ok... i had a hot flash.. this is what i want to do.....

[Fulthrotl]

is it legal to code?

i have a 75 kva dry type transformer, 480 pri, 120,208 sec. nema 3r
300 pounds or so....

i want to mount it next to a building, in an area not accessible to vehicles,
a planter if you will. nothing will be within 10' of it.

instead of forming and pouring a slab for it, could i use
one of those green pads they set A/C units on? put it
over a scoop of 3/4" gravel, level it up, before i put the
pad down, drill it and put 1/2" bolts up thru it to bold
the transformer to, so i have studs sticking up, and just
bolt the transformer to it before setting it with a crane?

i doubt it weighs any more than an A/C unit. would there
be any code violations?

 

[kingpb]

I'd say the question is more about, will the transformer manufacturer warranty it, if installed this way.

Not seeing it as an NEC thing.

 

[Dennis Alwon]

I agree I don't think the NEC has much to say about it so it comes down to mfg installation. I also think the pads should be fine unless there is an issue with heat and the pad material.

 

[dkidd]

Quasite makes pads.

http://www.hubbellpowersystems.com/enclosures/electric-utility/pad-mounting/equipment-flat-pads/

 

[iceworm]

..., could i use
one of those green pads they set A/C units on? ...

As in pressure treated lumber pad - say, 6 x 12s?

450.22 says as long as it is outdoor, 112.5kva or less, there is no restriction on distance to flammable material - so okay there.

I've seen plenty set on treated lumber timbers, and on pre-cast concrete pads - both set on leveled gravel pads. It's just a civil issue on the required strength/area of the pad.

If there are cold weather issues, the gravel pad has to be deep enough, big enough (area) so it doesn't heave in frozen ground. Generally, most also use flexible raceways.

And, with a wood pad, there is no CEE for a local ground.

It's a good method.

ice

 

[north star]

= = > - < = =

Just s`pose it were to be located in an active seismic
zone... now what would you do ? :blink: [ According to
the IRC, if this is a Residential application ]

= = > - < = =

 

[Fulthrotl]

= = > - < = =

Just s`pose it were to be located in an active seismic
zone... now what would you do ? :blink: [ According to
the IRC, if this is a Residential application ]

= = > - < = =

industrial occupancy.

turns out my wholesale house sells them,
to mount transformers on outdoors.

it's pretty common, he says. so much for my
brilliant insight.... :dunce:

so, i've got a 3'x3'x3" thick one on order for tuesday.

i'm going out the side of the xfmr with a pair of 3" lb's,
going down in a 3" schedule 80 90 degree bend,
entering into a soil box right next to it, where
i'm gonna pick up some conduits to go where
i need to go.

i'm happy. the soil at this exact spot is so
hard a clay spade on a jackhammer leaves blue
black marks that are shiny.

no digging, no forms, no concrete. yay.

seismic issues? i'm bolting the xfmr to the pad
before setting it, and i'm driving four 3' pieces
of strut into the sand base, with corners on them,
cutting them level and then bolting them to the
base, so it won't settle or move. it'll have 6" of
gravel under it for drainage.

 

[Ponchik]

seismic issues? i'm bolting the xfmr to the pad
before setting it, and i'm driving four 3' pieces
of strut into the sand base, with corners on them,
cutting them level and then bolting them to the
base, so it won't settle or move. it'll have 6" of
gravel under it for drainage.

It sounds like a concrete pad be ALMOST the same amount of work as what you are planning to do.