For the purposes of this article, let’s break down estimating into two types: hard bids (firm numbers based on engineered documents) and everything else (including budgets, conceptual, design-build and all of its cousins). This article is about hard bids.
I’m sure most of you are familiar with the continuing decline in the quality and completeness of bid documents. Because of these changes, I find myself looking for faster and better ways to complete a takeoff of today’s drawings. Let’s take a look at a few of the changes and some ways to deal with them.
The first change I saw was regarding HVAC. When I first started estimating, all of the information for the conduit sizes, wire sizes, disconnects and power source was on the floor plans. One day, while working on a new estimate, that information was missing. I was quite confused. After searching for a while, I found the information in a table. At first, I was pleased but soon found it was taking a lot of time switching between the floor plan and the table as I performed the takeoff. Eventually, I decided to list the branch for each piece of equipment in a schedule, similar to a feeder schedule. You can do this on paper, a spreadsheet or in your estimating software (if your software has a feeder listing function). List the from, to, conduit and wire size. Once the listing is complete, proceed with the takeoff. This worked out to be faster for me.
The next change was the disappearance of complete branch circuiting. Initially, engineers stopped marking branch that was larger than #12 because of voltage drop. Instead, a phrase in the specs required us to upsize anything over a certain length. Then, they stopped marking branch that was larger than #12 because it was on a greater-than-20-ampere (A) circuit breaker. Next, because of harmonic feedback, they stopped combining circuits. Thereafter, all we had on the drawings was a bunch of lines with no hashmarks and no size indication. Finally, in some cases, they started eliminating branch design altogether, giving us only circuit numbers at each outlet.
Let’s take this one item at a time. When dealing with voltage drop requirements, read the requirements carefully. Usually, they change depending on the voltage. An example would be to upsize a 120-volt (V) wire over 100 feet long, and a 277V wire over 75 feet long. Also, read the length calculation wording carefully. Some specifications say to measure the length to the first device, while others require measuring all the way to the end of the circuit.
Regarding circuits larger than 20A, this came as a complete time-consuming surprise. I had already taken off all the branch for a project. However, when taking off the panelboards, I noticed a lot of circuit breakers larger then 20A. When I went back to my branch takeoff, many of the runs I took off as #12 were incorrect and had to be remeasured. As a result, I started a new takeoff procedure for “upsized” branch. Now, before taking off branch, I go over the panel schedules looking for circuits larger than 20A. When I find them, they are listed on a schedule similar to the equipment schedule I described above. When the listing is complete, take off all the items on the schedule. When that is complete, all remaining branch is 20A.
Harmonic feedback was a problem that took the engineers a while to figure out. For those of you not familiar with it, the problem is most often caused by computer power supplies. These devices, called half-switched power supplies, cause a harmonic current to be induced on a circuit’s neutral wire. The problem started when a single neutral was used for three 20A circuits, also known to estimators as a four-wire system. The feedback from three circuits caused the neutral to overheat. Since the neutral is not protected by a circuit breaker, it becomes a problem. Many engineers’ first reaction was to prohibit multicircuit systems, which raised the cost of a project significantly, because every circuit was a separate homerun.
The next strategy I saw was making the neutral a #10 wire. Today, the most common requirement is a separate neutral for each circuit. This requires a three- circuit system to contain 3-phase wires, three neutral wires and, if required, an equipment ground.
The final item—no branch design at all—is only a problem if you were trained or required to measure branch. If that is the case, the estimator is now required to design the branch or use the branch-averaging method.
If you have any questions or suggestions for dealing with drawings, let me know. I will post the answers and ideas on my blog, electricalestimator.wordpress.com.
About The Author
CARR has been in the electrical construction business since 1971. He started Carr Consulting Services—which provides electrical estimating and educational services—in 1994. Contact him at 805.523.1575 or [email protected], and read his blog at electricalestimator.wordpress.com.