LTH Electronics MTD75 User manual

MTD75
Cooling Tower Controller
Operation Guide

Preface
MTD75 Operation Guide - 1 -
Preface
Product warranty
The MTD75 has a warranty against defects in materials and workmanship for three years
from the date of shipment. During this period LTH will, at its own discretion, either repair
or replace products that prove to be defective. The associated software is provided ‘as is’
without warranty. The warranty assumes the defective unit will be returned to our works
for inspection/repair and does not include for site visits to rectify faults.
Limitation of warranty
The foregoing warranty does not cover damage caused by accidental misuse, abuse,
neglect, misapplication or modification.
No warranty of fitness for a particular purpose is offered. The user assumes the entire risk of
using the product. Any liability of LTH is limited exclusively to the replacement of defective
materials or workmanship.
There are no user serviceable parts, including fuses etc., within the unit. Any attempt to
dismantle the controller will invalidate the warranty.
Disclaimer
LTH Electronics Ltd reserves the right to make changes to this manual or the controller
without notice, as part of our policy of continued developments and improvements.
All care has been taken to ensure accuracy of information contained in this manual.
However, we cannot accept responsibility for any errors or damages resulting from errors
or inaccuracies of information herein.
Copyright and trademarks
All rights reserved. Translations, reprinting or copying by any means of this manual,
complete or in part or in any different form requires our explicit approval.
MTD75 is a trademark of LTH Electronics Ltd
Sixth edition: March 2021
LTH Electronics Ltd
Chaul End Lane
Luton Telephone : [phone]
Bedfordshire Fax : [phone]
LU4 8EZ email : [email protected]
England Web : www.lth.co.uk

Preface
- 2 - MTD75 Operation Guide
Manufacturing Standards
Electromagnetic compatibility
This instrument has been designed to comply with the standards and regulations set down
by both the United Kingdom EMC Regulations S.I. 2016/1091 and the European EMC
Directive 2014/30/EU using BS EN 61326-1: 2013.
Safety
This instrument has been designed to comply with the standards and regulations set down
by both the United Kingdom Equipment Safety Regulations S.I. 2016/1101 and the
European Low Voltage Directive 2014/35/EU using BS EN 61010-1: 2010.
Restriction of Hazardous Substances
This instrument has been produced to comply with the standards and regulations set down
by both the United Kingdom Equipment Restriction of Hazardous Substances Regulations
S.I. 2012/3032 and the European Restriction of Hazardous Substances Directive 2011/65/EU
using BS EN IEC 63000 : 2018.
Quality
This instrument has been manufactured under the following quality standard:
ISO 9001:2015. Certificate No: FM 13843
Note: The standards referred to in the design and construction of LTH products are those
prevailing at the time of product launch. As the standards are altered from time to time, we
reserve the right to include design modifications that are deemed necessary to comply
with the new or revised regulations.
Disposal
As per regulation S.I. 2012/3032 and directive 2012/19/EU, please observe the applicable
local or national regulations concerning the disposal of waste electrical and electronic
equipment.

Preface
MTD75 Operation Guide - 3 -
Declaration of Conformity

Preface
- 4 - MTD75 Operation Guide

Contents
MTD75 Operation Guide - 5 -
Contents
Preface.........................................................................................................................1
Contents.....................................................................................................................5
Introduction..............................................................................................................9
MTD75 Controller Specification ..................................................................... 11
Installation – Safety & EMC............................................................................... 17
Noise suppression................................................................................................ 18
MTD75 Add-in Cards Installation................................................................... 19
MTD75 Installation .............................................................................................. 25
MTD75 Connections ........................................................................................... 29
Supply Voltage Connections..................................................................... 30
Relay Connections......................................................................................... 31
Current Output Connections..................................................................... 33
Redox Input Termination Information................................................... 36
Electrodeless Conductivity Input Termination Information.......... 42
pH Input Termination Information ......................................................... 47
Digital Inputs ................................................................................................... 52
Modbus RS485................................................................................................ 53
SD Card Interface ........................................................................................... 54
User Interface......................................................................................................... 55
The Front Screens .......................................................................................... 55
The Menu System .......................................................................................... 56
Security Code Access.......................................................................................... 58
Access Code Management......................................................................... 59
Enter New Code.............................................................................................. 60
Biocide A Control Functions ............................................................................ 61
Dosing by Volume ......................................................................................... 61
Timed Dosing .................................................................................................. 61
Dosing By Redox Level................................................................................. 61
Dosing From The Water Meter ................................................................. 61

Contents
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Output Configuration .................................................................................. 62
Bleed Inhibiting .............................................................................................. 62
Pre-Dose Bleeding......................................................................................... 62
Dose Alarm Timer .......................................................................................... 62
Manual Dosing................................................................................................ 62
Biocide A Menu..................................................................................................... 63
Biocide B Control Functions............................................................................. 71
Dosing By Ratio A : B..................................................................................... 71
Bleed Control Functions.................................................................................... 73
Bleed By Volume ............................................................................................ 73
Timed Bleeding............................................................................................... 73
Bleeding By Conductivity Level................................................................ 73
Bleed Alarm Timer ......................................................................................... 73
Manual Bleeding ............................................................................................ 73
Bleed Menu ............................................................................................................ 74
Inhibitor Control Functions.............................................................................. 79
Dosing By Volume ......................................................................................... 79
Timed Dosing .................................................................................................. 79
Dosing By Bleed Duration........................................................................... 79
Dosing From The Water Meter ................................................................. 79
Output Configuration .................................................................................. 79
Bleed Inhibiting .............................................................................................. 80
Pre-Dose Bleeding......................................................................................... 80
Manual Dosing................................................................................................ 80
Inhibitor Menu ...................................................................................................... 80
pH Control Functions ......................................................................................... 87
Dosing By Volume ......................................................................................... 87
Timed Dosing .................................................................................................. 87
Dosing By pH Level ....................................................................................... 87
Dosing From The Water Meter ................................................................. 87
Output Configuration .................................................................................. 88

Contents
MTD75 Operation Guide - 7 -
Bleed Inhibiting .............................................................................................. 88
Pre-Dose Bleeding......................................................................................... 88
Dose Alarm Timer .......................................................................................... 88
Manual Dosing................................................................................................ 88
pH Control Menu.................................................................................................. 89
Alarm Relay Configuration ............................................................................... 97
Redox Input Channel Setup............................................................................. 99
Electrodeless Conductivity Input Channel Setup..................................101
pH Input Channel Setup..................................................................................107
Redox Input Channel Calibration.................................................................111
Electrodeless Conductivity Input Channel Calibration........................117
pH Input Channel Calibration .......................................................................125
Resetting the User Calibration......................................................................139
Current Outputs .................................................................................................141
Current Output Calibration............................................................................143
Digital Inputs .......................................................................................................147
Configuration ......................................................................................................151
Update Software ................................................................................................157
Optional Software Functions.........................................................................159
Save, Restore & Reset........................................................................................161
Error Messages....................................................................................................163
Modbus RS485 ....................................................................................................165
Data Logging.......................................................................................................171
Live Trending.................................................................................................171
Setup Live Trending....................................................................................171
Live Trend Screen ........................................................................................174
SD Card Data Logging................................................................................175
Setup SD Card Data Logging...................................................................175
SD Card Data Logging Graph..................................................................180
Viewing the SD Card Data Log on a PC ...............................................181

Contents
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Appendix A – Customer Setup .....................................................................183
Appendix C – Temperature Coefficient.....................................................196
Appendix D – Modbus RS485 Registers ....................................................197
Standard Value Tables......................................................................................232
Appendix E – Modbus RS485 Coils..............................................................233
Appendix F – Modbus RS485 Discretes.....................................................235
Appendix G – Error Messages .......................................................................245
Appendix H – Fault Finding ...........................................................................253
Index .......................................................................................................................260

Introduction
MTD75 Operation Guide - 9 -
Introduction
Introduction
The MTD75 is a microprocessor controlled cooling tower controller, designed to provide
timed or measured control of pumps or solenoids for inhibitor, biocide, bleed and pH
control operations in a cooling tower system.
The unit can be optionally equipped to measure Conductivity, pH, Redox and Temperature
levels in the cooling tower, using these levels the controller can provide a more accurate
dosing and bleeding scheme.
Utilising a multifunction easy to read QVGA LCD the controller displays readings and
provides feedback to the operator on the status of the sensors and the controller’s outputs.
The unit possess and optionally activated RS485 Modbus interface to allow for remote
access, configuration and control of the controller.
Finally the controller also features an SD card interface which enables the user to backup
and restore controller settings, copy settings between controllers, log the controller
operation (optional extra) and to upgrade the controller’s software.
MTD75 Overview

Introduction
- 10 - MTD75 Operation Guide
Introduction
MXD75 Termination Overview

Introduction
MTD75 Operation Guide - 11 -
Introduction
MTD75 Controller Specification
Biocide A Output User defined Biocide A dose duration, triggered
from one of the user selectable sources:
Water Volume (From Water Meter Input)
Timed (Per week/day/hour)
Redox (when < set level)
Division of the Water Meter Input (X input pulses
give one output pulse)
Multiply by the Water Meter Input (One input
pulse gives X output pulses)
External Input (Contact Closure)
User selectable On/Off, Pulsed or Time Proportional
output.
Contact closure and 250VAC* supply terminals
provided (fused to 2A, accessible on the front
panel).
The Biocide A output can be initiated manually
through the menu system to permit testing and
priming of the system.
Biocide B Output User defined Biocide B dose duration, triggered
from one of the user selectable sources:
Water Volume (From Water Meter Input)
Timed (Per week/day/hour)
Division of the Water Meter Input (X input pulses
give one output pulse)
Multiply by the Water Meter Input (One input
pulse gives X output pulses)
Ratio (Biocide A : Biocide B)
External Input (Contact Closure)
User selectable On/Off, Pulsed or Time Proportional
output.
Contact closure and 250VAC* supply terminals
provided (fused to 2A, accessible on the front
panel).
The Biocide B output can be initiated manually
through the menu system to permit testing and
priming of the system.

Introduction
- 12 - MTD75 Operation Guide
Introduction
Bleed Output User defined Bleed duration, triggered from one of
the user selectable sources:
Water Volume (From water Meter Input)
Timed (Per week/day/hour)
Conductivity (when > set level)
External Input (Contact Closure)
On/Off output at 250VAC* fused to 2A (accessible
on the front panel).
The Bleed output can be initiated manually
through the menu system to permit testing of the
Bleed system.
Inhibitor Output User defined Inhibitor dose duration, triggered
from one of the user selectable sources:
Water Input (From water Meter Input)
Timed (Per week/day/hour)
Bleed (After accumulated Bleed Time)
Division of the Water Meter Input (X input pulses
give one output pulse)
Multiply by the Water Meter Input (One input
pulse gives X output pulses)
External Input (Contact Closure)
User selectable On/Off or Pulsed output.
Contact closure and 250VAC* supply terminals
provided (fused to 2A, accessible on the front
panel).
The Inhibitor output can be initiated manually
through the menu system to permit testing and
priming of the system.
pH Control User defined pH Control dose duration, triggered
from one of the user selectable sources:
Water Volume (From Water Meter Input)
Timed (Per week/day/hour)
pH (user selectable < or > level)
Division of the Water Meter Input (X input pulses
give one output pulse)

Introduction
MTD75 Operation Guide - 13 -
Introduction
pH Control Continued Multiply by the Water Meter Input (One input
pulse gives X output pulses)
External Input (Contact Closure)
User selectable On/Off, Pulsed or Time Proportional
output.
Contact closure and 250VAC* supply terminals
provided (fused to 2A, accessible on the front
panel).
The pH Control output can be initiated manually
through the menu system to permit testing and
priming of the system.
* Dependant on input supply levels
Alarm Relay A volt free normally open contact, rated at 5A 30V
DC / 5A 250VAC (non-inductive).
User configurable to energise on:
Power On Input Error
Dose Alarm Timeout Water Meter Timeout
Flow Switch Tank Level Alarm
Any Error
Redox Measurement
Input
(Optional)
Single ended or differential with solution ground.
Up to 100 meters cable.
Separate glass and reference electrode pair.
Combination electrode.
Other manufacturer’s sensors can be
accommodated.
Redox Range of
Measurement
-1999mV to +1999mV
Redox Accuracy ± 3mV
Electrodeless
Conductivity Input
(Optional)
ECS20 or ECS40 Series electrodeless conductivity
sensor. Up to 100 meters LTH 54E.
Electrodeless
Conductivity Input
Range of
Measurement
0 to 9,999 µS/cm
0 to 9,999 ppm
Electrodeless
Conductivity Input
Accuracy
± 1% of range

Introduction
- 14 - MTD75 Operation Guide
Introduction
pH Measurement
Input
(Optional)
Single ended or differential with solution ground.
Up to 100 meters cable.
Separate glass and reference electrode pair.
Combination electrode.
Other manufacturer’s sensors can be
accommodated.
pH Range of
Measurement
0.00 to 14.00 pH
pH Accuracy ± 0.05 pH
Temperature Input Electrodeless
Conductivity Input
PT1000
pH Input PT100 or PT1000
Temperature Range
of Measurement
-50 °C to +160 °C
Temperature
Accuracy
± 0.2 °C (When using a 4 wire PT1000 - ECS)
± 0.2 °C (When using a 3 wire PT1000 – pH/Redox)
Linearity ± 0.1% of range
Repeatability ± 0.1% of range
Operator Adjustment Slope
Offset
Redox NA ± 400mV
Electrodeless
Conductivity
± 10% NA
pH 60-120% 3 to 11pH
Temperature NA ± 50 °C
Current Outputs
(Optional)
4 Current Outputs each selectable 0-20mA or 4-
20mA into 1000 ohms max.
Fully isolated to 2kV.
Expandable up to 5% of any operating range and
offset anywhere in that range.
Current Output
Adjustment
±0.01mA, 3 point 0-4-20 mA for remote monitor
calibration

Introduction
MTD75 Operation Guide - 15 -
Introduction
Digital Inputs 5 contact closures for remote activation of user
defined operations. Can be configured to operate
in either normally open or normally closed modes
Digital Input Functions
1 Water Meter Input
2 Flow Switch Input
3-5 Off-Line, Interlock, Tank Level,
Remote Dose
Modbus RS485
Interface
(Optional)
Supports RTU and ASCII formats
Node Address: 1 to 247
Baud Rates (Bits Per Second) : 300, 600, 1200, 2400,
4800, 9600, 19200, 31250, 38400
Parity Options: Even, Odd, None
SD Card Interface Enables backing up and restoring of controller
configuration, on site upgrading of the controller’s
software and optional Data Logging. SD, SDHC and
SDXC-FAT32 cards supported.
Data Logging
(Optional)
3 User configurable Live Trending Screens of 2
readings
Data Logging All Operating Values to SD Card
User defined Trend and log Interval
User defined Time & Date to View data from the SD
Card onto the unit
Display 3 ¾” QVGA back lit LCD module.
Buttons 5 tactile feedback, micro-switched, silicone rubber.
Alarm LED’s 2 Yellow LED’s located above the main display area
for the controller’s alarm status, lit = active.
Dosing and Control
Relay LED’s
6 red LED’s located above the main display area
indicate the status of the dosing and control relays,
lit = active.
Ambient Operating
Temperature
-20°C to +50°C (-4°F to +122°F) for full specification
EMC S.I. 2016/1091 & 2014/30/EU using BS EN 61326-1:
2013.
Low Voltage Directive S.I. 2016/1101 & 2014/35/EU using BS EN 61010-1:
2010.
Power Supply Universal 80-265V AC or DC, 15W max (fused to 1A,
accessible on the front panel)

Introduction
- 16 - MTD75 Operation Guide
Introduction
Controller Housing UL 94-V0 PC/ABS.
Ingress Protection IP66 to IEC 60529
Weight Maximum 2.7 kilograms (controller only).
Dimensions 331 x 242 x 117 mm (H, W, D) excluding mounting
brackets.

Installation
MTD75 Operation Guide - 17 -
Installation
Installation – Safety & EMC
This chapter describes how to install the controller and how to connect the unit to a power
source and auxiliary equipment.
Although today’s electronic components are very reliable, it should be anticipated in any
system design that a component could fail and it is therefore desirable to make sure a
system will fail safe. This could include the provision of an additional monitoring device,
depending upon the particular application and any consequences of an controller or
sensor failure.
Wiring Installation
The specified performance of the controller is entirely dependent on correct installation.
For this reason, the installer should thoroughly read the following instructions before
attempting to make any electrical connections to the unit.
CAUTION ! : ALWAYS REMOVE THE MAIN POWER FROM THE SYSTEM BEFORE ATTEMPTING
ANY ALTERATIONS TO THE WIRING. ENSURE THAT BOTH POWER INPUT LINES ARE
ISOLATED. MAKE SURE THAT THE POWER CANNOT BE SWITCHED ON BY ACCIDENT WHILST
THE UNIT IS BEING CONNECTED. FOR SAFETY REASONS AN EARTH CONNECTION MUST BE
MADE TO THE EARTH TERMINAL OF THIS CONTROLLER.
LOCAL WIRING AND SAFETY REGULATIONS SHOULD BE STRICTLY ADHERED TO WHEN
INSTALLING THIS UNIT. SHOULD THESE REGULATIONS CONFLICT WITH THE
FOLLOWING INSTRUCTIONS, CONTACT LTH ELECTRONICS OR AN AUTHORISED LOCAL
DISTRIBUTOR FOR ADVICE.
To maintain the specified levels of Electro Magnetic Compatibility (EMC, susceptibility to
and emission of electrical noise, transients and radio frequency signals) it is essential that
the types of cables recommended within these instructions be used. If the installation
instructions are followed carefully and precisely, the controller will achieve and maintain
the levels of EMC protection stated in the specification. Any equipment to which this unit
is connected must also have the same or similar EMC control to prevent undue interference
to the system.
 Terminations at the connectors should have any excess wire cut back so that a
minimal amount of wire is left free to radiate electrical pick-up inside or close to the
controller housing.
 The terminal cover must be correctly re-assembled and securely fastened to maintain
a continuous electro-magnetic shield around the controller.
 N.B. The use of CE marked equipment to build a system does not necessarily mean
that the completed system will comply with the European requirements for EMC.

Installation
- 18 - MTD75 Operation Guide
Installation
Noise suppression
In common with other electronic circuitry, the controller may be affected by high level,
short duration noise spikes arising from electromagnetic interference (EMI) or radio
frequency interference (RFI). To minimise the possibility of such problems occurring, the
following recommendations should be followed when installing the controller in an
environment where such interference could potentially occur.
The following noise generating sources can affect the controller through capacitive or
inductive coupling.
 Relay coils
 Solenoids
 AC power wires, particularly at or above 100V AC
 Current carrying cables
 Thyristor field exciters
 Radio frequency transmissions
 Contactors
 Motor starters
 Business and industrial machines
 Power tools
 High intensity discharge lights
 Silicon control rectifiers that are phase angle fired
The controller is designed with a high degree of noise rejection built in to minimise the
potential for interference from these sources, but it is recommended that you apply the
following wiring practices as an added precaution. Cables transmitting low level signals
should not be routed near contactors, motors, generators, radio transmitters, or wires
carrying large currents.
If noise sources are so severe that the controller’s operation is impaired, or even halted, the
following external modifications should be made, as appropriate:
 Fit arc suppressors across active relay or contactor contacts in the vicinity.
 Run signal cables inside steel tubing as much as is practical.
 Use the internal relays to switch external slave relays or contactors when switching
heavy or reactive loads.
 Fit an in-line mains filter close to the power terminals of the controller.
 In cases of very high background RF and HF noise environments, LTH can supply a
length of proprietary RF suppressing mains cable.