750-211 (revised 2009)
Promethean Boilers, Model 4WI Manual
6-9
6.8 — High Limit Pressure Control: Steam
6.8 — High Limit Pressure Control: Steam
Set “cutout” (burner off) pressure on the main scale using the adjusting screw. The control will break a circuit when
pressure reaches this point. The setting should be sufficiently above the operating limit pressure control to avoid
shutdowns, and preferably not exceed 90% of safety valve setting.
The control requires manual resetting after tripping on a pressure increase. To reset, allow pressure to return to
normal and then press the reset button. Failure to do this will disallow restarting.
6.9 — Modulating Temperature Control: Hot Water
Turn the knob on the front of the case until the pointer indicates the
desired setpoint temperature. The desired setpoint is the center point of
a proportional range. The control has a 3º to 30º differential and may be
adjusted to vary the temperature range within which modulating action is
desired. With the cover off, turn the adjustment wheel until the pointer
indicates the desired range.
FIGURE 6-8. Hot Water Controls
6.10 — High Limit Temperature Control: Hot Water
Set the “cutout” (burner off) temperature on scale using the adjusting screw. The control will break the circuit and
lockout on a rise in water temperature above the setting. The setting should be sufficiently above the operating limit
temperature to avoid unnecessary shutdowns. On a 30 psig hot water boiler, the setting is not to exceed 240º F. The
control requires manual resetting after tripping on a temperature increase. To reset, allow the water temperature to
drop below the cutout setting less the differential, and then press the manual reset button. Failure to do this will
disallow restarting.
6.11 — Operating Limit Temperature Control: Hot Water
Set the “cutout” (burner off) temperature on the scale by inserting a screwdriver through the cover opening to
engage the slotted head adjusting screw. The “cut-in” (burner on) temperature is the cutout temperature minus the
differential. The differential is adjusted from 5º to 30º F.
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