Danfoss ECL Comfort 296 User manual

VI.LV.H1.02 | 1

ECL Comfort 296 / 310 controllers

Modbus networking guide

Service Guide

1.0 Contents

1.0 Contents....................................................................................................................................................................................................................................................1

2.0 Introduction .............................................................................................................................................................................................................................................2

3.0 Conclusion................................................................................................................................................................................................................................................2

4.0 Modbus network denitions .............................................................................................................................................................................................................3

4.1 Multipoint serial bus infrastructure .......................................................................................................................................................................................3

5.0 ECL 296 / 310 Modbus network specication .............................................................................................................................................................................4

6.0 Installation class and surge / lightning protection ....................................................................................................................................................................5

7.0 Annexure A: Modbus network wiring guidelines......................................................................................................................................................................6

7.1 Central heating station................................................................................................................................................................................................................7

7.2 Repeater stations (individual houses with repeater).......................................................................................................................................................8

7.3 Individual houses (without repeater)....................................................................................................................................................................................9

8.0 Annexure B ............................................................................................................................................................................................................................................ 10

8.1 Selection of parts........................................................................................................................................................................................................................10

8.2 Surge protector wiring..............................................................................................................................................................................................................11

8.3 “Modbus” to “mains” separation ...........................................................................................................................................................................................12

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Service guide ECL 296 / ECL 310 Modbus

2.0 Introduction

In smaller district heating networks ligthning can be a challenge for

the connected devices like ECL Comfort 296 / ECL 310 controllers.

If not protected, Modbus interfaces are subject for being burned in

case of lightning.

Based on several market inputs and analysis we identied a need for

information.

This has resulted in the present service guide which includes

recommendations for new installations.

The document is prepared in compliance with www.modbus.org

3.0 Conclusion

1. Each nodes in the“Modbus network” (central heating station,

repeater station or individual house) are highly recommended

to have“surge protector”. It must be selected as per section 6

and installed as described in section 7.

2. Phoenix“PT 1X2+F-BE”(or similar products from another manu-

facturer, as per the surge protection requirement in section 6)

must be used instead of“PT 1X2-BE” in individual house installa-

tions. Refer section 8.

3. Recommendation on Modbus reference common signal con-

nection, shield connection, termination resistor connection may

be referred in section 5, 6, 7 and 8.

VI.LV.H1.02

Service guide ECL 296 / ECL 310 Modbus

4.0 Modbus network denitions

4.1 Multipoint serial bus infrastructure

The below drawing gives a general overview of the serial bus

infrastructure in a Modbus multipoint serial line system.

1) = surge protector 2) = repeater

The following conventions are adopted in the gure above:

1. The interface with the trunk is named ITr (Trunk Interface)

2. The interface between the device (ECL 296 / 310) and the

Passive Tap ( surge protector) is named IDv (Derivation

Interface)

3. The interface between the device (ECL 296 / 310) and the

Active Tap (repeater) is named AUI (Attachment Unit Interface)

4. LT = line termination. Resistor: 120 ohm , 0,5 W or 150 ohm,

0,5 W

A multipoint Modbus serial line bus is made of a principal cable

(the trunk) and possibly some derivation cables.

Line terminations are necessary at each extremity of the trunk

cable for impedance adaptation.

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Service guide ECL 296 / ECL 310 Modbus

5.0 ECL 296 / 310 Modbus network specication

The ECL 296 / 310 Modbus physical layer interface is supported by

the half duplex RS485 interface (A, B, common signal - i.e ref GND).

1. Maximum trunk (Bus) length = 1200 meters for AWG24

(0,51mm diameter) copper (less AWG= bigger diameter: is bet-

ter).

Note: AWG= American wire gauge (AWG).

2. Maximum number of nodes in the network = 32 (including

master node, ECLs and repeater node).

Note: Each repeater node is capable of driving another 32

nodes (including repeater node) of 1200 meter.

I.e. 30 ECLs between two repeater stations (or) 31 ECLs in the

network connected to master node / repeater node. Refer the

gure below.

3. Maximum derivation cable length per node (per ECL) = 1,25

meters (calculated based on 40 m max. derivation cable length

for 32 nodes).

4. Line termination (to ensure the communication quality) = At

each extremity of the trunk cable (150 ohms (or) 120 ohms, 0,5

watts resistor at both ends.

Note: Repeaters are having internal termination resistors which

can be “switched on/ switched OFF” by the user.

If “repeaters” are used in the extremity of the trunk cable, then

switch on the repeater termination (striped block, represented

by 3):

If “repeaters” are used to make a branch from one of the interme-

diate nodes, then do not switch on the“repeater termination”

(unstriped block connected to ITr cable).

1) = surge protector

2) = repeater

3) = line termination (LT)

If the ECL is used in the extremity node of the trunk cable, connect

an external line termination (150 ohm / 120 ohm, 0,5 watts resis-

tor).

VI.LV.H1.02

Service guide ECL 296 / ECL 310 Modbus

5. Grounding arrangements (to improve “general electrical safety”

and “communication quality”) - the common signal (ref. GND)

must be connected directly to the protective ground (PE=

Earth), at the master device (ONE POINT ONLY).

6. Cables shield arrangements (to improve“general electrical

safety”) - One end of each cable’s shield must be connected to

protective ground (PE= Earth). Do not connect both ends of the

shield to PE as it forms an unwanted “group loop”.

6.0 Installation class and surge / lightning protection

“To secure the Modbus electronics (ECL 296 / 310, repeater…) from

surge / lightning in the network, “external protection devices”must

be selected based on the installation class of the network”and rightly

installed in “each site”.

Installation class 4 denitions:

Electrical environment where the interconnections are running as

outdoor cables along with power cables, and cables are used for

both electronic and electrical circuits.

“Surge protector requirements” for “installation class 4”(Modbus

network with ECLs):

Parameter Surge protection requirement PT 3-PB-ST and PT 1X2+F-BE

Class 4 - surge voltage: network:

1,2uS/50uS

4KV 10KV (8uS/20uSec)

Short circuit current (42 ohm impedance) Much higher than 95,2A 10KA. (Seems to be 2 ohm impedance

tester)

Maximum continious voltage - core to

core (A, B and ref. GND in ECL)

> 3,5V and ≤ 7V 5,2Vdc

Output voltage limitation at 1 kV/μs

(core-core) spike

Output voltage limitation at 1 kV/μs

(core-earth) spike

Much less than 1KV ≤ 700V.

Note:“common signal”MUST NOT be

shorted with “PE (protective earth)” in

surge protector base part

≤ 55V

≤ 700V

Output voltage limitation at 1 kV/μs

(core-core) static

Much less than 1KV ≤ 15V

Output voltage limitation at 1 kV/μs

(core-earth) static

Much less than 1KV ≤ 30V

As per the above details, “PT 3-PB-ST and PT 1X2+F-BE” from

Phoenix meet the requirements. Similar products from other sup-

pliers can also be used.

Installation guide:

• Outer eld cables (both IN and OUT eld cable wires) must

be connected to the“unprotected side” of the “external surge

protection device)

• Indoor local cables (both IN and OUT cable wires - which are

well separated from mains supply wires) used to connect com-

mination part of electronics (repeater / ECLs) to the network,

must be connected to the“protected side” of the “external

surge protection device)

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Service guide ECL 296 / ECL 310 Modbus

7.0 Annexure A: Modbus network wiring guidelines

Typical Modbus network consists of:

• Central heating station

• Surge protector

• RS485 (Modbus) repeater

• Modbus to Ethernet converter

• Repeater stations (individual houses with repeater)

• Surge protector

• RS485 repeater

• Individual houses (without repeater)

• Surge protector

Each nodes in the Modbus network (central heating station,

repeater station or individual house) can have “surge protector”.

Top level logical drawing:

# 1 = central heating station

# 2 = individual house W/O repeater

# 3 = repeater station

1) = surge protector

2) = repeater

VI.LV.H1.02

Service guide ECL 296 / ECL 310 Modbus

7.1 Central heating station

1) = surge protector 2) = repeater

Note:

Repeater channels are isolated. Based on the central heating

station architecture, more than one network (like left wing, right

wing) is possible. Single point earthing on common reference

signal (S.Gnd) and shield cable to be maintained (Refer section 5

point 5, 6).

Dot on the intersection lines (S.Gnd, Earth) means that those two

signals are electrically shorted.

Surge suppressor connection should match as in section 8.2.

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Service guide ECL 296 / ECL 310 Modbus

7.2 Repeater stations (individual houses with repeater)

1) = surge protector 2) = repeater

Note:

Normally repeaters’ inputs and outputs are isolated. Check the

resistance between input common reference signal (S.Gnd1) and

output common reference signal (S.Gnd2) using multimeter.

If signals are having >1 Mohm, then connect the output side com-

mon reference signal to earth.

Input cable (coming from central heating station) shield MUST be

oating and output cable shield is connected to earth.

This is to maintain single point earthing in each network, on com-

mon reference signal (S.Gnd) and shield cable (Refer section 5 point

5, 6).

Dot on the intersection lines (S.Gnd, Earth) means that those two

signals are electrically shorted.

Internal termination of repeaters can be switched ON if the con-

nection matches with section 5 point 4.a

Internal termination of repeaters is switched OFF if the connec-

tion matches with section 5 point 4.b

1) = surge protector

2) = repeater

3) = line termination (LT)

VI.LV.H1.02

Service guide ECL 296 / ECL 310 Modbus

7.3 Individual houses (without repeater)

1) = surge protector

As there is no repeater used in this node, there is no isolated channels created. S.Gnd is not connected to earth (PE).

Input cable (coming from central heating station) shield MUST be oating and output cable shield is connected to earth. Or the input and

output shield continuity is maintained and it is not connected to earth (As shown above).

This is to maintain single point earthing in each network, on common reference signal (S.Gnd) and shield cable (Refer section 5 point 5,

6).

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Service guide ECL 296 / ECL 310 Modbus

8.0 Annexure B

8.1 Selection of parts

There are many prebuilt connection options available on the market

on“surge protector base parts”, which lead to the unwanted ground

looping and hence low quality / loss of communication network

(section 5 point 5).

These parts look alike in part numbering system and in component

outlook. So care must be taken to select the right parts. Refer the

below for example:

Possibilities for grounding the base element:

• PT 1x2-BE - signal ground (pin 9/10) is shorted to PE (protective

earth) (3/4)

• PT 1x2+F-BE - spark gap between signal ground (pin 9/10) to

PE (protective earth) (3/4)

PT 1x2-BE

PT 1X2 +F-BE

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