Specifications

Logamax plus GB142 applications manual | 01.2012
Technical specifi cations are subject to change without prior notice
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GB142 Applications Manual
Appendix 2 - Multi-boiler cascade with
0-10V heat demand input
The MCM10 accepts a quantified heat demand from a building
management system, which can be used to control:
(1) the system supply water temperature
(2) power output of the boilers (boiler modulation)
Control of system supply water temperature
The MCM10 uses the 0-10V signal of the building management
system to compute the system supply water temperature set
point. This is a linear ratio (table 7).
Input
voltage
(V)
Supply temperature
set point
(boiler)
Status of
boilers
(°F) (°C)
0
32 0
OFF
0.5
32 0
OFF
0.6
59 15
ON/heat demand
5.0
122 50
ON/heat demand
10.0 194
90
ON/heat demand
Table 7
Control of boiler output (boiler modulation)
The MCM10 uses the 0-10V signal of the building management
system to compute how many boilers to fire and their
modulation. This also depends on supply and return water
temperatures, boiler run time, boiler size (if different boiler sizes
are used), load, etc. This is a linear ratio (table 8).
Input
voltage
(V)
Performance set
point (boiler)
[%]
Status of
boiler
0
0
OFF
0.5
0
OFF
0.6
6
Low load *)
5.0
50 Part-load
10.0 100
Full load
Table 8
*) The low-load performance depends on the device type. E.g. if the low
load of the device is 20% and the control signal is 1 Volt (= 10%), the
performance value setting is lower than the low load. In this case the
boilers may be cycling on and off.
Required components:
• GB142 boilers
• MCM10 module
Note: Do not use the AM10 in this configuration
Voltage
Supply temperature °F (°C)
194 (90)
167 (75)
140 (60)
113 (45)
86 (30)
60 (15)
32 (0)
Figure 37 0 -10V Diagram
0%
30%
50%
100%
2
4
6
80
10
Voltage
System power output
Figure 38 Control based on power output