Selecting the appropriate HVAC equipment for an AOR job can be compared to the work of a master chef. He whips the eggs just so. He tosses in a pinch of this spice and that spice, and cooks the eggs at a specific temperature. Cheese and other special ingredients are added. Voilà. The outcome is omelette perfection to tantalize the taste buds. It’s a form of art. Surprisingly (or not surprisingly), a simple omelette is not art when I cook it in my kitchen. Edible, but not art.
Thankfully the art of HVAC equipment selection has been simplified. Using Right-Suite Universal software will transform your work into art even if you are not the Guy Fieri of the HVAC world. You will still learn a lot of tricks of the trade from your mentors, but when it comes to relying on rules of thumb or intuition to guide you through the equipment selection process – forget those notions. They can’t be trusted to be accurate. Certainly AHRI data for equipment is better than nothing, but it just gives you total capacity data. (Aren’t we supposed to be factoring in sensible and latent data separately?)
Humidity is a Game Changer: 95° in Miami is a HOT Day but 95° in Phoenix is Pleasant.
The days of using a sling psychrometer to assess the wet bulb temperature are thankfully just a distant memory or something younger generations think of as a museum exhibit. Wrightsoft uses temperature/weather data from ASHRAE 2013, ACCA addendum E, microclimate data for CA, AZ, HI, and NV, and F280-12 data for Canada to give us daily temperature averages for every city in America. This data is used by Right-Suite Universal (as well as our mobile solutions) to make all the detailed calculations necessary to properly evaluate the HVAC system each individual home requires. Yet even with all this data, factoring in relative humidity (and many other variables) is crucial to the success of your HVAC design. Some factors to consider:
- What’s the outside temperature?
- What’s the return air temperature?
- Does the air flow need to be adjusted? Less air flow leads to lower capacity, but it also means the air spends more time on the coil which means less overall cooling. This might be advantageous if you live in Miami or in other high humidity zones.
- How leaky is the duct system? Can you simply reduce the leakiness by sealing the connections?
An example of an actual performance data worksheet for an equipment manufacturer (see attached data sheet) poses another pitfall to the process. This worksheet was designed to merely assist in the equipment selection process. Making an important equipment decision is an exact science. That being said, when the capacity of any given system might fall in between two different zones on the chart provided to you, it’s easy to see why two contractors might make two different decisions.
To give an example, if the wet bulb is 65 (a number between those listed on the graph), the return air is 80 and the outside air is 95, then do you choose the 31,500 btu number or the 33,600 btu number? We know 36,000 btus is a 3 ton unit and 30,000 btus equates to a 2.5 ton unit. When your number is 31,500 then the 2.5 ton system seems best, but if you choose the 33,600 number then the 3 ton system might seem like the better choice. Imagine how much more difficult the decision becomes if all the numbers fall between those listed on the graph. (Ex. 65 degree wet bulb, 89 degree outside temperature and 77 degree return air.) To do all the math involved can get a little excessive!
Your final equipment decision is potentially tricky at this point. A small number of artists can get by without using hard facts and still pull it all together somehow. Most contractors get acceptable results most of the time. Which is okay. Yet it’s that small percentage of the time when you end up making crumby omelettes that can really cost you.
MiTek-Wrightsoft is going to make every equipment decision headache fade away. Right-Suite® Universal (RSU) transforms acceptable results into amazing results, and it eliminates the crumby omelettes.
MiTek-Wrightsoft’s Manual S Selection Feature Transforms Every HVAC Contractor into an Artist
When you work with MiTek-Wrightsoft’s Right-Suite® Universal (RSU), it will guide you through the equipment selection process to ensure you don’t make a bad choice. All the equipment manufacturers will come up in a list for you to make your initial decision. When you choose a manufacturer listed in red font, you will have the option to check the “Select for Manual S” box. When this box is checked, all the data you have input into RSU will be factored into the list of HVAC systems it spits back at you. These “good choices” will be based on all the criteria necessary to fulfill the specific needs of that unique home. Under these circumstances, your choice will be easy because the only real decision at this point is for you to select the option you prefer from the list of approved choices. The possibility for you to make a “bad choice” (capacity-wise) has been eliminated. Voilà. You are now an HVAC artist and compliant with Manual S code requirements.
Why is this impressive? The Capacity Interpolator will reveal the extensive calculations running behind the scenes in RSU. Click on the “Perf” tab, then on the three dots to the right of the Sensible and Latent numbers to reveal all the extensive calculations on the Capacity Interpolator page.
If you aren’t impressed by this page, try doing the math by hand. Fair Warning: It might cause you to tear your hair out. It will undoubtedly cause you to suddenly be impressed.
Have you been considering MiTek-Wrightsoft? Download the demo version to test drive RSU today. It will make your equipment selection process easy and fast.
