Batboard

The place I work at is getting ready to bounce a few non-paying TX site tennants. Once they are gone, I get to upgrade the site. Already have a a copy of R56.

Question: For leased space rack cabinets, should you butt them together or is there a suggested distance between them? Racks will be lagged to the floor slab so the grounding bus can be run down the rear of the row.

why not butt them together?
Don't treat them like tennents, treat them like equipment and it makes sense.
If you are installing the gear its easy to make sure everything is R56 otherwise make sure its in your rental agreement that the tennent adheres to R56 standards.
We find tennents turn up with no polyphases, want to put cable on towers with no ground straps etc etc. We say sure put the requipment in the rack but you aint powereing it up yet until it conforms.

For reasons unrelated to grounding, the racks should be butted and tied together (near the tops). This will insure that for seismic analysis, they will react as a single unit (with a lower frequency response), rather than a bunch of individual smaller units or, worse, a bunch of individual smaller units that topple into the unit next to them.

Over the changes of time, the R56 standard has
undergone a number of changes. I am sure it will pass
through the tunnel of changes some more.

One of the least noticed but important changes is the
migration from single hole lug use to double hole lug
use. The prime reason for the change is the double hole
wire lugs are much less prone to come loose. Having
been in the cellular site construction field for many years,
I too have gone through that change.

The double hole lugs fare much better on ground bars
and cabinet grounding. You will also find that they stay
put much better on all the metal ground parts around a
building.

Liberal use of an anti oxide compound between the
ground lugs and the metal material help to reduce the
joint resistance over time. Don't forget to remove any
paint at the point of contact.

Jim

Jim202 wrote:The double hole lugs fare much better on ground bars and cabinet grounding. You will also find that they stay put much better on all the metal ground parts around a building.

Jim,
The plan is to connect the rack grounding jumpers to the ground lead with copper "H" clips that are swedged on with a 14 ton hydraulic press. From your perspective, does the swedged method work any better (or worse) then a bolted connection?

RKG wrote:For reasons unrelated to grounding, the racks should be butted and tied together (near the tops).

There are several different rack vendors. Is there a method of acomplishing this, short of drilling holes in the customers racks?

Martin

spareparts wrote: Racks will be lagged to the floor slab so the grounding bus can be run down the rear of the row.

You should put down a plinth first.
Something like 2 inch thick is good.
The idea is that the cabinet is isolated from the slabso you lag the plinth to the slab and the cabinets to the plinth.

It all has to do with single ground point

The hydralic compression crimp is far better than any
other compression fitting or ground lug. we use to buy
the 2 hole lugs by the box. Had then in differnt sizes to
match the wire size we were using.

Some cabinets come with grounding studs sticking out.
Most racks will need to be drilled to put in the bolts to
hold the ground lugs. We use to drill the holes into
the cabinets very carefully. Normally put some duct
tape on the inside and placed some or held a piece of
cardboard to diflect any chips inside the cabinets.

If there were other ownres of the cabinets, we normally
demanded that they provide a tech there to install the
holes and the grounding lug to the cabinet. As part of
the site lease, they are required to conform to the site
grounding standards. If they wouldn't abide, we just
simply pulled the plug to the power until they showed
up. We would place a tiewrap through the plug with a
note that said to contact site owner before power was
applied to the equipment again. Failure to do so would
result in equipment being removed from the site due to
breach of lease by the equipment owner.

Jim