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Space heating differentials (parameters 22 and 23)
•
the term "differential" is also referred to as "hysteresis."
•
Parameter 22 is the "On" differential. the water tem-
perature must be at least Parameter 22 less than the
calculated setpoint temperature for the boiler to turn on.
•
Parameter 23 is the "Off" differential. When the boiler is
firing, the water temperature must rise at least Param-
eter 23 above the calculated setpoint temperature for
the boiler to turn off.
•
See Figure #4 for an explanation of the "On" and "Off"
differentials of the boiler control. note that the differ-
entials are greater when a heat call starts or stops, as
shown. the differentials decrease with time until they
equal Parameters 22 and 23.
Setting "OFF" differential (parameter 23)
pARAMETERS 22 AND 23 (SpEACE HEATING ON AND OFF DIFFERENTIALS (hysteresis))
III - pARAMETER EXpLANATIONS
•
the factory default setting for Parameter 23 is 4° F.
this works well for most applications.
•
For low mass systems (fan coil), performance can be
improved by increasing Parameter 23. this compen-
sates for the quicker system temperature response of
low-mass systems.
•
When setting Parameter 23, make sure that Parameter
23 plus Parameter 4 is not over 193° F to avoid possible
nuisance lockouts.
Figure #4
10
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