OPTIONAL FEATURES
HeatNet Control REV 1.38-1
Page 30
MASTER will automatically call on other boilers
when the DHW Tank Temperature drops below
(DHW SETPOINT – DHW DIFF) even when no
Heat Demand signal is present. However, the
MASTER will only enable boilers for space
heating in response to a Heat Demand signal.
10.
Finally, go to
DHW BOILER?
. Select
YES
. If
JPS1 has not been cut, a message will appear
instructing to do so. Once this is done, the
MASTER boiler will control the temperature in
the tank using as many boilers as it has available
on H-Net.
DHW BOILER?
Does not need to be set to
YES
on MEMBER boilers, only the
MASTER boiler.
JPS1 MUST be cut on all boilers providing
DHW.
DHW METHOD 2: DHW Header
Sensor Input
1.
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. For this method, a
tank temperature band needs to be tolerated.
JPS1 MUST be cut on all boilers providing DHW
to ensure the maximum output temperature of all
boiler is limited for DHW operation.
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.
The temperature at which boilers are staged
ON,
and then
OFF
is controlled by the
SETUP:BOILERS: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
. 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 setpoint’s upper heat band
temperature.
4.
Enable the system by placing the
LOCAL/REMOTE switch on the Master to the
LOCAL position.
DHW METHOD 3: Space Heating
with DHW Override
This method is for controlling DHW utilizing a tank
thermostat connected to a Master or Member boiler.
This method can be used instead of the 10k thermistor
sensor. When the thermostat contact closes across the
input
OA OVR (J12A .7 & .8),
the control
will sense
this closure and enter the DHW heating mode.
In this mode, the boiler will fire to
100%
and be
regulated by the
OPERATE LIM
setting located in
SETUP:SETPOINTS.
The
OP LIM BAND
can be
used to keep the boiler from short cycling too much
by limiting the firing rate as it approaches the
OPERATE LIM
.
1.
Wire the dry contact from the thermostat on the
tank to the input on J12A terminal 7 & 8. Also, at
this time wire any pump or valve from the DHW
Pump relay (normally open) contact (J13
terminals 9, 10) to control flow of the heating
water into the tank’s coil.
2.
Enter the
DOMESTIC HOT WATER MENU
.
When prompted for
DHW BOILER?
, enter
NO
.
We will enter
YES
when we are finished entering
all parameters
Follow the same steps as used to program the 10k
thermistor sensor method, but when asked to
USE SENSOR?,
select
NO
.
Set the
DHW MASTER
to
NO.
A thermostat
can only control (1) boiler. H-Net is not available
with a thermostat on the tank.
Go to the
DHW BOILER?
, enter and select
YES
. The Master or Member will now control
the temperature in the tank.
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