Installation and Operations Guide
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Hardware installation
© Honeywell. All Rights Reserved. LT-VLXEXPAXMIOG Rev. 01
29
This design requires a transformer with a Nameplate rating of 100 VA (or in
excess of 4 Amps @ 24 V) to adequately provide unit power to the VLX, its one
EXP, and two AXMs. This serves only to supply unit power, and a separate
transformer must be used to supply BO power.
De te rmine the s ize o f the trans fo rme r for EXP/AXM BO po we r
1. Find the BO rating on each EXP/AXM. This is listed as “BO MAX
LOAD.” Each BO draws up to 12 VA from the AC source.
2. Add the power required by all devices
3. Multiply by a 25% safety factor:
192 VA X 1.25 = 240 VA
This design requires a second transformer with a Nameplate rating of 240 VA (or
10 Amps @ 24 V) to adequately provide power to BOs.
A 10 Amp fuse on the hot leg of the 24 VAC power supply is recommended.
Selecting cable for 24 VAC power
If you are considering long power supply wiring runs, the right cable is critical.
If the cable is too small, the resistance may be too high, resulting in low voltage
supply. This is line loss. Cable size is based on length of the run and current draw
of the units or loads to be powered. Use Figure 18 to determine cable size in
AWG. Obtain additional information from the transformer manufacturer.
De vic e BO MAX LOAD
EXP-10120 144 VA
AXM-10 4 8 48 VA
AXM-22 0 0 0
Total: 192 VA
Figure 18 Cable -se le ction chart for 24 VAC. Find inte rs e ction of distance (Fe e t
of Wire ) and curre nt (VA). The n re ad the diagonal line to the right to s e le ct
appropriate wire size in AWG.
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