Orion System VAV/Zone Controller - Manual (Page 7)

VAV/Zone Controller
Technical Guide
7
120 / 24VAC
120 / 24VAC
120 / 24VAC
120 / 24VAC
80 VA
Transformer
Minimum
See Warning
Note Below
40 VA
Transformer
Minimum
See Warning
Note Below
100 VA
Transformer
Minimum
See Warning
Note Below
75 VA
Transformer
Minimum
See Warning
Note Below
Power/Comm
Board
Power/Comm
Board
Power/Comm
Board
Power/Comm
Board
Total length of all modular cables used on each branch ( A to B) cannot exceed 240 Ft.
Total length of all modular cables used on each branch ( A to B) cannot exceed 240 Ft.
A
A
A
A
12 Devices At 6 VA = 72 VA
Use 75 VA Transformer 6 Devices At 6 VA = 36 VA
Use 40 VA Transformer
16 Devices At 6 VA = 96 VA
Use 100 VA Transformer
13 Devices At 6 VA = 78 VA
Use 80 VA Transformer
6 Devices Maximum Per Branch Circuit
6 Devices Maximum Per Branch Circuit
Figure 5: VAV/CAV Controller Transformer Sizing
Modular Devices - Transformer Sizing
Modular devices include the VAV/Zone Controller, Modular System
Manager & MiniLink Polling Device. All of these devices connect to
each other and a Power/Comm Board using prefabricated modular cables.
When sizing transformers for these devices it is important to design
your layout so that the fewest number of Power/Comm distribution
boards and the least number of transformers can be used.
In order to simplify wiring design and layout with modular devices the
following rules apply:
1. Power/Comm Board maximum transformer size = 100 VA.
This is due to the board circuitry and fusing. Each modular
device is to be calculated at 6 VA. This allows for a
maximum of 16 devices per Power/Comm board. If more
than 16 devices are required, multiple Power/Comm boards
must be used. Any Slaved Zone actuators used are
considered a modular device and must be accounted for at
6 VA. each. They also must be included in the branch
circuit maximum quantity of 6. See rule #2 below.
2. No more than 6 modular devices allowed per branch circuit.
(Each Power/Comm board has 4 branch circuits
available on the board )
3. The longest total run per branch circuit is 240 Ft. This is
due to voltage drop on the prefabricated cable. If cable runs
longer than 240 Ft. are required, additional Power/Comm
board(s) can be used. Each Power/Comm Board connected
in series with the first Power/Comm Board would allow for
an additional 240 Ft. of modular cable to be added to the
total cable run length.
See Figure 5 for information and some examples of transformer sizing
and branch circuit design.
Warning: Do not ground the 24 V transformer that is to be
used with the Power/Comm boards. Grounding
of the transformer will damage the Power/Comm
board and all boards connected to it. A separate
transformer must be used for each Power/Comm
board. No exceptions. Do not connect any other
devices to the transformer used for the Power/Comm
board.