What Details Should Be Noted During Rooftop Unit Installation?

What details should be noted during rooftop unit installation?

The core principles of rooftop unit installation are “preventing leaks, controlling vibration, and reducing noise.” Strict control is required across four key phases: foundation construction, pipe connections, equipment securing, and waterproofing. Every detail directly impacts equipment lifespan and user experience.

Foundation construction is the primary phase, where uneven foundations must be avoided to prevent equipment vibration or leaks. The foundation must be poured with C30 concrete, with a minimum height of 150mm (to prevent roof water accumulation from submerging the equipment base). Flatness tolerance must be ≤3mm (verified with a level), and a drainage slope of 100-150mm width (slope ≥5%) must be reserved around the foundation perimeter to direct rainwater toward the roof drain outlet. For accessible roofs, install 1.2m-high guardrails around the foundation perimeter to prevent falls. For non-accessible roofs, cover the foundation top with protective netting to prevent debris accumulation.

Pipe connections must prioritize leak prevention, particularly for refrigerant lines and condensate pipes. Refrigerant pipes (copper tubing) shall be connected using the “flared + nitrogen-shielded welding” technique, with flared end flatness tolerance ≤0.1mm. Post-welding pressure retention testing is required (R32 refrigerant retention pressure ≥2.8MPa, R410A ≥ 3.0MPa). Pressure drop after 24-hour pressure retention must be ≤0.02MPa. Insulation may proceed only after leak confirmation (insulation thickness ≥20mm using flame-retardant Class B1 rubber-plastic insulation material; joints sealed with tape). Condensate drain pipes must use UPVC piping with a slope ≥3‰. Install one air vent valve per 10m to prevent air locks causing drainage blockages. Install waterproof sleeves at pipe wall penetrations (sleeve height ≥50mm above roof level), filling gaps with waterproof mastic to prevent rainwater infiltration at pipe roots.

Equipment mounting must control vibration to prevent noise transmission. Install “spring vibration isolators” between rooftop units and foundations (select based on equipment weight; each isolator should bear 1/4 to 1/3 of total equipment weight with 5-10mm compression). Isolator spacing ≤1.5m; secure to foundation bolts (embedded depth ≥100mm) to prevent unit displacement during operation. If the equipment's rated noise level is ≥75dB(A), install “sound barriers” around the unit (height ≥1.2 times the equipment height, using a structure of soundproofing cotton + color-coated steel panels, with sound insulation ≥25dB), or lay soundproofing mats on the roof (thickness ≥50mm). This ensures noise at the roof edge is ≤55dB(A), preventing disturbance to nearby residents.

Waterproofing is critical for rooftop installations, requiring a dual-layer protection system of “equipment base + roof waterproofing layer.” Prior to foundation construction, inspect the existing roof waterproofing layer (if SBS membrane waterproofing is present, verify no cracks or blisters). Install an additional 4mm-thick SBS waterproofing membrane at the foundation location (extending 300mm beyond the foundation edges). Ensure overlaps ≥100mm and seal with a torch-applied hot-melt process. After equipment installation, fill the gap between the base and foundation with polyurethane sealant (width ≥50mm, thickness ≥10mm). Construct a water barrier (height ≥50mm, poured with cement mortar) around the base perimeter to prevent rainwater infiltration through base joints into the roof structural layer.