HydroTherm HeatNet KN -6 User Information page 17

SETUP & OPERATION
Figure 9 Boiler System Response 2
(1) KN6, (1) KN20, 60% Mod-Max
To correct this would require the KN6 to set the MOD-
MAX to roughly 90% (Boiler System Response 3: not as
efficient as it could be) in order to have a linear BTU
transfer when the KN20 is added (fired).
Figure 10 Boiler System Response 3
(1) KN6, (1) KN20, 90% Mod-Max
A KN6 running with a KN20 may not be an optimal choice
unless (2) KN6's are always functional and used in the
Priority 1 set or (3) KN6s and one is allowed to be taken
offline.
A system employing this redundancy where (1) is allowed
to be taken offline is listed in the MIXED BOILER
SYSTEM chart. The example system uses (3) KN2s and (3)
KN10s. Two of the KN2s are treated as one when adding
the min inputs of the Priority 1 set.
Figure 11 Boiler System Response 4
(2) KN2s, (3) KN6s
The above Boiler System Response 4 graph illustrates
another system where 80% is used as the MOD-MAX
clamp.
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.
HeatNet Control V3 2.x
Page 17