Hotel and Hospitality HVAC Service: PTACs, Guest Rooms, Humidity and Ventilation

What guest-room HVAC usually is

Packaged terminal air conditioners and packaged terminal heat pumps, or PTACs and PTHPs, are units that fit in a through-wall sleeve. The 2012 study, prepared for DOE by Pacific Northwest National Laboratory, monitored guest rooms in the Washington, Dallas and Los Angeles metropolitan areas. It reports that all of these properties use PTAC or PTHP equipment.

The units in its equipment table were rated from 7,000 to 12,000 Btu/hr of cooling output. The report also says guest room energy accounts for the majority of energy use in the hospitality industry, citing a 1998 source.

For how a sleeve and chassis fit together, see through-the-wall AC and PTACs. Buildings with central chilled water and room fan coils are covered on fan coil units.

Controls: empty rooms, guest settings and the front desk

The DOE study names the basic problem. Typically, guests choose settings on the unit's buttons or a wall thermostat, and those controls let units keep running while a room is empty. The report adds that housekeeping staff randomly changed set-points and turned units off during unrented periods.

An occupancy-based control, or OBC, is a thermostat that senses whether anyone is in the room. The study describes a door switch, an ultrasonic or a passive infrared sensor, or a combination. When the room empties, the OBC waits a set time and then holds a set-back temperature. The study says the OBC lowers the set-point in heating periods and does the opposite in cooling periods. The report says the maker sets the set-back temperature, but the building operator usually has input.

The study estimated energy savings per guest room, but warns that its results are specific to the properties, guests, makers and equipment it monitored. It also records building operators' concern that inaccurate occupancy detection could let a room become overly hot or cold, which would bring guest complaints. Many makers treat the room as occupied from a door opening until it closes, which protects sleeping guests but can miss real empty periods.

The report says some OBC products can network to the front desk property management system (PMS) and to a building automation system, but those features were not tested. GE's Zoneline manual describes a central desk control input. When its contacts are closed, the unit ignores input from external thermostats and user input, though its Sentinel modes still operate. ENERGY STAR's hotel checklist says a smart thermostat can pre-cool a space an hour before it is occupied.

Outdoor air, pressure and humidity in a guest room

EPA's 2013 moisture guidance says hot-weather condensation is more common where air conditioning is very large and hard to control, and in climates with thousands of hours of humid weather. It lists what goes wrong. When units do not run long enough to dehumidify, they cool the air without removing moisture. When exhaust exceeds makeup air, the building pulls in humid outdoor air through gaps and cracks.

Hotel bathrooms are the point here. EPA's guidance says to specify sealing of all exhaust duct connections to SMACNA seal class A using mastic. It says this sealing is important for all exhaust ducts, and especially for ducts with continuously operating exhaust fans, such as those in hotel bathrooms. EPA gives the example that water vapor driven in from outdoors may condense when it reaches a vinyl wall covering on the cool inside surface of an exterior wall.

EPA's targets are concrete. It says to keep the indoor dew point below 55°F during cooling. In warm, humid climates, EPA says keeping a slight positive pressure during cooling conditions adds protection against condensation in the building enclosure. It says to balance exhaust and ventilation airflows in humid weather so the building stays, on average, under slightly positive pressure (5 Pa or 0.02 inch water column). It says to reach that with dry ventilation air.

The unit itself is part of the outdoor air picture. GE's manual says that with the vent door open, some outdoor air is drawn into the room, which reduces heating or cooling efficiency. GE's makeup air models are designed to provide continuous outdoor air through the vent door (the manual also lets makeup air follow an occupancy sensor or auxiliary input), and the manual says they also dehumidify above a set humidity. Its Humidity Sentinel dehumidification setting ships switched off and is listed for only one of the three GE model lines the manual covers.

The DOE study found some units in poor condition or badly installed, with large gaps around through-wall sleeves letting outside air in. A room's outdoor air could come from the vent door, a makeup air module, central ventilation, or leaks around the sleeve. For mold findings, see mold in HVAC systems in Florida.

A maintenance program for a room inventory

GE's Zoneline manual says to clean the air filters at least every 30 days. It says clogged filters reduce cooling, heating and airflow. Running without filters lets dirt reach the indoor coil. If the vent door is open, GE says to clean the vent filter twice a year or as required. That job needs the unit removed from the wall sleeve. The manual also says to check the base pan periodically and clean the outside coils regularly.

The DOE study's own recommendations point the same way. It says units should be maintained so that filters and coils are cleaned regularly, and that each unit's fit in its sleeve should be checked for tightness. Where OBC thermostats are installed, it says to consider regular reviews of remote sensors and door switches. It notes the parts are prone to guest damage.

ENERGY STAR's checklist says HVAC components should be maintained by qualified staff or under an annual maintenance contract. It calls for a tune-up before both the heating and cooling seasons. It also says to keep supply and return registers clear of furniture.

EPA's guidance says to prevent normal condensate from cooling coils from overflowing drain pans, as recommended by ASHRAE Standard 62.1-2007. For filter basics, see HVAC air filters.

Florida notes

The Florida Department of Environmental Protection publishes a 2023 Florida Green Lodging Program best management practice on energy efficiency. It lists HVAC conservation measures. They include turning off heating and cooling in unoccupied rooms and changing filters regularly. They also include locking all thermostats that are accessible to the public.

The same document says to clean condenser and evaporator coils at least once every six months. It says dust accumulation leads to decreased efficiency. It also says heavy use of exhaust fans makes the HVAC system work harder. EPA's guidance, above, adds that when exhaust exceeds makeup air, a building draws in moisture-laden outdoor air.

The program also suggests asking the local utility for an energy audit, which it says many utilities provide. An energy management system, it says, is most commonly used to monitor the HVAC system.

What to put in a service scope

Before a contractor prices a hotel program, settle these in writing.

1. How many rooms use each make, model and heating type, and how old are they?
2. Do room units bring in outdoor air through vent doors or makeup air modules, or does a central system supply it? Which vent doors are open?
3. What exhaust runs continuously in guest bathrooms, and how is the makeup air for it dried?
4. Are occupancy controls or keycards installed, what set-back do they hold, and who owns those settings? Are they linked to the PMS?
5. What is the filter, coil and drain pan schedule per room, and where is it logged?
6. Which sleeves show gaps, water marks or loose fit?
7. Is the building's design dew point or humidity target known, and is anyone measuring it?

ENERGY STAR advises having contractors quote new equipment on high efficiency and reduced demand, and not buying a larger system than needed. For refrigerant rules, see EPA Section 608 refrigerant rules.