PVC conduit alternatives [RE-wrenches]

[Matt Lafferty]

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All,

There are two non-PVC non-metallic conduits allowed per 2002 NEC that I know
of.  One is Fiberglass, which I've never personally used.  The other is
HDPE, which I have used and rather like.  (Sounds like Brad B does as well) 

HDPE (High Density Poly Ethylene) conduit is available and Code compliant
for underground applications.  (Not cheap, but available & legal).  HDPE has
been in use as an underground duct by utilities for years... Predominately
Telecomm & Gas Companies.  Another industry that uses it is the geothermal
heat pump guys... Makes a dandy ground-loop.  (Which is where I first became
aware of and used it close to 20 years ago)  If you've driven down the road
and seen those big colorful reels of tubing next to directional boring
operations installing Telecomm lines, that's this stuff.

The stuff can be bought in lengths of 20 & 40 feet, but is more commonly
available in long rolls on reels.  Google <HDPE Conduit> and you'll get a
bunch of info.  In general, your "bigger" electrical wholesale houses will
be more familiar with it than the smaller ones.  In this part of the country
it's used a lot more in boring applications than open-trench, probably due
to the cost, which is related to sales volume.  It is vastly superior to PVC
for pulling in behind a bore rig.  I can't think of a good reason why it
"shouldn't" be used in open-trench apps, other than it is more time
consuming to do the joints than just slopping on some glue and throwing it
into a ditch.  Used to be that manufacturers required their distributors to
sell only to guys who were certified or had a certified guy working for
them.  (Due to the criticality of the joint-welding)  I don't know what the
status of all that is these days. 

I've only used it as power conduit in a couple of applications, personally.
Worked really great all the way around.  Both of these were out on ranches
with rolling hills and LONG runs.  Both were Direct Bore jobs.  (One of the
owners happened to be the long-time Ditch Witch Dealer... He wanted to play
with their new DB rig, so he figured it was as good a time as any to run the
power out to a couple of spots on his property that he'd been thinking
about.  I hooked my other customer up with him and they got to be buddies,
so the boring rig was a freebie on both jobs.  Come to think of it, so was
the beer.  After work.)  Since I had a manufacturer's certification card for
doing the joint-welds, the distributor was able to lend me the cutter,
facer, & iron at no charge.   

For you Code Disciples, here are the NECH 2002 References:

Falls under Article 352 for installation do's & don'ts; Rigid Nonmetallic
Conduit (RNC).  Annex C, Tables C-10 & C10(A) give the # of conductors
allowed per trade size.  (Same tables as Sch. 40 PVC) 

The Handbook explanation for all types of RNC is as follows: 

The 2001 UL General Information Directory (White Book) describes three types
of rigid nonmetallic conduit recognized for use in the NEC, as described in
the following extract.   
(1)	Rigid nonmetallic Schedule 40 and Schedule 80 PVC conduit (DZYR)  
(2)	Rigid nonmetallic underground conduit, plastic (EAZX)  
(3)	Rigid nonmetallic fiberglass conduit (DZKT)
 
Rigid Nonmetallic Schedule 40 and Schedule 80 PVC Conduit (DZYR)  <SNIP - We
don't need to read that one... Again>
 
Rigid Nonmetallic Underground Conduit, Plastic (EAZX) 
Plastic types of rigid nonmetallic conduit, for use only when installed
underground, may be (1) polyvinyl chloride (PVC) Type A or Type EB, or (2)
high-density polyethylene (HDPE) Schedule 40. The various conduit types
differ in their inside and outside diameters. 
The conduit is intended for underground use under the following conditions,
as indicated on the listing mark: (1) when laid with its entire length in
concrete (Type A); (2) when laid with its entire length in concrete in any
location (Type EB); and (3) direct burial with or without being encased in
concrete (HDPE Schedule 40). The conduit is intended for use in ambient
temperatures of 50°C or less. Unless marked otherwise, Type A and HDPE
Schedule 40 conduit are intended for use with wires rated 75°C or less. Type
EB conduit and Type A conduit encased in concrete in trenches outside
buildings may be used with wires rated 90°C or less. HDPE Schedule 40
conduit, when directly buried or encased in concrete, may be used with wires
rated 90°C or less. 
Where conduit emerges from underground installation, the wiring method shall
be of a type recognized for the purpose. 
PVC conduit is designed for joining with PVC couplings by the use of a
solvent-type cement. HDPE conduit is designed for joining by threaded
couplings, drive-on couplings, or a butt fusing process. Instructions
supplied by the solvent-type cement manufacturer describe the method of
assembly and precautions to be followed.

Reinforced Thermosetting Resin Conduit (DZKT) [formally referred to as Rigid
Nonmetallic Fiberglass Conduit and sometimes Fiberglass Reinforced Epoxy
Conduit (FRE) conduit.] 
Reinforced thermosetting resin conduit (RTRC) marked “Below Ground” or “Type
BG” has been evaluated for underground use only—for direct burial, with or
without encasement in concrete. 
RTRC conduit marked “Above Ground” or “AG” has been evaluated for use
aboveground, underground, and for direct burial with or without encasement
in concrete. This conduit has been evaluated for concealed or exposed work
where not subject to physical damage. 
Reinforced thermosetting resin conduit has been evaluated for use with wires
rated 90°C or less. 
Reinforced thermosetting resin conduit is listed in sizes 1/2 to 6 in. in
IPS, ID, RTRC 40 and RTRC 80 dimensions, as marked on the product. Listing
includes straight conduit, elbows, bends, and other fittings, unless
otherwise noted. 
Reinforced thermosetting resin conduit, elbows, bends, and other fittings,
which have been investigated for direct exposure to reagents, are identified
by the designation “Reagent Resistant” and are marked to indicate the
specific reagents. 
Reinforced thermosetting resin conduit is designed for connection to
couplings, fittings, and boxes by use of a suitable epoxy-type cement or
drive-on bell and spigot. Instructions supplied by the epoxy-type cement
manufacturer describe the method of assembly and precautions to be followed.

For use of Schedule 80, see 300.5(D), 551.80(B), and 300.50(B). 


If you want to look up the UL Listed manufacturers for either of those, UL's
Category Search Page is at:
http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/ccnsrch.html  

(Type in EAZX for HDPE or DZKT for Fiberglass)

OK.  Hope that helps anybody who's interested.  

Stop leaching chlorine gas into our air!

Matt Lafferty
Universal Energies Institute
mlafferty at universalenergies.com
(415) 252-0343
(916) 914-2247 Fax

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