HVAC
First full cooling season with A2L equipment in volume and I want to compare notes while it is fresh. What the training covered fine: mildly flammable classification, no open flame, sensor and mitiga...
2100 sq ft, 2019 build, decent envelope, blower door at 3.1 ACH50. Ran a full Manual J with actual measured infiltration, real window specs, and the true orientation. Comes back 27,400 BTU sensible at...
Simple question that gets answered differently depending on who's in the room. When brazing copper refrigerant lines, what nitrogen purge pressure are you using, and why that number? I've heard 2 PS...
Mitsubishi City Multi, four BC controllers across three floors. One of them, third floor east, floods its drain pan about every six weeks and drops water into the ceiling below. The other three have n...
Carrier 38MGQB36 VRF outdoor unit, 8 indoor units, 14 months in service. Started getting E9 communication faults 3 weeks ago. Random IDUs drop, no pattern to which unit. Communication wiring: 3-wire ...
Doing a Manual J for a 2,000 sq ft home in Phoenix, AZ (design temp 110°F). The calc is spitting out 58,000 BTU cooling load which rounds to a 5-ton system. That feels large even for Phoenix. Existin...
Still learning refrigeration theory in school. We've been taught that TXV systems should be charged by subcooling, not superheat. But my instructor also said superheat tells you about evaporator perfo...
Small commercial, two 400 MBH condensing boilers in lead-lag. Owner had a controls contractor add outdoor reset last fall. Since then the boilers cycle roughly every four minutes at mild outdoor temps...
HVAC student, 6 months in. We had a lab exercise today where we induced a low-charge condition on a practice unit. I expected to see icing at the outdoor unit (evaporator) but the ice formed on the su...
Wrapped up a Carrier 48TCA036 to 48TCEA042 changeout today. 3.5-ton to a 3.5-ton, but the old unit was a 1998 and efficiency was in the low 10s. New unit is 15.2 SEER2. Crane pick was the fun part — ...
With R-410A phase-down underway, our distributor is pushing us toward R-454B (Opteon XL41) equipment. But I'm also seeing R-32 units from Mitsubishi and Daikin at competitive pricing. For those alrea...
Customer has a Mitsubishi MXZ-3C30NAHZ hyper-heat system, two heads. Works great above 25°F. Below 25°F, they're complaining about it "not heating" and the aux electric strip is running constantly. C...