Rigid vs. PVC for Service Entrance Mast

gregoryfast · Oct 31, 2003

My POCO is thinking about changing our requirement for 2" galvanized rigid conduit for all services to allow 2" PVC schedule 80. The main reason is to save the homeowner some money in material and labor. We would still require 2" galvanized rigid conduit for all periscope services, but allow PVC for gable end masts where there is a large eyebolt as the utility point of connection.

I know that NEC would permit this. However, I feel that there are good reasons to keep it all 2" galvanized rigid conduit.

My reasons are:
1. There is a large amount of potential fault current in the SEC that would be better contained in rigid.
2. In the event of damage to the triplex such as a tree falling on it or a truck catching it, the SEC would be better protected in a 2" galvanized rigid conduit. The PVC would just break.
3. In the event of a house fire, the PVC would burn allowing the SEC to arc together and contribute to a larger house fire.

Would do you think?

Am I off base to insist that we not allow this?

What is the practice in your area?

Any and all responses greatly appreciated.

Thank you,
Gregory

iwire · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

We use SE cable, no raceway many times around here.

IMO the order of use would be.

1)SE or SER

2)PVC

Distant third.

3)Rigid, only used on a house in an area that is definitely subject to damage

Guest · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

I personally feel that the order should be:
1. Metal pipe.
2. PVC.
3. SE.

The line side of the main breaker takes a big hit to blow the PoCo fuses. Metal pipe is cheap insurance against an accidental penetration. Arc flash potential is greater I believe. The price difference between PVC & metal is less than a $20 bill unless it's a long run.

NEC 230.50(A)leaves ambiguous latitude for all parties involved in deciding what's subject to physical damage & how to address it.

It comes down to owners option; budget; AHJ special rules; PoCo rules.

Question: How does one use SE and make a raintight connection to the meter base?

PS: Charlie made a good point on the PoCo side that PVC SCH-80 can be helpful for making in-place field repair of conduit (by sectioning out the PVC then patching the PVC with a PVC repair coupling).

[ October 31, 2003, 06:23 PM: Message edited by: awwt ]

iwire · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

awwt, I certainly understand your angle on this, more or less unprotected conductors. (There is primary OCP)

From previous threads I get the impression that your area uses mostly raceways and having always seen it done that way with no problems it would be easy to say pipe is the way to go.

But in this area SE is the norm and you know what? honestly I have never seen any incident with it that would not have happened with rigid.

After a storm I fixed a friends SE that had been ripped off the house and out of the meter socket when a tree fell on the utility's service drop.

Had it been rigid it still would have ripped off the house it was a good size tree.

I can not argue with your thought that SE is more easily penetrated than rigid but I have only seen one piece of SE penetrated in 20 years on the job and that was an example in a code class.

A cable installer drilled from inside the house to outside and right into the SE. I am sure it looked good from the outside.

[ October 31, 2003, 06:45 PM: Message edited by: iwire ]

russellroberts · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

We usually use 2" rigid here.Some of the older homes have SE cable. Pvc for an oh service is not common here unless its a pole service for a mobile home.

Most new services here are underground,an OH is a rare bird.I think we've built 1 new OH in the last 5 yrs other than a few repairs of existing ones.

Russell

jro · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

In Dallas, Texas (residential) we use 2" galvanized ridgid conduit if the installation is a thru the roof w/mast kit, if it is gable mounted we use emt, emt size depends on service amps,SEC is not the norm. rarely used, mostly in repair.

iwire · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

It is interesting to hear all the different ways we do things.

I hope I did not give the impression that I thought using a raceway is bad, just trying to give a view from an area that has and is using a lot of SE.

Gregory one thing, you are not really talking about service "masts"?

gregoryfast · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

Thanks iwire,

You are right. I am not really talking about the service mast.

I just mean the riser up to the service point, not the support for the point of attachment.

Sorry if I didn't make that clearer.

big john · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

Originally posted by awwt:
Question: How does one use SE and make a raintight connection to the meter base?

Answer: Tons of duct-seal and then paint it ASAP to fill in the cracks! :roll:

-John

hbiss · Oct 31, 2003

Re: Rigid vs. PVC for Service Entrance Mast

...How does one use SE and make a raintight connection to the meter base?

Duct seal. We are required to apply a bead of duct seal around the SE where it enters the compression connector on the top of the meter pan. We will get red tagged without it. Problem is even a rain tight meter pan is going to leak and rust after awhile.

As to a what would happen if a fault were to occur before the main disconnect, I believe the service drop would probably burn first considering that the POCO uses aluminum wire several sizes smaller than what we are required to use.

As to PVC, I've used to a few times and see no problem with it. The norm here is also SE although on my own house I used rigid aluminum for the 200A service. Bends easier than rigid steel and will not eventually corrode.

noxx · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

You know....I"m sure this is simply because I'm from an area where overhead services are always enclosed in GRC, but the idea of dropping SE into a compression connector at the meter, then slathering it with duct seal doesn't sit very well with me.

If it's accepted well it's accepted, but it seems a little shoddy to me.

charlie · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

If it's accepted well it's accepted, but it seems a little shoddy to me.

You are absolutely correct, it is shoddy and looks bad if you are used to looking at conduit.

There are some real problems with everyone getting used to the way something is done in a particular area. The biggest problem is not recognizing that another way is just as good as the way you do it in your area. Let me address some of the discussion.

SE cable, like Bob indicated, is not bad. If it were dangerous, it would have been removed as a wiring method ages ago. Some areas, Indianapolis is one of them, prohibited SE cable from being used as service entrance. Indianapolis has finally seen the error of their ways and now permits the installation of SE cable.
A metallic raceway is much better than the other wiring methods is a false statement. SE cable and PVC do not rust like the metallic raceways. EMT is especially prone to rust because the coating of galvanizing is so thin. A metallic raceway will not protect a home any better than SE or PVC under fire conditions (see below).
The electric utility's fuse will provide some protection is a false statement. Where transformers and taps are installed from the "main line" primary distribution, the fuses are sized to protect the line in front of the fuse, it is not overcurrent protection for anything downstream from the fuse.
In the case of a fire, steel is much better than PVC or SE cable is not correct. The reality is that the enclosed wire in a steel conduit will short out to ground much faster. The wire in a PVC or SE cable will hold up for a longer period of time without shorting out.
You are going to have to trust me on this one, I have been involved in a lot of storms where trees have taken services down. Most of the time the cable or conduit is ripped off the building and the hub is broken on top of the meter fitting. Sometimes the wire is pulled up into the conduit. Generally, no additional damage is incurred from a short circuit or a ground fault. No, the fuse did not let go, the fault burned open. We are talking 120/240 volts and it will self extinguish (480 volts and higher will not).

I am wondering how the local electric utility can require a particular wiring method on any building? If their service drop were to hit the mast, they have the right to require the point of attachment to be strong enough to hold their cable. Since this discussion is about drops to the building and not the mast, I think they are out of their jurisdiction.

goldstar · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

The norm here in NJ for residential services is aluminum SE cable unless it's on the side of the house with a driveway and/or subject to damage. In that case you can use PVC for protection. The only time we use GRC is if a mast is required. However, I believe there are some areas (cities- specifically local requirements) that require GRC and copper SE conductors no matter what.

Just a side bar to this thread, awwt asked how a raintight connection could be made into a meter pan using SE cable. Duct seal is the norm also here in NJ but is anyone still bending "drip loops" in the ungrounded SE conductors once inside the breaker panel ? Some of my colleagues here still do that but I find it a great inconvenience and it takes up a lot of space at the top of the breaker panel. Any thoughts ?

Phil

iwire · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

Originally posted by charlie:

Originally posted by noxx:
If it's accepted well it's accepted, but it seems a little shoddy to me.

Click to expand...

You are absolutely correct, it is shoddy and looks bad if you are used to looking at conduit.

I guess it is all in what you are used to.

But I take offense to anyone saying my work is shoddy.

The duct seal on top of this connector is not truly required by the NEC. (I agree inspectors want to see it)

As long as you get the right size raintight connector it will not leak without duct seal.

That said I will use it just to keep up the tradition and avoid questions. :roll:

Bob

[ November 01, 2003, 10:27 AM: Message edited by: iwire ]

pierre · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

Phil, Bob and Charlie

Those are good posts

There are always those who will disagree,that is not such a bad thing, it is part of what keeps this site alive.
What drives this industry and any other industry is people. People have different ideas and experiences, that is why we have different requirements in different areas, not necessarily because one method is better than the other. Experience, environment and other situations may be good reasons for the differences.
Charlie, it is nice to have a POCO person here who also has good knowledge of the NEC.

Pierre

iwire · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

Thanks Pierre.

What works well in one area may not work in another.

Here I have never seen EMT used on a service outside.

IMO EMT does not stand up well in this area with it's good deal of rain, snow and humidity.

For jro in Dallas, Texas it may be great, I have not been there but I imaging it is a much dryer area.

It is good that the code has some leeway in it to fit the area it is being applied in.

noxx · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

Frankly, I've never seen SE in overhead use, and I think I'm not the only one. Anyone care to post a photo or two so we have a reference point for some of these questions?

Personally I'm wondering how one would ensure that a "gooseneck" as required by art 230.54 stays in place in an SE installation.

charlie · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

But I take offense to anyone saying my work is shoddy. SE like rigid can be installed professionally and look good or it can be installed by someone who does not take pride in their work and look bad.

Bob, I hope you did not take my statement to mean that SE work is shoddy. Please note the first sentence of my first bullet point. I am just indicating that to a person who seldom sees an SE installation that in their eyes it is a shoddy installation.

I have used RGC, EMT, PVC, and SE cable for service entrance. I hated working with RGC the most because it was so heavy (that was before the serving electric utility would permit IMC be used for landing a service drop). EMT was an easy metallic system to work with but it rusted too quickly. If a customer were going to paint the house, I would install it with the caveat that he would paint the conduit. I ended up liking PVC and SE cable the most. PVC would not rust and always looked good. SE cable was easy to work with, you could follow the building contours easier, it would not rust, and always looked good.

Pierre, thanks for the kudos. I hope I have not offended anyone else.

iwire · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

Originally posted by noxx:
I've never seen SE in overhead use, and I think I'm not the only one. Anyone care to post a photo or two so we have a reference point for some of these questions?

Noxx I am not sure what you mean by overhead, what I am talking about and I think the others is SE out of the panel to the meter socket (um cash register

bill addiss · Nov 1, 2003

Re: Rigid vs. PVC for Service Entrance Mast

noxx,

Here's 2 pictures (sorry about quality) showing what a typical SEU or 'Rope' Service looks like at the top and bottom picture shows a piece of Sched 80 used as a sleeve above meter enclosure. (we're required to protect the SEU to 8 feet off the ground)

- Bill

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