Setpoint readout
3-22
Operation
These values are related as follows. A pump is allowed to dissipate
34.4 watts per element on a continuous basis. If excess power above
this value exceeds 3.56 watt-hours per element, the DIGlTEL enters
cool-down. The number of elements is determined from the 'S'
parameter.
Example 1:
A 220 1/s pump is operating at 51OOV, 19 mA. The power is 5100 x
0.019, or 96.9W. 96.9/8 = 12.1 watts per element. Since this is less
than 34.4, the pump runs under these conditions indefinitely.
Example 2:
A 60 1/s pump is operating at the above conditions. The power per
element is 96.9/2 = 48.5W/element. Excess power is 48.5 - 34.4 =
14.lW/elements. The power limit is reached in 3.55/14.1 0.25
hours, or 15 minutes.
The P value can be used to determine how close the pump is to
reaching power limit shutdown. These limits are shown in Table 3-9.
Pump Size
S Value
P Value
20-25
1
11
60-80
2
21
120-150
4
42
220-270
8
84
The current parameter works like power but it is not dependent on
pump size. A value of 50 mA is used continuously. When 50 mA-hr
of excess current has accumulated, the cool-down cycle is initiated.
Example
A pump uses 120 mA. Excess current drawn is 120 - 50 = 70 mA The
cool cycle is entered due to excess current after 50/70 0.71 hours or
43 minutes. This occurs when the I parameter reaches a value of 88.
Excess current and power parameters do not reset when the cool-down
is entered, but slowly decrease as 50 mA and 34.4W, respectively, is
subtracted from them.
The value of various setpoints can be read out. The format is:
where Xis:
1 for setpoint 1
2 for setpoint 2
3 for the bakeout setpoint
