CleaverBrooks Hawk 1000, Operation Manual

Page: 68 / 82

Section 5 — Commissioning Hawk 1000
5-14 Part No. 750-366
Figure 5-25. Outdoor reset curve
5.7.3 Revert to Pilot (CB 120E only)
Revert to Pilot (RTP) reduces cycling by eliminating the purge sequence.
When RTP is initiated the boiler returns to low fire, output O:6.4 is energized, and the Revert to Pilot signal
is sent to the flame safeguard. The RTP sequence is managed by the FSG: pilot is energized, and upon proof
of pilot the main gas valve de-energizes and the boiler remains on pilot. When demand returns or digital input
J:5.7 is ON the main gas valve is energized.
When RTP is on a “Rev to Pilot” indicator will appear on the Overview and Firing Rate screens.
Initiated by process variable
If ‘Initiate by process variable’ is selected, Revert to Pilot is initiated when steam pressure is greater than or
equal to “Revert to Pilot Pressure” and de-activated when steam pressure is below the boiler “On Point”.
Revert to Pilot Pressure = Off Point - (Revert to Pilot dP% x Off Point) [ensures that the RTP setting is always
less than or equal to the boiler off point]
-60 -40 -20 0 20 40 60 80
175
180
185
190
195
200
205
Setpoint
Outdoor
Temperature
OUTDOOR RESET CURVE
Set point is linear in relation to the outdoor temperature.
Range for outdoor temperature transmitter is 4 ma = -50 deg F, 20 ma = 900 deg F.
In this example:
Outdoor Temp Range Low = 0 deg F
Set Point Range High = 200 deg F
Outdoor Temp Range High = 60 deg F
Set Point Range Low = 180 deg F