Commercial Architecture September 2017 - 47

PROJECT

hvac

Left. A California middle school renovation upgraded HVAC-system heat pumps.
Inset. Heat pumps needed to fit in the restricted space in the existing mechanical closets.

tors were field programmed to match the motors to

over two months of the 2016 summer shutdown.

the job conditions. Model EC units are two-com-

The system was successfully started in time for the

pressor water-source heat pumps with variable-fre-

fall semester. After startup, the engineers complet-

quency drives for the supply fans that stage airflow

ed air balancing, control programming, graphi-

to match compressor stages. Insulated bulkheads in

cal-interface modifications, and commissioning of

vertical EC models separate the compressor and

the system.

blower sections.

Edgton Wright from Bosch Thermotechnology,

The closets are a return plenum and operate un-

Ft. Lauderdale, FL, performed training as a key

der a high negative pressure due to a restricted re-

component of the commissioning service. Having a

turn-air system. To lower the negative pressures in

manufacturer perform start-up consulting has a

each closet, the airflow/ton was reduced and acous-

number of benefits, including greater potential for

tically treated, and transfer grilles were installed

lower energy and operational costs, facility staff

above the closet doors. To compensate for the re-

training for improved technical support, end-user

duced pressure and variable-supply airflow, each

confidence in product functionality and perfor-

heat-pump closet has a variable-flow EC motor out-

mance, documentation of start-up activities and

door-air fan. Outdoor-air fan speed is reset based on

guidance for warranty support, and an ongoing per-

carbon dioxide levels in the classrooms. Each wa-

sonal touch through technical support for the dura-

ter-source heat pump has a pressure-independent

tion of the start-up program.

two-position water valve that closes when the compressor is off.

"Training for the facilities staff was very productive," said Matt Waller, P.E., senior engineer with

Units are designed to be serviced from the front.

IDS, the design firm that worked as a sub-consul-

The project included high-performance window

tant to Enovity that developed the system design

tints, which allowed some heat pumps to be re-

and prepared construction documents. "It incorpo-

duced in size.

rated a comprehensive presentation, plus hands-on

The new central plant is variable water flow. Individual heat-pump design flows were reduced from

training in front of an installed heat pump unit inside a vertical utility closet."

the original 4 gpm/ton to 2 1/2 gpm/ton, and the

Darren Smith agreed. "It's not often you receive

condenser water pump motor size reduced from 40

positive comments about training, so we were

HP to 25 HP.

pleased to hear that [they found the training pro-

The replacement cooling tower is counterflow,

ductive]," he said.

with three variable-speed 5-HP propeller fans, and a

The Bosch consulting service offers support

variable-speed 7 1/2-HP basin pump that replaced a

across the entire Bosch FHP line of products, from

40-HP centrifugal fan blow-through tower with a

the beginning product-selection phase by the user

5-HP basin pump. When additional heating is re-

to post installation and start up. Each consulting

quired, two modulating boilers inject heat into the

package includes a visit from an expert field techni-

water loop. The DDC control system integrates cen-

cian to provide start-up consulting services, includ-

tral plant variable-frequency drives, boilers, and

ing on-site supervised start-up assistance, hands-on

chemical treatment controllers.

personnel training, and a review of the job.
After the project was completed, Smith said that

SYSTEM BENEFITS

the newer pumps were a worthwhile investment

Construction began in late 2015, and installation

and proved to be quieter and more efficient than

of the facility's heating/cooling system took place

the former units. CA

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SEPTEMBER 2017

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Table of Contents for the Digital Edition of Commercial Architecture September 2017