dslreports logo
 
    All Forums Hot Topics Gallery
spc
uniqs
46
Hahausuck
Premium Member
join:2003-12-14

1 edit

Hahausuck to lutful

Premium Member

to lutful

Re: [Tech Ops] Motorola R56 Document

said by lutful:
said by Hahausuck:

What I meant was those entries are used for exactly what I stated ... I've never seen them used for anything otherwise though one could do such if they wanted to.

If you are given clear and written directions by an engineering firm to use the same integrated bulkhead panel to bring in AC power, RF coax, POTS, telco, misc control, and even fibers with metallic strength members, ... please do not change the design based on what you think is correct or allowed.

Why would someone do that? Example: If we are given directions to do something we follow them to the T. Hence, we follow R56 to a T as all of our designs are based on R56. When we plan our own sites we build the site following R56 word for word, no more no less.

Are you assuming I or anyone else would blatantly disregard the directions of the system designers?
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

2 edits

lutful

Premium Member

Click for full size
said by Hahausuck:

If we are given directions to do something we follow them to the T. Hence, we follow R56 to a T as all of our designs are based on R56. When we plan our own sites we build the site following R56 word for word, no more no less.
What do you do when R56 provides multiple alternatives? Can we choose clamping instead of exothermic bonds? Can we choose bonding/grounding path through building structure instead of copper conductor?

But I really wanted to ask some more relevant and important follow-up questions. Please consider above telecom shelter diagram from R56.

Assume operator wants to bring in some copper T1 and POTS lines into same shelter from different service providers for redundancy.

Assume you have decided to use separate entry panel "per service" because you think it is prohibited to run them through unused conduits in that panel.

What is the R56 guidance on minimum physical separation between separate entry panels?

Do you use one [panel/conduit] per T1? One per service provider if they supply both T1+POTS lines? One for all T1 lines together even if they come from different providers? I reduced some text clutter and drew in 2 panels but you can suggest any number of panels/conduits located anywhere around the shelter.

Where/how do you bond these separate service entry panels/conduits and related surge protectors to the external/internal grounding system?

And one more question, should they have put some more distance between AC and coax entry panel? For a bit more "protection" from lightning surge perhaps.
Hahausuck
Premium Member
join:2003-12-14

1 edit

1 recommendation

Hahausuck

Premium Member

When there are multiple alternatives one should follow the document for those types of situations. When there are questions, one should consult Motorola (if following R56) or contact the appropriate EE firm specializing in grounding and earthing.

Telco typically enters in through the designated telco entry area, be it near the RF feeder entrance or elsewhere in the shelter. This is how all shelters are built from what I have found in the USA. The only thing entering the shelter through the RF cable entry port is RF cables (antenna lines, CCTV, POE, IF+power, etc). That is it, nothing more. I don't know why that is such a hard concept for you to grasp but it is just done that way. I am sure the documents that everyone follows (be it R56, RO Associates, Bell, etc) have it stated as such. It just is how it is done and no one is about to change, so even though you may not accept it (your choice) myself and the rest of the industry is not about to change unless we are told so by the manufacturers or industry standards change.

Sheath bonding (both CU and Optical cables) and SPD's shall be bonded using an appropriately installed SSGB and bonded back to the MGB which is then in turn naturally bonded to the EGB and site ground system. If there are multiple entries then those should be treated the same as far as grounding and bonding. Everything bonds to the MGB. Please read the section on the MGB for further information.

As far as spacing of electrical, I do not find anything dictating X distance but this is stated throughout the manual:

To facilitate single-point grounding, request that electrical service enter the site building on the same wall as and near to the entry point for the antenna transmission lines.

I cannot answer any more questions, i suggest reading the entire document, that should clarify all of your questions. Further questions should be directed to Motorola Engineering. I am sure if you had some valid reasons to not do something they would be interested in listening to them provided they meshed with the standard communications site installation practices and other industry standards and rules and laws.
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

1 edit

lutful

Premium Member

said by Hahausuck:

be it near the RF feeder entrance or elsewhere in the shelter ...
There must be some guidance electricians follow on maximum distance? Because the physical distance between conductor entry points, even if bonded with zero ohm path, determine the real danger to both humans and equipment during a lightning surge.

That is why R56 document contains clear guidance such as "AC Power, Telephone Circuits, Cable TV, CCTV, and card access control cables must enter within the same area" for absolutely critical installations like dispatch center in the first diagram I copied. That is also why the AC entry is so close to the integrated bulkhead entry in the second diagram.

Even 3ft separation between well-bonded/well-grounded/well-protected entry points may kill someone and damage lots of equipment with a sufficiently strong surge. The relevant electrical engineering calculations are simple and "as built" installations can be tested with simulated lightning surge.

No need to wait for detailed engineering analysis after an unfortunate event like Sago coal mine in Virgina.
Hahausuck
Premium Member
join:2003-12-14

Hahausuck

Premium Member

I assume so on the distance.

I just don't have any concrete answers on this part, other than what the books say to do/not do coupled with the fact that all of the shelters I have been at either have it on the same wall as the entrance, OR the power enters from a spot across the room on a completely different wall.

This experience holds true for cellular site installations, and I am pretty sure they have qualified engineers design those systems.
lutful
... of ideas
Premium Member
join:2005-06-16
Ottawa, ON

4 edits

lutful

Premium Member

said by Hahausuck:

OR the power enters from a spot across the room on a completely different wall
So far I found these general guidelines about service entry:

" preferred configuration for a stand-alone equipment shelter is to have all utilities enter the structure through a common wall as close as practical to the transmission line entry port location."

"Antenna transmission lines and other communications cables with metallic sheaths shall be grounded as close as practical to their point of entry into the building or shelter"

"RF transmission SPDs shall be bonded to the MGB within 610 mm (24 in.) of entry"

"RF transmission line SPDs may also be bonded directly to ... integrated entry panel"

"purpose of the external ground bus bar (EGB) is to provide a convenient grounding (earthing) termination point for antenna transmission lines (coaxial cables) and other cables prior to their entry into a building or shelter"

Logically combining such clear guidance, it seems to me that R56 will allow all telecom services to enter through a single "integrated cable entry" system.