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The Deep End with Roman Baugh: Live Call, Grounded Compressor, Mitsubishi Mini-Split

By Roman Baugh

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In this short podcast, Roman Baugh takes over with his new series, “The Deep End,” where he shares tech support conversations. This time, Roman is on the other end of a live tech support call about a grounded compressor with an existing Mitsubishi mini-split (Mr. Slim heat pump). The unit in this case had an unclear service history due to the homeowner moving in recently.

In this issue, the compressor kicked on and kicked off immediately. After the technician in this scenario told tech support that he had no continuity from the compressor to ground, tech support asked him to check the resistance (which was 43 ohms from black to ground and 43 from white to ground). Tech support concluded that the compressor was grounded, and it needed to be replaced (along with the PCB). However, the resistance disappeared mid-call, and intermittent resistance readings don’t always indicate a failed winding; it’s worth noting that cool ambient temperatures that enable liquid refrigerant to migrate into the compressor could potentially skew electrical readings.

Roman recommended shutting the system down and trying to get the system to run. His rationale was that if the unit ran and didn’t keep stopping, the system may have been overcharged or lacking a crankcase heater. However, that did not show any improvement in operation; the compressor rattled for about a second and shut off. A resistance test confirmed that the compressor was grounded, pointing to a mechanical issue with the compressor and not just a one-off instance of refrigerant migration. This type of failure can happen when there are repeated instances of liquid refrigerant in the crankcase over time.

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#compressor #continuity #hvac #resistance #tech support #troubleshooting

Author:

Roman Baugh

Company: Kalos Services

Position: Director of Commercial HVAC

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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 of the HVAC School Podcast, Bryan sits down with Chris Howells, senior training manager at AprilAire, to talk about what really makes a filtration system perform. Chris has nearly thirty years in the industry, including fifteen as a technician, and brings a field-first perspective on why filtration is more than just “a filter.” Bryan also admits up front that his own contracting company is looking to put more high-efficiency filters into the field, so this conversation doubles as a practical learning session.

The discussion starts with a common misconception: that a “thicker” filter is simply a filter with thicker media. Chris explains that what matters is surface area, face velocity, and pressure drop, not the width of the cabinet. They cover why using the full face of the filter is one of the easiest wins, how a poorly designed return can load just one section of the media, and why a high MERV rating does not automatically mean high resistance. Cabinet design, media construction, and overall system design all play a role, and modern ECM blowers make low static pressure more important than ever.

From there, the conversation turns to bypass air and measurement. Chris describes how AprilAire’s cabinets use top and bottom rails and a self-seal media overhang to force air through the filter, backed by a 10-year clean coil guarantee. He and Bryan stress using the right tools, including a dual-port manometer and a proper static pressure probe, and checking pre-filter and post-filter pressure drop against manufacturer performance data at around 500 feet per minute. Chris also debunks the idea that deeper media is always more restrictive, pointing out that a typical retail one-inch pleated filter can raise pressure drop dramatically compared with a basic fiberglass filter.

The final stretch is about communication and growth. Chris and Bryan share simple, natural questions technicians can use to start air quality conversations without sounding like a sales pitch, and they encourage listeners to stay curious and keep asking “why.” Chris closes with resources for learning more, including AprilAirPartners.com and the AprilAire Academy, and mentions that the Santa Fe and UltraAire product lines are now part of the AprilAire family.

Topics Covered

Why “thicker” filters are really about surface area, face velocity, and pressure drop
Using the full face of the filter and avoiding uneven loading
How filters affect blower performance, system capacity, and equipment protection
Why filtration is a high-value upgrade compared with bulbs and modules
AprilAire’s new high-efficiency product line and its three-layer media design
Reducing bypass air with rail design, self-sealing media, and the 10-year clean coil guarantee
Measuring static pressure correctly and using manufacturer pressure drop charts
Sizing media cabinets by CFM and face velocity instead of what fits under the air handler
Common myths about MERV ratings and restriction
Conversation starters that help technicians talk about indoor air quality
How to learn more through AprilAirePartners.com, the AprilAire Academy, and local distributors

This episode contains embedded sponsor messages from Refrigeration Technologies, Carrier, Copeland, Santa Fe Dehumidifiers, and TruTech Tools.

Resources

Purchase your tickets or learn more about the 8th Annual HVACR Training Symposium at https://hvacrschool.com/symposium.

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