CONTROL METHODS HeatNet Control V3
Page 51
This method is used to provide combination space heating
and DHW heating. The boiler may be stand alone or in a
HeatNet configuration. It is meant to fire an individual
boiler in a DHW heating priority mode when that boiler’s
local tank temperature has a call for DHW heat (tank
sensor’s temperature drops below the DHW Setpoint +
LOWER BAND). The boiler will stop space heating (if
running) and switch to DHW heating. The DHW
pump/valve will be engaged and the water temperature in
the tank will be maintained by the boiler at the DHW
setpoint. Once the tank temperature exceeds the Setpoint +
UPPER BAND temperature, DHW heating will stop and
the pump/valve’s post purge will start.
When a tank’s temperature sensor is connected directly to
a boiler and the BOILER MODE is set to LOCAL. The
boiler will go offline from HeatNet and service the DHW
needs of its local tank. If the boiler is running in space
heating mode, then the “SHARING” setting may be used
to determine how, or if, to shut down before starting a
DHW cycle. When the DHW cycle is complete (includes
the post purge time of the DHW pump), the boiler will go
back online with HeatNet and become available to fire.
During a DHW cycle the DHW setpoint will be loaded
along with the UPPER and LOWER BAND limits. Also,
the SETTINGS: DISTRIBUTED CONTROL:
MASTER TYPE: is set to AUTO.
When a 10k Type II sensor is used with this method, the
OR OVR input functions as an enable/disable. This allows
the DHW heating function to be enabled or disabled much
in the same way as the Heat Demand input for space
heating.
When using this method, a DHW band is also available in
the Home Screen. The space heating band will be
displayed on the left and the DHW Heating band on the
right. The bands will operate in a split screen view.
1. Connect a 10k thermistor from the DHW tank’s
sensor well to J10B terminals on any boiler. Wire a
pump or valve from the DHW pump or the System
pump (normally open) relay contact to control flow of
the heating water into the tank’s coil or system loop.
The System pump will always be enabled as long as
the Heat Demand input is closed and the SETTINGS:
PUMP PRIORITY is set to NO. The DHW pump
will be enabled whenever there is a DHW call for
heat.
A DHW call for heat is when the DHW temperature is
below the (DHW SETPOINT – LOWER BAND) or
when the DHW temperature is below the (DHW
SETPOINT + UPPER BAND) and boilers are firing.
After a DHW call for heat ends:
A. The pump will remain on during a post purge
pump cycle until the post purge timer expires.
2. Next, enter the DOMESTIC HOT WATER menu
on the Master boiler. Go to BOILER MODE and
enter LOCAL.
3. Change the DHW SETPOINT to the desired target
temperature of the water in the tank. Once the control
determines there is a call for DHW, the DHW
SETPOINT is loaded and the boiler will target the
setpoint.
4. Now, change the LOWER BAND 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 when the DHW tank’s water temperature
is below the temperature (DHW SETPOINT –
LOWER BAND).
How long the temperature of the tank stays below the
temperature (DHW SETPOINT – LOWER BAND) is
used to determine when boilers are started along with
the ADD BOILER DELAY TIME.
5. 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.
6. Change the DHW PRIORITY. Setting this
value to YES will turn OFF the system pump
when the DHW mode is active (when the DHW
pump is on). Setting this value to NO leaves the
system pump on.
7. Now got to the POST PURGE menu. This is
the time that the DHW pump relay remains
energized after the DHW SETPOINT has been
satisfied.
A. The pump will remain on during a post
purge pump cycle until the post purge
timer expires.
8. Now, go to the USE SENSOR menu and select
YES. This will allow the boiler to control the
local tank or DHW loop temperature using the
DHW sensor. The upper and lower differential
temperatures will also be loaded.
9. Got to SHARING and set it to OFF or CYLE
if the boiler is currently running in space
heating and needs to be shut down before
starting up in DHW.
If SHARING is set to NO CYCLE, a hot swap
will occur. A hot swap is when the boiler is
running in space heating mode and does not
To Next Page
Loading...
Need help?
General