Crown Boiler BWF Series Installation Instructions Manual page 41

11. Operation (continued)
!
WARNING
Improper adjustments to control parameters
could result in unreliable boiler operation,
property damage, personal injury, or loss of life.
Adjustments should only be made by a qualified
heating technician.
C. Using Adjustment Mode
A list of parameters which can be changed
on this control are shown in Table 11.6. To
enter Adjustment mode and change
parameters:
1. Press and hold I, ↑, ↓ together for at least 3
seconds.
2. Use I to advance to the parameter which is to
be changed.
3. Use the ↑ or ↓ buttons to change the setting
or select from possible choices. See below
for additional information on the use of these
parameters.
4. If other parameters are to be changed, use
the I button to advance to the next parameter
needing adjustment and change it in the
same way.
5. After all parameters have been changed, use
the I button to advance until bAc is shown on
the display.
6. Press either the ↑ or ↓ key to return to Status
mode. Alternatively, the control will return
to Status mode if no key is touched for 5
minutes.
HL (High limit Set point) - Burners shut down if the
boiler water temperature exceeds this setting. The
circulator will continue to run. The high limit setting
also serves as the water temperature set point (SP)
during calls for both heat and DHW.
dF (High limit differential) - If the boiler shuts off on
high limit, the water temperature must fall by an
amount equal to the differential during the same
call for heat before the burners will again start. For
example, with HL=180 and dF=15, the burners
will shut off if the water temperature exceeds 180F
and stay off until the temperature falls to 165F
(180 - 15). Note that if all calls for heat end while
the burners are off on high limit, the burner will not
restart during the next call for heat until the thermal
purge requirements described below are met.
Or (Circulator Overrun) - Determines how long the
Heating Circulator will operate after the call for heat
ends. In some cases, this can help reduce energy
consumption by sending heat stored in the boiler
out into the system. At the same time, caution
should be exercised before setting this value to
109836-01 - 04/20
something other than zero. Before doing so, verify
that the system will permit flow (e.g. flow is not
completely cut-off by closed zone valves) and that
the overrun will not cause overheating problems.
Circulator overrun is only possible on the heating
zone. The DHW Circulator will not over-run, even if
the DHW zone is used as a second heating zone.
PP (Thermal Purge Time) - Upon a call for heat, the
boiler will prevent burner operation until either:
• The water temperature drops below the
Thermal Purge start temperature (St) OR:
• The thermal purge time has passed
For some examples of this operation, see Table
11.7. If the "DHW" zone is used for space heating
(dh=tt2), this thermal purge function will also keep
the burner off at the beginning of a call from the
thermostat connected to the "DHW" terminals in
the manner described above. If the "DHW" zone
is being used for DHW (dh=dh), the burners will
immediately come on upon a call for DHW as long
as the water temperature is below the high limit
setting.
Thermal purge is only invoked when a call for heat
first appears and the boiler is not already firing. For
this reason, if the boiler is already firing in response
to an call for heat, and a call for heat appears at
the second zone, the boiler will continue to fire.
St (Thermal Purge Start Temperature) - See
description for Thermal Purge Time above.
Pt (DHW Priority) - If this feature is turned on, and
simultaneous calls for heat and DHW are present,
the heating circulator will be forced off for as long
as it takes the boiler to satisfy the call for DHW.
This feature is sometimes useful when the boiler
size is marginal for the peak DHW demand, but
should be used with caution as it can result in
lack of heat if the DHW call is very long, or if there
is a problem with the DHW zone which causes
the DHW demand to be indefinite. Figure 11.8
describes the behavior of both the Heating and
DHW Circulators with Pt turned both ON and OFF.
dh (Use of DHW zone) - Although the second zone
on the boiler is designated "DHW", it can be used
as a second heating zone by setting dh = "tt2"
instead of dh="dh". When the "DHW" zone is used
for heating, the thermal purge function is active
when this zone calls for heat. When dh=tt2, the
setting of Pt (DHW priority) is ignored.
rst (Reset) - Used to reset the boiler from a
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