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CAUTION
Danger of sharp metallic edges. Can cause injury.
Take care when servicing unit to avoid accidental
contact with sharp edges.
Supply Air Installations − With Plug
This section is used when replacing a supply air smoke
detector which is equipped with a 15−pin plug.
1− Install the sampling tube bracket in the smoke
detector bracket. See figure 2.
2− Install smoke detector and bracket in unit as shown in
figure 3. Secure both in place using four 5/8" screws.
3− Connect the smoke detector plug to unit J102.
Supply Air Installations − No Plug
This section is used when replacing a supply air smoke
detector which is NOT equipped with a 15−pin plug.
1− Some units have a separate power source for the
smoke detector instead of the main circuit breaker.
Disconnect the 24 volt wires as shown in figure 4.
CAUTION – Transformer has 120 VAC input.
SMOKE
DETECTOR
SMOKE
BRACKET
DETECTOR
SMOKE DETECTOR BRACKET (SUPPLY AIR INSTALLATIONS)
EXHAUST
TUBE
2− Open the cover of LD4120 smoke detector. Remove
and discard the 6− and 15−pin plugs and harnesses.
3– Use foil tape to cover the open access hole. Knock
out the optional access hole on the end of the
detector. See figure 3.
4– Remove the cover from the old smoke detector. Mark
wires with terminal number if not already marked.
Disconnect wiring from old terminal strip.
5– Route wiring through new access hole and connect to
new LD4120 smoke detector according to terminals
shown in table 1. Replace cover.
6– Remove sampling tube brace from smoke detector
bracket. Install on the opposite side of smoke detector
bracket using the holes provided. See figures 2 and 3.
7– Install the smoke detector on the smoke detector
bracket and install the bracket in the unit. Drill new
mounting holes if required.
8– Reconnect the smoke detector wires to the
transformer.
FIGURE 2
Page 2
SAMPLING
TUBE
SAMPLING
TUBE
BRACKET
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