Section II
General Product Information
006-0007097 02/14/2019
Rev E
22 of 52
UPS-1250DC Guide www.synqor.com
Power Cable Wire Size
SynQor recommends the following cables for use with the UPS-1250 DC Output Series:
AC Input:
SYN-9101 UPS connection to NEMA 5-20 Plug, 10’
SYN-9104 UPS connection to NEMA 5-15 Plug, 10’
SYN-9102 UPS connection to Hardwire Termination, 10’
DC Input:
SYN-9151 UPS connection to Ring Connectors, 10’
SYN-9154 UPS connection to NATO Connector, 10’
DC Output:
SYN-9174 UPS connection to Harwire Termination, DC Output, 10’
SYN-9175 UPS connection to Fork Connectors, DC Output, 10’
Other options may be available. Contact [email protected] or visit the website: http://www.synqor.com for
more information. If it is necessary to develop custom cables for your application, please read through the
following section for some important considerations. Damage caused by improper wiring of cables will not be
covered under SynQor’s warranty.
Both the input and output cables of the UPS carry substantial current, and since the wires in these cables have
resistance the current flowing through them causes a voltage drop from one end of the cable to the other. In
other words, the voltage across the cable at its downstream end is smaller than the voltage across the cable at its
upstream end. Mathematically, the amount that the voltage drops is equal to the resistance of the cable’s wire
multiplied by the current flowing through the wire. It is therefore important to make sure that the resistance of
the cable’s wire is small enough to keep this voltage drop to an acceptably small value.
While this is an issue for all of the power cables, it is particularly important for the DC INPUT and DC Output
cables because the current flowing through it is very high (as high as 65 A for the UPS-1250 DC Output Series)
and the voltage across it is already relatively small (as low as 22 V). In fact, a common problem that arises
(when the DC INPUT cable has too small a wire) is that the voltage seen at the DC INPUT of the UPS falls below
the minimum specified value of 22 V even though the voltage at the source of the DC power is greater than 22
V. Under this condition the UPS will switch to the internal battery pack for its power source even though the
voltage at the DC source of power appears to be available and at a proper level.
The resistance of a wire depends directly on its length. A wire twice as long as another will have twice the
resistance, holding all other things constant. The resistance also depends on the reciprocal of the cross-sectional
area of the wire, which in turn depends on the square of the wire’s diameter. A wire with half the diameter of
another will therefore have four times the resistance, holding all other things constant.
Therefore, the longer a cable is, the more important it is that the wire’s diameter be large. Alternatively, a cable
can have multiple pairs of wires to achieve a larger “effective wire diameter”. This second approach gives a more
flexible cable. For 10 ft long cables, SynQor recommends that for the UPS-1250 DC Output Series:
• The AC INPUT cable has 3 wires (one for the ground) of 12 AWG
• The DC INPUT cable has 6 wires (three for each connection) of 12 AWG
• The DC OUTPUT cable has 6 wires (three for each connection) of 12 AWG
Additional details about the effects of a resistance-related voltage drop are included in “Trouble-Shooting
Guide - Cable wire resistance is too high”.