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I completed an internship at DPC Consulting Engineers over the summer of 2013. It is a mechanical engineering firm that specializes in HVAC and Plumbing. We are generally hired to create systems for large residential buildings. My normal job is as an office assistant; I help by cleaning up drawings for use, doing data entry, answering the phone, etc., but for my internship, I had a different project.


In order to design an air conditioning system for a room, one needs to know how much energy it takes to heat up or cool down the room. Different materials and weather conditions change this, so it can be difficult to know what to build for. The difficulty therein is because of all the variables -- you need to know when it will be hottest on each side of the room. Maybe on an average June day the Northern wall will be hottest at 4pm, but maybe the Eastern wall gets almost as hot on an August day at noon and the Eastern wall is bigger than the Northern one. Which is the worst-case scenario? We had an old system of calculations that would help to figure out what the worst case scenario was, but it required a lot of manual inputs and outside research. My job was to redesign this system of calculations to be more accessible and user-friendly.


More than anything, this project required that I have a good understanding of how to use Microsoft Excel, since that was the program the calculations were done in. There were plenty of things I had to do that I didn’t even know were possible in Excel before, such as creating drop-down menus, referencing different sheets, and writing long code that would work for many different cells at a time. I also needed to understand what the equations meant and how to figure out the right ones to use -- the task required lots of intuition. In the end, I managed to get it completely running, and learned how to use Excel very well in the process. The major obstacle I encountered was trying to keep the file size down -- the average file is probably like 200kb and it wound up being around 20mb because of the many redundant calculations it needs to do. Even with lots of editing, that remains its biggest (and probably its only) flaw to date. It is slow to save and load, but otherwise perfectly functional.


Honestly, I found the project to be far more fun and rewarding than I expected. Finding clever workarounds for issues I had made me feel very smart and I felt like I made a real, substantive contribution to the business when I finished. When I started out, I had no idea how huge of an undertaking the task was; when I first opened the book, I was so lost that I thought it would be impossible. I finished both feeling accomplished and with a much better understanding of how HVAC works.

Day 1: Today was my first day of my official internship. I am doing this at the same business I normally work for, but I am doing a different project for the internship itself. My boss seems excited about it, especially since this time of year seems to be relatively easy compared to the rush I experienced at the end of the year. The project I'm working on is creating a new calculation system for HVAC unit sizing. I spent the whole day looking through a codebook, trying to understand what type of calculations I'll be coding and why they are done. It seems kind of boring and confusing right now, but I haven't really gotten to the work yet, so I'm still hoping it gets more interesting.


Day 3: After poring through the books, looking at old calcs, and having a couple false starts, I've actually started on my own calc now. First is the slow process of transcribing data from the books into the calc; there are lots of tables of data for many different building contexts (e.g. wall material, wall orientation, and time of year). Fortunately, typing is one thing I am actually quite good at and something I can enjoy doing -- I need to do a lot of almost thoughtless typing at this stage.


Day 6: At this point, I've gotten into the coding -- if you could call it that. I'm writing commands for Excel, mostly looking up numbers in the tables to multiply together based on a few user inputs. I think Excel's LOOKUP function is my new best friend. Having done countless of these calcs before, I think I did a great job of making the input section; it is simple and elegant. The calculations themselves are not as pretty, but I have "hidden" them in other sheets. After brainstorming with my boss & coworker, we've decided that each month's calculation is going to be its own sheet, all of which will be compared to one another in yet another sheet. There's a lot of sheets now.


Day 10: The calc is finished! I'm really happy with it, except that the file size is HUGE -- most definitely because of all of the repetitive sheets. My boss seemed to think that arrays would be some magic fix to the unweildy repitition of the formulas, but I think they only had a minor effect. I don't see it as a huge problem though, it just takes a while for the file to open and to save. Otherwise it works perfectly and very accurately. I'm very excited to use it for a real project and not just a test one.

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