Guest Room HVAC Systems

System Selection Fundamentals

Guest room HVAC system selection determines capital cost, operating expense, maintenance requirements, and guest satisfaction for the property’s operational lifetime. The decision framework evaluates first cost against lifecycle costs, noise performance against guest expectations, and maintenance complexity against available technical expertise. No single system type proves optimal for all applications—each presents trade-offs between competing priorities.

Packaged Terminal Air Conditioners (PTAC)

PTACs dominate economy and mid-scale hotel markets due to low first cost, simple installation, and distributed maintenance characteristics. Each self-contained unit mounts through an exterior wall sleeve, providing heating and cooling for a single guest room without central plant infrastructure. This distributed approach eliminates central chillers, boilers, and hydronic piping, reducing first costs by 30-50% compared to central systems.

Operating Principles

PTACs combine a direct-expansion cooling cycle with electric resistance or heat pump heating in a chassis designed for through-wall installation. The outdoor coil mounts flush with exterior wall, while the indoor section extends into the room below a window or at floor level. Integral controls provide thermostat, fan speed selection, and mode switching (cool, heat, fan only).

Cooling capacity ranges from 7,000-15,000 Btu/hr at standard rating conditions (95°F outdoor, 80°F/67°F WB indoor). Units achieve EER of 10.0-12.5 Btu/W-hr for cooling and COP of 2.8-3.5 for heat pump models. Electric resistance heating provides supplemental capacity at COP = 1.0, used during defrost cycles or when outdoor temperature drops below heat pump economical operation point (typically 35-40°F).

Installation Requirements

Wall sleeve installation requires 16-inch minimum wall depth to accommodate chassis depth plus insulation. Sleeve positioning places the unit 6-12 inches above finished floor for standard models, or within furniture casework for low-profile designs. Exterior grilles must clear ground level by 12 inches minimum to prevent snow blockage and ensure adequate airflow.

Electrical service provides 208-230V, 20-30A circuits depending on heating element size. Dedicated circuits serve each unit to prevent nuisance tripping when multiple rooms cycle simultaneously. Branch circuit length should not exceed 75 feet to prevent voltage drop below equipment nameplate requirements.

Condensate drainage relies on gravity flow through sleeve to exterior or collected in base pan with evaporative disposal. Exterior drainage requires freeze protection in cold climates through heat tape or sloped drain lines. Units installed above occupied spaces must use sealed drain pans to prevent ceiling damage from condensate overflow.

Performance Characteristics

Noise levels represent the primary guest complaint with PTAC systems. Compressor cycling, fan motor operation, and refrigerant flow generate 42-48 dBA at 3 feet, exceeding NC 35 targets for upscale properties. Manufacturers offer “quiet” models with improved compressor isolation and multi-speed fans achieving 39-42 dBA, approaching acceptable noise levels at premium cost.

Advantages and Limitations

PTACs excel in applications prioritizing low first cost and distributed maintenance. Individual unit failure affects only one room rather than entire floors, permitting rapid response through spare unit replacement. Maintenance staff perform routine repairs without specialized refrigeration certification using plug-in components and standardized chassis designs.

Energy efficiency lags behind central systems due to less optimal equipment sizing, single-stage operation, and elevated parasitic losses from air leakage around wall sleeves. Annual energy costs run 20-40% higher than equivalent fan coil systems in moderate climates, increasing to 40-60% premium in extreme climates requiring year-round operation.

Ventilation compliance requires supplemental systems since standard PTACs provide no outdoor air. Modern code-compliant installations add continuous ventilation fans (15-25 CFM) ducted from corridors, dedicated outdoor air dampers on PTAC chassis with corridor makeup, or separate DOAS serving multiple rooms. These additions increase first cost by $400-800 per room.

Fan Coil Units

Fan coil systems provide quiet, energy-efficient conditioning using central chilled water and heating hot water plants. Each guest room contains a fan coil unit (FCU) with hot and cold water coils, while central equipment generates and distributes thermal energy. This centralized approach increases first cost but reduces operating expense and improves controllability.

Two-Pipe versus Four-Pipe Systems

Two-pipe systems circulate either chilled water or heating hot water through a single supply and return pipe pair. Seasonal changeover from cooling to heating occurs building-wide based on outdoor temperature, typically 55-60°F. This limits guest comfort during swing seasons when some rooms require cooling (sunny south exposures) while others need heating (shaded north exposures).

Four-pipe systems maintain simultaneous cooling and heating capability through separate chilled water and hot water distribution. Each fan coil contains independent cooling and heating coils with separate control valves. Guests select heating or cooling mode regardless of season or adjacent room operation. This flexibility increases guest satisfaction at 40-60% higher piping first cost.

Equipment Configuration

Typical fan coil units deliver 300-500 CFM across cooling coils (12-18 ft² face area) and heating coils (6-10 ft² face area). Cooling coils use 3-4 rows of 10-12 fins per inch for 40-45°F entering water temperature, achieving 8,000-12,000 Btu/hr capacity at design conditions. Heating coils employ 2-3 rows with 8-10 fins per inch for 140-160°F water, providing 15,000-20,000 Btu/hr.

Multi-speed fan motors offer low/medium/high operation at 200/350/500 CFM. Guest-accessible controls typically provide only low/auto/high settings, with automatic speed modulation based on thermostat demand. ECM motors improve efficiency by 30-40% compared to PSC motors while enabling continuous low-speed operation for air circulation.

Units mount horizontally above ceilings, vertically in closets, or recessed in wall cavities depending on building configuration. Horizontal installations minimize noise transmission into occupied space but require accessible ceilings for maintenance. Vertical units simplify piping connections but transmit more mechanical noise unless properly isolated.

Hydronic System Requirements

Chilled water systems maintain 42-45°F supply temperature at 10-12°F temperature differential, requiring 2.0-2.4 GPM per 12,000 Btu/hr cooling capacity. Total system flow for a 200-room hotel reaches 400-480 GPM assuming 0.65 diversity factor. Primary-secondary pumping or variable primary flow distributes water with pressure differential sufficient to operate two-way control valves (15-20 psi).

Heating hot water operates at 140-160°F supply with 20°F delta-T, flowing 1.5-2.0 GPM per 15,000 Btu/hr capacity. Lower temperature differentials simplify control valve sizing but increase pumping energy. Condensing boilers achieve optimal efficiency with 120-140°F return temperatures, favoring larger delta-T operation.

Water treatment prevents scale formation, corrosion, and biological growth in hydronic systems. Closed-loop systems require chemical treatment maintaining pH 8.5-9.5 with corrosion inhibitors and algaecides. Makeup water introduces dissolved solids necessitating regular blowdown and treatment chemical replenishment.

Noise Performance

Fan coil units achieve 35-40 dBA noise levels when selected for low-speed operation at design load. Proper selection sizes coils and fans so that low speed meets 85-90% of load hours, operating on medium or high speed only during peak conditions. Oversized units cycle frequently on low speed, generating objectionable on-off noise patterns.

Vibration isolation mounts prevent structure-borne noise transmission. Spring isolators (0.5-1.0 inch static deflection) or neoprene pads separate unit base from mounting surface. Flexible piping connections (12-18 inch braided hoses) prevent vibration transmission through water lines.

Supply air diffusers and return grilles contribute to acoustic environment. Low-velocity diffusers (300-500 FPM) with acoustic boots minimize air noise. Return air paths should avoid direct line-of-sight to fan coil to prevent transmission of mechanical noise into room.

Variable Refrigerant Flow Systems

VRF technology brings multi-zone heat pump efficiency to hotel applications, particularly properties over 100 rooms where energy savings justify higher first cost. Systems achieve part-load efficiencies exceeding conventional equipment through variable-speed compressors, electronic expansion valves, and simultaneous heating/cooling capability with heat recovery.

System Architecture

VRF systems connect one or multiple outdoor condensing units to numerous indoor fan coil units via refrigerant piping. A single outdoor unit serves 8-64 indoor units depending on capacity and manufacturer. Outdoor units range from 8-72 tons cooling capacity with modulating compressors operating at 10-100% capacity.

Indoor units install in guest rooms similarly to hydronic fan coils—horizontal above ceiling, vertical in closets, or recessed in walls. Each unit contains electronic expansion valve and controls allowing independent temperature setpoint and operation. Refrigerant distribution branches from main headers using refnet joints or manifold systems, with individual liquid and suction lines to each indoor unit.

Heat recovery VRF systems enable simultaneous heating and cooling across zones. Rooms requiring cooling reject heat through outdoor condenser or redirect it to rooms requiring heating. This heat recovery reduces total building energy consumption by 20-30% compared to heat pump systems without recovery capability. Three-pipe heat recovery configurations use common suction line with separate hot-gas and liquid lines for maximum flexibility.

Capacity Control

Variable-speed inverter-driven compressors modulate capacity from 10-100% matching actual building load rather than cycling on-off. This enables superior part-load efficiency since hotel buildings operate at design load less than 2% of annual hours. At 50% part load, VRF systems achieve EER of 16-22 Btu/W-hr compared to 11-13 Btu/W-hr for staged systems.

Electronic expansion valves (EEV) control refrigerant flow to each indoor unit maintaining optimal superheat regardless of operating conditions. Precise superheat control (3-5°F) maximizes coil utilization while preventing liquid floodback to compressor. EEVs respond to load changes within seconds compared to minutes for thermostatic expansion valves.

Combined capacity modulation and superheat control deliver exceptional temperature stability. Guest rooms maintain ±0.5°F of setpoint compared to ±2°F for single-stage PTAC systems. This precision improves comfort perception and reduces guest thermostat adjustments.

Installation Considerations

Refrigerant piping replaces hydronic piping and central plants, typically reducing installation labor by 20-30% compared to four-pipe fan coil systems. Maximum equivalent piping length runs 500-1,000 feet depending on manufacturer, with elevation differences up to 150 feet between outdoor and indoor units. These constraints suit mid-rise hotel construction (6-10 stories) but challenge high-rise applications.

Outdoor unit placement requires attention to noise, service access, and aesthetics. Units generate 65-72 dBA at 3 feet, necessitating setbacks from property lines and guest room windows. Rooftop installation provides optimal serviceability and aesthetics but increases refrigerant piping lengths. Grade-level equipment courts minimize piping but require screening and security measures.

Branch circuit wiring supplies each indoor unit (0.3-1.2 kW) plus outdoor unit (8-45 kW for 10-60 ton capacity). Electrical infrastructure costs approximate fan coil systems when accounting for reduced central plant electrical loads. Communication wiring connects all units for coordinated control and monitoring.

Comparison to Other Systems

Split Systems and Through-Wall Units

Ductless mini-split systems provide distributed cooling similar to PTACs but with outdoor condensing unit connected to indoor air handler via refrigerant lines. This separation allows quieter indoor operation (28-35 dBA) since compressor noise remains outside. Applications include boutique hotels, renovations where wall sleeves are undesirable, and properties with architectural restrictions on exterior equipment.

Through-wall units combine PTAC operating principles with improved aesthetics and performance. Slim-line designs recess into walls with only supply grille visible in room. Separate outdoor condensers reduce indoor noise to 35-40 dBA while improving efficiency through optimized heat exchanger design. First costs run 40-60% above standard PTACs but deliver noise performance approaching fan coil systems.

Ventilation Compliance Strategies

ASHRAE 62.1 Requirements

Guest rooms require 5 cfm/person plus 0.06 cfm/ft² outdoor air per ASHRAE 62.1. For a 300 ft² room with 2-person occupancy, this calculates to:

$$OA = (5 \times 2) + (0.06 \times 300) = 10 + 18 = 28 \text{ CFM}$$

This outdoor air must deliver continuously during occupancy or at sufficient average rate to maintain equivalent air quality. Intermittent ventilation systems require higher instantaneous rates to compensate for off-cycle periods.

Implementation Approaches

Dedicated Outdoor Air Systems (DOAS): Central DOAS conditions and distributes outdoor air to each guest room via dedicated ductwork. Systems incorporate energy recovery (60-75% effectiveness) to minimize heating and cooling of outdoor air. DOAS supplies treated air at 65-70°F, introducing neither heating nor cooling load to room terminal units.

Corridor Makeup Air: Outdoor air introduced to corridors at slight positive pressure (0.02-0.03 in. wc) flows into rooms through door undercuts (1-inch gap = 20-30 CFM at 0.02 in. wc). Guest room terminal units recirculate this air providing temperature control. This simple approach works for moderate climates but struggles in extreme conditions where unconditioned corridor air creates comfort issues.

Outdoor Air Dampers: PTAC and fan coil units equipped with motorized outdoor air dampers draw 15-30 CFM directly from exterior. Dampers close during unoccupied periods for energy savings. Corridor pressurization provides makeup air to prevent building depressurization. This approach adds $300-600 per room equipment cost plus corridor makeup air system.

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