3 Water Level Control
04.09.2016 Mk8 MM Expansion Features Installation and Set-Up Guide Page 65
3.9 Water Level Control Functions
This section describes the additional functions used to accurately control the water level.
3.9.1 Pre-Alarms
In addition to the water level alarms for high water, 1
st
low and 2
nd
low, pre-alarms can also be set
which include pre-high and pre-1
st
low.
The table below shows the expansion options for pre-alarms.
Expansion Option Description
7 Pre-high alarm percentage
8 Pre-first-low alarm percentage
The pre-high level is set as a percentage between the control point and high water level, with the
control point representing 0% and the high water level representing 100%. If the water exceeds this
pre-high level, a warning will occur and the burner will continue to fire.
The pre-1
st
low level is set as a percentage between the control point and 1
st
low level, with the control
point representing 0% and the 1
st
low level representing 100%. If the water falls below this pre-1
st
low
level, a warning will occur and the burner will continue to fire.
3.9.2 Pump Bypass
The pump bypass operation is prevents the pump pushing water against a closed feed water valve. The
terminal used is TB pump bypass contactor.
The table below shows the expansion options for pump bypass.
Expansion Option Description
17 Pump bypass operation
18 Pump bypass switch point
19 Pump bypass hysteresis
The pump can be bypassed at a percentage set in expansion option 18, above or below the switch
point. The switch point is set as percentage of the feed water valve open position set in expansion
option 16.
For pump bypass on above switch point, the pump bypass will turn on at a percentage above the
valve open range set as a switch point, and it will turn off at a percentage below the switch point set as
the hysteresis from the switch point.
For pump bypass on below switch point, the pump bypass will turn on at a percentage below the valve
open range set as a switch point, and it will turn off at percentage above the switch point, set as the
hysteresis from the switch point.
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