CONTROL METHODS
HeatNet Control V3
Page 36
DHW Method 2: Failsafe Combination DHW and Space Heating with a MASTER
Boiler and Member Boilers Utilizing Pumps (Master Type: Combination)
In this example the Master is not a DHW boiler.
DH
W
P
u
m
p
DH
W
P
u
m
p
Member 2
Cold Water
Makeup
E
xp
a
n
sio
n
T
an
k
Backflow
Prevention
Pressure
Reducing
Ball Valve
Lo
ca
l P
u
m
p
Member 3
Master
Lo
ca
l P
u
m
p
Domestic Hot
Water
Supply
Make
Up
Dual
Tank Sensor
WM
Water Meter
Lo
ca
l P
u
m
p
O
u
td
o
o
r
A
ir
S
en
so
r
Heating
Only
Combination
Failsafe
Heating
Combination
Failsafe
DHW
Sy
st
em
P
u
m
p
System Return
System Header Sensor
System Return Sensor
System Pump
MIN 3X PIPE DIAMETERS
MAX 10X PIPE DIAMETERS
BETWEEN CENTERS
DH
W
S
en
so
r
DH
W
S
en
so
r
Sy
st
em
P
u
m
p
Sy
st
em
P
u
m
p
System Supply
HeatNet
Su
p
p
ly
H
ea
d
er
Se
n
so
r
HeatNet
HeatNet
Su
p
p
ly
R
e
tu
rn
Se
n
so
r
DHW METHOD 2: Failsafe Combination DHW and Space Heating using a MASTER Boiler and Member boilers with
pumps
In this method the Master simultaneously controls both space heating and DHW heating. The Master is piped to only service
space heating, and both members are piped to service space heating and DHW heating demands. The Master’s
Heat Demand
input enables space heating by energizing the system pump and maintaining the Heating Setpoint at the System Header Sensor.
The Master’s
OR OVR
input enables the DHW heating, by maintaining the DHW Setpoint at the DHW Sensor located in the
DHW tank.
Boilers are staged to meet both the Space Heating Setpoint, and the DHW Setpoint based on their runtime. When a boiler is fired
to service a space heating demand it will enable its local pump, and when a boiler is fired to service a DHW demand it will enable
its DHW pump. The Master modulates the boilers in order to maintain the setpoints.
This method allows for a Member boiler to provide
Failsafe
mechanisms in the event the Master fails and stops communicating
to the Members. Member 2 is configured to provide failsafe space heating, and Member 3 is configured to provide both failsafe
space heating and failsafe DHW heating.
