same
Detail showing
wiring of 4-wire
Pt 100 temperature
sensor when fitted
4. Alarm relay
The relay is volt-free and goes to the alarm
position when the TDS is above the alarm set
point and also when the controller is switched
TDS Probe
3. Transmitter output
The transmitter output represents the controller
range e.g. 0-6000 ppm and may be used for
remote TDS display, as a chart recorder input,
or as an input to a computer monitoring system.
The output is isolated and floating and either
side may be connected to earth if required. If the
transmitter output is not to be used there is no
need to link terminals 10 and 11.
Links fitted
when Pt 100
temperature sensor
not used
2. Temperature sensor wiring
If a temperature sensor is not to be used, link
terminals 5 and 9, and 6 and 7.
Wiring to the temperature sensor requires a 3
core screened cable with the screen connected
as shown. Do not connect the screen to the
sensor. Suitable cable is Pirelli FP 200 or Delta
Crompton Firetuf OHLS, 1mmВІ. Maximum cable
length 100m.
A 4 wire sensor must be linked as shown for 3
wire connection.
6. Mains supply
The controller should normally be supplied from
the boiler control panel control phase although
a separate mains supply may be provided if
preferred. In this case fit a local isolating switch
and fuse as shown and ensure that it is on the
same phase as the rest of the boiler controls.
The controller is supplied for 240V mains supply.
To change the mains supply voltage refer to
'Setting up the Controller'.
and BCV 30 bl
erminal TDS probe
and BCV 30 blowdown valve
Control Relay
(3A max. resistive)
Alarm Relay
(3A max. resistive)
Internal Fuse Link
DS Probe
BC 3000 enclosure
Local isolating
switch and
3A Fuse
0 or 4-20 mA
Transmitter output
max 1000Ω
Mains Supply
Note:- Controller supplied for 240V.
Select other voltages by moving
internal fuse link
N Y1 Y2 21
3 4 5
BCV 30
box if
0 or 4-20 mA
Transmitter output
max 1000Ω
Plug tail
TDS Sensor
or relay
in enclosure
box if
3. Control relay
The control relay is volt-free and goes to the
high position to open the blowdown valve when
the TDS is above the control set point. When
the TDS is low the valve closes. Remember to
link a live supply into terminal 17.
On multi-boiler installations where there is a
blowdown valve on each boiler, to ensure that
there is no live supply to the blowdown valve
when the boiler is switched off, a contactor or
relay is recommended as shown. The supplies
from each boiler should only be live when the
boiler is running (from the feed pump circuit for
example). Since there are multiple live supplies
in the relay enclosure a suitable warning label
should be applied.
Transmitter output, alarm relay, and mains supply
- see page 4.
2. Temperature sensor wiring
Should a temperature sensor not be used, link
terminals 5 and 9, and 6 and 7, as shown on
page 4.
The Pt 100 temperature sensor cable is also
1.25m long and may be connected directly to
the controller, but in most applications a junction
box and 3 core screened cable will be required.
Connect the screen only as shown,do not
connect at the junction box. A suitable cable is
Pirelli FP 200 or Delta Crompton Firetuf OHLS,
3 core 1mm2. Maximum cable length 100m.
1. TDS sensor wiring
Ensure that the fibre joint washer is in place
then insert the plug tail PT2 into the TDS sensor
and tighten the brass union nut. The heat
resisting cable is 1.25m long and for most
applications will need to be extended via a
junction box. When the layout permits the plug
tail cable may be connected directly to controller
terminals 2 and 3 but it is then essential to link
terminals 1 to 2 and 3 to 4. When mechanical
protection of the heat resisting cable is required
the nut may be removed from the plug tail
revealing an M16 thread to suit a flexible conduit
When a cable length longer than 1.25m is
needed a junction box and a 4 core screened
cable to the controller is required. Note that
whilst pairs of the cable are linked at the junction
box, the 4 wire connection is required to
compensate for voltage drop along the cable.
Connect the screen only as shown, do not
connect at the junction box. A suitable cable is
Pirelli FP 200 or Delta Crompton Firetuf OHLS,
4 core, 1mm2.
Wiring Diagram - 2 terminal TDS probe and BCV 20 blow
Wiring - BCS 2 and condensate
contamination detection
Supplies to
the blowdown
valves on
each boiler
(Neutrals and
Earths not
BC 3000 enclosure
rminal TDS probe and BCV 20 blowdown valve
Control Relay
(3A max. resistive)
Alarm Relay
(3A max. resistive)
Internal Fuse Link
Local isolating
switch and
3A Fuse
0 or 4-20 mA
Transmitter output
max 1000Ω
BCV 20
Mains Supply
Suggested wiring layout
on multi-valve installations
Note: Controller supplied for 240V.
Select other voltages by moving
internal fuse link.
or relay
in enclosure
Supplies to
the blowdown
valves on
each boiler
(Neutrals and
Earths not
Boiler 1
Boiler 2
Boiler 3
Live supplies from
control circuit of each boiler
Setting up the controller
The controller is supplied set up as follows:В— For a mains supply voltage of 240V
В— For the high TDS range
(See controller label for values)
В— For a transmitter output of 4-20mA
Probe conditioning circuit (If fitted)
В— Probe conditioning circuit off
В— 3 minutes operating time
To change any of these settings proceed as
follows:WARNING: Ensure mains supply is isolated
before removing terminal cover or front panel.
Even when the controller is operating on a
24V or 110V supply, 240V will be generated
at the 240V fuse socket..
1.-To change the mains supply voltage:Ensure mains supply is isolated
В— Remove terminal cover.
On the lower circuit boardВ— Remove fuse cover to right of terminals.
В— Remove the 250mA fuse from its socket
В— For 220V or 110V supplies plug the fuse
into the required socket.
В— For 24V supply discard the 250mA fuse and
plug the 2A anti-surge fuse supplied into the
24V socket.
В— Remove 4 corner screws securing front
panel/upper circuit board assembly.
В— Lift out assembly, being careful not to strain
the ribbon cable.
В— Change settings as required.
В— Use a small screwdriver to operate switches
on upper circuit board.
After changing settingsВ— Refit front panel /upper circuit board assembly.
Do not overtighten screws.
В— Reconnect mains supply
220V 110V 24V
Spirax Part No.
Farnell Part No.
Spare fuses may be obtained from Spirax Sarco
or Farnell Electronics Components, Leeds.
В— Replace the fuse cover and terminal cover.
2.-To change the TDS to low range
On the upper circuit board
В— Slide switch S100 inwards for low range
Ribbon Connector
3.-To change transmitter output to 0-20mA
On the upper circuit board
В— Slide switch S112 inwards for 0-20mA
Ribbon Connector
4.-To switch on the probe conditioning facility
On the lower circuit board
If this facility is fitted there will be a switch and
LED to the left of the terminals.
В— Slide switch downwards to switch on.
5.-To adjust probe conditioning timer
This should not normally be necessary unless
poor feedwater treatment has previously caused
boiler and probe scaling. It is essential to attend
to such problems promptly as serious boiler
damage could otherwise occur.
On the lower boardThe conditioning time is adjusted by a
potentiometer to the top left of the transformer.
В— Turn the potentiometer clockwise to increase
the time.
S112 S100
S112 S100
High Range
Low Range
Potentiometer VR9
1 minute
15 minutes
conditioning time
High Range
Low Range
Digital display normally shows the measured
conductivity in parts per million (ppm), or microSiemens per centimetre, (ВµS/cm). The display is
updated only every 15 seconds under normal
running conditions to avoid a constantly changing
display. Note that the final digit of the display is
always zero.
Green LED: Lit when the measured conductivity
is below the set point. The blowdown control
valve is normally closed under these conditions.
Amber LED: Lit when the measured conductivity
is above the set point. The blowdown control
valve is opened under these conditions.
Flashing Red LED: Flashes when the measured
conductivity is above the alarm value. The alarm
relay signals alarm under these conditions.
Increase buttons: Increase the displayed value,
but only when the relevant calibrate, set point or
alarm button is pressed. Value increases slowly
for a few steps when first presed then increases
at a greater rate, after a few seconds pause.
Decrease buttons: As above but decreases the
Calibrate button: Allows the display to update
at a faster rate when pressed. Used in
conjunction with the increase/decrease buttons
for 'calibrating' the controller.
Set point button: Displays the controller set
point. When released the display reverts to the
measured conductivity value. Used in conjunction
with the increase/decrease buttons for changing
the set point.
Alarm button: Displays the alarm value. When
released the display reverts to the measured
conductivity. Used in conjunction with the
increase/decrease buttons for changing the
alarm value.
Setting the controller set point.
The set point is the conductivity level at which
the blowdown valve will open. The valve will
close at a conductivity level approximately 4%
below the set point.
Press and hold the set point button then use the
increase or decrease buttons as necessary to
change the displayed set point value.
Note: The 4% operating band is built in to avoid
В‘huntingВ’ of the blowdown valve and will cause
the valve to remain open even though the
conductivity level is below the set point. This is
normal and can be ignored.
Setting the alarm value.
The alarm value should be set higher than the
controller set point so that it gives a high
conductivity alarm if the measured conductivity
rises too far. To set the alarm value press and
hold in the alarm button then use the increase or
decrease buttons as necesary to change the
displayed alarm value. The alarm resets approx
4% below the alarm value.
Set point
Increase buttons
Digital display
Alarm button
Decrease buttons
Green LED
Calibrating the controller
The controller must be 'calibrated' before the
system is ready for use. Calibration compensates
for the various differences between boilers
including the effects of:В— Boiler pressure and temperatures (where
temperature compensation is not fitted)
В— Boiler water alkalinity.
В— The exact 'cell constant' or geometry of the
conductivity probe and boiler connection.
В— The exact make-up of the impurities in the
boiler water.
To calibrate the controller, with the boiler at
normal operating pressure, proceed as follows:
В— Take a sample of boiler water through a
sample cooler and measure its conductivity
by your normal method. As an example
assume the measurement is 2000 ppm.
В— Press and hold in the calibrate button then
use the increase or decrease buttons as
necessary to change the displayed value
to 2000 ppm.
В— Release the calibrate button. The controller
is now calibrated and the display and
transmitter output should follow any
variations in conductivity.
Note:- For new or recently refilled boilers, the
TDS level may be very much lower than the
desired set point. If this is so, re-calibration is
advised once the boiler has been working for a
while and the TDS level has risen nearer to
During operation the controller will continously
display the boiler water TDS and should control
this figure very closely by periodically opening
the blowdown control valve to reduce the TDS.
This should normally result in consistent TDS
readings as measured with a portable
conductivity meter such as the Spirax Sarco
MS1, typically within the range of plus or minus
10%. Factors reducing the accuracy of control
include large variations in boiler pressure (where
temperature compensation is not fitted) and wide
pH swings.
The probe conditioning circuit (Patent Applied
For) is fitted to some versions of the BC 3000,
and can help keep the probe working even where
boiler water treatment conditions are less than
It may not be able to cope with severe sludge
and scale conditions, however, and should not
be regarded as a substitute for adequate
feedwater treatment.
The circuit comes into operation whenever the
mains supply is switched on and when first
activated (see В‘Setting up the controllerВ’).
It will continue to operate for the set time, and
will then switch off for approximately twelve hours
before repeating the cycle.
An LED to the left of the main terminals is lit
during this operation.
During this time the display is disconnected from
the probe and the reading should be ignored.
It will automatically display the true TDS level
when the conditioning cycle finishes.
No special maintenance of the controller is
necessary. The following maintenance however,
is recommended on the system. For details see
separate instructions.
Weekly: Take a sample of boiler water through
a sample cooler, measure its TDS and check
the controller calibration with the boiler at normal
operating pressure. Check that the blowdown
control valve shuts off when the green LED is lit
or when power is removed. Operate the stop
valve to ensure that it shuts off and remains
Annually: With the boiler depressurised, vented,
and emptied sufficiently, remove the conductivity
probe. Clean the tip with fine abrasive paper
and the insulation with a brush or cloth. Examine
the blowdown control valve, stop valve, check
valve and probe elbow. Clean and replace any
parts necessary.
Checking the controller calibration
Whenever the TDS is measured by taking a
sample of boiler water, the figure should be
compared with the controller display. If the boiler
is operating normally yet the readings differ
significantly the controller may simply be recalibrated to the new TDS reading. If frequent
re-calibration becomes necesary then something
is wrong. It could be that the water treatment is
not sufficiently well controlled to ensure a
reasonably steady pH value in the boiler.
Probe conditioning circuit
If scale is forming on the probe tip it is a certain
warning that scale will also be forming on the
boiler tubes. Boiler water treatment must be
Fault Finding
If problems are experienced during
commissioning it is very likely that a mistake
has been made in the wiring. We recommend
that a complete check is made for such faults as
the neutral not connected to the supply, the live
supply not linked to the controller terminal 17 or
the links not fitted (terminals 5 & 9, 6 & 7) when
the temperature sensor is not used. Always
check the wiring to the conductivity probe
particularly carefully since it is easy to make a
mistake with the probe terminals.
A simple test may be made on the controller
even when the boiler is shut down or empty.
Disconnect the conductivity probe and connect
a resistor as shown.
The table below shows the approximate resistor
value required to give a half scale reading,
allowing the various controller functions to be
Controller range
Resistor value
In case of problems refer to the following points.
1. The digital display always reads very high
and the amber LED and flashing red LED are
This probably indicates a short in the conductivity
probe circuit; in the boiler; in the probe itself or
in the wiring. The position of the fault may be
located by disconnecting the probe plug or the
wiring. Note that it takes a minute or so for the
displayed value to drop after a short in the probe
circuit. A high reading may also be caused by a
short circuit in the temperature sensor or its
wiring (where fitted) since the controller will
receive a low temperature input. If the links 5 &
9, 6 & 7 are disconnected the display will also
read high.
2. The digital display always reads very low
and the green LED is lit.
If the boiler is empty, has just been filled with
pure water, or if the boiler is cold (without a
temperature sensor fitted) this should not be
Half scale
regarded as a fault. As the boiler steams, the
boiler water TDS and conductivity will increase
and normal operation should follow. If the boiler
water TDS is in its normal range, however, the
low reading probably indicates an open circuit in
the TDS probe, or in the wiring.
3. The boiler water TDS continues to rise
above the set point although the amber LED
is lit and blowdown is being discharged
through the blowdown control valve.
The controller is operating correctly but
insufficient blowdown is being discharged. It may
be possible to adjust the blowdown control valve
to a higher flowrate setting (see separate
instructions). Alternatively the valve or pipework
may be partially blocked or where a heat recovery
system is installed, the blowdown may be
contaminating the feedwater system.
An increasing boiler water TDS may also be
caused by condensate or feedwater
contamination from any source.
4. The boiler water TDS continues to fall
although the green LED is lit and the
blowdown control valve is closed.
Check that the valve shuts off tight and that
other blowdowns are not excessive.
Examples could be a leaking bottom blowdown
valve, unnecessary manual blowdown or leaking
level control chamber drain valves.
5. The increase or decrease buttons
sometimes do not appear to work.
The controller incorporates a pair of digitally
controlled potentiometers for the functions
calibrate, set point and alarm. For each function
there is a coarse and a fine potentiometer
arranged so that the fine potentiometer steps for
the first few seconds after the increase or
decrease button is pressed, followed by steps
from the coarse potentiometer. A problem occurs
when the fine potentiometer reaches the end of
its range since there will be no change of the
display for the first few seconds. The answer is
simply to hold down the increase or decrease
button until the coarse potentiometer takes the
display past the required value, then step back
in the other direction.
6. The display shows a high reading when
first switched on.
This is normal and the controller will take up to 1
minute before the display shows the correct
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