Burnham CHG225 - Manual (Page 45)

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In standby mode, it is possible to view both the heating supply set point temperature and the “domestic hot water
reference set point”. The “domestic hot water reference set point” plus 45°F equals the boiler supply set point when
it is responding to a call from the indirect water zone. It is not the actual domestic hot water set point. The CHG is
designed for use with a storage type indirect water heater such as the Burnham Alliance™. The domestic water set
point is controlled by the thermostat on the indirect water heater. The “default domestic water reference set point”
is 135°F and target boiler supply temperature when responding to a call from the indirect water heater is therefore
180°F (135°F +45°F). The default heating supply set point (parameter 4) is 180°F.
In standby mode it is also possible to turn on or off either the heating or domestic water zone. There is normally no
reason to turn off either of these zones and doing so is not recommended.
In standby mode, if “Mode” and either “+” or “-“are simultaneously pushed and held for at least 2 seconds, the
burner can be forced into either high or low fire. This feature is used for running combustion tests. After 15 minutes,
the burner will automatically revert to modulation. If it is desired to revert to modulation before 15 minutes has
passed, simultaneously pushing “+” and “-“ will restore modulation.
In Parameter mode both set points can be changed and both zones turned on or off. In addition, both zones can be
configured for continuous pump operation. If the heating zone is set for continuous pump operation (parameter 3 set
to 3), the heating pump will still shut down when there is a call for domestic hot water.
If either the heating supply set point (parameter 4) , or the DHW reference set point (parameter 1) are set above
their factory set values, the boiler supply temperature will exceed 180°F and there is a possibility that the safety
temperature limit will open. If this happens, the boiler will shut down and a “b26” error will appear on the display.
The boiler will resume normal operation without manual intervention when the safety limit closes (this behavior is
common on conventional boilers).
Information mode is used to view various temperatures and settings but cannot be used to change parameters or
otherwise control the boiler. The information available is shown in Figure 11.2 and is largely self-explanatory. The
digit to the left of the decimal point is the Step number and the digits to the right are the corresponding temperature.
In information mode, the “supply water temperature set point” (Step 6), is the supply temperature set point for the
zone to which the boiler is currently responding (either heat or DHW). If an outdoor sensor is connected to the
boiler, and the boiler is responding to a call for heat, this value will be the current point on the reset curve. When no
call for heat or DHW is present, Step 6 shows the heating supply set point.
In some cases a “-22” will appear in Information Mode for a particular reading. This means that the reading is not
applicable. For example, “-22” will appear for the outdoor temperature (Step 4) if no outdoor sensor is connected to
the boiler.
CauTION
PushINg aND hOlDINg ThE “+” whIlE IN sTaNDby mODE wIll PrEVENT ThE
BoILER FRoM RESPoNDING To A CALL FoR HEAT. PuSHING AND HoLDING THE “-”
whIlE IN sTaNDby mODE wIll PrEVENT ThE bOIlEr frOm rEsPONDINg TO a
CALL FoR DoMESTIC WATER. IF THIS HAPPENS, “CoFF” oR “DoFF” WILL APPEAR
oN THE DISPLAy. To TuRN BACk oN THE HEATING FuNCTIoN, PRESS AND HoLD “+”
uNTIl “C” aND ThE sET POINT TEmPEraTurE aPPEars ON ThE DIsPlay. TO TurN
BACk oN THE DoMESTIC WATER FuNCTIoN, PRESS AND HoLD “-” uNTIL “D” AND
ThE sET POINT TEmPEraTurE aPPEars ON ThE DIsPlay. afTEr PrEssINg aNy
kEyS, AND BEFoRE LEAVING THE INSTALLATIoN, VERIFy THAT THE BoILER FIRES
IN rEsPONsE TO a Call fOr hEaT aND DOmEsTIC waTEr.