Ironridge pipe suggestion

[jagjohn2000]

I have a guy that wants to use ironridge ground mount. Do you think 2 or 3

[DanS26]

Go to the IronRidge design site. Spec the job both ways and compare costs.

You can use foreign 3" EMT galvanized pipe instead of Sch 40 which will also save a bunch although unlikely to get a stamp if you go that route.

[jagjohn2000]

I was told many use rigid conduit, not sure if this aluminum has a schedule rate ng.

[J.P.M.]

The design, including the foundation will need to be strong enough to withstand all design loads from wind, seismic, dead and occasional loads as required to pass permitting requirements.

Same section size/shape of aluminum is not as strong as steel.

Don't forget corrosion requirements: Aluminum in direct contact with concrete can have corrosion problems if a lot of chlorides are present in the mix. How much seems a still somewhat open question. Current practice calls for coating the AL w/bitumen/tar before embedment. Ground screw anchors are a possible alternative.

Steel/aluminum contact will be subject to galvanic corrosion.

[solarfrank]

You can't use electrical conduit, you need to use galvanized steel pipe schedule 40, they sell it usually a piece of 21 ft long.

[J.P.M.]

You can't use electrical conduit, you need to use galvanized steel pipe schedule 40, they sell it usually a piece of 21 ft long.

There is not a specific structural reason you can't use electrical conduit as long as you can prove it can withstand the imposed forces and moments that are used for the design strength calcs. and material compatibility is considered.

EMT is actually tubing, not pipe but is dimensioned to exterior pipe sizes, and is thinner wall than pipe (gage wall thicknesses rather than pipe schedule thicknesses like schedule 40, sch. 80, etc. ). Being thin walled, it can't be threaded. Fixing/anchoring/connecting EMTis often done with set screws and/or compression couplings/etc. which may not be structurally satisfactory. That may knock EMT out of consideration for structural applications or at least require some additional design or design checking.

For that and other reasons (One such reason being is the interior EMT coating compatible with concrete embedment ?), I wouldn't recommend it out of the box without calc'ing the design, and checking material compatibility and suitability for the application. There may also be other reasons such as code requirement issues that would eliminate some EMT type materials. But in theory, there is no structural reason why schedule wall thickness pipe must be used. As a matter of fact, using most diameters of schedule 40 pipe for solar racking is gross overkill with respect to stresses in pipe sections, with those stresses usually being on the order of, say, 10% or less of anything approaching the yield stress of the material.

Still, for all the hassle involved in what may be a redesign or reinvention of the wheel, I'd stick with schedule thickness pipe.