CONTROL METHODS HeatNet Control V3
Page 38
6. Now, change the LOWER BAND to the
desired temperature (DHW SETPOINT –
LOWER BAND) 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 BAND).
7. Next, change the UPPER BAND to the desired
temperature (DHW SETPOINT + UPPER
BAND) 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 BAND). Setting the SHED BOILER
DELAY TIME = 0 will shut off all boilers
immediately once the (DHW SETPOINT +
UPPER BAND) is exceeded.
8. Change the DHW priority menu item PUMP
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. Go to the POST PURGE menu item. 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 BAND
temperature and this DHW boiler has shut off (DHW
SHED BOILER DELAY TIME), the post purge time
will begin.
10. Now, go to USE SENSOR Select YES. This
will allow the boiler to control the tank or
DHW loop temperature using the DHW sensor.
The upper and lower band temperatures will
also be loaded when set to YES.
11. The next menu is the SHARING menu. Sharing
determines what happens when a DHW boiler is
needed and none are available (all boilers are running
is space heating and DHW heating). This means the
Master needs to steal a space heating boiler that is
running or no more boilers can fire in DHW.
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 has 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 has priority.
12. Next is the LOCAL PUMP OFF menu. When a
DHW heating cycle begins, what to do with the local
pump/valve is determined:
NO The local pump/valve will remain running during
DHW heating.
YES The local pump will shut off with a delay
determined by LOCAL DELAY: seconds. This
allows the DHW pump/valve to prove before
shutting off the local pump.
Piping of the system will determine which setting
to use.
13. Go to the PURGE TO menu. After a DHW cycle
completes, the pump/valve can be selected to either
purge to the TANK, or to the SPACE for the duration
of the post purge time. This selection can use the
space to dump the heat from the boiler and not
overheat the DHW tank/load.
14. Set the HYB SENSOR = OFF. This sensor is
selectable for Method 5A only.
15. Finally, go to the BOILER MODE menu. If JPS1
has not been cut, the selection will appear grayed out.
Cut JPS1. Once this is done, set the BOILER MODE
to Combination. The MASTER boiler will control
the temperature in the tank using as many boilers as it
has available on H-Net along with any the space
heating needs. The boilers must be piped
appropriately for this method to function correctly.
Now set up the Member boiler(s).
BOILER MODE Set to Combination on MEMBER
boilers, only the MASTER boiler.
DHW SETPOINT This does not need to be set on
MEMBER boilers, only the MASTER boiler.
LOWER BAND This does not need to be on
MEMBER boilers, only the MASTER boiler.
UPPER BAND This does not need to be set on
MEMBER boilers, only the MASTER boiler.
PUMP PRIORITY This does not need to be set on
MEMBER boilers, only the MASTER boiler.
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