Patterson-Kelley MACH-05 Installation Manual page 26

MACH® Series Gas-Fired Boiler
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
Setpoint
Low Temp. Differential
High Temp. Differential
Low Temp. Setpoint
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
175
170
165
Boiler Temperature
160
155
Boiler Turns On
150
145
0 10
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:
Parameter Value Allowable
4 160
22 10
23 9
5 68
Boiler Turns Off
Boiler Set Point
20 30 40
Time
DHW Setpoint
DHW Setpoint Addition
DHW Status
DHW High Temp. Differential
DHW Low Temp. Differential
DHW Options
In the above example, the boiler temperature will be
Range
set to the DHW Setpoint + the DHW Setpoint
68-185
Addition (140ºF + 30ºF = 170ºF) when the DHW
0-36
temperature controller indicates a call for heat from
0-36
the DHW system. When the DHW system calls for
59-140
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).
Page 22
Item Parameter
1
33
2
25
24
35
Installation
Value
140
30
1
6
6
13