CONTROL METHODS
HeatNet Control V3
Page 43
This method will control a tank temperature when the tank
temperature setpoint needs to be maintained for extended
periods with minimal cycling. Multiple boilers can be used
via the H-Net, as this method employs the same PID
algorithm as for space heating.
SETTINGS:
DISTRIBUTED CONTROL: MASTER TYPE:
AUTO.
1.
JPS1 must be cut on all boilers providing
DHW to ensure the maximum output
temperature of all boilers is limited to 200F for
DHW operation.
This Method is very similar to the DHW only
method, but:
A.
The display will not indicate that it is a
DHW heating boiler.
B.
The DHW Heating band will also not
be displayed.
C.
The heating band will use the space
heating band and not the UPPER and
LOWER DHW heating band limits.
D.
DHW settings are not used.
E.
Set the
SETTINGS: DISTRIBUTED
CONTROL: MASTER TYPE:
to
AUTO
.
F.
This method is for backwards
compatibility.
2.
Use the
Heat Demand Control Method 1
located in the CONTROL METHODS section
on page 22. Instead of placing the Header
sensor in the Header pipe, place it in a well, in
the tank, or a DHW loop.
The temperature at which boilers are staged
ON,
and then
OFF
is controlled by the
SETTINGS: SETPOINTS: HEAT BAND
differential. This can be understood by referring
to the INTRODUCTION section on the
MASTER in the beginning of this manual.
This differential has the added effect of heating
the tank above the tank’s setpoint temperature.
If the tank setpoint is set to 140F and the heat
band is set to 10F, then the tank temperature
will rise to 145F before the first boiler turns off
(setpoint =140F +/- heat band/2). With (2)
boilers running, the
SHED BOILER DELAY
time could add to the tank temperature. So, to
ensure that all boilers are shut off at the upper
point of the heat band, set the
SHED BOILER
DELAY time to 0 or other small value
. This
will effectively turn off all boilers at the upper
heat band point of: (example) 145F.
Now, there is one more thing to consider, the
pump’s post purge time. Dumping the heat from
all boilers (that were running) using a pump
post purge cycle will have an effect on the
tank’s water temperature. Consider this when
establishing the local pump’s
POST PURGE
TIME
.
3.
Connect the Local Pump relay contact on J13 to
enable the DHW pump. Set its post purge time
to dump the boiler’s heat into the tank when the
boiler shuts off.
Be aware that this may heat
the tank above the upper heat band of the
setpoint temperature.
4.
Enable the system by placing the
LOCAL/REMOTE switch on the Master to the
LOCAL position.
