SETUP & OPERATION
HeatNet Control REV 1.38-1
Page 16
Figure 10
Boiler System Response 2
(1) KN6’s, (1) 28A-W-5’s, 54% Mod-Max
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
In
p
u
t,
%
System Load, Btu/Hr
Blr 1+2 (1756 MBTU)
To correct this would require the KN6 to set the MOD-
MAX to roughly 85% (
Boiler System Response 3
) in order
to have a linear BTU transfer when the 28A-W-5 is added
(fired).
Figure 11
Boiler System Response 3
(1) KN6’s, (1) 28A-W-5’s, 85% Mod-Max
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
In
p
u
t,
%
System Load, Btu/Hr
Blr 1+2 (1756 MBTU)
A system employing redundancy, where (1) Priority 1 is
allowed to be taken offline is shown in the
Boiler System
Response 4
chart. The example system uses (2) KN6s and
(2) 28A-W-5s. Two of the KN6s are treated as one when
adding the min inputs of the Priority 1 set.
Figure 12
Boiler System Response 4
(2) KN6’s, (2) 28A-W-5’s, 85% Mod-Max
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
In
p
u
t,
%
System Load, Btu/Hr
Blr 1+2 (1200 MBTU)
Blr 1+2+3 +4 (3512 MBTU)
Blr 1+2+3 (2356 MBTU)
The mixed system may also have boilers with condensing
and non-condensing types as has been illustrated. The
reason for creating a mixed system is primarily to control
the system cost.
In summary, the system should be tuned using the boiler
selection charts and the MOD-MAX value so that boilers
are brought on and fired in their respective efficiency curve
while maintaining continuity in BTUs. Since selecting the
Priority 1 boiler is integral to the fault tolerance of the
system, it is important to note any discontinuities in BTUs if
a Priority 1 boiler fails when multiple Priority 1 boilers are
used.
