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What Is DX? – Short #185

By Bryan Orr

In this short podcast episode, Bryan tackles the following question: What is DX?

In short, DX stands for “direct expansion,” which means that you cool the end product via the refrigeration cycle. We blow air over an evaporator coil, which allows the refrigerant to take up heat from the air and directly expand. Chillers, boilers, and chilled water systems are NOT direct expansion systems; they use a secondary fluid like water or glycol to move the heat throughout the structure, not an evaporator to take up heat directly. They also have heat exchangers to move heat from the refrigerant to the secondary fluid.

DX systems tend to be smaller, and chillers and boilers tend to be larger. Chillers are advantageous in cases where we’re working with toxic or flammable refrigerants or large refrigerant charges; we can keep the refrigerant charge away from the structure and space or product(s) needing to be heated or cooled.

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#boiler #chiller #direct expansion #dx

Author:

Bryan Orr

Company: HVAC School

Position: Founder

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HVAC School – For Techs, By Techs

Real training for HVAC ( Heating, Ventilation, Air Conditioning and Refrigeration) Technicians. Including recorded tech training, interviews, diagnostics and general conversations about the trade.

In this episode, Bryan sits down with Leilani for an introduction to GRIT Camps — the hands-on program that brings skilled trades exposure to youth ages 12–17 through community events led by working tradespeople. Leilani explains that a GRIT Camp pairs recruited mentors with students for a day of modules covering safety, carpentry, electrical, brazing, and plumbing, including torch work, PVC and copper fitting, and disassembling HVAC components. Students also learn to read a jobsite-style blueprint and receive a six-in-one screwdriver to take apart and explore. Bryan and Leilani emphasize that while GRIT supplies the curriculum, guides, and structure, the host — typically a contracting business or trade organization — owns the event: recruiting students and mentors, securing a venue, and building real community connections around the day.

A large portion of the conversation walks through who does what. Hosts provide the facility, materials (plywood, 2x4s, copper, PVC, and more, all detailed in GRIT’s guide), and lunch for up to around 30 people, plus a local host facilitator to coordinate logistics and serve as GRIT’s point of contact. Mentors must be certified skilled tradespeople who complete GRIT’s required video course and pass a background check before working with students; volunteers who don’t interact directly with kids are not required to undergo a background check. GRIT, in turn, supplies the camp curriculum, host and mentor guides, registration and marketing materials, badges, student blueprints and PPE, background check coordination, and on-site program leadership from staff like Ty, GRIT’s head of training, who typically arrives the day before to walk the facility with the host.

Bryan and Leilani also dig into planning specifics: camps run from about 9:30 a.m. to 3:30 p.m., cap out at 16 students with a two-students-per-mentor ratio (so eight to nine mentors for a full camp), and generally need 10 to 12 weeks of lead time to hit deadlines for mentor certification, materials gathering, and student registration. They cover the realities of choosing a torch and joining system — MAPP gas and propane versus oxyacetylene for brazing, and why oxyacetylene can’t be used for the popular aluminum-repair activity — along with commonly overlooked items like correctly sized Forstner bits, spare drill batteries, extension cords, and pre-cut lumber. They close with guidance on budgeting (camps typically run $1,500 to $5,000), sourcing a sponsored lunch, handling allergies, inviting community press, and what makes a camp genuinely successful: preparedness paired with passion from both mentors and hosts.

Topics Covered

What a GRIT Camp is and which skilled trades are covered (safety, carpentry, electrical, brazing, plumbing)
Camp roles: host, host facilitator, mentor, students, and volunteers
What hosts are responsible for providing: facility, materials, and lunch
What GRIT provides: curriculum, guides, registration, marketing, background checks, and on-site leadership
Required mentor certification course and background checks
Ideal space setup, table stations, and indoor/outdoor considerations
Student and mentor ratios (16 students max, two students per mentor)
Planning timeline: 10–12 weeks of lead time and key deadlines
Confirming a camp date and the host interest assessment process
Recruiting students and mentors, including waitlists and communication
Choosing a torch and joining system: MAPP gas/propane vs. oxyacetylene brazing
Commonly overlooked or underestimated materials and tools
Safety planning, PPE, and emergency preparedness
Estimated costs and ways to offset them through sponsorships
Lunch planning and handling food allergies
Community and marketing value for hosts
Policies on parents and visitors attending
What makes a GRIT Camp successful