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2008-10-01
(6) As the water is boiled away, the minerals left behind increase the conductivity of
the water in the cylinder. As soon as the conductivity is greater than design, the Ta
to boil from A to D will be shorter than To and a drain cycle is initiated.
(7) The fill valve always opens during timer drains, adding cold water to mix with the
hot water from the cylinder during automatic drain cycles. This tempering process
is required to meet plumbing codes.
(8) As can be seen from a typical sequence depicted in Figure 4, the P+I Auto-
Adaptive system allows the unit to be self-regulating. It drains only when necessary
and only the amount of water to maintain optimum operating conditions.
(9) Relying on the proportional (P) feedback only to decide how much to drain is like
guessing what is happening based on a ‘snapshot’ only. By taking into
consideration a series of “snapshots”: (one from each of the past ten cycles for
example), the control system has more data on which to base its decision to drain.
The integral (I) part of the P+I Auto-Adaptive system provides this added feedback.
(10) The proportional (P) and integral (I) factors have been weighted as to the relative
influence each will have when the NHTC/NHPC calculates a drain. The
preprogrammed weighing was derived through extensive field and laboratory tests.
When supply water conductivity is extremely high (requiring substantially more
drains), the NHTC/NHPC will see the pattern developing in cycles stored in
memory. It will then initiate additional drains to adjust the contained water
conductivity.
(11) If low conductive water conditions occur, the P+I control will reduce the drains
necessary to maintain optimum operating conditions within the cylinder. If extreme
water conditions are encountered, the NHTC/NHPC can be reprogrammed with
factory instructions to compensate.
(12) NORTEC’s P+I Auto-Adaptive control system has been designed to benefit users
who demand very tight control of the relative humidity. It maintains steam output
above the B level, even during auto drains. (See Figure 4.)
(13) The P+I Auto-Adaptive control system allows the humidifier to maintain tighter
humidity control without the problem of rh depression during drain cycles that occur
with other humidifiers. This results in more consistent space rh levels, even with a
simple on/off control system.