I have been mentioning “branch” in general in my articles for the last several months. Now, let’s get specific.
First, let’s define branch. Generally, in estimating terms, branch is smaller conduit and wire. This includes conduit that is 1 inch and smaller and wire #6 and smaller. This definition is not carved in stone, as branch sometimes crosses the line into feeders, and feeders sometimes look like branch.
For example, a circuit fed from a panelboard is going to a receptacle with a configuration of 1 inch with three #4 and one #10. The conduit is branch-sized, but the wire is both branch- and feeder-sized. To help with this confusion, I usually determine the conduit and wire coming from panels for receptacles, light fixtures and small miscellaneous loads to be branch.
Feeders, on the other hand, are larger conduits running between pieces of switchgear, panels and bigger loads. Bigger loads can be items such as large motors and HVAC units.
Cost is the main reason I differentiate between branch and feeders. Branch is relatively inexpensive, while feeders can become very expensive and cost up to hundreds of dollars per foot. Most commercial projects have many more branch conduits compared to feeder conduits. For these reasons, the way I takeoff branch is less precise than the way I takeoff feeders.
I use two methods to takeoff branch. The first is to measure each conduit. I was taught to measure conduits by my employers and NECA classes. Every one of my employers in Southern California expected me to measure branch. I continued to measure branch after starting my career as an independent estimator, until I started working on East Coast projects.
My first East Coast project did not have the branch conduit designed and neither did any that followed. The first method I used to solve this problem was to design the branch myself, which was very time-consuming. I mentioned the problem during a phone call with the late George Hague, the former owner of ConEst Software Systems, Londonderry, N.H. As well as being a software developer, he was a very experienced electrical estimator working mostly on East Coast projects. He was amazed that I measured branch and informed me that the right way to takeoff branch was to use the averaging method.
The averaging method consists of assigning a length of conduit and wire to each outlet. Examples would be 20 feet per receptacle, or 15 feet per light fixture. Hague taught me the only conduit he measured was the homerun to the panelboard.
Since I had been measuring branch for 30 years, I was uncomfortable with this method. I understood that Hague had been successfully using this method for his entire career. It worked for him because he had the project history and experience that made averaging possible. At the time, I did not. I have worked to become confident using this method, and I have been successful on commercial projects with fairly regular layouts. I do not use averaging for industrial work or oddly spaced commercial work, such as an auditorium.
Today’s electrical drawings often use several methods of indicating branch on a single project. A project I am currently estimating has designed branch, branch circuit numbers mentioned at outlets, branch shown in a panel schedule, some in an HVAC table and branch that is not designed or specified at all.
Wow. That’s a lot of different ways to indicate (or not indicate) branch. Therefore, it is your responsibility to make sure every electrical item on the drawings gets a circuit run to it. Of course, this takes more time than when the branch was completely designed on the power and lighting plans.
Before starting your branch takeoff, read the specifications and notes carefully. Look for phrases—such as requirements for voltage drop, grounding and combining circuits—that indicate work the engineers are no longer putting on the drawings.
Let’s talk about combining circuits, which was standard practice when I started estimating. For instance, a run of conduit that is feeding fixtures would start with three circuits, consisting of three hot conductors and one neutral conductor. Today, this practice is much more complex due to nonlinear loads, which cause harmonic voltages to be induced on the neutral conductor. When three circuits contribute to the harmonic current running on one neutral, it can cause overheating. The primary culprit in commercial work is computer power supplies, which exist in almost everything today, including LED fixtures. As an estimator, it is your responsibility to understand the circuit combining restrictions for your project as defined by the bid documents, NEC and local authorities. More on this next month.