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#88393 - 05/31/04 04:33 AM When are expansion fittings required?
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA

Is this installation missing the expansion fittings?
_________________________
Joe Tedesco, NEC Consultant

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#88394 - 05/31/04 05:15 AM Re: When are expansion fittings required?
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
I will give it a shot.

Expansion fittings might be required for the raceways in the picture.

If a concrete side walk is being poured around these raceways the inspectors I have had will not ask for expansion fittings.

Or if this is an area of the country that does not have frost heaves and settling is not expected, expansion fittings are not required.

This picture looks like a landscape area, I would expect some setting would occur.

IMO expansion fittings should have been used.

 Quote:
300.5(J) Ground Movement. Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, direct-buried conductors, raceways, or cables shall be arranged to prevent damage to the enclosed conductors or to equipment connected to the raceways.


Bob
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#88395 - 05/31/04 11:47 AM Re: When are expansion fittings required?
dfe Offline
Member

Registered: 05/25/04
Posts: 18
Loc: n.h. calif. usa
I will put my 2 cents in, I'll end up being incorrect.... But I will learn something ... That's why I am here, mistakes here do not harm anyone, or cost. Great place you have here, many thanks for letting me join.

Is this installation missing the expansion fittings? ..I don't think it needs them unless the pvc underground is long enough for it to be required.
overall it looks like a neat installation.
looking at the coupling under the main, do the join right on to 90's if so are they deep enough, are they from the utility company and not fused?. most utility's in my hood want 3' of cover ( I can't tell if they are sweeps).
Also where I work we would stub gal ridge or imc to protect the pipe from damage.

Just judging by how it's looks I would say that it meets the code for the area it was installed... or the electrician do what he was doing.

Bill

p.s Looking at it again I become concern about the vertical gutter.. Is that rated for outdoor use in the direction its installed??



[This message has been edited by dfe (edited 05-31-2004).]

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#88396 - 05/31/04 02:52 PM Re: When are expansion fittings required?
cpal Offline
Member

Registered: 05/17/04
Posts: 165
Loc: Cohasset MA
Expansion joints are required wher the rate of expansion (contraction) is expected to be .25" between two fixed points. This might be between two enclosures or if the raceway can push against a stationary object.

Article 352. 44 the Table will give a resonable measurement for anticipated expansion. Also if the raceway is installed in high amb. temp it may contract in cooler weather.

ground movement requires a fitting listed for ground movement don't confuse thermal expansion with ground movement.

Also I guess we are assuming the raceway is Sch. 80 or installed in an area not subject to physical damage.??

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#88397 - 05/31/04 03:13 PM Re: When are expansion fittings required?
iwire Offline
Moderator

Registered: 01/05/03
Posts: 4343
Loc: North Attleboro, MA USA
Welcome cpal to ECN.

I agree thermal expansion is a separate issue but using an expansion joint is a common method around this area to comply with 300.5(J).

Bob


[This message has been edited by iwire (edited 05-31-2004).]
_________________________
Bob Badger
Construction & Maintenance Electrician
Massachusetts

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#88398 - 05/31/04 03:29 PM Re: When are expansion fittings required?
Ryan_J Offline
Moderator

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
I think we also need to know the climate of the area. Is this in Alaska? Is it in Florida? I can't think that frost heave can be much of an issue in the south (but I've been wrong before...lots of times )
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Ryan Jackson,
Salt Lake City

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#88399 - 05/31/04 03:57 PM Re: When are expansion fittings required?
Joe Tedesco Offline
Member

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
This picture was taken in March 2003 in Indianapolis. I posted it here to generate this discussion. I did not inspect this work, and have no knowledge of the installation.

If the fine print note to iwires reference was reviewed it would show that an expansion fitting would be OK, and or additional lengths (slack) in the feeders and laterals to allow for movement caused by settlement or frost.

Exposed runs of RNMC would have to comply with the comments related to that in Article 352 and I agree.

I am happy with all of the comments here and see where we all have something to add that helps the new persons understand.

Really is better than arguing!

The wireway "Gutter" is one designed for use in this wet location. I have a close up of the label, and will post it here when I can find it, the trouble with me is that I am always moving my pictures around on my computer.

On another note before "expansion fittings" were introduced into the NEC we were always allowed to use "Expansion Joints" but now I see that they are not allowed by 300.7(B) and the FPN calls attention to the RNMC article too.

 Quote:
300.7(B) Expansion Fittings (used to say Joints).

Raceways shall be provided with expansion fittings (used to say joints) where necessary to compensate for thermal expansion and contraction.

FPN: Table 352.44(A) provides the expansion information for polyvinyl chloride (PVC). A nominal number for steel conduit can be determined by multiplying the expansion length in this table by 0.20. The coefficient of expansion for steel electrical metallic tubing, intermediate metal conduit, and rigid conduit is 11.70 × 10-6(0.0000117 mm per mm of conduit for each °C in temperature change) [6.50 × 10-6 (0.0000065 in. per inch of conduit for each °F in temperature change)].


Personally, I would still allow the "expansion joint" we made using a flexible raceway like greenfield or sealtight between the runs of RMC, for example at the building expansions.

How about you other AHJ's?
_________________________
Joe Tedesco, NEC Consultant

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#88400 - 05/31/04 04:07 PM Re: When are expansion fittings required?
Ryan_J Offline
Moderator

Registered: 08/19/03
Posts: 1355
Loc: West Jordan, Utah, USA
 Quote:
Personally, I would still allow the "expansion joint" we made using a flexible raceway like greenfield or sealtight between the runs of RMC, for example at the building expansions.

How about you other AHJ's?


I would and I have. I have seen EMT used in buildings that have a full structural expansion joint right in the middle of them (my city hall, for example), and I personally allowed for flex to be used as an expansion fitting.
_________________________
Ryan Jackson,
Salt Lake City

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#88401 - 05/31/04 04:10 PM Re: When are expansion fittings required?
Electricmanscott Offline
Member

Registered: 01/12/02
Posts: 1478
Loc: Holden, MA USA
I think this would require provisions for "Ground movement". As mentioned most people use expansion fittings for this. An instructor at a class I took said expansion fittings were not rated for "ground movement". I have used an extra amount of sand for backfill for this and I have used expansion fitings. I have also heard that some expansion fittings have pulled apart.

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#88402 - 05/31/04 04:52 PM Re: When are expansion fittings required?
CharlieE Offline
Member

Registered: 04/23/04
Posts: 204
Loc: Indianapolis
The verticle sections next to the main junction cabinet (it has horizontal bus bars mounted inside) are not required to be raintight or rainproof. Only the horizontal sections are required to be NEMA 3R rated for the service entrance conductors. This is by agreement between IPL and the city of Indianapolis. The PVC under the junction cabinet are placed acording to IPL specifications for IPL cables. The remaining portions are between the EC and the AHJ.
_________________________
Charlie Eldridge, Indianapolis Utility Power Guy

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