Setting up a backboard for a freestanding service

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Electron_Sam78

Electron_Sam78

Senior Member
Location
Palm Bay, FL
I'm putting together a proposal for a new 800a service. It's a freestanding service -no attachment ot a building. I've got a 42"Wx62"H safety switch, a 42"Wx76"H MDP, and a 22" wide sub panel. In the past I've just used pressure treated lumber but I've noticed some old services around here like that that have the post rotting out. So, I want to build this using galvanized and stainless steel. For the piers I'm going to use 4"x4" galvanized square steel tube 1/4" thick but that's about as far as I've gotten as far as framing. Maybe Unistrut accross the piers to mount the equipment? Will that be hefty enough to hold the stuff?
 
ceb58

ceb58

Senior Member
Location
Raeford, NC
Electron_Sam78 said:
I'm putting together a proposal for a new 800a service. It's a freestanding service -no attachment ot a building. I've got a 42"Wx62"H safety switch, a 42"Wx76"H MDP, and a 22" wide sub panel. In the past I've just used pressure treated lumber but I've noticed some old services around here like that that have the post rotting out. So, I want to build this using galvanized and stainless steel. For the piers I'm going to use 4"x4" galvanized square steel tube 1/4" thick but that's about as far as I've gotten as far as framing. Maybe Unistrut accross the piers to mount the equipment? Will that be hefty enough to hold the stuff?
Click to expand...

If you are mounting the equipment side by side you may want to consider a center post. I would use 1 5/8 galv. strut for the horizontals and forget stainless unless the price doesn't matter.
 
V

Vod-Vil

Member
Can't you just buy some 800a switchgear with a main,distribution,and a sub-panel built into the same enclosure.Pour an equipment pad,anchor it down and youre done.
 
H

hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
LarryFine said:
Where does the metering equipment go?

I can't imagine a P.T. 6x6 rotting away.
Click to expand...

P.T. lumber embedded in concrete will rot off in no time, I found some heat shrink plastic tubes to slide over the PT post at TSC so when you poor the concrete around it the PT lumber doesn't contact the concrete.

but I also agree an all in one pedestal R-3 MDP with main mounted on a pad would make this job a snap, I would assume the CT's would be done in the transformer? so make sure you check you POCO's standards as to how they want the CT and meter, here we run a 1 1/2" RMC into the transformer and anchor uni-strut to the transformer pad to mount their meter, they wire that part.

I have used 2" deep galv. strut for legs to make a rack to a 6 gang meter pack, I don't see why maybe 4 across would not hold up a MDP?
 
renosteinke

renosteinke

Senior Member
Location
NE Arkansas
I've done it both ways: with lumber, and with strut. Both have their advantages.

Strut: Visit the McMaster-Carr site. You'll find easy access to all manner of strut that you didn't know existed- including some 'double size' and -double sided' stuff. Otherwise, the downside to strut is that the mounting holes of your components never line up, so you wind up with a more involvolved arrangement than you planned.

Lumber: I have not had the rot issue some have mentioned, but then I'm in the 'high desert.' I was very, very happy with a panel I made using tongue & groove 2x6 lumber. The boards locked together (so they will warp / weather as a piece) and there's enough thickness to mount your stuff using 1/4x1-1/2" lag bolts. Cordless impact driver, Simpson hex-head lags are a great combination.

Perhaps a combined plan is what you want: steel uprights with a lumber panel.

Whatever you do, I advise against plywood. It just doesn't seem to weather well. ANY wood needs to be thoroughly sealed / varnished / painted before you start hanging stuff on it.
 
Electron_Sam78

Electron_Sam78

Senior Member
Location
Palm Bay, FL
Electron_Sam78 said:
That's a good idea
Click to expand...


...of course that would make future circuit installs more dificult. With a the equipment mounted on a board I could just dig up to and right below the panel and install a circuit. With a padmount that would be more difficult. Of course we could install extra, capped stubs underground but it still seems less flexible to me
 
Electron_Sam78

Electron_Sam78

Senior Member
Location
Palm Bay, FL
renosteinke said:
I've done it both ways: with lumber, and with strut. Both have their advantages.

Strut: Visit the McMaster-Carr site. You'll find easy access to all manner of strut that you didn't know existed- including some 'double size' and -double sided' stuff. Otherwise, the downside to strut is that the mounting holes of your components never line up, so you wind up with a more involvolved arrangement than you planned.

Lumber: I have not had the rot issue some have mentioned, but then I'm in the 'high desert.' I was very, very happy with a panel I made using tongue & groove 2x6 lumber. The boards locked together (so they will warp / weather as a piece) and there's enough thickness to mount your stuff using 1/4x1-1/2" lag bolts. Cordless impact driver, Simpson hex-head lags are a great combination.

Perhaps a combined plan is what you want: steel uprights with a lumber panel.

Whatever you do, I advise against plywood. It just doesn't seem to weather well. ANY wood needs to be thoroughly sealed / varnished / painted before you start hanging stuff on it.
Click to expand...

I used the 2x6 TNG boards and 6x6 posts in my last few free-standing service installs but since then I've seen old 6x6s nearly rotted in half at ground level and it got me thinking about a more durable install.
 
M

mgmelec

Member
Location
new jersey
first energy calls for 2-3" gal. buried 24"min. with poured concrete for the posts. for the horizontal coss members, u-bolt uni strut to posts. good luck sounds like a nice job.
 
G

gk351

Senior Member
Location
IL
Glad I read this post, I have a very similar installation coming up with almost the same equipment. 600A 480V MDP, PT/CT Cabinet(still haven't found what I need). In the past I have used good 4x6 or 6x6 Lumber. I don't necessarily believe concrete will rot it off??? I have seen lots of PT Lumber buried in Concrete. So did some suggest using 3" rigid? IMC? or just random galvanized pipe??? The only thing about using steel where Im from is rust...just seems it doesn't take long for things to rust:(
 
Fulthrotl

Fulthrotl

~Autocorrect is My Worst Enema.~
Location
HB, CA (19 Hrs. 22 Min. from Winged Horses)
Occupation
E
Electron_Sam78 said:
I'm putting together a proposal for a new 800a service. It's a freestanding service -no attachment ot a building. I've got a 42"Wx62"H safety switch, a 42"Wx76"H MDP, and a 22" wide sub panel. In the past I've just used pressure treated lumber but I've noticed some old services around here like that that have the post rotting out. So, I want to build this using galvanized and stainless steel. For the piers I'm going to use 4"x4" galvanized square steel tube 1/4" thick but that's about as far as I've gotten as far as framing. Maybe Unistrut accross the piers to mount the equipment? Will that be hefty enough to hold the stuff?
Click to expand...

if it were mine to do, and i didn't want to use a piece of switchgear,
i'd use back to back strut, galvanized. either 16" hole 3' deep, or
sonotube, and put the double strut in it as uprights, 4' on center.

then 1 5/8" strut across as needed, using allen head cap screws,
flat washers, and spring nuts to hold it, instead of square washers
and hex nuts, so the surface of the strut is available for mounting
without obstruction.

if space permits, you can mount stuff on both sides of this, and
nipple between them, for a clean install.

a single piece of 2 1/2" strut across the bottom of this sets
your conduits at the right amount of standoff

unless you are in a food prep area, galvanized is better than
stainless steel. especially in saltwater environments. i've seen
stainless eaten near the beach, while hot gal right next to it
was unaffected.

stainless steel US made often has a great deal more nickel in
it that "unsourced" stainless, which can come from anywhere,
and often has just enough nickel in it to not rust till the check
clears the bank.

if it says "304 type stainless", that is what you are generally looking
for.

you can't afford "316 type stainless". nobody can. :roll:
i tried pinging for a price on 304 strut, and could only find "call us"
 
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D

dexterg

Member
Location
New Braunfels, TX
Plenty of Concrete

Plenty of Concrete

Just be sure to use plenty of concrete in the footings and make them 30" deep minimum because the rack will be top heavy and after time it will lean forward if not anchored properly.
:)I liked the earlier post that said pour a pad and use switchgear, quicker, easier, looks better. You can add a couple extra PVC stub outs for future, no big deal.
 
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