Danfoss ECL Comfort 296, ECL Comfort 310 Service guide
Service Guide
ECL Comfort 296 / 310 controllers
Modbus networking guide
1.0 Contents
1.0 Contents... ... ..............................................................................................................................................................................................................................................1
2.0 Introduction ............................................................................................................................................................................................................................................. 2
3.0 Conclusion .... ............................................................................................................................................................................................................................................ 2
4.0 Modbus network definitions ............................................................................................................................................................................................................. 3
4.1 Multipoint serial bus infrastructure .......................................................................................................................................................................................3
5.0 ECL 296 / 310 Modbus network specification .............................................................................................................................................................................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 Modbus 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.
This has resulted in the present service guide which includes
recommendations for new installations.
The document is prepared in compliance with www.modbus.org
This document is handling protection of the Modbus network.
Please be aware of the protection of the main site (230Vac) i.e. by
installing a Phoenix PLT-SEC-T3-230-FM.
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. A surge protection with a spark gab between Signal GND and
Protective Ground (PE) is required in the individual house installation.
3. Recommendation on Modbus reference common signal connection, shield connection, termination resistor connection may
be referred in section 5, 6, 7 and 8.
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4.0 Modbus network definitions
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 figure 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 up to 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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5.0 ECL 296 / 310 Modbus network specification
The ECL 296 / 310 Modbus physical layer interface is supported by
the half duplex RS485 interface (A, B, Signal Ground (S. Gnd.)).
1. Maximum trunk (ITr) length = 1200 meters for AWG24 (0,51mm
diameter) copper (less AWG= bigger diameter: is better).
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
figure 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.
a.
If “repeaters” are used in the extremity of the trunk cable, then
switch on the repeater termination (striped block, represented
by 3):
b.
If “repeaters” are used to make a branch from one of the intermediate nodes, then do not switch on the “repeater termination”
(unstriped block connected to ITr cable).
1) = surge protector
2) = repeater
3) = line termination (LT)
c.
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 resistor).
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5. Grounding arrangements (to improve “general electrical safety”
and “communication quality”) - S. 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 definitions:
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”, IEC 610004-5, (Modbus network with ECLs):
Parameter Surge protection requirement Recommended protection,
PT 3-PB-ST and PT 1X2+F-BE
Class 4 - surge voltage: network:
1,2µs / 50µs
Short circuit current (42 ohm impedance) Higher than 95,2A 10kA
Maximum continious voltage - core to
core (A, B and S. Gnd. in ECL)
Output voltage limitation at 1 kV/μs
(core-core) spike
Output voltage limitation at 1 kV/μs
(core-earth) spike
Output voltage limitation at 1 kV/μs
(core-core) static
Output voltage limitation at 1 kV/μs
(core-earth) static
As per the above details, “PT 3-PB-ST and PT 1X2+F-BE” from
Phoenix meet the requirements. Similar products from other suppliers can also be used.
4kV 10kV 1,2µs / 50µs
5kA 8µs / 20µs
> 3,5V and ≤ 7V 5,2Vdc
Less than 1KV ≤ 55V
≤ 700V. Note: “S. Gnd.” MUST NOT be
shorted with “PE (protective earth)” in
surge protector base part.
Much less than 1KV ≤ 15V
Much less than 1KV ≤ 30V
≤ 700V
Installation guide:
• Outer field cables (both IN and OUT field cable wires), ITr / AUI,
must be connected to the “unprotected side” of the “external
surge protection device)
• The cables (IDv - which are well separated from mains supply
wires) must be connected to the “protected side” of the “external surge protection device)
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