MACH® Series
Gas-Fired Boiler
Installation
Page 23
above settings. Using the values in the table above,
the boiler setpoint will be 80° F when the outdoor air
temperature is 70° F. As the outdoor air temperature
drops, the boiler setpoint will be increased until the
outdoor air temperature is 20° F. At this point the
boiler will reach its maximum setpoint of 180° F. If
the outdoor air temp drops further, the boiler setpoint
remains at 180° F.
The boiler shutoff temperature can be used to turn the
boiler off at a given setpoint. For example if you
wanted to shut the boiler off when the outdoor air
temperature was above 65° F you would set the boiler
shutoff temp to 90° F since this is the setpoint that is
called for at 65° F outside air temp.
Analog Input to Adjust Setpoint:
Analog Input S etpoint
0
50
100
150
200
0
1
2
3
4
5
6
7
8
9
10
V oltage
Bo
il
e
r S
e
tp
o
in
t
B oiler Setpoint
Non adjustable C urve
The control must be configured for a remote analog
input setpoint according to the following table:
Item Parameter
Value
°F
Allowable
Range °F
Maximum Setpoint
4
180
68-185
Minimum Setpoint
5
80
60-140
Boiler Configuration
34
03
The setpoint of the boiler is controlled by an external
0-10 VDC signal. A signal of at least 0.5 VDC is
required to start the boiler. At 0 VDC the setpoint is
32° F; at 10 VDC the setpoint is 212° F. This setpoint
is low and high limited by maximum and minimum
setpoint parameters. The controlled setpoint voltage
range narrows when these limits are used. If the above
tables values are used the boiler setpoint will be 80° F
when the voltage is anything less than approximately 3
VDC. It will then increase linearly with voltage until
approximately 8.5 VDC when it will be 180° F. The
setpoint will remain at 180° F even if voltage is
increased further.
Analog Input to Control Firing Rate:
Analog Input Firing Rate
0
10
20
30
40
50
60
70
80
90
100
0
1
2
3
4
5
6
7
8
9
1 0
V oltag e
Fi
ri
n
g
R
a
te
The control must be configured for analog input direct
drive by setting parameter 34 to 02.
The firing rate of the boiler is controlled by an external
0 to 10 VDC signal. At a voltage greater than 0.5
VDC the boiler turns on and runs at low fire until 1.8
VDC is reached. The firing rate increases linearly with
voltage until high fire is reached at 10 VDC. The
boiler setpoint Parameter 4 remains active to shut
down the boiler when the temperature in the boiler
exceeds this value plus the high temp differential.
These voltage levels, as explained above, are all “non-
adjustable”.
3.12.2 Burner Setup
The MACH® C1500/C2000 boilers are equipped with
a Honeywell combined gas/air control and gas safety
shut off control valves. The valve functions in series
with the variable speed combustion blower to supply
the correct gas air ratio for optimum performance and
efficiency. The combustion blower speed is controlled
automatically and determines the amount of negative
pressure felt at the gas safety shut off / control valves.
The gas/air regulator adjusts gas flow to maintain the
proper pressure at the outlet nozzle of the associated
valve.
