
SETUP & OPERATION
HeatNet Control V3 3.x
Page 20
Once the Mixed Boilers menu has been entered, the firing
order and stop order of the Priority boiler set can be selected
based on up to (3) conditions in the conditional settings
menu. All conditional settings apply to the Priority 1 boiler
set. When the conditional settings do not apply to the
Priority 1 set, the conditional settings will apply to the
Priority 2
boiler set.
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.
See: SETTINGS: HEAT EXCHANGER TEMP DISAB:
START/STOP
PRIORITY CONDITIONS
The following is an example using mixed
condensing and non-condensing boilers:
FIRE FIRST
Condensing boilers may be configured to
Fire First
(set to
Priority 1) when:
1. The Return water temperature is below 140°F and
condensing occurs. (The MASTER’s system return
water would need to be used.)
2.
The Outside Air Temperature is above a setpoint
determined by the system configuration. This setpoint
ensures that the more efficient condensing boilers run
first during shoulder months (Spring and Fall) when
minimal heating is required. Below this setpoint, larger
boilers should be brought on first to “base load” the
system.
3.
Greater efficiency is required.
STOP FIRST
Condensing boilers may be configured to
stop first
(set to
Priority 1) when:
The Return water temperature is above 140F and
condensing is minimized, thus leaving the larger lower cost
boilers running to carry the load.
1.
The Outside Air Temperature is below an adjustable
setpoint determined by the system configuration. This
setpoint ensures that the larger non-condensing boilers
run during the coldest months when maximum heating
is required. Above this setpoint smaller condensing
boilers should be brought on first to run the system as
efficiently as possible.
2.
Maximum heating is required
START PRIORITY 1 SET
Selections
(always the lowest runtime first):
The
condensing boiler set
(Priority 1) has a
higher Priority to
fire
when one of these
conditions is met. Values are adjustable.
FIRST
:
The condensing boilers (Priority 1) are always
started FIRST
OA T > 15F
:
The condensing boilers (Priority 1) are
started when the OA temperature is greater than the Mixed
Boiler Outdoor Air Temperature setting.
RET < 140F
:
The condensing boilers (Priority 1) are
started when the Return water temperature is less than the
Mixed Boiler Return temperature setting (This may not be
applicable in most configurations since the local return
temperature on the MASTER is used to provide a difference
temperature across the heat exchanger). A System Return
sensor will be required. However, the return temperature
sensor may have been moved on the MASTER to provide
system return temperature on existing installations and is
still supported).
STOP PRIORITY 1 SET
Selections
(always the highest runtime first):
The
condensing boiler set
(Priority 1) has a
higher Priority to
stop
when one of these
conditions are met. Values are adjustable.
LAST
:
The condensing boilers (Priority 1) are always
stopped LAST.
OA T < 15F
:
The condensing boilers (Priority 1) are
stopped first when the OA temperature is less than Mixed
Boiler Outdoor Air Temperature setting.
RET > 140F
:
The condensing boilers (Priority 1) are
stopped first when the Return water temperature is greater
than the Mixed Boiler Return temperature setting. (This may
not be applicable in most configurations since the local
return temperature on the MASTER is used to provide a
difference temperature across the heat exchanger).
However, the return temperature sensor may be moved on
the MASTER to provide system return temp if the
difference temp is not required)
Start/stop settings
Any combination of Start Conditions and Stop Conditions
can be used to optimize the mixing of condensing