Install Instructions

9
VII - DPM-2 SETUP
COMMON TERMINOLOGY
RESET RATIO: The ratio between supply water temperature
and outdoor temperature. For example, a ratio of 1.0 or 1:1
means that, for every one degree that the outdoor tempera-
ture decreases, there will be a one degree increase in supply
water temperature.
MAX. TEMP: The maximum supply water temperature when
the outdoor temperature is 0°F.
DIFFERENTIAL: A measurement used to determine when
the boiler will turn on and off. A ten degree differential will turn
the boiler on at ve degrees below the control point and off at
ve degrees above while a twenty degree differential will turn
the boiler on at ten degrees above and off at ten below. The
effect of differential is to prevent quick cycling of the boiler.
TO SET UP THE DPM-2 CONTROL
1. Determine the reset ratio and adjust the “Reset Ratio Trim Pot.”
If the heat curve is unknown, try a ratio of 1.0.
2. Turn the “Max. Temp. Trim Pot” to the design temperature of the
supply water (the water temperature needed when the outdoor
temperature is 0°F).
IMPORTANT: Boiler high limit must be set higher than the “Max.
Temp.” setting plus the “Differential” or the unit may operate er-
ratically.
3. Set the “Differential Trim Pot” to scale (10°F). The boiler will turn
off when the water is 5°F above the control point and back on
again when the water is 5°F below the control point. If the boiler
does “Quick Cycle,” increase the trim pot. Optimal performance
is obtained when this setting is as low as possible, but still allows
for a reasonable cycle time.