In this video, TRACE 700 operation is discussed from beginning to end. The variables manipulation is discussed as it goes from load design, to hourly loads, to hourly energy consumption, and finally to monthly cost.
TRACE 700 Sequence of Operation
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While every TRACE 700 user must familiarize themselves with the inputs in TRACE 700, not many understand the sequence of operation when calculating. For that reason, I think it is important that we go over what happens when you click the Calculate button. There are four options: Design, System, Energy and Economics. Most users don't pay a lot of attention to this, they just make sure they are set to Ready, check the boxes and click Calculate. However, a solid understanding of each of these components might save you time, and will certainly save you some frustration. What's important to understand, for starters, is that each subsequent input takes the output from the previous portion. For instance the System takes information from the Design, Energy takes information from the System, and Economics takes information from Energy. This will all be quite clear in a minute.
Load Design Mode
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We'll start by running a Load Design mode. If we select Load Design Mode, we already know that it determines the peak load of the building. However, a clear illustration of this is not always available. When TRACE calculates design, it calculates one 24 hour day per month of the year, so 24 x 12. It calculates 288 hours and finds the hour with the highest peak. In most cases the cooling design peak does not occur in January, February, or December, so we'll skip some months and start with April. In this graph, we have the BTUs on the left, the hour of the day on the bottom and some components in the middle. We see that the internal loads are set to constant - all 24 hours. This is because we want the air conditioning system to be able to handle the full amount of internal loads, regardless of the building peak.
The calculation for TRACE goes something like this: it starts with January, February, March, gets to April in this case, and then it goes to May. As you can see, there is a bar called maximum so far (Maxsofar) tracking the peak load year to date. As we go to June that value increases. As we go to July that value increases further. When we get to August we notice that the peak loads are lower. As we get to September this is further illustrated, so there is no need to go any further. We've already identified the peak. Of course, TRACE doesn't know this and it will continue to calculate through December if specified. However, let's take a look back at the peak. The building peaks in July at hour 12, though that's not entirely visible on this graph. Remember, the Load Design mode isn't looking for just the peak month, it's looking for the peak hour. In this case we've selected hour 12, the peak hour of the year. From this peak hour of the year, TRACE calculates the building Airflows and the building supply air temperatures which are determined from the building's sensible and latent loads.
From this data, though there are many more variables, TRACE can print out the System Checksums, the Room Checksums, and the Zone Checksums. From this data we can also determine what size air conditioner unit we need, and thus pick out an air conditioner.