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The BCP-8W has multiple operating modes that satisfy most hydronic systems. When the
Outdoor Reset is selected, it can change the System Set Point based on outdoor temperature.
Or, it can be set to Set Point and sequence stages to achieve a manually adjusted Set Point.
In Outdoor Reset, the BCP-8W controls a hot water heating system to provide a building with
comfortable and even heat levels. The BCP-8W varies the Target temperature of the circulating
heating water in response to changes in the outdoor temperature.
The BCP-8W also controls the system circulating pump with an adjustable Outdoor Cutoff.
When the outdoor temperature is above the Outdoor Cutoff, the System Pump will be off
and no heating water is circulated through the system. When the outdoor temperature drops
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circulate through the system. The temperature of the heating water is controlled by the Reset
Ratio parameters or the Set Point.
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When a building is being heated, heat escapes through the walls, doors, and windows to
the colder outside air. The colder the outside temperature, the more heat escapes. If you
can input heat into the building at the same rate that it is lost out of the building, then the
building temperatures will remain constant. The Reset Ratio is an adjustment that lets
you achieve this equilibrium between heat input and heat loss.
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temperature drops, the temperature of the heating water will increase one degree. The
starting point of the curves is adjustable, but comes factory selected at 70°F Outdoor
Temp. and 100°):DWHU7HPS)RUH[DPSOHZLWKD2'6<6UDWLRLIWKH
outdoor temperature is 50°F, this means the temperature has fallen 20° from the starting
point of 70°F. Therefore, the heating water temperature will increase 20° to 120°F.
Each building has different heat loss characteristics. A very well insulated building will
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degrees to increase the water temperature 1 degree. On the other hand, a poorly insulated
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This means that for each degree the outdoor temperature dropped the water temperature
will increase 2 degrees. The BCP-8W has a full range of Reset Ratios to match any
buildings heat loss characteristics.
A heating curve that relies not only on Outdoor temperature but also on the type of
radiation will improve heat comfort. The following are suggested initial settings for
different types of radiation based on average building insulation and heat loss. The
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Radiators (Steel & Cast Iron) 1.00 (OD) : 1.00 (SYS) Û)
Baseboard (Finned copper tube& Cast Iron) 1.00 (OD) : 1.00 (SYS) Û)
Radiant (High Mass/Concrete) 4.00 (OD) : 1.00 (SYS) Û)
Radiant (Low Mass/Joists) 2.00 (OD) : 1.00 (SYS) Û)
Fan Coils & Air Handlers 1.00 (OD) : 1.00 (SYS) Û)
Outdoor Temperature
Water Temperatur e
70 405060
130
120
110
100
Outdoor Temperature
Water Tem perature
70 405060
110
100
90
80
Outdoor Temperature
Water Tem perature
70 405060
150
140
130
120
1:4
With a 0° Offset, the
ratio curves begin at
100° Water Temperature.
With a -20° Offset, the
ratio curves begin at
80° Water Temperature.
With a +20° Offset, the
ratio curves begin at
120° Water Temperature.
1:4
1:4 1:1
1:1
1:1
4:1
4:1
4:1
90
100
+20 Offset
-20 Offset
(O) Outdoor Temperature (in °F)
70 60
50
40 20
30 0 -10
10 -20
100
120
110
130
140
150
160
180
170
190
200
210
220
1:3 1:2 1:1.5
1:1.25
1:1
1.25:1
1.5:1
2:1
3:1
4:1
(S) Water Temperature (in °F)
Reset Ratio Curves
Reset Ratio is Presented as
Outdoor Temp.(O) : Water Temp.(S) Ratio
1:4
8:1
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