Design Guide — Doc. 9292A
Cresnet® Network • 21
2. Under Power Suppliers, enter the quantity of the desired Cresnet servers and power
supplies within their applicable table rows.
3. Under Power Consumers, enter the quantity of the desired Cresnet clients within their
applicable table rows.
The Estimated Usage column on the right of the screen updates dynamically to show the current
power surplus or deficit value based on the selected device quantities.
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Select Print Results to print a summary of the selected devices and estimated power
usage.
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Select Clear Results to clear all quantity values entered within the calculator.
Calculate Power Requirements for Wire
Runs
The correct wire gauge must be selected to ensure that a wiring run can supply sufficient power
to the Cresnet clients on a particular network leg. The length of the wiring run and power draw
of the Cresnet client(s) must also be considered.
Wire Gauge Overview
The black and red twisted pair (24VDC power and ground) is used for powering Cresnet clients.
Therefore, only the wire gauge for this twisted pair is required when calculating power
requirements for wire runs.
The blue and white twisted pair (Y and Z data) does not factor into Cresnet power calculations.
Data distances are independent of power requirements and are calculated using 22 AWG
(0.33 mm
2
) with a maximum run of 1,500 ft (457 m) per Cresnet server. Data wires are a twisted
pair with foil shield, helping to reduce noise and interference.
Resistance Equation Formula
The following formula is used to calculate the correct wire gauge required for a particular leg of
a Cresnet wiring run. The formula can also be rewritten to solve for other variables (such as
length of wiring run).
Resistance Equation: R < 40,000 / (L x PF)
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R = Resistance value, in ohms (refer to the following table)
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L = Length of wiring run (or chain), in feet, from the power source or supply
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PF = Cresnet power factor of the entire wiring run (or chain) for all Cresnet client devices
