Manufacturer: Johnson Controls |
|
Description: ENTHALPY LOGIC CENTER
Category: Electrical Controls
N-9000 Enthalpy Logic Center
The N-9000 Enthalpy Logic
Center is a pneumatic logic
network designed to provide true
economizer control for all air
handing units capable of using
outside air for free cooling. By
selecting the appropriate air
stream (outside or return air),
the N-9000 imposes the lowest
cooling load on the mechanical
cooling equipment. This
selection is based on enthalpy
when outside air has the higher
moisture content and on
sensible heat when return air
has the higher moisture content.
Operation
Based on the transmitter
inputs, the N-9000 calculates
the outside air and return air
enthalpy. When outside air
enthalpy is greater than return
air enthalpy or when outside air
temperature is greater than
return air temperature, the
N-9000 provides a maximum
output signal of 10 PSIG
(70 kPa) or greater. This signal
returns the outside air damper
to its minimum position (see
Fig. 4). Note: If outside air
temperature is greater than
return air temperature, the
output signal is at maximum
and will not be reduced by a
change in the humidity
signal.
When outside air enthalpy is
less than return air enthalpy and
outside air temperature is less
than return air temperature, the
N-9000 provides a 0 PSIG
output signal. This signal
places the dampers under
control of the system controller
to obtain free cooling. By
enthalpy and sensible head
comparison of both outside and
return air conditions, the N-9000
provides the most efficient use
of free cooling and thus true
economizer operation.
Controls
Operation of the N-9000
requires input signals from
temperature and humidity
transmitters in the outside and
return air streams. These
transmitters are T-5210
temperature (0 to 100F) and
H-5210 humidity (0 to 100%
RH) with 3 to 15 PSIG (21 to
105 kPa) output pressure
ranges. The Enthalpy Logic
Center is furnished with internal
supply air restrictors to allow the
transmitters to be connected
directly.
An in-line filter is provided on
the supply connection and must
be used for protection of the
internal circuitry against
contamination.
Note: This
in-line filter cannot be
depended upon to remove all
contaminants.
Mounting
The N-9000 is equipped with an
integral mounting bracket and
two #8 sheet metal screws for
mounting on a wall, duct or
control panel. Air connections
can be made with 5/32 or 1/4 in.
O.D. polytubing to barbed
fittings on the unit. The supply
air connection should be made
with 1/4 in. tubing to the in-line
filter furnished with the unit.
Replaces Part Numbers: N-9000-1, CARN-9000-1