Stuart Turner SPU 180 Maxi Guide

STUART
Installation, Operation & Maintenance
Instructions
Please leave this instruction booklet with the end user as it contains
important warranty, maintenance and safety information
Read this manual carefully before commencing installation.
This manual covers the following products:
SPU 180 Maxi
Pt. No. 46725
SPU 280 Maxi
Pt. No. 46726

Cont ...
- 2 –
PRODUCT DESCRIPTION
Heating and cooling system pressurisation top up unit with integral water storage
tank and electric motor driven peripheral pump, automated control system consisting
of pressure transducer and water level sensors. The tank includes an AB air gap for
category 5 fluid isolation (BS EN 1717).
APPLICATION
The SPU Maxi range is designed to provide initial system fill and intermittent water top
up to compensate for intermittent losses in system pressure in heating and cooling
systems in commercial or industrial applications. These could include slight leaks,
air venting, etc. The units are not designed to deal with sudden losses of system
pressure due to major water losses over extended periods. They are also not to be
used for water boosting applications.
STORAGE
If this product is not to be installed immediately on receipt, ensure that it is stored in a
dry, frost and vibration free location in its original packaging.
CONTENTS Page
Checklist....................................................................................................................... 4
Important Facts – read before commencing installation ........................................... 5
Location ....................................................................................................................... 6
Key Features ................................................................................................................ 8
Installation.................................................................................................................... 9
Electrical Installation.................................................................................................... 11
Commissioning ............................................................................................................ 15
Operation ..................................................................................................................... 22
Maintenance................................................................................................................. 24
Environment Protection .............................................................................................. 25
Technical Specification................................................................................................ 26
Trouble Shooting ......................................................................................................... 27
Product Log ................................................................................................................. 28
Warranty ...................................................................................................................... 31

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WARNINGS:
This appliance must not be used for any other
application without the written consent of Stuart
Turner Limited.
This appliance can be used by children aged from
8 years and above and persons with reduced
physical, sensory or mental capabilities or lack of
experience and knowledge if they have been given
supervision or instruction concerning use of the
appliance in a safe way and understand the hazards
involved. Children shall not play with the appliance.
Cleaning and user maintenance shall not be made by
children without supervision.
Children should be supervised to ensure that they
do not play with the appliance.
This product should not be used for the supply of
water to more than one heating/cooling system at
a time.
The electrical installation must be carried out in
accordance with the current national electrical
regulations and installed by a qualified person.
The motor is not accessible in normal operating
mode. The unit must only be operated with the
front cover in place.
The electrical installation must be carried out in
accordance with the current national electrical
regulations and installed by a qualified person.
In the interests of electrical safety a 30 mA
residual current device (R.C.D. not supplied)
should be installed in the supply circuit. This may
be part of a consumer unit or a separate unit.
This appliance must be earthed via the terminal
block.
Please read installation details carefully as they are intended to ensure this product
provides long, trouble free service. Failure to install the unit in accordance with the
installation instructions will lead to invalidation of the warranty.

Cont ...
- 4 –
CHECKLIST
IMPORTANT: With the appliance removed from its
packaging check for any damage prior to installation.
If any damage is found contact Stuart Turner Ltd within
24 hours of receipt.
Electrical rating
plate and serial
number
Inlet
Overflow
B
A
Outlet
Fig. 1
Item Description Qty Item Description Qty
ASPU 1CTop cover 1
BFront cover 1
Note:
Your product may vary slightly from the picture above.
C

Cont ...
- 5 –
1IMPORTANT FACTS: READ BEFORE COMMENCING PUMP INSTALLATION
AWater storage capacity.
1.11 The SPU Maxi has a usable water volume of approximately 18 litres; the length
of time the SPU takes to pressurise a system will be dependent on:-
The pressure differential between the cold fill and set pressures and also the
refill rate of the tank
1.12 Ensure the pumps are primed as described in the priming section before
starting, to avoid causing damage to the pump shaft seal. See Section
6.26 Hydraulic commissioning.
BWater temperature
This unit is designed to pump cold water only which should not exceed the
following values:
1.13 The maximum allowable water temperature is 23 oC (see Technical Section).
1.14 The minimum allowable water temperature is 4 oC.
CPipework – General
1.15 Do not drill holes or put fastenings into the SPU Maxi tank, this will cause
leakage.
1.16 Secure pipework: Ensure pipework to and from pump is independently
supported & clipped to prevent forces being transferred to inlet and outlet
branches of the unit. Do not secure pipework to the SPU Maxi, this will cause
damage and possible leakage.
1.17 Flux: Solder joints must be completed and flux residues removed prior to SPU
Maxi installation (flux damage will void any warranty).
1.18 Pipework design: Care should be taken in the design of pipework runs to
minimize the risk of air locks e.g. use drawn bends rather than 90o bends.
1.19 DO NOT introduce solder flux to flexible hose, tank, pump or any
parts manufactured from plastic.
1.20 DO NOT allow contact with oil or cellulose based paints, paint
thinners or strippers, acid based descalents or aggressive cleaning
agents.
1.21 DO NOT bend the flexible hose beyond 90o. It must be installed as
detailed, DO NOT kink. See Installation Section 4.15.
DPlumbing installation regulations
1.22 The plumbing installation must comply with the current water and building
regulations.
1.23 The plumbing installation must be installed by a qualified person.

Cont ...
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2LOCATION – GENERAL
2.11 Location: The preferred SPU Maxi location is on a smooth level floor,
of sufficient strength to support the filled weight of the SPU Maxi,
close to the water source and a suitable overflow position
(see Section 9 – Technical Specification for filled weight). The SPU
Maxi must not be installed in a loft space. It must also be
considered that the noise and vibration from the SPU Maxi may be
transmitted through the structure it is sited on. Ensure the
minimum clearance requirements are followed to allow servicing of
the unit
2.12 Access and minimum clearance requirements: For emergencies
and maintenance the SPU Maxi must be easily accessible and have
the minimum clearance around it as laid out in Fig. 2. Additional
access to the front of the unit will be required to operate the
keypad and view the display.
Fig. 2
2.13 Protection: The SPU Maxi must be located in a dry, frost free area.
2.14 Ventilation: Ensure an adequate air flow to cool the SPU Maxi.
Separate the SPU Maxi from other appliances that generate heat.
Do not block the vent holes on the front cover.
2.15 Water retention: Site the SPU Maxi in a location where in the
unlikely event of a water leak, any spillage is contained or
routed to avoid electrics or areas sensitive to water damage.
As part of the AB airgap (CAT 5 fluid isolation) the SPU has a weir
type overflow on the front, water will be discharged from this area
in the event of the failure of the inlet valve or non-return valves.
2.16 Supply inlet pressure: The water supply inlet pressure must not exceed 7 bar.
2.17 Ambient temperature: The SPU Maxi must be sited in a location where the
ambient temperature does not drop below 4 °C or exceed 40 °C.
2.18 Pipework: For optimum performance inlet and outlet pipework must be a
minimum of 15 mm pipe.
150
150
500
300
300

Cont ...
- 7 –
2.19 Static outlet pressure: The static outlet head must be 3 metres below pump
maximum cold fill pressure (vertically above the appliance).
2.20 Isolating valves: Separate system isolating valves (non-restrictive) must be
fitted to allow easy service of the SPU Maxi. Isolating valves must be mounted
where specified to allow the system isolation and removal of the SPU Maxi
if needed. See Section 4.15 for installation details.

Cont ...
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3KEY FEATURES
3.11 The SPU Maxi comprises of the following main components:-
1. Cabinet – The cabinet of the SPU Maxi houses the water break tank,
controller, pumps and pipework. The cabinet is manufactured in corrosion
resistant stainless steel.
2. Pump assembly – One or two brass peripheral pump units powered by
induction motors, with integrated non return valves and venting screw.
Mounted to a removable mounting plate to allow easy maintenance if
required.
3. Programmable controller – Stuart Turner designed, user set controller,
allowing system set up and easy alarm connection.
3
Fig. 3
3.12 Principle of operation: The pressurisation unit consists of a break tank and
one/two peripheral pumps. The break tank is supplied with mains water from
the right to a float valve and includes an overflow and weir to maintain an
AB air gap in the tank. The unit is connected to the heating/chiller system
via the connection on the right hand side of the cabinet. The pumps are
connected to the tank via flexible hoses.
A pressure transducer monitors system pressure and if a reduction in system
pressure is detected, the controller runs the pumps until the system is re-
pressurised to the required pre-set level. If the unit only has a single pump
connected it will run continuously until this level is reached, if the unit is a
twin pump model the pumps run in duty standby mode (the controller will
alternate which pump starts first to even the wear on the pumps). The pumps
are fitted with non-return valves to ensure system pressure is maintained once
pressurised.
2
1

Cont ...
- 9 –
4INSTALLATION
4.11 Cold mains feed connection: The connection to the cold water mains inlet is
made using the upper G ½ male threaded connection. See Fig. 4.
When tightening ensure the fill valve within the tank is not rotated. If the
valve is rotated it may not function correctly with the risk of flooding.
4.12 Floor installation:
1. Ensure the SPU Maxi is located so it cannot be kicked or knocked over.
2. Ensure the floor surface on which the SPU Maxi is located is flat and level.
3. If possible locate the unit against a wall for added stability.
4. If the SPU Maxi is located in an area that might be subjected to flooding,
mount the SPU Maxi on a raised plinth.
4.13 Pipework connections & guidelines:
1. Before connecting the SPU Maxi to the system ensure that system flushing
has been performed correctly and all foreign matter, including pipe scale,
has been removed.
Note: Foreign material from the system coming into contact with the
expansion vessel bladder could cause premature failure of the expansion
vessel.
2. Isolating valves MUST be installed on the unit inlet and outlet, to allow the
unit to be isolated if required. The isolation valve on the outlet should be
of a lockshield type. See Fig. 5.
3. A drain valve must be fitted on the outlet of the SPU Maxi before the
isolation valve. See Fig. 5.
Warning pipe
Main cold feed
Fig. 4

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SPU Maxi
Warning pipe
Expansion
vessel
Isolation
valves
Return
header
Drain
valve
Fig. 5
4. The warning pipe should be connected to a suitable drain via a tundish
enabling visual warning of an overflow condition. The overflow fitting is
designed to use 19 to 23 mm diameter plastic waste pipe or connect to
G ¾ threaded pipe. Ensure there is a demountable joint in the pipe to
allow the removal of the SPU Maxi if needed. See Fig. 4.
5. Non-return valves, pressure reducing valves and RPZ valves MUST NOT
be installed between the SPU Maxi and the heating/cooling system. These
devices will prevent the pressure sensor from reading the system pressure
and will lead to incorrect operation of the unit.
6. The SPU Maxi should be connected to the system return header along with
the expansion vessels as specified in BS 7074. See Fig. 5.
4.16 Typical installation diagram:
4.17 Vessel sizing & location:
1. System expansion vessel sizing should comply with the BS 7074 Expansion
Vessel sizing calculation.
2. The pressurisation unit and expansion vessels should be connected to the
system at the same point, to provide a neutral pressure reading.
3. A lockshield valve and drain valve should be installed at the inlet of each
expansion vessel to allow for servicing.
Lockshield
valve
Fig. 6
Drain valve

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5ELECTRICAL INSTALLATION / EARTHING
5.11 Regulations: The electrical installation must be carried out in
accordance with the current national electrical regulations and
installed by a qualified person.
5.12 Safety: In the interests of electrical safety a 30 mA residual current
device (R.C.D. not supplied) should be installed in the supply circuit.
This may be part of a consumer unit or a separate unit.
5.13 Before starting work on the electrical supply ensure power supply is
isolated.
5.14 DO NOT allow the supply cord to contact hot surfaces, including the
motor shell, pump body or pipework. The cord should be safely
routed and secured by cable clips.
5.15 Adjacent pipes: Adjacent suction and delivery pipes should be fitted with
earthing clamps in accordance with current regulations (Fig.7).
Earth continuity
connection
Fig. 7
5.16 Earthing: This appliance must be earthed via the terminal block under the top
cover.
5.17 Pipework: Copper or metallic pipework must have supplementary earth
bonding where the continuity has been broken by flexible hoses or plastic
components.
5.18 Additional earthing: Certain installations may require additional earthing
arrangements such as equipotential bonding. Reference should be made to
the relevant regulations concerning this subject to ensure compliance.
5.19 Connections: The SPU Maxi must be connected to a dedicated fused spur via
a lockable isolator to avoid authorized disconnection.
5.20 The electrical connection must be made adjacent to (not behind) the SPU
Maxi to allow disconnection of the electrical supply should the pump module
need to be removed for service or maintenance.
Cont ...
Metallic
pipework

- 12 –
5.21 Wiring of connection unit:
WARNING: This appliance must be earthed.
This product range must be permanently connected to fixed wiring and is
provided with a set of terminals which allow the connection of a flexible
supply cord.
Select a supply cord and fuse size based on the full load current and the
surrounding conditions and wired with the following code:
Green and Yellow: Earth
Blue: Neutral
Brown: Live
As the colours of the wires in the mains lead of this appliance may not
correspond with the coloured markings identifying the terminals in your
connection unit proceed as follows:
The wire which is coloured green and yellow must be connected to the
terminal in the connection unit which is marked with the letter E or by the
earth symbol: or coloured green or green and yellow.
The wire which is coloured blue must be connected to the terminal which
is marked with the letter N or coloured black.
The wire which is coloured brown must be connected to the terminal
which is marked with the letter L or coloured red.
Ø6.3 × 32 mm Fuse
Fig. 8
5.22 Boiler interlock safety function:
Brown: Live
Green and Yellow: Earth
Blue: Neutral
The SPU Maxi is fitted with a volt free contact specifically assigned for boiler/
chiller shut down in the event that the SPU Maxi detects system pressure
above the Hi alarm pressure or below the Lo alarm pressure.
The boiler interlock contact will be open circuit below the Lo alarm pressure
and above the Hi alarm pressure.
When thesystem pressure is in its normal operating pressure range (above Lo
alarm pressure and below Hi alarm pressure settings) the contact is
closed circuit
Always refer to the boiler/chiller manufacturer’s instructions for correct
integration.

Cont ...
- 13 –
Fig. 11
Fig. 12
NO
Boiler Interlock
NO
Common Alarm
NO
High
pressure alarm
NO
Low pressure alarm
Fig. 9
5.23 Alarm and boiler interlock connections:
Circuits connected to the relays are limited to 5 Amps, 230 V a.c.
maximum. The Installer MUST fit a 5 Amp fuse in the circuit to the
alarm relay to protect the SPU Maxi from damage.
For connection of output relays follow the steps and images below:
1) Remove the required green connector from the right hand side of the
control board.
2) Strip 6–8 mm insulation from the end of the connection wire (Max 1.5 mm2
CSA).
3) Insert wire into connector and screw down terminal screws to secure
(0.6 Nm max.).
Fig. 10

Cont ...
- 14 –
4) Re-insert connector into the correct location on the control board and
route the cable to the back of the SPU Maxi and exit the cabinet via one of
the 20 mm holes and a suitable cable retention and sealing system to
either the left or right hand side. Blank off the remaining unused cabinet
holes with the blind grommets supplied. See Fig. 13.
5.24 RS 485 Modbus – BMS Connection:
Fig. 13
RS 485 is available on this product for BMS connection and is enabled in the
Advanced settings menu.
5.25 Fuses: The following fuse size should be used:
Model Fuse Size (AMPS)
All models 5
The SPU Maxi is fitted with an internal re-settable fuse, see section 11
5.26 Supply cord replacement:
The supply cord and internal wiring within the terminal box are
routed and secured to ensure compliance with the electrical
standard EN 60335–1. It is essential that prior to any disturbance
of this internal wiring, all cable routing and securing details are
carefully noted to ensure re-assembly to the same factory pattern
is always maintained.
If the supply cord is to be changed or is damaged, it must be replaced with a
special cord assembly available from Stuart Turner or one of their approved
repairers.
On disassembly note the cord retention and routing system. Re-assemble to
the same pattern.
For information on cable connection consult the wiring diagram.
Blind
grommet

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6COMMISSIONING
6.11 Pre-commissioning checklist:
Before starting the commissioning process the following conditions must be
met. If these conditions are not adhered to, damage to the equipment,
system and property may result.
Ensure the unit is sited in a frost free area, away from precipitation and
water sprays/jets.
All necessary pipe/electrical connections should have been made to a
satisfactory standard by a qualified person.
The temperature and pressure at the point of connection are within the
operating limits of the pressurisation unit.
The heating/cooling system is fitted with a safety valve and expansion
vessel sized appropriately.
6.12 In order for the pressurisation unit and heating/cooling system to function
correctly the following conditions must be met. If these conditions have not
been met, the commissioning process should not continue.
Ensure the system connection has been made into the heating/chiller
system return header.
Ensure Non-return valves, pressure reducing valves or RPZ valves are NOT
installed between the pressurisation unit and the heating/cooling system.
The expansion vessel is pre-charged to the correct pressure (equal to
initial system design pressure).
6.13 Prior to commissioning fill the heating/cooling system via a filling loop if
possible. If this is not possible, the pressurisation unit can be used to fill the
system after commissioning has taken place. Depending on the size of the
system, this may take a considerable amount of time. The system fill
function of the unit will stop after 24 hours, if further filling is required,
reset this function.
Ensure the heating/cooling system is filled and pressurised to the required
cold fill pressure, with the water at approximately ambient temperature.
Ensure the system is dosed with a suitable corrosion inhibitor. Note the
SPU Maxi is not designed for dosing chemicals into the system, this must
be done via other means.
6.14 Expansion vessel setting:
To set or check the expansion vessel charge pressure the lock-shield
valve between the SPU Maxi and the vessel must be closed and the
vessel drained using the drain valve.
A suitable gauge should be used to check the charge pressure.
If the charge pressure is too high it can be reduced by releasing air from
the vessel pre-charge valve or by using a pressure gauge with an integral
air release valve.
If the charge pressure is too low a small increase can be provided using a
car foot pump otherwise an oil free compressor or nitrogen bottle is
recommended.
When the correct pressure is set the Schrader valve protective cap must
be replaced.
Check the integrity of the pipe-work. Ensure the lock-shield valve
between the system and the expansion vessel is open and the drain
valve is closed. Cont ...

- 16 –
Fig. 15
D
6.15 Controller overview
The Stuart Turner SPU controller is designed to be intuitive to use and allows
functions and alarms to be set by the installer/user. It also allows faults to be
monitored and logged to enable easier system fault diagnosis.
The functions are set using the 4 buttons (A, B, C & D) on the front of the
controller and with the help of on screen prompts via the back lit LCD display.
On the front of the SPU a green ‘power on’ light will be displayed whilst the
unit is powered. If an alarm or error is raised the red ‘Error’ light will be
displayed.
A number pressure set points can be set using the menus, these set points are
detailed below, 1 to 4 and in the description of the function.
Fig. 14 SYSTEM FILL MODE NORMAL OPERATION
A
B
C
Button A Scrolls up through menus or increases set values.
Button B Enters menus or selects values.
Button C Scrolls down through menus or reduces set values.
Button D Returns to previous menu
PUMP 'OFF'
HIGH ALARM SET VALUE (1)
SYSTEM PRESSURE SET VALUE (2)
DIFFERENTIAL SET VALUE (3)
PUMP 'ON'
LOW ALARM SET VALUE (4)
TIME
PRESSURE

- 17 –
6.16 Function list & explanation
The functions are contained within an initial display and 3 menus:-
Setting menu (pass code protected) see Section 6.18.
Advanced setting menu (pass code protected) see Section 6.19.
Test menu (pass code protected) see Section 6.20.
6.17 Initial display
On start up, and during operation, if the SPU has had no button inputs for
1 minute, a home screen (see Section 7.11) will be displayed with system
pressure, tank water level, any active alarm and any pump that is operating at
the time.
By using buttons A & C to scroll up or down the following screens will be
displayed:-
System pressure
Active errors
System fill status
Pump activity
Pump run time
Alarm reset
6.18 Setting menu
(Pass code protected, if set)
The following functions can be set and modified:-
System pressure (2)
see Fig. 14
Sets the required system pressure. Set in 0.1 bar
increments up to the maximum set value for the SPU model. SPU
180 & 280 – 8.0 bar max.
Differential pressure (3)
see Fig. 14
Sets the pressure the SPU will turn on at as the system
pressure falls. Relative to the system pressure. Set in
0.05 bar increments below the System pressure (2), cannot be
set above 0.1 bar below the System pressure (2).
Hi Alarm (1)
see Fig. 14
Sets high system pressure alarm. Set in 0.05 bar
increments above the System pressure (2). Cannot be set below
System pressure + 0.05 bar. Alarm auto resets when system
pressure is reduced below alarm level.
Lo Alarm (4)
see Fig. 14
Sets low system pressure alarm. Set in 0.05 bar increments
below the System pressure (2) – Differential pressure (3) – 0.05
bar. Alarm auto resets when system pressure is increased above
alarm level
System fill
Turns on system fill option. System fill option will turn off
once the System pressure (2) has been reached or a period of
24 hours has passed since it was set to ‘on’. Lo alarm and Max
runtime functions are disabled whilst System fill is turned on.
Pumps will stop if the System pressure (2) or Hi alarm pressure
(1) is reached.
Start Activity High
Alarm triggered if the SPU starts more than the preset
limit in 24 Hours.
Set to minimum of 100 starts per 24 hrs. Set in increments of
100.

Cont ...
- 18 –
6.19 Advanced setting menu
(Pass code protected, if set)
The following functions can be set and modified:-
Common alarm relay allocation
Can be set to operate if one of the following alarms activate:-
Low water
Pump fail
Pump run time
Pump activity high
Sensor error
Common alarm relay operation
Allows the relay to operate either as normally open or normally
closed.
Pump Exercise Allows the Pump Exercise function to be turned off or on, the
default is on. Read Section 7.12 before turning off
Modbus address Sets the Modbus address
Modbus enable Allows the Modbus communication function to be turned on,
default is off
Run time limit
Sets the maximum time a pump can run before the pump run
time alarm is activated. Set in increments of
10 minutes up to 60 minutes maximum. Disabled when the
System fill option is turned on.
Passcode change Sets a 4 digit passcode, defaults to 0000 (off). Can be user set
to limit access to Setting, Advance setting and Test menus.
Pump run on delay
Sets the time the pump will continue to run after the system
pressure (2) is reached on rising pressure. Adjustable from 3
to 120 seconds, pre-set to 10 seconds. Reducing this time will
improve the pressure setting on lower volume systems
Pump start delay
Sets the time delay in starting the pump after system pressure –
differential pressure (3) is reached on falling pressure. Adjustable
from 3 to 120 seconds, pre-set to 3 seconds. Increasing this time
will reduce un-wanted SPU Maxi operation during rapid system
pressure fluctuations (circulator pump starts)

Cont ...
- 19 –
6.20 Test menu
(Pass code protected, if set)
The following functions can be set and modified:-
Pump test Forces pump 1 (LH) or 2 (RH) to run for 5–10 seconds to enable
operation of the pump to be confirmed.
System fill volume
Monitors the volume of water pumped into the system since it
was last reset. Displayed in cubic metres (1m³ = 1000 litres). Can
be user reset.
Fill rate Monitors the rate at which water is flowing into the system and
is displayed as a real time flow rate (l/min).
Power interrupt log
Monitors how long the electrical power has been applied to the
SPU. Resets when power is removed or during a power cut. No
user input.
Controller info Displays software revision and pump set up. No user input.
Alarm log Displays the last 10 alarm events. Can be user reset.
Pump run time log Displays how long each pump has run. Can be user reset
Pump activity log Displays which pump has run and how long it ran for. Can be
user reset.
6.21 Pre-set values
The SPU will be delivered with the following pre-set values:-
6.22 Setting menu
Set Pressure 2 bar
Differential 0.2 bar
Hi Alarm 2.5 bar
Lo Alarm 1.3 bar
System fill off
Run activity high 1000
6.23 Advanced setting menu
Relay allocation Pump fail
Relay operation normally open
Pass code 0000 (not active)
Run time limit 10 minutes
Pump run on delay 10 seconds
Pump start delay 3 seconds

- 20 –
6.24 Controller menu diagram
Power ‘on’ Home screen
Setting menu
Advanced menu
Test menu
Set system
pressure
Set differential
pressure
Set Hi alarm
Set Lo alarm
System Fill
`
Pump run on
delay
Common relay
operation
Run time limit
Enter pass
code
(If set)
Delay
Push to test
pump
Pump activity
log
Power
interrupt log
Alarm log
Start up screen
Display logo &
phone number.
See page 5, column
4 & 5
Pump run time
log
System fill
volume
System
pressure
display
Error display
System fill
status display
Pump activity
display
Pump run time
display
Alarm reset
Controller info
display
Setting menu
Advanced
menu
Test menu
17 Sept 2019
Passcode
change
Start Activity
High
Common relay
allocation
Pump start
delay
RS485
MODBUS
address
RS485
MODBUS
enable
Pump Exercise
on/off
Fig. 16
Cont ...