Engineer spec'd for EC to provide fault-current info..... new to me.

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brantmacga

brantmacga

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Bid on a job down in south Florida.... All the gear is spec'd as 22kaic. Engineer put a note that said, and I'm paraphrasing, "electrical contractor to provide available fault current calculations to owner and order distribution equipment rated to withstand it". He even wrote specifically what software they want us to use for the calc. I excluded it, wrote that's a fee-based engineering service, and perhaps the owner should find a full service electrical engineering firm to complete the drawings. Gear quoted as-drawn. Idk man that rubbed me the wrong way, especially the part about specifying that we should have this specific software to meet his demands; I haven't seen that specifically before, but I've been seeing a lot more in bid sets lately where the engineer will put work on the EC that should be part of their design services. I did make the minimal effort and attempt to call the utility contact as listed on the drawings, but they actually put the wrong phone number in the drawings so I couldn't reach this person. And I'm getting pretty tired of doing extra legwork for them just to bid a job. Its not that we can't do it, I'm just not doing it for free. I had something along the lines awhile back where they asked us to provide the load calc as part of the bid so they could go ahead and buy the permit and know what size electrical service to put. Again, no. Not for free. I ended up doing that job, but made them write a check for the load calc before handing it over.

I bid another job today where the building in the E-sheets wasn't the same building in any other drawing included in the bid set... like they copied and pasted from the wrong set of drawings. I called all six GC's bidding the project and asked if anyone had pointed this out yet, as the bid was due today at 6PM, and they said not one person had called them on that. Bid it as-drawn, with the stipulation they send the right freaking drawings for the job to re-bid before signing a contract. Its not a big job, but its a $1M+ project.
 
I agree. It seems to me that an engineer is putting himself at risk by not detailing available fault current through out the entire system. How do they get this by plan review in most areas, particularly south Florida? I can't this flying in a place like Miami-Dade county.
 
Selective coordination studies do require specific software. This should be provided by the gear mfr and included in their bid
 
cdslotz said:
Selective coordination studies do require specific software. This should be provided by the gear mfr and included in their bid
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Wouldn't site specific information be required for these calculations? Why should it be the gear manufacturer's responsibility to obtain it?

I agree with the OP, the engineer should providing these calculations (of course I was an EC so I naturally take this position, :) )
 
I have an ongoing argument with the State regarding this issue. It has been going on for around 10 years or so.

My simple question was how can you issue an E permit BEFORE the design is done.
They initially agreed and left it up to me to prove this was happening.
In less than a month they had copies of 15 jobs across 3 different counties....and their response changed to "It is being handled on the back-side".
In about a month I will be visiting those jobs and show them it has not been.
 
There’s a lot going on here. I will offer my perspective on several items.

  • If you are talking only about the main service panel (be it switchgear, switchboard, or something else), then the fault current available to it can be obtained from the utility. That, however, is not an “available fault current calculation.”
  • If the requirement had to do with other panels throughout the building, then the fault current calculation should have been performed by the Designer of Record (i.e., the engineer).
  • Several commercially available software packages can perform fault current, selective coordination, voltage drop, conductor sizing, and other calculations. If the owner wants a specific software to be used, it is likely that they have the same software, and will require you to give them your files for their future use. However, I can think of no reason that an engineer would require a different party (such as the EC or the vendor) to use a specific software.
  • Selective coordination calculations can be performed without use of a computer. However, it probably has been many decades since any engineer has used the manual method.
  • If a selective coordination study is required for a project, I always require the contractor to provide that study. They always transfer the responsibility to the equipment supplier. I can’t do it before the project goes to bid, because it requires complete knowledge of the make, model, and settings of all the breakers, and that information is not known until the contract is awarded, and the EC has made arrangements to purchase the gear.
  • Site specific information is not relevant to a selective coordination study. That study compares two breaker types at a time, based only on their trip characteristics.
 
Eaton Bussman has a nice free app for the available fault current calculation. The NEC 110.24 states, "Service equipment in other than dwelling units shall be legibly marked in the field with the maximum available fault current. The field marking(s) shall include the date the fault currentcalculation was performed and be of sufficient durability to withstand the environment involved." This app makes this easy.
 
There are typically three different studies that I specify on projects.
1. Selective coordination - I can't do this until I have all the details for make and model of all overcurrent devices. Also need the settings for any adjustable relays. This cannot be done during design without sole sourcing equipment. I can do it and require the contractor to update it based on their submittals if they differ (which they always do), but then the owner pays for it twice. I used to include TCCs in bid docs but they almost always end up being worthless.
2. Available fault current - I run the calcs and indicate the estimated available fault current, but a lot of times I can't get information from a utility on a new utility service. Most utilities I have worked with won't design their upgrades and run the calcs until there is a contractor involved and working on the project. I can only come up with a worst case number.
3. Arc Flash analysis - See #1. I also need to know wire lengths and conduit materials which usually falls under the contractor's purview based on conduit routing. Again, if I perform the work during project design the owner pays twice for it. Also see #2, you can't use worst case scenario from the utility for this calc.

This is standard practice for the last 10-12 years on every significant project I have worked on as a design engineer. I have worked for two companies and in two different industries during that time. As an engineer I can't do all this work ahead of time as explained above. After the project bids, I can't do this work without directing the vendor/contractor to make changes ($). I would rather do the calcs myself because, when they are specified, they are done in a bid environment by the cheapest person a contractor/vendor can find an I usually spend more time poking holes in mediocre calculations than it would take for me to just do the calcs myself.

As far as specifying a software, I have only done this when an owner has standardized that all calcs should be done in a software platform that they use. This is always SKM, because there is SKM and then there is everything else.
 
As long as it is requested in the bid package I didn't have a problem with it, I just had the gear manufacturer include everything in their number.

Roger
 
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