KAH Operation & Maintenance Guide
Page: 61 of 88
Krueger | 1401 N Plano Rd | Richardson, TX 75081 | 972.680.9136 | [email protected] | www.krueger-hvac.com
SECTION 4 - SERVICE & REPAIR
FIGURE 71 - CONSTRUCTION OF PITOT TUBE
FIGURE 72 - MINIHELIC FILTER GAUGE
PITOT TUBE
The pitot tube consists of an impact tube within a larger
static tube. When the impact tube is pointed directly
into the air stream, the small static pressure holes are
perpendicular to the air stream and are not affected by air
velocity as shown in Figure 70 on the previous page.
To read velocity pressure, the total pressure tap at the end
of the pitot tube is connected to one leg of a manometer and
the static pressure tap at the other leg of the manometer
as shown in Figure 71 (right).
INCLINED MANOMETER
This instrument is a simple, fool proof device, which
responds directly to the air pressure exerted against
it (transmitted from the pitot tube), and reads directly in
inches of water. Ranges vary. The technician should have
one or more instruments to cover the range of 0-8 inches
of water as shown in Figure 71 (right).
Before using the inclined manometer, ensure the
instrument is level, and then adjust the meniscus to the
zero mark. The adjustment knob is located at the base of
the fluid reservoir.
MINIHELIC FILTER GAUGE
The Minihelic Filter Gauge, a diaphragm-operated gauge,
has several advantages over a liquid manometer.
Unless extreme accuracy is required, this instrument
may replace the manometer for average air conditioning
work, and like the manometer, is available in a variety of
ranges. The dial is only two inches in diameter and has
a limited scale; several instruments are required to cover
the normal ranges encountered in average air conditioning
jobs as shown in Figure 72 (right).
The Minihelic Filter Gauge should be factory-installed level.
The adjust indicator to zero with no airflow or pressure
difference across the sensors. The adjustment screw is
located at the bottom behind the plastic cover. When the
airflow is initiated, the indicator should move to the right. If
it moves in the opposite direction, reverse the tubes.