How to solve Unmet hours in eQUEST

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In this tutorial, we’re going to cover how to solve unmet hours in eQUEST. Naturally, every single file that has unmet hours is going to be different, so we’re going to solve unmet hours in this file because it has a good representation of typical causes of unmet hours. However, virtually anything can cause an unmet hour. There are several things that are the most common, and of course, the first question is: how do I find how many unmet hours I have, and how do I see where those unmet hours are occurring? 

What’s important to know is that an unmet hour only has to occur in one room. If every single room in a building has an unmet hour at noon on January 3rd, then it only counts as one unmet hour. If every room in the building has an unmet hour at a separate time, in this building that amounts to 30-some, 40-some unmet hours.

You can only have one unmet hour per any given hour, and that makes it even more confusing. The main issue is typically capacity or airflow, but it can result from other things. First thing we want to do in this building here — we’ve got this nifty shading device — we can see that we have all sorts of different loads, and so on. We want to see where the unmet hours are. We’ve simulated this already. We go to View Simulation Output, and you want to go to the BEPS report. 

The unmet hours can be seen in the BEPS report: “Hours any zone above the throttling range,” and you can see here that we have over 2,000 unmet heating hours, and 300 unmet cooling hours. The ASHRAE 90.1 rule is that we need to have less than 300 unmet hours total, so this is a lot. The most that you can have is 8,760. Really, having anything more than 1,000 is considered quite a lot, and anything more than 300 total is not going to pass per lead unless you have a very good reason why. 

So we look at this, we have that many unmet hours. That really means nothing, so we say, “Now what?” In my experience, the best thing to do next is to look at the SSR report. We can scroll through by system type, so we start with the air conditioning unit 1. In here we can see that there’s only 16 hours that are under-heated, and zero that are under-cooled. Scroll once. I’m using the mouse wheel to scroll through this component. Here we have 518 that are under-heated, so we want to make a note that A/C 2 has some potential issues, and we can also note that they’re primarily in the men’s restroom, with 437 under-heated hours. 

A/C 3, we can see that there’s quite a few unmet hours again. Now, notice that these are constant volume zones, with several zones in each system type. They’re constant volume systems rather than constant volume zones, constant volume systems. We have several zones in one constant volume system. Now that’s important to make a note of. You also want to look at the total run hours, as well. Just to get an idea of what percentage of the hours that you’re under-heated or under-cooled. 

If you notice, this totals to 836 under-cooled hours, but we only had 378 (or something like that) unmet cooling hours. That tells us that a lot of these under-cooled hours are occurring at the same time. We keep scrolling. Again, we have another system with under-cooled hours. We get to A/C 7 and we can see this is our major problem, because one of these zones has 2,000 under-heated hours. Any particular zone that has the most under-heated hours, that is going to be your minimum number of unmet hours, because a zone can only have one unmet hour for any given hour, and if a zone has 500 unmet hours, it guarantees that your project will have at least that. 

Our last system, we have virtually none. Having a few unmet hours isn’t a problem, it’s actually very normal. We notice this, we look at the systems, we look at the individual zones and notice that there’s three zones here. We notice that we have unmet hours through every system, but primarily just in one system is our main problem. 

One of the first places that we want to check out is to see if our sizing is incorrect. The place to do that, we go to the Air Side HVAC spreadsheet, and we can start with cooling coil capacity, as well as heating coil capacity. We have all of these entered, even though eQUEST would auto-size them if they weren’t entered. So what we could do is we could run a Save As here. File > Save As, and then we could restore the default here for all of these systems, and then we re-run it. I’m going to save us the time, and we are not going to do that in this case, because in this case I can already tell you that I tried that first thing, and it didn’t really fix any of the problem. It would be the first step that I would recommend, just to get everything out of the way. It’s really easy to do, you can do a Save As and then you can throw that file out once you save it as, if it doesn’t solve your problems. 

Sometimes the problem’s just that maybe you entered the wrong amount, or maybe you have two different models. You’ll have a design model that came up with the sizing, and then you used a different lighting power density in all of your spaces that are in this zone, and it’s not producing enough heat to accommodate the amount of heat that you actually require. Then again, that was the first thing that I tried on this model, and that didn’t really solve anything. The next question that I asked myself, is there a capacity issue? The next thing that I would ask myself is, is it an air flow issue? We just look at any system. We can look at, since we had mostly cooling hours and heating hours in system 7, even though it may not be defined for heating directly, the air flow is typically defined by cooling, which will subsequently impact your heating. 

We check if the design cfm is indeed entered. Don’t want to create a new system, there. What we can do here — we could restore the default on that and run all of that at once. In fact — if you just wanted to know if it was a capacity or air flow issue to start with, you could set all of these to 0 and re-run the model, and see if that’s the problem. Now, I am warning you that doing both of those things gives the project a lot of degrees of additional freedom, and just doing that is likely to solve some unmet hours. Believe it or not, in this project, it didn’t solve much. 

The two big things are: is it the capacity? and subsequently, is it the air flow? We could also consider the supply temperature. Your heating — we have a maximum supply temperature of 120 degrees. If you had accidentally entered something lower, that could be a problem. 120, of course, is plenty warm, and we wouldn’t want air warmer than 120 degrees blowing on us