What I do at work:

Whenever people ask me exactly what I do at work, I find it very hard to describe. I usually give them a vague reply like “I design the mechanical systems in buildings”. Although, I know that this doesn’t really mean much to most people. So I thought I’d write a blog post where I try to actually explain what I do at work.

The mechanical systems that I design are the heating, ventilation, air conditioning and plumbing systems within buildings. This might sound straightforward but there are a lot of different variables involved.

The first thing that needs to be determined is which type of systems will be used and how heating and cooling will be provided. Most commonly, an air handling unit is used to heat and cool air which is then blown into the space that you are trying to heat or cool.

There are a few different options for how heating and cooling will be provided. Here are some examples of how the air can be heated within the air handler:

-Hot Water Coils: Hot water runs through metal coils and a fan blows the air over the coils so that the heat will transfer from the hot water to the air.
-Electric heat: Air is heated by being blown over electric heating coils.
-Gas heat: Gas is burned within the units to heat the air.

Every system has pros and cons. For example, hot water coils are very efficient but require a lot of space because a boiler is required to heat the hot water (and pumps to circulate the hot water).

Once you’ve figured out how you are going to provide heating and cooling, you need to figure out how you are going to keep all of the spaces that the air handler services comfortable at the same time. The air handler will service many different spaces and they won’t always need the same amount of heating and cooling. Here are a couple different options for that:

-Control Air Volume (CAV) Systems with terminal re-heat: Use your air handler to heat the air to the lowest temperature required by any of the spaces you are controlling. Then use a small re-heat unit in each space to increase the temperature for just that space to whatever it requires. (Now you have to go back and determine how you will provide this heat - hot water or electric?).
-Variable Air Volume (VAV) Systems: Use your air handler to heat the air to be really hot (or really cold) but control the amount of air which flows into each room. If a room is already a good temperature, don’t supply it with air. If a room is really cold, provide it will lots of air. Etc...

Each of these systems has their own pros and cons. A CAV system is great if your rooms will usually all need the same amount of heating and cooling but a VAV system is better if there is lots of variation between the rooms.

Next, you need to determine how much heating and cooling each space will likely require. This is done by determining where you will loose heat and where you will gain heat. For example, windows will make the space loose heat and people will make the space gain heat. This is important so that you can determine how much airflow each room will need and how large your air handling unit must be.

Once you’ve decided all of that, you need to determine how you will get the air to the space (i.e. with ductwork). This requires lots of coordination with the architect and structural engineer to make sure that ducts will fit within the ceiling space.

Once you’ve brought the air into each room, you need to select diffusers appropriate for the space. When selecting diffusers, it is important to consider noise and speed. You don’t want your diffusers to be sending out so much air that they make a whistling noise or that people feel drafts of hot (or cold) air blowing on them.

Ultimately, what I love about my job is that every day is different because every building is different. This means that I am constantly learning and everyday provides a new challenge.

The classes that most strongly relate to what I do at work are heat transfer and fluid mechanics.