Vaisala MHT410 User Manual

M211737EN-H

User Guide

Vaisala Moisture, Hydrogen and Temperature

Transmitter for Transformer Oil

MHT410

PUBLISHED BY

Vaisala Oyj

Vanha Nurmijärventie 21, FI-01670 Vantaa, Finland P.O. Box 26, FI-00421 Helsinki, Finland

[phone]

Visit our Internet pages at www.vaisala.com.

© Vaisala 2021

No part of this document may be reproduced, published or publicly displayed in any form or by any means, electronic or mechanical (including photocopying), nor may its contents be modified, translated, adapted, sold or disclosed to a third party without prior written permission of the copyright holder. Translated documents and translated portions of multilingual documents are based on the original English versions. In ambiguous cases, the English versions are applicable, not the translations.

The contents of this document are subject to change without prior notice.

Local rules and regulations may vary and they shall take precedence over the information contained in this document. Vaisala makes no representations on this document’s compliance with the local

rules and regulations applicable at any given time, and hereby disclaims any and all responsibilities related thereto.

This document does not create any legally binding obligations for Vaisala towards customers or end users. All legally binding obligations and agreements are included exclusively in the applicable supply contract or the General Conditions of Sale and General Conditions of Service of Vaisala.

This product contains software developed by Vaisala or third parties. Use of the software is governed by license terms and conditions included in the applicable supply contract or, in the absence of separate license terms and conditions, by the General License Conditions of Vaisala Group.

		Table of contents
Table of contents
1.	Safety...................................................................................................................	7
1.1	ESD protection..................................................................................................	8
2.	About this document.....................................................................................	9
2.1	Documentation conventions..........................................................................	10
2.2	Regulatory statements...................................................................................	10
2.2.1	FCC Part 15 compliance statement........................................................	10
2.3	Trademarks........................................................................................................	11
3.	Product overview...........................................................................................	12
3.1	Main features....................................................................................................	12
3.2	Product parts and package contents............................................................	13
3.3	Measurement parameters and units..............................................................	15
3.4	Oil types............................................................................................................	16
3.4.1	Oil type information in order code.........................................................	16
3.4.2	Oil-specific coefficients for ppmw moisture measurement................	16
3.5	Data logging.....................................................................................................	17
3.6	Status LEDs......................................................................................................	17
4.	Installation........................................................................................................	19
4.1	Planning the installation.................................................................................	19
4.1.1	Recommended installation locations...................................................	20
4.2	Mechanical installation....................................................................................	21
4.3	Electrical installation......................................................................................	28
4.4	Loop-powered display....................................................................................	31
4.4.1	Wiring the loop-powered display..........................................................	32
4.5	Checklist after installation.............................................................................	33
4.6	Oil fittings check after installation...............................................................	34
4.7	Removing the transmitter.............................................................................	34
4.8	Re-installing the transmitter in new location..............................................	35
5.	Analog output................................................................................................	37
5.1	Analog output overrange behavior..............................................................	37
6.	Modbus.............................................................................................................	39
6.1	Overview of Modbus protocol support........................................................	39
7.	Vaisala Industrial Protocol........................................................................	40
7.1	Connecting to MHT410 via service port........................................................	41
7.1.1	Installing driver for the USB service cable............................................	41
7.1.2	Connecting USB service cable...............................................................	42
7.1.3	Configuring terminal application settings...........................................	42
7.2	Serial commands summary..........................................................................	44
7.3	Device information and status commands.................................................	46

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7.4	Serial line output and communication commands.....................................	52
7.4.1	Measurement output commands..........................................................	52
7.4.2	Measurement output format commands.............................................	56
7.4.3	Serial line communication commands..................................................	59
7.5	Analog output commands............................................................................	63
7.6	Calibration and adjustment commands.......................................................	67
7.7	Other commands............................................................................................	68
8.	DNP3 protocol.................................................................................................	71
8.1	Taking DNP3 protocol into use......................................................................	71
9.	Vaisala MI70 Handheld Indicator...........................................................	73
9.1	MI70 indicator overview................................................................................	73
9.1.1	MI70 indicator parts................................................................................	73
9.1.2	Basic display.............................................................................................	74
9.1.3	Graphical display.....................................................................................	74
9.1.4	Main menu................................................................................................	75
9.2	Installing and recharging MI70 batteries.....................................................	75
9.3	Connecting MI70 to service port..................................................................	76
9.4	Holding and saving the display.....................................................................	76
9.5	Recording data................................................................................................	77
9.5.1	Starting and stopping the recording.....................................................	77
9.5.2	Viewing recorded data...........................................................................	78
9.5.3	Clearing data memory............................................................................	78
9.6	Comparing readings with MM70 probe.......................................................	78
9.7	Changing the rechargeable battery pack....................................................	79
10.	Vaisala Indigo520 Transmitter.................................................................	81
10.1	Taking Indigo520 Modbus settings into use in MHT410.............................	81
10.2	Cabling and cable gland................................................................................	82
10.3	Indigo520 and MHT410 wiring diagram......................................................	83
10.4	MHT410 status messages shown in Indigo520...........................................	84
10.5	Settings in Indigo520.....................................................................................	84
11.	Calibration and adjustment......................................................................	85
11.1	H2 calibration and adjustment......................................................................	85
11.1.1	Taking DGA sample and saving current H2 reading............................	85
11.1.2	Entering DGA H2 reading to transmitter..............................................	87
11.1.3	Clearing H2 calibration and adjustment...............................................	88
11.2	RS & T calibration and adjustment...............................................................	89
12.	Troubleshooting.............................................................................................	91
12.1	Error states.......................................................................................................	91
12.2	Changing bleed screw...................................................................................	92
13.	Technical data................................................................................................	93
13.1	MHT410 specifications...................................................................................	93
13.2	Spare parts and accessories..........................................................................	97

2

		Table of contents
13.3	Dimensions......................................................................................................	98
13.4	Wiring diagrams.............................................................................................	99
13.5	Recycling.........................................................................................................	101
Appendix A: Operating principle..............................................................		104
A.1	Method used for measuring moisture in oil...............................................	105
A.2	Transformer oil..............................................................................................	105
Appendix B: Modbus reference.................................................................		107
B.1	Default Modbus communication settings..................................................	107
B.2	Function codes..............................................................................................	107
B.3	Data encoding...............................................................................................	107
B.3.1	32-bit floating point or 32-bit integer format....................................	108
B.3.2	16-bit integer format.............................................................................	108
B.4	Register map.................................................................................................	108
B.5	Modbus registers..........................................................................................	109
B.5.1	Measurement data registers................................................................	109
B.5.2	Status registers........................................................................................	111
B.6	Device identification objects........................................................................	112
B.7	Exception responses......................................................................................	112
Appendix C: Moisture ppmw calculation for transformer oils.............		113
C.1	Calculation model with average coefficients..............................................	113
C.2	Calculation model with oil-specific coefficients.........................................	113
Maintenance and calibration services........................................................		115
Technical support...........................................................................................		115
Warranty...........................................................................................................		115

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List of figures

Figure	1	MHT410 order code example (first digit 1 = mineral oil)........................	16
Figure	2	Recommended installation locations.........................................................	20
Figure	3	Loop-powered display 242003....................................................................	32
Figure	4	Analog output overrange behavior............................................................	38
Figure	5	Analog output overrange behavior............................................................	64
Figure	6	MI70 indicator parts........................................................................................	73
Figure	7	MI70 basic display............................................................................................	74
Figure	8	Example of MI70 display with MHT410 in port I and
		MM70 probe in port II. Shown parameters: aw (I), aw (II), aw........	79
Figure	9	Wiring between Indigo520 and MHT410 screw terminals....................	83
Figure 10		MHT410 transmitter dimensions..................................................................	98
Figure	11	Wiring Option 1: Wiring with four power supplies.
		Separate loop-powering and galvanic isolation for
		analog outputs. In transmitters ordered with Vaisala
		cable CBL210392-5M, the cable is pre-wired according
		to this option.....................................................................................................	99
Figure 12		Wiring Option 2: Wiring with two power supplies.
		Common loop-powering and galvanic isolation for
		analog outputs...............................................................................................	100
Figure 13		Wiring Option 3: Wiring with one power supply. Non-
		isolated configuration for analog outputs sharing
		transmitter power supply............................................................................	100
Figure 14		Wiring Option 4: Wiring with one power supply.
		Alternative wiring to option 3, providing reduced
		current loop area for analog outputs........................................................	101
Figure 15		Materials for recycling...................................................................................	102
Figure 16		Measuring hydrogen and moisture in oil with MHT410.......................	104
Figure 17		Water solubility of transformer oils versus temperature.
		The margins show the range of variation of water
		solubility found in mineral oils....................................................................	106

4

List of tables

List of tables

Table	1	Document versions (English)...........................................................................	9
Table	2	Related manuals..................................................................................................	9
Table	3	Analog output values in di‡erent transmitter statuses..........................	37
Table	4	Default serial interface settings....................................................................	40
Table	5	Service port serial interface settings...........................................................	43
Table	6	Serial commands..............................................................................................	44
Table	7	? command.........................................................................................................	46
Table	8	alarm command................................................................................................	47
Table	9	errlog command...............................................................................................	48
Table 10		errs command....................................................................................................	49
Table	11	help command...................................................................................................	50
Table	12	system command.............................................................................................	50
Table	13	time command....................................................................................................	51
Table 14		vers command....................................................................................................	51
Table	15	intv command....................................................................................................	52
Table 16		log command.....................................................................................................	52
Table	17	r command..........................................................................................................	55
Table 18		send command..................................................................................................	55
Table 19		form command..................................................................................................	56
Table 20		Output parameters for form command......................................................	57
Table	21	Modifiers for form command.........................................................................	58
Table 22		unit command....................................................................................................	59
Table 23		addr command..................................................................................................	59
Table 24		close command.................................................................................................	60
Table 25		open command.................................................................................................	60
Table 26		sdelay command..............................................................................................	60
Table 27		seri command.....................................................................................................	61
Table 28		smode command..............................................................................................	62
Table 29		aerr command...................................................................................................	63
Table 30		aover command.................................................................................................	63
Table	31	asel command...................................................................................................	64
Table 32		atest command..................................................................................................	66
Table 33		cdate command.................................................................................................	67
Table 34		ctext command..................................................................................................	67
Table 35		h2 da and h2 db commands..........................................................................	68
Table 36		h2 x command...................................................................................................	68
Table 37		dnp3 addr command.......................................................................................	68
Table 38		filt command......................................................................................................	69
Table 39		frestore command............................................................................................	69
Table 40		reset command..................................................................................................	70
Table 41		oil command......................................................................................................	70
Table 42		h2 is command..................................................................................................	70
Table 43		Default communication settings....................................................................	71
Table 44		MHT410 communication settings for Indigo520.......................................	81
Table 45		MHT410 status messages shown in Indigo520.........................................	84

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MHT410 User Guide		M211737EN-H
Table 46	Possible error messages via Vaisala Industrial Protocol.........................	91
Table 47	MHT410 measurement performance...........................................................	93
Table 48	MHT410 operating environment...................................................................	94
Table 49	MHT410 inputs and outputs...........................................................................	94
Table 50	MHT410 mechanical specifications..............................................................	95
Table 51	MHT410 compliance.........................................................................................	96
Table 52	Display with relays (external option)..........................................................	96
Table 53	MHT410 spare parts and accessories..........................................................	97
Table 54	Vaisala cable CBL210392-5M wire colors (when pre-wired)................	99
Table 55	Materials for recycling....................................................................................	103
Table 56	Optimal sensor positions..............................................................................	104
Table 57	Default Modbus RTU communication settings.......................................	107
Table 58	Supported Modbus function codes............................................................	107
Table 59	Interpretation of 16-bit signed integer values.........................................	108
Table 60	Modbus register blocks.................................................................................	109
Table 61	Modbus measurement data registers (read-only).................................	109
Table 62	Modbus status registers (read-only)............................................................	111
Table 63	Modbus device status bits..............................................................................	111
Table 64	Device identification objects.........................................................................	112
Table 65	Modbus exception responses........................................................................	112

6

Chapter 1 – Safety

1. Safety

Vaisala Moisture, Hydrogen and Temperature Transmitter MHT410 for Transformer Oil delivered to you has been tested for safety and approved as shipped from the factory. Note the following precautions:

CAUTION! Read the Quick Guide (including installation instructions) carefully before installing the product.

WARNING! Ground the product and verify installation grounding periodically to minimize shock hazard.

DANGER! Severe risk of death and of damage to transformer:

Pay attention to transmitter installation depth and possible energized parts inside the power transformer to minimize electric shock hazard and equipment damage.

CAUTION! Do not modify the unit or use it in ways not described in the documentation. Improper modification or use may lead to safety hazards, equipment damage, failure to perform according to specification, or decreased equipment lifetime.

CAUTION! Do not try to close the ball valve when the transmitter is fully installed. The probe body goes through the valve into the oil flow, and trying to close the valve will damage the probe body and/or the valve.

If you must close the ball valve while the transmitter is on the valve, first open the small tightening nut and pull the probe body out as far as possible. Then close the valve.

CAUTION! To avoid damage to the installation valve of the transformer, do not step on the transmitter when the transmitter is installed.

CAUTION! Follow the safety regulations related to the application and installation site.

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MHT410 User Guide

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1.1 ESD protection

Electrostatic Discharge (ESD) can damage electronic circuits. Vaisala products are adequately protected against ESD for their intended use. However, it is possible to damage the product by delivering electrostatic discharges when touching, removing, or inserting any objects in the equipment housing.

To avoid delivering high static voltages to the product:

•Handle ESD sensitive components on a properly grounded and protected ESD workbench or by grounding yourself to the equipment chassis with a wrist strap and a resistive connection cord.

•If you are unable to take either precaution, touch a conductive part of the equipment chassis with your other hand before touching ESD sensitive components.

•Hold component boards by the edges and avoid touching component contacts.

8

Chapter 2 – About this document

2. About this document

Table 1 Document versions (English)

	Document code	Date		Description
	M211737EN-H	March 2021		This document.
				New chapters:
				•	Vaisala Indigo520 Transmitter (page 81)
				•	Clearing H2 calibration and adjustment (page 88)
				Updated content:
				•	Added silicone oil to the list of supported oils
				• Serial commands summary (page 44)
				• Calibration and adjustment commands (page 67)
				•	Error states (page 91)
				•	MHT410 specifications (page 93)
				•	Status registers (page 111)
	M211737EN-G	November 2018		Previous version. Added natural and synthetic ester oil
				support information and instructions on checking the oil
				type set at the factory from the product label. Added
				instructions on configuring oil-specific moisture in oil
				calculation coefficients. Clarified the information on the
				temperature range for accurate measurement in hydrogen
				and temperature accuracy specifications and added
				sensor head temperature tolerance specification. Added
				instructions on using a safety pin with a warning label to
				lock the valve handle in open position after installation.
	M211737EN-F	May 2018		Updated installation instructions regarding PTFE tape and
				installation depth. Added DNP3 protocol information.
				Added clarification about using the RS-485 line of the
				screw terminals with Modbus or Vaisala Industrial Protocol.
				Added maximum power consumption specification.
				Added new parameter options for analog outputs: daily,
				weekly, and monthly ROC and 24-hour average for H2 and
				H2O. Added clarification about the calculation of rate of
				change (ROC) readings. Changed unit "ppm" to "ppmv"
				for H2 and to "ppmw" for H2O.
	Table 2 Related manuals
	Document code		Description
	M211736EN		Vaisala MHT410 Quick Guide
	M212287EN		Vaisala Indigo520 User Guide
	M211784EN		Loop-Powered Display 242003 for MHT410 Technical Note

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MHT410 User Guide

M211737EN-H

2.1 Documentation conventions

WARNING! Warning alerts you to a serious hazard. If you do not read and follow instructions carefully at this point, there is a risk of injury or even death.

CAUTION! Caution warns you of a potential hazard. If you do not read and follow instructions carefully at this point, the product could be damaged or important data could be lost.

Note highlights important information on using the product.

Tip gives information for using the product more efficiently.

Lists tools needed to perform the task.

Indicates that you need to take some notes during the task.

2.2 Regulatory statements

2.2.1 FCC Part 15 compliance statement

This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at his own expense.

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Chapter 2 – About this document

CAUTION! Changes or modifications to this equipment not expressly approved by the party responsible for compliance could void the user's authority to operate the equipment.

This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and

(2) this device must accept any interference received, including interference that may cause undesired operation.

2.3 Trademarks

HUMICAPâ is a registered trademark of Vaisala Oyj.

Modbusâ is a registered trademark of Schneider Automation Inc.

All other product or company names that may be mentioned in this publication are trade names, trademarks, or registered trademarks of their respective owners.

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MHT410 User Guide

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3. Product overview

Vaisala Moisture, Hydrogen and Temperature Transmitter MHT410 for Transformer Oil is designed for online monitoring of insulating oil in power transformers. The transmitter provides an accurate real-time measurement result of moisture, hydrogen and temperature measured in oil, enabling reliable conclusions on the transformer's condition without delay.

The transmitter provides digital and analog outputs of all the measured parameters.

3.1 Main features

•Reliable online measurement of transformer oil for the following parameters:

•Moisture: relative saturation (%RS), water activity, and water content (ppmw)

•Hydrogen concentration (ppmv in oil)

•Temperature (°C and °F)

•Compatible with mineral oils, natural ester oils, synthetic ester oils, and silicone oils

•No need to take oil samples for measurement

•Installable and retro-fittable on a ball valve (ball valve thread: female 1.5" NPT)

•Low maintenance requirements due to excellent long term stability

•Outputs

•Digital: Modbus, DNP3, and Vaisala industrial protocol over RS-485

•Analog: three channels with scalable current output

•Status indication LEDs in the front panel

•Built-in data logging

•USB connectivity for service connections using an optional USB M8 cable

•Display options:

•Loop-powered display for continuous use

•MI70 handheld meter for temporary use

•Compatible with Vaisala Indigo500 series transmitters

More information

Oil types (page 16)

Status LEDs (page 17)

Data logging (page 17)

Connecting to MHT410 via service port (page 41)

Loop-powered display (page 31)

Vaisala MI70 Handheld Indicator (page 73)

Technical data (page 93)

12

Chapter 3 – Product overview

3.2 Product parts and package contents

1

2

3

4

5

6

7

8

9

10

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MHT410 User Guide

M211737EN-H

5 mm

+

3 mm

	11	12	13	14
No.		Item
1	=	Electronics housing.
		The front cover is additionally connected to the housing with a grounding wire.

2= Weather shield

3= Bleed screw

4= Probe body

5= Small tightening nut, used to adjust and fix the depth of the transmitter in the valve. You can move the tightening nut and the mounting nut along the probe body.

6= Mounting nut, used to fasten the transmitter in the ball valve.

You can move the tightening nut and the mounting nut along the probe body.

7= Hydrogen sensor

8= Moisture and temperature sensors under the filter

9= Product label

10= Lead-throughs (2 pcs) with a minimum of one cable gland (size M20x1.5) or conduit fitting.

Unused lead-throughs are plugged.

Installation Kit:

11= PTFE tape roll

12= Allen keys (3 mm and 5 mm)

13= Extra bleed screw and sealing ring

14= Extra terminal blocks (4 x 4 screw terminals)

More information

Dimensions (page 98)

14

Chapter 3 – Product overview

3.3 Measurement parameters and units

Parameter	Abbreviation	Unit
H2 concentration in oil
• 1 h average	H2	ppmv
• 24 h average
Rate of change of H2 concentration
In a day	Daily ROC	ppmv/day
In a week	Weekly ROC	ppmv/week
In a month	Monthly ROC	ppmv/month
Moisture in oil
Relative saturation	RS	%RS
Water activity	aw (=RS/100)	(no unit)
H2O concentration in oil	H2O	ppmw
(current)
H2O concentration in oil (24 h	H2O	ppmw
average)
Rate of change of H2O concentration in oil
In a day	Daily ROC	ppmw/day
In a week	Weekly ROC	ppmw/week
In a month	Monthly ROC	ppmw/month
Temperature
Oil temperature	T	°C or °F

The rate of change (ROC) for H2 and for H2O shows the di‡erence in ppm between the latest

24-hour average and the 24-hour average 1 day ago (daily ROC), 7 days ago (weekly ROC), or 30 days ago (monthly ROC). ROC readings are updated every 12 hours.

After starting up or resetting the transmitter, ROC readings are available as follows:

•Daily ROC: after 2 days

•Weekly ROC: after 8 days

•Monthly ROC: after 31 days

Before the ROC readings are available, the ROC measurement registers in digital outputs contain a "NaN" value, and the ROC analog outputs are set to 3.0 mA (= measurement not ready).

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MHT410 User Guide

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3.4 Oil types

MHT410 is compatible with the following oil types:

•Mineral oils

•Natural ester oils

•Synthetic ester oils

•Silicone oil

CAUTION! Never use MHT410 with any other oil type than the one configured for the unit at the factory. Using the transmitter with a di‡erent oil type requires sending the unit to Vaisala for reconfiguration.

The oil type that MHT410 measures (mineral oils, natural ester oils, synthetic ester oils, or silicone oil) is selected when ordering the transmitter. For instructions on checking the oil type set at the factory from the product label, see Oil type information in order code (page 16).

3.4.1 Oil type information in order code

MHT410 has been configured for a specific oil type based on the selection made when ordering the transmitter, and must not be used with other oil types. The oil type configuration set at the factory can be checked from the first digit (1, 2, 3, or 4) of the order code in the MHT410 product label.

1

MHT410 1 B E G 0

Figure 1 MHT410 order code example (first digit 1 = mineral oil)

1First digit of the order code. The oil type configuration is shown in the first digit as 1, 2, 3, or 4:

•1 = Mineral oils (shown)

•2 = Natural ester oils

•3 = Synthetic ester oils

•4 = Silicone oils

3.4.2 Oil-specific coefficients for ppmw moisture measurement

MHT410 can be ordered with ppmw moisture output (average mass concentration of water in oil). The calculation model that MHT410 uses for ppmw measurement is based on the average

water solubility behavior of transformer oils (see Calculation model with average coefficients (page 113)). If additional accuracy is required, you can configure oil-specific coefficients into MHT410 using Vaisala Industrial Protocol serial commands (see Table 41 (page 70)), or contact Vaisala about setting the coefficients.

16

Chapter 3 – Product overview

More information

Moisture ppmw calculation for transformer oils (page 113)

Other commands (page 68)

3.5 Data logging

The transmitter automatically saves the measurement readings and other events in a log every 12 hours (configurable interval). The log can contain approximately 32000 entries.

The following events are logged:

•Hydrogen (ppmv) reading as 1 h average or 24 h average

•Moisture in oil (%RS and ppmw) and temperature (°C) readings as instant values or 24 h averages

•Power outages

•Short power outages that don't turn o‡ transmitter power (flagged "UPS")

•Long power outages that turn o‡ transmitter power (flagged first as "UPS" and then as "Reset")

•Manual resets (flagged as "Reset")

•Uptime and total operating time

•Occasions of exceeding hydrogen alarm level (optional)

To view the log and change the logging settings, use Vaisala Industrial Protocol.

You can save the log as a file from PuTTY by configuring the following settings in PuTTY before opening the connection:

In the Session > Logging view:

•Session logging: Select "Printable output".

•Log file name: Type a name for the log file (use the file extension .txt) and browse to the save location.

To prevent the log from getting very long, consider saving and then clearing the log every few years.

More information

Vaisala Industrial Protocol (page 40)

Measurement output commands (page 52)

3.6 Status LEDs

When the transmitter is ON, one of the LEDs is always illuminated (solid or blinking). If no LED is illuminated, the transmitter is OFF.

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MHT410 User Guide			M211737EN-H
LED color and text			Description
Green, blinking:			Transmitter is preparing H2 measurement after start-up or reset.
		Wait...
Green, solid:			Transmitter is measuring.
		OK
Red, blinking:			H2 concentration is above the alarm limit.
		Alarm
Red, solid:			Transmitter is in error state.
		Error

18

Chapter 4 – Installation

4. Installation

Before you install the transmitter:

•Go through the check list in section Planning the installation (page 19).

•Read this whole guide carefully.

CAUTION! Make sure the oil type of the transformer matches the oil type configured for MHT410. See Oil type information in order code (page 16).

The installation instructions in this section are the same as in the MHT410 Quick Guide.

4.1 Planning the installation

•Choose the installation location on the transformer (see Recommended installation locations (page 20)).

CAUTION! Make sure the installation valve and threads are appropriate from the valve specifications. The correct thread of the valve is female 1.5" NPT. Do not install the transmitter in a valve with a di‡erent thread. For example, the R thread is incorrect. If you use a di‡erent thread than female 1.5" NPT, your equipment may be damaged and the connection is not leak tight. If you are not sure which thread your installation valve has, verify the thread with a 1.5" NPT thread gauge.

•Make sure the oil type of the transformer matches the one configured for MHT410 (mineral oil, natural ester oil, synthetic ester oil, or silicone oil).

•Make sure you have all the required tools for installing the transmitter. The required tools are presented in the installation instructions.

•Choose the output signals: analog and/or digital.

•Choose the electrical wiring option. If the transmitter was ordered with the Vaisala cable CBL210392-5M, the cable is already pre-connected to the transmitter according to Wiring Option 1.

More information

Wiring diagrams (page 99)

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M211737EN-H

4.1.1 Recommended installation locations

The probe must always be installed in a valve. The correct thread of the valve is female 1.5" NPT. Do not install the transmitter in a valve with a di‡erent thread. For example, the R thread is incorrect. If you use a di‡erent thread than female 1.5" NPT, your equipment may be damaged and the connection is not leak tight.

Figure 2 Recommended installation locations

	Recommendation	Description
		This is the best location for the transmitter.
		The oil is measured in flow, which makes the oil sample
	Recommended:	representative and instant. This is essential especially for correct
	Straight section in the	oil moisture measurement.
		Compared to the radiator inlet pipe, oil in the outlet pipe is
	radiator’s outlet pipe.
		cooled, preventing unnecessary heating of the sensors and the
		transmitter.

20

		Chapter 4 – Installation
Recommendation		Description
		An instrumentation valve is recommended. This is a typical valve
		that is meant for oil analysis.
Possible alternative:		Moisture response time is moderate depending on the oil volume
Wall of the oil tank, high		and transmitter installation.
enough from the bottom to
		DANGER! Severe risk of death and of
enable proper oil movement.
		damage to transformer:
		Pay attention to transmitter installation depth
		and possible energized parts inside the power
		transformer to minimize electric shock hazard
		and equipment damage.
		The moisture response can be poor due to static oil flow. There is
		also a risk of separated water (leading to wrong results) and oil
Not recommended:		sludge (risk of sensor contamination and clogged filters).

Drain valve of the oil tank.

4.2 Mechanical installation

CAUTION! Before you install the transmitter:

• Make sure there is no negative pressure in the transformer. If there is negative pressure when you open the bleed screw during installation, air will flow into the transformer oil tank.

•Do not open the ball valve on the transformer until you are instructed to do so in this guide.

•Make sure the bleed screw on the mounting nut is closed.

•2 wrenches (50 mm and 36 mm)

•Allen key (3 mm, provided)

•PTFE tape (provided)

•Gloves

•Bucket and cloth

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MHT410 User Guide

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1. Remove the protective cap with sorbent packet from the mounting nut. In case of rain, do not let any water fall on the filter.

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Chapter 4 – Installation

2.Apply PTFE tape tightly on the mounting nut threads.

a.Before you start, clean the threads with a cloth.

b.To make sure you wrap the tape in the correct direction, hold the transmitter so that the product label is facing you and the mounting nut points away from you.

c.Start wrapping counter-clockwise from the second thread on the tip of the mounting nut.

d.Wrap each round very tightly about half way on top of the previous round so that the tape overlaps. Stretch the tape for optimal tightness. Apply a couple of rounds of tape.

PTFE

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MHT410 User Guide

M211737EN-H

3.Make sure the bleed screw is closed. Fasten the mounting nut on the ball valve to fingertightness with your hand. Leave the bleed screw directly on top of the nut.

If you cannot position the bleed screw on top of the mounting nut by tightening just with your hand, you can use a wrench (50 mm) to turn the mounting nut a maximum of a ½ turn.

CAUTION! If you need to loosen the mounting nut after you have fastened it on the valve, you must remove the transmitter from the valve, remove the PTFE tape, and start again from step 2 with new PTFE tape.

4. With a 3 mm Allen key, loosen the bleed screw. Place a bucket under the mounting nut.

OPEN max. 3 × 360°

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Chapter 4 – Installation

5. Start opening the valve very carefully to let air out through the bleed screw.

CAUTION! If you open the valve too quickly, the air inside the mounting nut will flow into the transformer instead.

When oil flows out, close the bleed screw. Clean the area with a cloth and open the ball valve fully.

SLOW	CLOSE

6.Continue tightening the mounting nut with a wrench. Be very careful not to over-tighten the connection. Approximately 5 ... 8 mm of the mounting nut threads remain outside the valve.

If the connection leaks after you have tightened the mounting nut, check the thread type of the installation valve.

•If the valve thread is other than female 1.5" NPT (incorrect), do not install the transmitter in that valve.

•If the valve thread is female 1.5" NPT (correct), close the valve, open the mounting nut and remove the transmitter, remove old PTFE tape and apply a thicker layer of new PTFE tape. Then continue from step 3.

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MHT410 User Guide

M211737EN-H

7.Push the probe to the correct depth. The correct depth depends on where the installation valve is located: radiator pipe or transformer wall.

•Valve in radiator pipe: Install the probe so that the back of the weather shield is 180 ... 190 mm from the pipe surface.

180 ... 190 mm

•Valve in transformer wall: Install the probe so that the back of the weather shield is 200 mm from the transformer wall.

200 mm

DANGER! Severe risk of death and of damage to transformer:

Pay attention to transmitter installation depth and possible energized parts inside the power transformer to minimize electric shock hazard and equipment damage.

When the probe is in the correct depth, turn the transmitter 90 degrees two to three times to remove any air bubbles from the sensor area.

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Chapter 4 – Installation

8. Tighten the small tightening nut with a wrench until the probe is securely fastened.

9.Press the caution sticker on the MHT410 weather shield or other visible location nearby, and lock the handle of the valve in the open position with the safety pin.

DO NOT CLOSE VALVE

WHEN TRANSMITTER

IS INSTALLED!

HOW TO CLOSE VALVE:

1	2

PULL INSTRUMENT OUT BEFORE CLOSING VALVE

3

1 2

3

More information

Dimensions (page 98)

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MHT410 User Guide

M211737EN-H

4.3 Electrical installation

When connecting MHT410 to the Indigo520 transmitter, see also Indigo520 and MHT410 wiring diagram (page 83).

If MHT410 was ordered with the Vaisala cable CBL210392-5M, the cable is already pre-connected to MHT410 according to Wiring Option 1.

If cable is not pre-wired:

• Allen key (5 mm, provided)

•2 medium wrenches (24 mm)

•Flat head screwdriver (2.5 mm)

•Wire-cutting pliers

•Suitable cable. You can order the following cables from Vaisala:

•5 m shielded PUR cable (order code: CBL210392-5MSP)

•10 m shielded PUR cable (order code: CBL210392-10MSP)

1. Open the electronics housing with a 5 mm Allen key to access the screw terminals.

SERIAL
Device COMMANDS			SERVICE
	information	?
List of errors		ERRS	PORT
List of	commands		19200 b/s, 8, n, 1
		HELP
See manual for further
commands.
www.vaisala.
	com/MHT410

RS-485 TERMINATION

RS-485 Modbus default address: 240

NALOG
	CH2
3	+
	4

OUTPUTS
CH2		CH1
–		+
5	6	7

CH1

– 8

OFF ON

9

SHLD 10

RSGND D
	–
11	12

+

D 13

SHLD 14

POWER
Vs	Vs
+	–
15	16

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