HydroTherm HeatNet KN -6 User Information page 19

SETUP & OPERATION
not happen. Even then, the load may be too great. The
following note will explain an alternative way (not
depending on the ADD BOILER DELAY) to keep non-
condensing boilers from firing in a condensing mode.
When running with a remote BMS setpoint, care must be
taken that an Outside Air reset setpoint (or other setpoint)
sent by the BMS is not set too low. If the BMS system is
controlling the setpoint close to the condensing temperature,
the return water temperature may never rise sufficiently to
keep boilers out of a condensing mode. HeatNet online is a
good way to monitor this scenario if suspected.
NOTE:
If the firmware version for a HeatNet V2 board is at least
3.47(or a version 3 board), the non-condensing boiler
may hold itself off from being added to the HeatNet
Master's available to fire list. This would effectively keep
the non-condensing boiler from firing in a condensing
mode, but as a result, may not satisfy the system setpoint.
In order to use this feature, the version 2 board would
need to monitor the system or local return temperature.
This can be done locally by setting SETUP: AUX
FUNCTIONS: HEAT EXCHNAGER: TEMP DISAB:
RETURN if the there is no pump/valve limiting flow
continuously through the boiler. If there is a pump/valve
limiting the flow through the boiler, the SETUP: AUX
FUNCTIONS: HEAT EXCHNAGER: TEMP DISAB: SYS
RET needs to be set. Then the Master boiler needs to set
SETUP: AUX FUNTIONS: HEAT EXCHNAGER: SEND
RETURN: to which of its return temperatures it would
send to all boilers. These include the Local Return
temperature or the System Return temperature.
The Member's menu "SETUP: AUX FUNCTIONS: HEAT
EXCHNAGER: TEMP DISAB:" if set to RETURN or SYS
RET, will force the boiler to become unavailable to
HeatNet when the SETUP: AUX FUNCTIONS: HEAT
EXCHNAGER: TEMP< 140F. This value is adjustable to
135F if a forced air fan is used. When the SYS RET or
RETURN temperature is <140F the boiler responds to a
HeatNet Master's request as" unavailable". As soon as
the return temperature reaches 140F, the boiler will
respond to the Master's request that it is available to fire.
If the Master boiler is a version 2 board, the Master will
always transmit its Local Return temperature to all
boilers. If the Master is set to Priority 1 and all other
non-condensing boilers are set to Priority 2, the Master
should always remain on if there is a call for heat. This
requires that the Priority 1 boiler be set up to start first
and stop last. Using this method should always send a
valid return temperature to the Member boilers. This
method can also be used with a version 3 board, but a
system return sensor is preferred.
When this condition is in effect, the STATUS * screen will
indicate "blr offline". While the boiler is in this "not
available" state, it can still be fired locally and failsafe is
still available.
SETUP: AUX FUNCTIONS:HEAT
EXCHANGER:SEND RETURN:
OFF
RETURN
SYS RET
SETUP:AUX FUNCTIONS:HEAT
EXCHANGER:LOW TEMP:
OFF
RETURN
SYS RETURN
SETUP:AUX FUNCTIONS:HEAT
EXCHANGER:TEMP < 140F
Adjustable threshold temperature below which the
boiler will take itself offline.
(1) degree F of hysteresis is provided so as to not
toggle offline<-to->online at the threshold temp.
Since the FIII boiler is non-condensing, the efficiency vs.
input is relatively flat. The MOD MAX value will not have
the same impact if the FIII non-condensing boilers were
placed in the Priority 1 set.
HeatNet Control V3 2.x
The Master sends its return
temperature to all boilers
The Master sends its return
temperature to all boilers
The Master sends the system
return temperature to all
boilers
No check is made to the return
temperature – boiler remains
online
Uses the boilers own return
sensor (No pump /valve
present)
Uses the System Return temp
received from the Master Boiler
(its Local or System Return).
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