Commercial Architecture March 2018 - 49

PROJECT

hvac

system maintains the set temperature by constantly

ASHRAE MINIMUM STANDARDS

monitoring the capacity needs-ramping up or down

Building codes require "ventilation for acceptable

to meet those needs based on the demand.

indoor air quality" in a guestroom whenever the

Because variable-speed inverters work at a lower

space is occupied. There are two primary methods

capacity, on average, less power is consumed, offering

by which hotel owners meet ASHRAE and ICC/IBC

quieter operation and significant energy savings. In-

code requirements: a full dedicated outdoor air sys-

verters allow the system to consume only the exact

tem (DOAS) directly ducted to the guestroom, or an

minimum amount of power required at any given

outdoor air PTAC/VTAC unit.
Hotel franchises, such as Hilton, Marriott, IHG,

moment.
This precision is especially helpful because PTAC

and Hyatt, meet-and sometimes exceed-ASHRAE

systems are often specified for the worst-case scenar-

minimum fresh-air ventilation rates for hotel gues-

io-oversized, for maximum load. Inverter technolo-

trooms. To achieve LEED certification, buildings

gy will allow hotels more flexibility in how they design, and because sharp fluctuations in the load are
eliminated, the life of the system should be extended.
The disadvantage of inverter technology is that
until inverters become more common, they'll add an
additional level of complexity for field repairs.

Above. Because hospitality is a service industry and hotel guests spend much of their
time indoors, thermal comfort and IAQ are especially consequential.
Below. With nearly 5-million guestrooms in the U.S., the hotel industry has an opportunity to reduce America's overall energy use. The number of installed PTAC units is
expected to grow significantly.

should comply with ASHRAE minimum fresh-air
requirements.
"In most cases, the codes are based on ASHRAE
standard, so we would not want to go less than
ASHRAE standard because doing so may not comply
with local codes," said Hilton's Rick Frey.

INVERTER-COMPRESSOR VTAC

MARKET SEGMENTATION

According to Marriott's Terry Smith, a significant

Very few major hotel brands own their building as-

advance in PTAC technology is about to change the

sets. While some assets not owned by the hotel brand

industry's thinking.

are still managed and operated by the brand (who

"Friedrich now has an inverter-compressor PTAC

are thus incentivized to optimize energy savings),

unit on the market," explained Smith. "Because of

the majority of hotel building assets in the U.S. are

the inverter-compressor technology, the energy sav-

franchise properties, paying royalties and fees to the

ings you get are unbelievable."

hotel brand.

In fact, Friedrich, San Antonio (friedrich.com),
already

markets

the

hotel

industry

The select-service product market has grown very

price-competitive in recent years. About 2,800 invest-

inverter-compressor VTAC (a vertical PTAC), which

ment ownership groups have possession of almost all

Marriott has successfully tested. VTACs are clos-

franchise properties. Investors include pension funds,

et-mounted single-packaged units.

LLCs, insurance companies, and owner-developers.

"We had Friedrich run some energy analysis for

The investment community is short-term, first-cost

us on it," said Marriott's Terry Smith. "It's in the two- to

air, unrestricted, up through the series of fans and intro-

driven, to the point that payback from energy efficiency

three-year payback. It can be upward to four years, but it's

duces it to the front primary evaporator coil that is al-

ranks far down the ladder of importance.

pretty darn good."

ready doing the normal workload of the system.

With nearly 5-million guestrooms in the U.S., the ho-

Friedrich brands the vertical unit "VRP," and accord-

"We should get the same benefits out of the invert-

tel industry holds a tremendous opportunity to reduce

ing to Blair Hildahl, principal at Base4, the VRP is highly

er-compressor PTAC that you get out of the inverter-

America's overall energy use. The number of installed

effective at providing in-room humidity control and ad-

compressor VTAC once it's available," said Marriott's

PTAC units is expected to grow significantly, along with

dressing IAQ concerns.

Terry Smith.

the growth of the industry itself.

Hilton's Rick Frey agrees. "Most PTACs and VTACs

The efficiency of the Friedrich unit is twofold: the

More efficient PTAC units should be a logical inclu-

can control temperature, but any humidity control is sub-

system eliminates the secondary micro-compressor

sion in high-performance buildings. They are inexpen-

sequent, or ancillary, to the temperature control. The

found in other systems, and it is also the first variable re-

sive first-cost units, with simple maintenance, in which

Friedrich VRP unit specifically cools and addresses room

frigerant flow, inverter-compressor PTAC unit on the

downtime affects only one guestroom.

humidity," he said.

market. As the units should therefore bring in more out-

With the latest PTAC technology providing low-cost

side fresh air, they will lessen the requirements for dedi-

ventilation, thermal comfort, and humidity control, the

INVERTER PTAC

cated rooftop make-up air systems, allowing a downsiz-

hotel industry can seize this opportunity and take a lead-

Similar to Friedrich's VRP vertical unit, the new Frie-

ing of the whole building make-up air.

ing role in global HVAC energy reduction. CA

drich inverter PTAC unit brings in fresh outside air
through a distinctively unique method. The Friedrich
PTAC bypasses the constraints of the secondary 6-in.
coil module, opting instead to blow fresh air across the
primary evaporator coil.
Rather than a separate micro-compressor-as other
PTAC manufacturers use to precondition the incoming

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