HydroTherm HeatNet KN -6 User Information page 42

OPTIONAL FEATURES
may require in its backup role. Then one of the local DHW
control methods can be used to implement DHW heating.
One advantage to this configuration is that a BMS can
control the system through the Master. It can also monitor
system status through a central location (Master boiler) by a
BMS, or HeatNet Online. This failsafe method can also be
used in the Mixed DHW/Space Heating Simplified
Drawing.
Set up the Master boiler first:
Connect a 10k thermistor from the DHW tank's sensor
1.
well to J10B terminals on the MASTER, and connect a
Header Sensor to the SYSTEM HEADER input. Wire
any pump or valve from the DHW Pump relay's
(normally open) contact to control flow of the heating
water into the tank's coil or DHW loop.
2. Now, set the ADVANCED SETUP: DISTRIBUTED
CTRL: MASTER TYPE: to MIXED. This setting
informs the HeatNet control that (2) PIDS are to be
used to control DHW and space heating.
3. There are two MODULAR BOILER SETTINGS, one
for space heating and one for DHW heating. These (2)
menus appear when the ADVANCED SETUP:
DISTRIBUTED CTRL: MASTER TYPE is set to
MIXED. The (2) Modular boiler settings are located in
the ADVANCED SETUP: MODULAR BOILER
SET: menu. Normally, there is only one, but with (2)
independent PIDs, the (2) heating setpoints may behave
differently due to their loads or for other various
reasons. These allow for separate ADD, SHED,
MODULATE DELAY TIME, and MOD MAX
settings for DHW and space heating.
4. Next, enter the DOMESTIC HOT WATER menu.
When prompted for DHW BOILER?, enter NO. We
will enter YES when we are finished entering all
parameters
5. Change the DHW SETPOINT to the desired target
temperature of the water in the tank/ or DHW loop.
Once the control determines there is a call for DHW
heat, the DHW PID will target this SETPOINT.
6. Now, change the DHW LOWER DIFF to the
desired temperature (DHW SETPOINT –
LOWER DHW DIFF) below which boilers are to
be added. This setting corresponds to the
minimum water temperature required in the tank.
DHW heating will be initiated by starting boilers
when the DHW tank's water temperature is
below the temperature (DHW SETPOINT –
LOWER DHW DIFF).
7. Next, change the DHW UPPER DIFF to the
desired temperature (DHW SETPOINT + UPPER
DHW DIFF) above which boilers are to be shed.
This setting is the maximum tank temperature.
Setting the SHED BOILER DELAY TIME
correctly will limit the maximum tank
temperature to the (DHW SETPOINT + UPPER
DHW DIFF). Setting the SHED BOILER
DELAY TIME = 0 will shut off all boilers
immediately once the (DHW SETPOINT +
UPPER DHW DIFF) is exceeded.
8. Press the DOWN arrow key again to position the cursor
beside the menu item DHW PRIORITY?. Setting this
value to YES will turn OFF the system pump when the
DHW mode is active. Setting this value to NO leaves
the system pump on. This time includes the DHW post
purge of the DHW pump/valve.
9. Press the DOWN arrow again and the menu item POST
PURGE should appear. This is the time that the DHW
pump relay remains energized after the DHW
SETPOINT has been satisfied. Once the tank has
exceeded the DHW SETPOINT + UPPER DHW DIFF
temperature and this DHW boiler has shut off (DHW
SHED BOILER DELAY TIME), the post purge time
will begin.
10. Scroll down to USE SENSOR? Press the
SELECT key and select YES, then press the
SELECT key again. This will allow the boiler to
control the tank or DHW loop temperature using
the DHW sensor. The upper and lower
differential temperatures will also be loaded when
set to YES.
11. Press the DOWN arrow, the menu item: SHARING:
will be displayed. Sharing determines what happens
when a DHW boiler is needed and none are available
(all running is space heating and DHW heating). It
needs to steal a space heating boiler that is running.
OFF Is first come first serve. If a Boiler is not
available because all boilers are firing, the DHW
firing algorithm waits until one becomes
available, even though at least one is running as a
space heating boiler. If a space heating boiler is
needed, a DHW running boiler cannot be stolen
for space heating. Space heating has priority
when DHW is trying to steal.
CYCLE The DHW algorithm can steal a space heating
boiler and fire it as a DHW boiler. The space
heating boiler stops and then restarts as a DHW
boiler. DHW priority.
NO CYCLE The DHW algorithm can steal a boiler
that is already running as a space heating boiler.
Instead of shutting down the space heating boiler,
it does a hot swap, engaging the DHW pump and
leaving the local pump running or shutting it off.
Use this in conjunction with the LOCAL PUMP
OFF: and the LOCAL DELAY: settings. DHW
priority.
12. Press the DOWN arrow, the menu item: LOCAL
PUMP OFF: is displayed. When a DHW heating cycle
HeatNet Control V3 2.x
Page 42