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MACH® Series
Gas-Fired Boiler Installation
Page 22
Internal Setpoint:
The internal setpoint is set with parameter 4. The
boiler temperature control modulates the boiler to
maintain this internal setpoint. The upper and lower
temperature differentials are used to instruct the boiler
at what temperature to turn on and at what temperature
to turn off.
Item Parameter Value Allowable
Range
Setpoint 4 160 68-185
Low Temp. Differential 22 10 0-36
High Temp. Differential 23 9 0-36
Low Temp. Setpoint 5 68 59-140
The boiler will modulate to try to maintain 160° F. If
the temperature increases above 169° F which is the
setpoint 160° F + High Temp Differential 9°F the
boiler will shut off. Once it shuts off it will not restart
until the temperature drops below 150° F which is the
setpoint – Low Temp Differential. The Low Temp Set
Point will not permit the operator to adjust the setpoint
below 68° F. (See graph below.)
Internal Setpoint
145
150
155
160
165
170
175
010203040
Time
Boiler Temperature
Boiler Set Point
Boiler Turns On
Boiler Turns Off
Domestic Priority:
If an indirect domestic hot water (DHW) tank is
connected, the DHW function of the boiler will
activate when the DHW temperature controller
(supplied by others) closes (Terminal 5 to 8 TB 1,
refer to Section 6.1.1), indicating a call for heat from
the DHW system. The parameters should be set as
follows:
Item Parameter Value
DHW Setpoint 1 140
DHW Setpoint Addition 33 30
DHW Status 2 1
DHW High Temp. Differential 25 6
DHW Low Temp. Differential 24 6
DHW Options 35 13
In the above example, the boiler temperature will be
set to the DHW Setpoint + the DHW Setpoint
Addition (140ºF + 30ºF = 170ºF) when the DHW
temperature controller indicates a call for heat from
the DHW system. When the DHW system calls for
heat, the Central heat pump output (Terminal 10
TB2) de-energizes and the DHW pump output
(Terminal 11 TB2) energizes providing 120 VAC
power is provided to energize a relay coil for the
DHW pump. The DHW status should be set to 1
(DHW system ON).