Prefab shop

[brantmacga]

We're discussing the idea of starting a prefab shop; I've never done this or worked anywhere that did.

We do mostly fast food restaurants and some small retail here and there.

Where's a good place to start on figuring this out?


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[peter d]

Well, I have no experience with this, so my opinion is not worth much. But, what are the assemblies you use the most of? It seems you wouldn't have much need for prefab with the kind of work you do, prefab is really geared toward multi family and high rise kind of of installation.

 

[Fulthrotl]

We're discussing the idea of starting a prefab shop; I've never done this or worked anywhere that did.
We do mostly fast food restaurants and some small retail here and there.
Where's a good place to start on figuring this out?

i've worked for large shops that did extensive prefab.

where it works well, is TI office stuff, where they cut MC into whips,
put ends on it, etc.

a common thing was a 4S box on a sheet metal foot, with a box and
ring attached, and a small bent 90 on the sheetmetal to keep it from
flopping back into a 2 1/2" steel stud wall. you shot them down to
the floor thru the bottom track.

scatter.
shoot down.
punch two holes above every box with a stud punch.
throw a precut MC cable box to box.

throw lights up in the grid.
precut MC cable between fixtures
switchleg down to switch box.

shoot up ceiling wires and bundle everything up.
it works well if you are doing floor after floor of suites.

sasco was the undisputed king of this sort of work. they
were the 4th largest EC in the country, and doing it all
on TI work in LA and orange county.

i'm in a lot of fast food restaurants, and i'm wondering
how much good this would do you.

what could you make beforehand that would save you?

 

[cdslotz]

We're discussing the idea of starting a prefab shop; I've never done this or worked anywhere that did.

We do mostly fast food restaurants and some small retail here and there.

Where's a good place to start on figuring this out?


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Prefab is always a smart thing to do if the job has repetitive situations. We did it in the back of our shop on workbenches, with all of the materials for that particular run.
Simple stuff like fixture whips, recept stub-ups, etc. We also welded frames for switchgear. we would have 277/480 panel, transformer, and 120/208 panel installed to the frames, delivered to the jobs and bolted in place. Sometimes before walls go up.
Here in the DFW area, all of the really big EC's have prefab, and it is to an extreme engineered level. Like the switchgear framing as described above, but also hopital headwall units, complete hospital or hotel rooms wiring with devices trimmed out, and the entire room plugs together.
When you get into prefab with devices trimmed, panels trimmed, etc....then those must be UL listed assemblies. These guys even have in-house UL cetification.
Here is a local companies prefab services
http://www.walkertx.com/services/#pre-fabrication

 

[JFletcher]

a common thing was a 4S box on a sheet metal foot, with a box and
ring attached, and a small bent 90 on the sheetmetal to keep it from
flopping back into a 2 1/2" steel stud wall. you shot them down to
the floor thru the bottom track.

Like this?

https://www.youtube.com/watch?v=-N8bBhmDtE8

 

[brantmacga]

I think we're going to start small and try some things. Pre-cut and fab all the block wall stubs, overhead lighting boxes, and some of the interior wall receps.

Definitely a lot of things in this particular work that can't be pre-fab, but it seems like there is the potential for at least some.

They're all repetitive, so I don't think it would be too difficult to try some things and see if it works out.

Thanks


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[JFletcher]

Never had a pre-fab shop, but when I was doing v/d/v, there is a lot of what I call "pre-work", i.e. work that can be done off the jobsite. This included:

~ punching KOs out of steel boxes and installing ENT connectors and lockrings
~ cutting and reaming EMT stubs for fire wall penetrations
~ putting a lockring with every connector
~ putting captive screws in covers
~ sticking an F connector with every coax plate
~ removing and throwing away all unnecessary packaging
~ backing out screws on 4 terminal phone plates
~ spray painting the heads of any long screws the appropriate color
~ setting out what was needed by floor

this is really trivial stuff but multiplied by 400 or more adds up to hours and hours of labor. Better to do it at home or hotel room watching TV than on the site in 25 or 100* weather. Also made packing the truck and transporting to their final location a lot easier by condensing materials; less trips to get everything from A to B.

with electrical, I can see pre-tailing boxes with EGCs, maybe even pre-wiring receptacles if you're using Wagos or the like and have MWBC. Anything at all that can be done at your leisure doesnt seem like work, which is really nice with the ultra repetitive tasks.

On site (new hotels mostly), I'd usually lay out all of one device, like coax wall plates, already pre-screwed and F connector handy, and chuck em into the rooms. Take just the tools needed for that task and a small bag to catch the double cut coax trash pieces. Saved a lot of time on cleanup and there were almost never trips to the truck for more materials. When they were done, coax tools went back on the truck and then I'd move to keystones or 4 screw POTS wallplates. No more toting around a CLC bag full of every telecom tool known to man.

Dunno how many other types of commercial work could be done like this but I liked the system. Anything where you can develop a rhythm will save time over starting and stopping and switching tools and tasks.

 

[Fulthrotl]

Like this?

https://www.youtube.com/watch?v=-N8bBhmDtE8

nope. think of a foot spotwelded to the box, that
you shoot to the floor.

16 ga. holds the box the right height off the floor.
doesn't need a stud to attach to. has a bent tab
at the top of the box, to keep it from flopping
back and forth in a 2 1/2" wall.

looking at it edgeways, it would look like this:


_____|
|
........ |
. |
4S . |
. |
........ |
|
|
|
|
|
|_____

you shoot two pins thru the bottom track
to hold it down. a muppet scattering them,
and a guy with a hilti shooting them down,
can blow out a 10,000 sq. ft. floor in two
or three hours.

the guy scattering the boxes, as soon as he
was done, he'd grab a ladder and a stud
punch, and pop two holes thru the top plate
above each box.

the guy shooting down would follow behind
commander hole puncher, tossing pre cut and
stripped MC cable between boxes.

when commander hole puncher was done, he'd
start putting up switch boxes, and throwing whips
up from them.

as soon as you are out of the walls, you call for rough
wall inspection.

then both of them start throwing fixtures up in the
ceiling. when they are up, the muppet starts putting
jumpers between fixtures, and the journeyman starts
making up.

then comes the apprentice with the pole gun, blowing
ceiling wires in.

finally, you put home runs in, and make up the panel.
then everyone wires up fixtures and whips.

the precut whips and box stands save an awful lot of
time.

sasco was the first kid on the block to do this, and
were paying full union scale, and winning all the bids
against everyone....


edit... my little ascii drawing didn't survive the forum posting. sorry.

 

[GoldDigger]

You can preserve ASCII art by putting inside a CODE format section in the post.
It is still hard to actually compose the line drawing as you post though.
Same applies to tables with columns.

mobile

 

[brantmacga]

Like this?

https://www.youtube.com/watch?v=-N8bBhmDtE8

We bought some of those ......

So far we've pre-fab'd all the slab 90's, made boxes up with MA's for them, and put some boxes on those brackets.

We also made up all the overhead lighting boxes with whips and EMT connectors.

A lot of our boxes have to be on an exact dimension, and we use caddy screw gun box brackets. I found they make an adjustable bolt for the brackets where we could go ahead and attach the box and have it still be adjustable; not sure how much time we would really save with that. My supplier sent us a sample box with mc connectors built in and the bonding jumper already installed. Probably going to give those a shot.


What we are really trying to figure out now is a way to prefab all the gear. We talked about ordering some cabinets and pre-punching the tops out and swap with the gear package for the job, and just keep them in rotation. And pre fab all the stubs coming out the top.

We've got a college kid coming in making all this stuff up at half what guys in the field are being paid.

Seems like every little bit will help. Especially with the time. Even if the labor savings isn't that significant, it frees up time for guys in the field to move on to other jobs.


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[brantmacga]

you shoot two pins thru the bottom track
to hold it down. a muppet scattering them,
and a guy with a hilti shooting them down,......

We don't use a Hilti gun..... I like that idea though.

Pretty effective for shooting boxes and straps to the block walls? I've been perusing the hilti website.

Muppet..... haha that made me laugh pretty good.



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[jeremysterling]

you shoot two pins thru the bottom track
to hold it down. a muppet scattering them,
and a guy with a hilti shooting them down,
can blow out a 10,000 sq. ft. floor in two
or three hours.

I knew a guy who wanted to make a point to the GC. The GC complained that the EC was too far behind the framers. The EC sent two men with a pallet of "kickstands" to an upper floor with no framing yet. The electricians laid out the walls and shot down the kickstands.

The next day when the GC started complaining about how far behind the EC was getting, the GC was invited to the upper floor and shown the fields of waving kickstands with not a single wall anywhere on the floor.

 

[jeremysterling]

Sorry about the anecdote. For the OP: I would think you could look for some deals on tools like a brake, a shear, a spotwelder, a large bandsaw, etc. I don't know where you find these things, estate sales, asset liquidations or auctions maybe.

If you get a sheetmetal brake, ideas on how to use it may come to you and then you're prefabbing.

 

[brantmacga]

The next day when the GC started complaining about how far behind the EC was getting, the GC was invited to the upper floor and shown the fields of waving kickstands with not a single wall anywhere on the floor.

I've seen that before when the framers were late.


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[brantmacga]

Things are progressing nicely with this test run; we've been able to pre-fab most all of the boxes needed, equipment whips, disconnects, etc.....

Now we need to talk about transporting. What's the best way to accomplish this? I was thinking about large Rubbermaid type containers that are labeled as to what each contains, and loaded onto a job trailer. I am concerned they won't hold up over time though.

Preferably it would be something on a pallet we can load with the forklift.


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[packersparky]

Things are progressing nicely with this test run; we've been able to pre-fab most all of the boxes needed, equipment whips, disconnects, etc.....

Now we need to talk about transporting. What's the best way to accomplish this? I was thinking about large Rubbermaid type containers that are labeled as to what each contains, and loaded onto a job trailer. I am concerned they won't hold up over time though.

Preferably it would be something on a pallet we can load with the forklift.


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Google "steel pallet cage". These are what i have seen used for prefab stuff.

 

[Brotherforlife]

The company "Southwire.com"may be of good help in regards to your Q&A on prefab.They have alot to offer and are always available to have field reps.come to job site.You can see their products in action on U-Tube.MO

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[brantmacga]

Thought I'd give an update on this.

We just finished our first pre-fab job, and we reduced our total labor hours by 30%. I think I mentioned earlier we do mostly restaurant work, so we know exactly how many hours are involved on these projects to calculate the savings. Of the time involved, 10% of the labor hours were spent in the pre-fab shop, and that labor cost was 50% of the guys in the field. I'd say it was pretty dang successful.

They absolutely walked over every other trade on-site.

We've got three more jobs already pre-fab'd sitting in the shop ready to go.

Learning from this job, I feel like we could potentially cut up to another 5-10% of time on-site off. I've gotten good feedback from the guys that it's simplifying their job.

This really opens up opportunities to take on more work we've had to to turn away.

As for material, I haven't totaled up the entire job costs, but I know we've definitely reduced waste in the field.

I've got some other ideas now on simplifying the larger wire pulls on equipment and feeders that should cut down on more time and material waste.


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[brantmacga]

I'll share a few pics of some of the basics ....

Here's a section of overhead pipe racks, all numbered and stacked in the order to install.

Some lighting and equipment disconnects.

Some boxes for slab stub-ups, and overhead lighting boxes with whips attached. Joints are already made with wago connectors.

Here are some wall receps with the devices already installed. It was $0.30 more for a deep 4"sq box; that gave us room to push the devices up in the box. The wall finish is FRP so no paint to worry about.

More boxes with whips already attached and joints made.

Slab stub-ups for receps and feeders

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[Cow]

We do just a little prefab on our jobs. Nothing to extensive though. Pigtailed lighting receps, 4 squares with emt conn and grd pigtails, etc.

I'd be curious what you think when you get around to installing it. Please post your thoughts when you do.