Constant outside air (oac) control, In. od tubing. for runs over 150 ft, use, Sensor (wall mount version shown) – Carrier 39L User Manual

Page 50: Fig. 40 — ventilation rates based on co, Set point, Fig. 43 — probe manifolding 50

Constant Outside Air (OAC) Control —

This fea-

ture ensures a continuous supply of outside air to the unit
and occupied space. The OAC control monitors the outside
air velocity pressure (OAVP) with a probe and pressure trans-
ducer. The pressure transducer is factory-installed; the probe
is factory-supplied for field installation in the outside air ducts.
See Fig. 41 and 42.

PROBE INSTALLATION — Locate each probe in a straight
portion of the outside air duct with any dampers, elbows, or
fittings at least 2 diameters away. The probe should be in a
portion of the duct where the airflow is uniform, so that the
probe senses the average air velocity in the duct. The probe
must also be located so that measurements at the probe are
not influenced by the opening or closing of the outdoor-air
dampers.

Install the probe at a 90 degree angle to the airflow and

ensure that the holes in the probe are facing and in line with
the airflow. The probe tube that is closest to the incoming
airflow measures velocity pressure; the rear tube measures
duct static pressure. Use approved plenum tubing to connect
the probe to the bulkhead fittings on top of the control box.
For runs up to 150 ft, use

⁄

-in. OD tubing. For runs over

150 ft, use

⁄

-in. OD tubing. Use at least 25 ft of tubing to

prevent pulsations and erratic operation. Coil any extra tub-
ing if necessary.

If the outside air duct is large, additional probes can be

installed in the duct and manifolded to obtain a more accu-
rate velocity pressure reading for the entire duct. Manifold
tubing must be larger than the plenum tubing connecting the
manifold to the control box. See Fig. 43 and the preceding
for recommended tube sizes.

Fig. 39 — Air Quality (CO

) Sensor

(Wall Mount Version Shown)

CONCENTRATION (PPM)

Fig. 40 — Ventilation Rates Based on CO

Set Point

24 V

ac.

OUT

PRESSURE

SPAN

ZERO

PRESSURE

TRANSDUCER :

Part Number :

Range : 0 -

0 . 1 in.

of water

CARRIER

CORPORA

TION

T40 - 001C - 04 - 012

9A32201

Fig. 41 — OAVP Transducer (P/N HK05ZG004)

Fig. 42 — OAVP Probe (P/N 35DN40007001)

NOTE: High-pressure manifold connections shown. Low-pressure con-
nections are identical and must duplicate high-pressure connections.

Fig. 43 — Probe Manifolding