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Author Topic: Shop building racks vs. onsite onstruction  (Read 7124 times)

Al Clayton

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Shop building racks vs. onsite onstruction
« on: January 19, 2011, 12:26:48 pm »

The good new is business is growing, and we are doing larger installs. The bad news is, we do a lot of public work and must pay prevailing wage when my guys are on site. Obviously the less time they spend on-site, the more profitable the job will be.

So I'm thinking I would like to be doing more pre-construction/wiring of racks in the shop.

Since the racks interface with field wiring, I wonder how practical it really is to wire in the shop. Certainly there is a savings to  be realized on the internal wiring. But are there ways to increase the speed/efficiency of terminating the field wiring in the rack?

It seems like a field termination would need to be made either way.

Does anyone have a good resource for best practices when it comes to this kind of thing? What do you do? Comments,suggestions,welcome. Pictures?
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Al Clayton

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Re: Shop building racks vs. onsite onstruction
« Reply #1 on: January 19, 2011, 12:42:20 pm »


Musings part II

There also are the issues transporting the racks themselves. A 77" rack, loaded with amplifiers and other electronics can easily exceed 600 lbs. So even if the rack is pre-wired, we often have to remove equipment just to transport the rack.

Especially if the amplifier room is on the second floor and the on access is a stairwell.

Inevitably the Electrical contractor wants the racks ahead of time so he can "Pipe" into the and pull cables. How do those of you who build racks in your shop handle those issues?

Just brainstorming a little here...
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Tom Young

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Re: Shop building racks vs. onsite onstruction
« Reply #2 on: January 20, 2011, 07:00:23 am »

Lots of issues with building racks in a shop versus at a job site.

Regarding terminations, I think that most contracting firms utilize screw terminals mounted on rack panels on the rear of each rack. These and the wires are labeled and correspond to shop drawings. Rack-to-rack wiring is sometimes done with multipin connectors whch are disconnected for transport. I prefer to not do this as it adds another connection point which can fail.

In some cases we connect directly to the equipment connectors.

Most of the racks I oversee are transported with equipment in them but in some cases we remove all, or the heaviest, gear and reinstall (plus re-terminate) them on site.

But trucking empty racks along with boxed equipment plus installation tools and equipment requires more truck space or additional runs.

It has been mostly my own smaller projects where the racks get built and wired on site. Seldom is it as easy due to lack of room and no easy means to elevate the rack (if it is less than full size) to make it easier to see and work on. It is also often a huge PITA to deal with boxes and other rubbish removal at the job site. Testing and signal tracing is much easier in the shop.

Running wire and bundling, supporting bundles, creating service loops and terminations (including teflon tube over shields and heat shrink, plus wire numbers) is easier in the shop where you have access to all tools and parts and no other-trade distractions or interference.

Although it perhaps would be easier to have the electrical tie-ins done with an empty rack, we always leave plenty of room for AC power and oversee where they knockout or create holes for connection of conduit. Perhaps half the time we do all inter-rack AC wiring and they work with our stub outs (at the top, usually) with a J-box and then make their terminations/splices.

There are other issues I cannot think of right now. I will be curious to read what others have to say.
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Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com

Charlie Zureki

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Re: Shop building racks vs. onsite onstruction
« Reply #3 on: January 20, 2011, 10:15:57 am »

  Hello,

  For my past installs, I've always considered the final location and the transportation of the racks, although the only real concern has been wall mounted racks. I would never expect anyone to try and hang a rack that's fully loaded.  Razz


 In most cases, I've installed the equipment and prewired and terminated all interconnects....then, the only tasks left are to terminate signal runs and connect the power feed to the rack.
(I use rack power rails of different lengths)

 If the racks are full heigth amp racks, I only install the bottom half of the rack and wheel in...the remaining amps to be installed on site.

  With two Techs and a refrigerator dolly it's pretty painless to get any rack where you need it.

   The racks today are so much lighter than the racks of 20+ years ago... ever try to move a 30 year old Cabtron rack?  Even an empty Cabtron rack?  Rolling Eyes   They weigh as much as a Buick!

 So...to sum up my answer...it depends on where the rack is going to live and how hard it is to get there.

 Cheers,
 Hammer
 

   
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Joseph Macry

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Re: Shop building racks vs. onsite onstruction
« Reply #4 on: January 20, 2011, 11:02:58 am »

My habit: Attached (wall mounted) racks with hard-wired terminations get built on site. Portable racks meant to plug into, say, wall plates are built in shop then delivered. Portable racks destined to be hard wired, I build in the shop unless the electrician needs to install flex conduit or install an outlet inside the rack.

Here, it doesn't make a big difference because our guys get the same wage on site or in the shop. But building in the shop usually saves a few trips to the job site.
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Joseph Macry
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Brad Weber

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Re: Shop building racks vs. onsite onstruction
« Reply #5 on: January 25, 2011, 02:58:29 pm »

Two points to possibly consider.  One is that if you work in some geographic areas then the Union E.C. will be pulling all cable and terminating it.  Period, end of discussion.  Another is that assembling and testing the racks in the shop offers some benefits and is often required by Consultants.  I don't know what your future plans are but if they may involve either of those situations then they could be factors.

I think it may also depend on the systems involved.  For instance, if you are dealing with AMX or Crestron control systems then building racks in the shop and even mocking up some of the connectivity to other components such as projectors can let the control system programming be tested and tweaked prior to going on site.

A division of the Contractor I worked for designed and installed the International Broadcast Centers for the Atlanta, Nagano and Sydney Olympics.  For Atlanta, since it was local much of the IBC was site built, however after the games were over they simply 'Sawzalled' through the cables (something like 16 semi loads worth) at the racks and loaded the racks on trucks.  After that experience, for Nagano and Sydney the venues there were mocked up in a warehouse here and palletized 'modularized' systems were completely built and tested here in Atlanta before being broken into the component modules and shipped overseas to be put back together on site.
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Brad Weber
muse Audio Video

Tom Young

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Re: Shop building racks vs. onsite onstruction
« Reply #6 on: January 25, 2011, 06:10:29 pm »

Quote:

Two points to possibly consider. One is that if you work in some geographic areas then the Union E.C. will be pulling all cable and terminating it. Period, end of discussion. Another is that assembling and testing the racks in the shop offers some benefits and is often required by Consultants. I don't know what your future plans are but if they may involve either of those situations then they could be factors.


Good points.

While the work I see on projects done in greater/metro NYC by the electricians can be very good, you do not want them terminatng to the rear panels of the equipment, or rather it is less daunting when they terminate the external wiring to shop-fabricated (and tested) termination panels at the rear of the racks. Our shop folks are more adept at routing, bundling and terminating within rack enclosures and the conditions within the shop allow for more delicacy.

Most of our consultant-designed projects require shop inspection during which we demonstrate that signals derived from within or fed into the rack are present and at appropriate levels, etc. at the outputs of the racks, or groups of racks.

FWIW
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Tom Young
Electroacoustic Design Services
Oxford CT
Tel: 203.888.6217
Email: dbspl@earthlink.net
www.dbspl.com

Brad Weber

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Re: Shop building racks vs. onsite onstruction
« Reply #7 on: January 26, 2011, 11:03:43 am »

Tom Young wrote on Tue, 25 January 2011 18:10

While the work I see on projects done in greater/metro NYC by the electricians can be very good, you do not want them terminatng to the rear panels of the equipment, or rather it is less daunting when they terminate the external wiring to shop-fabricated (and tested) termination panels at the rear of the racks. Our shop folks are more adept at routing, bundling and terminating within rack enclosures and the conditions within the shop allow for more delicacy.

The other option is to have the E.C. terminate to panels with pigtails out of the rack to those panels.

Tom Young wrote on Tue, 25 January 2011 18:10

Most of our consultant-designed projects require shop inspection during which we demonstrate that signals derived from within or fed into the rack are present and at appropriate levels, etc. at the outputs of the racks, or groups of racks.

Quite frankly, the main reason I require it is after running into a series of projects where the systems were not ready when they were supposed to be due to DOA, improperly operating or damaged equipment that had been sitting in the shop for weeks but was never even unboxed until everything was assembled in the field, at which point it was too late to address the problems in a timely manner.  Build the racks in the shop and make sure everything works and passes signal in advance and you then have time to address any such issues that do come up even if you can't get on site until the last minute.

When I was with a Contractor we built the racks in the shop whenever possible.  Along with better work space, another advantage to this was that it meant not needing to have as much parts inventory on the trucks (blank and vent panels, rack screws, lacing bars, etc.) and less of not having the parts needed at hand.
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Brad Weber
muse Audio Video

Al Clayton

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Re: Shop building racks vs. onsite onstruction
« Reply #8 on: January 27, 2011, 01:54:33 pm »

Great discussion guys. Lots of good stuff here. Just what I was hoping for.

Re: Union EC's pulling and terminating, I have found that it's a 50-50 proposition. Sometimes you get a guy who knows what he's doing, other times you get some H.S. dropout, flunky, apprentice who doesn't know a soldering Iron from a screwdriver...which is why I like my guys to do the terminations.

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