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Instruction manual
Part number 550-141-860/0107
5
Setup
① Determine ratio and adjust Reset Ratio dial (if heat curve is unknown, try 1.0 ratio). The
reset ratio dial number is the number of degrees (°F) the supply temperature control point
will change for each 1 °F change in outdoor temperature. See page 8 for more information.
② Set Max Temp to the supply water temperature needed at design outdoor temperature.
This will be the maximum temperature called for by the WM-ODR Outdoor Reset Control.
The boiler high limit must be set higher than the Max Temp setting.
③ Set the Differential Trim Pot to midscale (10°F). The boiler will turn off when the water is
10°F above the control point and turns back on when the water is 10°F below the control
point. The effect of differential is to prevent quick cycling of the boiler. If the boiler does
“quick cycle”, increase the Differential setting. Optimal performance is obtained when
this setting is as low as possible, but still allows for reasonable cycle time.
④ Do not use trim pots in the upper left corner of the control. These must be used only for
factory calibration.
Reset Ratio
Max Temp
Differential
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