Mounting in an inaccessible location
1. Determine the mounting location for the low limit
control.
- Avoid any moving parts within the duct, such
as dampers.
- When the duct is covered with insulation,
mount the control to a standard electrical
4- square box and cover.
2. Using Figure 5 as a guide, measure the duct and
calculate the required length and height of the
element support.
3. Use 1/2 in. (1.3 cm) of EMT to build the support
assembly outside of the duct.
Note:
You can substitute 3/8 in. (1 cm) of
hard copper tubing for 1/2 in. (13 mm) of
EMT when you build the support. These
instructions assume the use of EMT.
4. Starting at the bottom of the coil, distribute the
sensing element around the support and use a tie-
wrap to secure it in place. Keep the loops horizontal
or inclined slightly downward at an angle not
greater than 5° and uniform in size (see Figure 5).
5. Consider the use of Minerallac conduit hangers
or equivalent to provide anchoring points on the
support where needed.
6. Place a 1/2 in. (1.3 cm) EMT connector on each end
of the support. These connectors protrude through
the knockout hole on the 4 in. (10.1 cm) box covers,
which are used as mounting plates at each end of
the support.
7. At the upper end of the duct, use a large hole saw
of minimum size 2-1/4 in. (57 mm) to drill the entry
hole for the sensing element or support assembly.
8. At the lower end of the duct, drill another hole. Use
the same hole saw that you used to cut the entry
hole.
9. A larger hole provides easier access for mounting.
Position this hole so that the lower portion of the
sensing element is within 6 in. (152 mm) of the
bottom of the coil.
10. Cut a notch in another 4 in. (10.1 cm) box cover.
Use the notch to secure the upper end of the
support assembly. Locate the notch so that you can
position the capillary (whip) close to the support.
11. Place a 4 in. (10.1 cm) box cover, with the center
knockout removed, over the upper end of the
support assembly, and use a lock nut to fasten the
support to the box cover.
12. Feed the sensing element or support assembly
through the entry hole at the upper end, and
position the lower end of the support to protrude
through the exit hole at the bottom on the far side.
13. Place a 4 in. (10.1 cm) box cover with the center
knockout removed over the end of the support and,
using a lock nut, fasten the support in place at the
lower end.
Figure 6: 4-square cover upper mount with center 1/2
in. knockout.
Table 5: 4-square cover upper mount callouts
Callout Description
A
Use a hacksaw to cut a slot for the
sensor to pass through.
B
Use a drill to cut a 1/4 in. hole. Cover the
element with poly for protection.
C
To secure 1/2 in. EMT to the box cover.
14. Carefully place the capillary tube in the slot and
apply a short piece of 1/4 in. (6.4 mm) poly tubing,
slit lengthwise, around the capillary where it passes
through the notch.
15. Screw down the corners of the box cover to hold
the upper end of the support assembly in place.
16. Use the mounting bracket and self-tapping screws
to fasten the control to the side of the duct,
ensuring a downhill element all the way to the
bottom of the control.
Wiring
For most AHU installations, it is more cost-effective to wire
the low limit and other safeties with low voltage Class 2
wiring and add a shutdown relay at the motor starter.
This practice provides the control to share raceways with
other low voltage cables for the system.
CAUTION
Risk of Electric Shock
Disconnect power supply before making electrical
connections to avoid electric shock.
Important:
Make all wiring connections in
accordance with local, national, and regional
regulations. Do not exceed the electrical ratings.
A11 Series Low Temperature Cutout Control Installation Guide
5
