Engineer/Installer etiquette

[Designer69]

gents, I would like to understand something and hear from both engineers and electricians.

Say I have specified a 3/4" conduit, correctly sized, to fit some power or control cables. The conduit is sized properly for field bends and straight runs however if the electrician needs to use an LB fitting, the minimum bend radius of the cables is too large for a standard 3/4" LB fitting.

Electrical Contractor would be required to use a larger sized LB fitting, say 1.5" and bushing reducers to make it work.

Whose task would you say this is, the Engineers' to initially have specified large LB fittings if req'd or the electricians' to wire per NEC.

Note: Wiring and raceway were called out to be 'field to route'.

Thanks!

 

[mcelweec@gmail.com]

Does the ec know this cable needs a large radius bend?

 

[infinity]

Unless there's something in the spec about large radius cables and conduit bodies, IMO the contractor would only be obligated to provide a standard size LB.

 

[Cow]

Unless there's something in the spec about large radius cables and conduit bodies, IMO the contractor would only be obligated to provide a standard size LB.

I could see this going either way.

It'd be a real pain to assume you're only going to be pulling #14 THHN control wires through something when instead it's a multiconductor tray cable. Seems like the question should be asked before the piping begins.....

 

[don_resqcapt19]

I think that the oversized fitting needs to be specified by the engineer. It is unlikely that at the time of bid that the contractor would know the minimum bending radius of the cable. If it was not specified in the contract documents, I would be asking for a change order, once I was made aware of the bending radius.

 

[skeshesh]

I think if the engineer showed the routing it is his responsibility, specially if it's a completely new construction or where field conditions allow for a full understanding of the conduit route that the engineer has chosen.

It does depend a lot on the level of details on the plans. For example for work in an existing building with a crowded ceiling space and poor as-builts, I simply don't have the time or resources to go open up all the ceiling areas and cut walls and other means a contractor will have available to determine the exact routing. I think in such cases it serves both the engineer and contractor best to call on plans for the route to be determined based on field conditions. In such a case I think it would be the contractor's responsibility. Having said that, in some cases even when lacking a full understanding of the field conditions, I end up choosing a route. If I do, and despite having notes clearly stating that the route is diagrammatic and field conditions need to be accounted for, I still consider cable radius based on the route that I chose; if the contractor deviates based on field conditions, it's their responsibility to account for how that would affect conduit size.

 

[SAC]

Assuming an installation was done that violated the NEC, this sounds like it is likely a mistake on both parts. Since it specified a raceway size, and I assume the conductor sizes, engineering should have anticipated the issue and specified how it was to be handled. On the other hand, installation should know the NEC, and not knowing violate the NEC during install. So the issue should have been flagged and addressed before install, at which point it was an engineering issue. Once it is installed, then both engineering and implementation are at fault. At least that is my take on it...

 

[__dan]

If the conduit run on the drawings is spec'd 3/4" EMT, use of 3/4" conduit bodies is implied. The exception would be if in the spec's there is a call for specific variance from the industry standards, "if the problem is forseen". The usual verbiage is the run is specified but not every fitting, turn, and bend location.

3/4" pipe was run and later found that the wire does not fit because of the bend radius in the conduit bodies. When was the problem found, at design, or at the wire pull. If you want the electrician to calculate the bend radius and appropriate fitting for the run, it's easy enough to assign that work to the EC in the spec, otherwise, it would be assumed the 3/4" run of pipe on the drawing would be suitable for the application. 3/4" pipe with 1 1/2" conduit bodies would be very non standard. I would have to see that on the drawing.

If it was missed on the drawing, missed on the spec, missed on the walk thru, no addendum, how can you think it's already in the contract and paid for. Do you want to pay for the work or do you want to say it's in the boilerplate.

Do you want a low price or do you want sole source contractors with the implicit or explicit understanding that they can carry healthy contingencies in the bid and reach in their pocket to pay for a few extras at a later date.

My first GC job they changed something, a couple hundred bucks. I was in a hurry and said no problem i'll take care of it. I made the offhand comment that I expected to be called for work and make it up in the future. The project manager, who had grown up in his father's business building schools in Boston immediately replied "you never make it up". I recognized the wisdom but did not know if he was right. He was right.

IBM tells a story, in the 60's they built one of the first computers for the government. They were done and the thing would not do what they said it would do. Someone high up made the call and said the government would not have to pay a dime on the contract. IBM computers fly on the space shuttle, do you think they go out for bid for that or do they give the work to IBM and ask how much the bill will be.

 

[eric9822]

I would hope the contractor would catch it assuming I specified the cable at the time of the bid. If they did not I would understand and issue a change order.

 

[sameguy]

If you know it going in then why play games, say so up front. Contractors are trying to make money too and the men hate to go back and do rework even if the Co. is getting paid.

 

[Designer69]

very interesting. Thanks for your input guys

3/4" pipe with 1 1/2" conduit bodies would be very non standard.

Dan, this raises another question. You say 3/4" pipe with 1-1/2" conduit is non-standard but at the same time, am I supposed to upsize the normally sufficient 3/4" to 1-1/2" the whole run just to account for a few LB fittings that may be required? Thanks

 

[charlie b]

I do not, as the design engineer, tell the contractor how to run conduit. I will say that a given feeder or branch circuit requires a certain combination of wires and a certain size conduit. That is where I stop talking. I see it as the EC's job to figure out the routing and to figure out the fittings. I think the specs will go so far as to say that.

There are occasions, usually in crowded pathways shared by pipes and ducts, in which I may show details of the conduit routing. But I have never declared which size fitting must be used on any given conduit run. That is not an engineering task. The EC will know far better than I how to do that part of the project.

 

[dkidd]

I agree. Conduit bodies are supposed to be marked with volume and maximum wire size. The EC is responsible to select them appropriately.

 

[weressl]

gents, I would like to understand something and hear from both engineers and electricians.

Say I have specified a 3/4" conduit, correctly sized, to fit some power or control cables. The conduit is sized properly for field bends and straight runs however if the electrician needs to use an LB fitting, the minimum bend radius of the cables is too large for a standard 3/4" LB fitting.

Electrical Contractor would be required to use a larger sized LB fitting, say 1.5" and bushing reducers to make it work.

Whose task would you say this is, the Engineers' to initially have specified large LB fittings if req'd or the electricians' to wire per NEC.

Note: Wiring and raceway were called out to be 'field to route'.

Thanks!

What you point out here is an inherent problem of installing multi-conductor cables in a conduit. Obviously conduits and their fittings were designed for single conductor cables. Oversizing is a fix and a fix is 'overcoming' a problem without resolving the original conflict.

There are far more undersized conduit body installations for tray cable installation than correctly sized. This trend will continue. This is not the only major thing that is wrong with 'tray cable in conduit' installation. The conduit is routinely left open at the end, protected only with a plastic bushing for abrasion, thus open to collect water and debris, not restoring the NEMA 1/3R/4 rating of the CLOSED conduit system.

To address properly this miserable situation is that the engineer and designer should note in the documentation that the conduit system in this case is used not as a raceway, but as a support system. They should highlight that each fitting should be sized to accommodate the manufacturers bending radius limitation for the cables, better yet they can supply a table to show what is the maximum cable OD allowable for each size fitting to maintain the proper bending radius. (Normally I would consider this responsibility to lie with the trade, unfortunately the low bid will go to the guy who did NOT include oversized conduit bodies.)

I would like to see the Code discouraging if not prohibiting semi-closed conduit systems for multi-conductor cable installation, but I also expect this to be as realistic as a snow-blizzard in hell.

 

[construct]

I think that the oversized fitting needs to be specified by the engineer. It is unlikely that at the time of bid that the contractor would know the minimum bending radius of the cable. If it was not specified in the contract documents, I would be asking for a change order, once I was made aware of the bending radius.

I agree that the designing engineer should be the one to address the issue. When I do a plan review, I do my best to catch non-compliant design. I am human and don't catch everything. If a plans examiner catches everything on the prints, then the contractor that got the bid has a much smoother time.

That said, when I inspect in the field, I inspect per code, not per plans. The catch 22 is this: The designer wants his prints followed, and the contractor usually knows this. The unfair thing for the contractor is that he is the one responsible for doing the work in a manner that is compliant with code. So the contractor tries to follow the design sometimes not realizing that particular part of the design does not meet code.

If we lived in a perfect world, we would not have these issues would we? :roll::roll:

 

[sameguy]

Ever see some thing like this?
The plan and spec. is for bid purposes and bidder must bid to a complete working system, regardless of the print/spec.. If I missed some thing you need to have it in your bid and at the most conviluted most expensive way as no money will be allocated for any thing I missed. P.S. if you are reading this than it is too late to RFI any questions.

 

[JWCELECTRIC]

Who said the LB fitting could be used? If the conduit with cable between points 'A' & 'B' is on the drawings and in the specs, then the EC owns it, and needs to install it per cable manufactuer's recomendations. Unless the engineer tells the EC exactly how to install it with every fitting and calls for the smaller fittings that can't be used with spec'd cable, then EC should go for the change order.

 

[__dan]

very interesting. Thanks for your input guys



am I supposed to upsize the normally sufficient 3/4" to 1-1/2" the whole run just to account for a few LB fittings that may be required? Thanks

Given the description, I immediately thought the 3/4" pipe with the 1 1/2" LB's was a great solution. You're trying to avoid pull boxes because the boxes would need independent support.

The only question was providing the information at design and bid so the guys knew what had to be done. If the necessary information was missed and it got built wrong, the additional work should be paid for.

Many times I've seen things at design or bid and tried to make changes, the reply is usually always "do it exactly as the drawing shows". Bids are as per plans and specs.

I look at the drawings and say 'it's obvious they did not do a load calculation' or, because of the plumbing or controls I'll say "the boilers or pumps will only last two or three years working like this", "this will never work". I've called the equipment reps and they'll say "where is that job, I'm pulling the warranty off that equipment".

Even after all that it's very common for the changes to not be made and the job gets built with problems after I've tried. There's a list of jobs the equipment either failed or got ripped out in three years because it did what I told them it would do. Significant money.

So, probabilitywise, that's what I would be afraid of, the changes not being made and everyone walking away from knowing what needed to be done.

Liability for the code violation is a grey area. I've read some case law in magazines, if a PE licensed person walks the job and specifies something, he is liable for the mistake. If the same thing happens and the specifier is not licensed (as required by law) the judge may say 'why did you listen to this guy , he does not have a license'.

That's what I see now, I see stuff on the drawings and say, "there's no way these guys have licenses". Then I look them up online, as has become necessary, and they have no licenses of any kind. They are responsible for a different code violation, representing themselves as engineers without having the engineer's license, providing drawings with no stamp when the law requires a stamped drawing for that applicaton. Even presented with this information, NEC and state statute violations on the drawings, they will still decline to make necessary changes.

 

[bluesmoke...oops]

I do not, as the design engineer, tell the contractor how to run conduit. I will say that a given feeder or branch circuit requires a certain combination of wires and a certain size conduit. That is where I stop talking. I see it as the EC's job to figure out the routing and to figure out the fittings. I think the specs will go so far as to say that.

There are occasions, usually in crowded pathways shared by pipes and ducts, in which I may show details of the conduit routing. But I have never declared which size fitting must be used on any given conduit run. That is not an engineering task. The EC will know far better than I how to do that part of the project.

This sums up quite well how I go about it. Unless I'm contractually obligated to show conduit runs, inside a building I will show the panel locations, and where things are. It's to give the ec lots of leeway in how they want to run things.

 

[Npstewart]

Ive never seen a set of electrical engineering documents that called out the size of the LB fitting with respect to the bend. If the engineer DID call it out then it would be his fault, if he didn't then thats an installation issue. Either way, a change order could be warrented.