I have previously mentioned that I’ve had difficulties understanding the language used in specifications and on plans. I decided to offer you an example and analyze it. Importantly, the following note is not on the same plan sheet as the switchgear, which emphasizes the need to read the notes on each plan sheet.

“In switchgear No. 3, contractor shall verify that the existing fuses are size 450E. If they are not, replace them and provide the owner with a minimum of 6 spare fuses of each type and size. The existing fuses removed shall be turned over to the owner.”

First, let me lay out the application. The requirement above applies to a 2,000A, 2,400V (2.4-kilovolt) switchboard. One of the circuits feeds an existing variable-frequency drive (VFD), which feeds a 1,250-horsepower pump. The VFD, feeder, conduit and wire are being replaced. There are no revisions to the switchgear, other than removing the existing wire terminations and terminating the new wire.

My problems with the note

My first problem is that there is a lack of a reference to this note on the original plan sheet. Usually, a number in a circle, square or hexagon refers the estimator to a note on the same or different page. The lack of a reference is only a minor problem in this case, as it specifically names the switchgear it applies to. It makes sense that the note is in reference to the single circuit being modified, but that does require the estimator to make an assumption. The word “assume,” in all its various forms, is not something estimators should be comfortable with, as it often comes with financial risk.

Next, I am concerned by the author’s use of the word “if.” I did not know a lot about medium-voltage fuses when I started this article, as they have always been provided with the switchgear. I know much more now, including the approximate cost of the required 450E fuse. A quick internet search revealed they cost between $3,500 and $5,000. That represents a lot of risk. If the fuses do require replacement, that requires spending $31,500 for nine (three, plus six spare) fuses. That’s just at the low end. If one of your competitors does not include the new fuses, that could certainly be enough to make your bid notably high.

In educating myself about medium-­voltage fuses, I learned the callout (450E) is not enough information to purchase the new fuses. Using information from an Eaton document on medium-voltage fuses, I was able to narrow down the fuse type to HLE. However, the document says there are a “wide assortment of mountings.” It became clear that getting these fuses quoted would require help from an expert.

‘Each type and size’

The most confusing—and concerning—part of the note is at the end of the first sentence: “ … of each type and size.” This requirement is something I often see for a project that has many new fused devices, such as HVAC, motors and new switchgear. There are no new fused devices on this project; just reconnecting one circuit to a pump of the same horsepower. Of course, the new fuses may be needed because of engineering requirements beyond my current knowledge, such as those of the new VFD and pump motor.

However, I have other questions about the “each type and size” requirement. If the phrase applies to all existing circuits in the switchgear, we need to include even more fuses in the estimate. There are three sizes of medium-voltage fuses in the switchboard, which would require 18 spare medium-voltage fuses, plus the three replacements on the circuit we are updating. 

The cost for 21 fuses at $3,500 each is $73,500. If the requirement also applies to the control circuit fuses, that would mean purchasing nine 2,400V fuses on the primary side of the control transformers and nine 120V ones on the secondary side, for which I do not have pricing yet.

The most extreme interpretation of the note may be that the replacement requirement applies to the other three 1,250-horsepower motors fed by switchgear No. 3. This would add another nine fuses to our previous total of 21, for a final total of 30 medium-voltage fuses, which would take the total up to $105,000. Again, this is a lot of money to include in an estimate based on a poorly written note.

I have sent a request for information through proper channels, and I will be talking to experts for more education on the use and application of medium-voltage fuses. This time could have been saved by a little more precision in the original note. I will let you know how it works out in a future column.

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