Installation guide

DECarray Site Preparation
Proper grounding between the DECarray and any enclosures connected
through a common DSSI bus is required.
WARNING
If the enclosures are not connected to a common ground, there is a
potential for a personal safety hazard.
If the ground offset voltages generated in the power distribution system exceed
allowable limits, data transmission across the DSSI bus can be affected. In
this case, the system(s) could experience significant performance degradation
or possible data corruption.
For a DSSI installation, the maximum ground offset voltage differential
allowed between enclosures is as follows:
DSSI Bus Length
1
Allowable Offset
Meters Feet DC AC
Up to 20 Up to 65 200 mv 70 mv
(rms)
20-25 65-82 40 mv 14 mv
(rms)
1
The total length includes all DSSI cable lengths, internal and external to the enclosures.
Ensure that the power distribution systems meet local codes prior to DSSI
system installation. In a properly wired power distribution system(s) with
properly functioning equipment (no ground faults) connected to it, there
is generally no need for any further attention to grounding. The power
distribution system provides a satisfactory path between enclosures.
To make sure that this is the case, perform a power system survey before
installation. Check for the following conditions:
1. Do any outlets being used not have power ground connections?
2. Is the grounding prong missing on any of the computer equipment power
cords?
3. Are any of the power outlet neutral connections actually ground
connections?
4. Are the grounds for any of the power distribution circuits (outlets) not
connected to the same power distribution panel?
DECarray Site Preparation 2–3