Lochinvar 000 - 2 - Manual (Page 31)

High-Fire Offset
The temperature control operates a two-stage firing system.
The two stages are High-Fire and Low-Fire. High-Fire
operates all burners while Low-Fire operates approximately
one-half of the burners.
The High-Fire knob specifies the number of degrees below set
point that the High-Fire stage shuts down. At that point, the
unit will continue to operate at the Low-Fire stage until the set
point is reached.
The High-Fire offset knob has settings between 0°F and 20°F.
If set at 0°F, the High-Fire offset is disabled and the unit will
operate at the High-Fire stage until the set point is reached and
the temperature control shuts the unit off.
When the High-Fire offset knob is set to 0 or 1, the unit will
light at Low Fire and operate for approximately 10 seconds
before the High-Fire stage actuates. When set to 2 or above,
the unit will operate at Low Fire for 2 minutes before the High
Fire stage actuates.
Outdoor Air Reset Option
For boilers ordered with the Outdoor Air Reset option, there is
an additional control (see Figure 36). There are three setting
knobs for Shutdown, Outdoor Air Max., and Ratio. There is
also a switch to turn the outdoor air sensor On or Off. An O.A.
Sensor is also included.
Shutdown
The Shutdown knob specifies the outdoor air lockout
temperature at which the control would prevent the unit from
operating. This feature can be enabled/disabled with the O.A.
Shutdown switch.
Outdoor Air Max (O.A. Max)
The O. A. Max knob allows a reset up to the maximum outdoor
air temperature specified by this knob setting. When the
outdoor air temperature is above the specified setting, the unit
will not function in the O.A. Reset Mode, but will continue to
run at the selected set point temperature.
Note that the set point knob will now indicate the “minimum”
boiler temperature. Target temperature is determined by the
ratio and outdoor air temperature below the O.A. Max setting.
Ratio
The Ratio knob allows the control over the reset ratio to be
used during Outdoor Air Reset. The allowable ratios are as low
as 0.5:1 or as high as 1.5:1.
Selecting the 0.5:1 ratio will increase the set point 0.5°F for
every 1.0°F drop in outdoor air temperature up to the
maximum set point temperature.
Selecting the 1.5:1 ratio will increase the set point 1.5°F for
every 1.0°F drop in outdoor air temperature up to the
maximum set point temperature.
See Figure 37 for an outdoor air reset chart example.
Figure 36 - Optional Outdoor Air Reset Control
Installation and
Service Manual
31
R4R
4
R6R
6
R8R
8
R16R
1
6
R15R
1
5
C7C
7
C9C
9
C10C
1
0
VR2 VR2 VR3 VR3
OJ1 OJ1
OJ2 OJ2
D4D
4
J4J
4
CN1 CN1
CN2 CN2
CN9 CN9
CN7 CN7
CN8 CN8
CN3 CN3
CN4 CN4
CN5 CN5
CN6 CN6
W1 W1
TST2314 TST2314
20 20
15 15
10 10
5 5
(F-)0 (F-)0 15 15
14 14
13 13
12 12
11 11 10 9 9
8 8
7 7
6 6
5 5
OFF OFF
120 120
240 240
220 220
200 200
160 160
140 140
SETPOINT SETPOINT
DIFFERENTIAL DIFFERENTIAL HIGH-FIRE HIGH-FIRE
OFFSET OFFSET
(c)2002 L.C. (c)2002 L.C.
SHUTDOWN
45
50
45 1.3
O.A. MAX.
70 40
VR1
65
RATIO
VR2
0.6
0.5
0.7
1.4
1.5
W1 W2
W3
60 50
70 40
55
60
VR3
65
DISABLE
O.A. SHUTDOWN
1.0
0.9
0.8 1.2
1.1
O.A. SENSOR
ENABLE ON
SW1
55 CN1