Installation Instructions

Document No. 546-00011

Rev. 2, October, 1999

Page 2 of 5

Siemens Building Technologies, Inc.

Electronic Actuation

Wiring the AO-E Module and differential pressure

transmitter to the Fume Hood Controller.

FHET Installation

Installation of the FHET in the exhaust duct or on

a fume hood.

1. There are two locations to place the FHET:

•

In the exhaust duct.

•

On a fume hood.

Slip-Slip and Flange-Flange ends are for placement

within the exhaust ductwork; Bellmouth ended units

are for mounting onto a fume hood only (Figure 2).

Terminal measurements are included in Table 1 and

Table 2.

Flange-Flange or Slip-Slip Ends Mounted in Duct.

Bellmouth End Mounted on Fume Hood.

Figure 2. Mounting the FHET.

For installations other than the Bellmouth

unit, which is mounted directly to the fume

hood, the FHET must have at least 2 ½

duct diameters of straight rigid ductwork

upstream of it (Figure 3). Failure to have 2

½ duct diameters upstream of the FHET

will adversely affect the flow measurement,

accuracy and stability.

Figure 3. FHET Properly Installed after an

Elbow Duct Section.

2. Use accepted trade practice to weld or bolt the

ends of the FHET to the duct or fume hood. Seal

and check all duct connections for air leaks after

installing the FHET. For Bellmouth units, remove

any excess sealant from the inner surface of the

Bellmouth.

Always mount the FHET equipment

enclosure on the side of the duct

(vertically) (Figure 4). Mounting the

equipment enclosure on the top or bottom

of the duct (horizontally) will adversely

affect the measurement accuracy.

Figure 4. FHET Installed Properly.