Engineered Comfort Fan Coil Controller EZstat Dokumentacja Pobierz pdf (Strona 2)

8-20-07

FAN COIL UNIT CONTROLS

ECM/EPIC

FAN TECHNOLOGY

• Significant energy savings (67% average

compared to PSC motors)

• Unique factory pre-set air volume capability

(+/- 5%)

• Pressure independent fan operation

• LED for visual indication of air volume

• Field adjustable fan air volume controller

• Remote fan air volume adjustment capability

from BAS

• Larger turndown ratios mean more flexibility

for tenant changes

Since 1985, equipment manufacturers have used ECM

motors in residential air conditioners and furnaces. These

motors have made it possible to achieve SEER ratings of 12

and higher. Until more recently though, they were only

manufactured in 120 and 240 VAC, which precluded their use

in commercial applications. Following two years of research

and development and the availability of a new 277 VAC

version, Nailor Industries was first to introduce the ECM motor

to the commercial HVAC market (Ashrae Journal, April 1997)

as an option for use in commercial fan powered terminal unit

applications.

WHAT IS AN ECM MOTOR?

The ECM (Electronically Commutated Motor) is an ultra high

efficiency programmable brushless DC motor utilizing a

permanent magnet motor and a built-in inverter. DC motors

are significantly more energy efficient than AC motors and

much easier to control. The major weakness of commercial

fan coil units until now, has been their low fan motor efficiency.

The widely used three speed fractional horsepower shaded

pole and permanent split capacitor (PSC) induction motor in

combination with a 3 speed switch or an electronic SCR

speed controller is extremely inefficient at typical operating

conditions. Due to acoustical considerations, the fan motor is

usually adjusted to operate at considerably less than full load

(where PSC motor efficiencies may be as high as 62%). PSC

motor efficiency drops off dramatically when turned down;

typically by at least half. Installed PSC motor efficiencies are

therefore typically in the range of only 12 – 45%. ECM motors

in contrast, maintain a high efficiency of 65 – 72% at all

speeds.

In addition to lower operating costs, EPIC Fan Technology

allows Engineered Comfort to pre-set the fan airflow volume

at the factory.

The graphs below show the lower watts per cfm (translating

into lower operating costs as shown on the next page) and

wider operating ranges of commercial fan coils employing

EPIC Fan Technology

versus PSC induction motors.

FEATURES AND BENEFITS

Soft starts and slewed speed ramps are programmed into the

ECM motor eliminating stress transmitted to the mounting

bracket or hardware. They incorporate ball bearings providing

permanent lubrication unlike sleeve bearings requiring a

minimum rpm operation for oiling. The wider operating range

of the ECM motor allows each model to actually replace two

models using induction motors. This feature alone provides

several benefits: a simpler product line to choose from, little or

no equipment changes necessary, more similar sized units on

the job, decreased spare parts inventory and increased

contractor flexibility. The low operating temperature of the

ECM motor (essentially ambient) requires very little energy to

offset the heat gain from the motor versus PSC motors which

run hot, typically around 90 – 150ºF (32 – 66ºC).

These features also extend the life of the ECM motor, which

are expected to provide an average 90,000 hours of operation

(versus 50,000 hours for a typical PSC motor). This translates

into about 10 years for a typical fan coil as opposed to 7 for

one using a PSC motor.

EPIC FAN TECHNOLOGY

In addition to the above standard features, Nailor Industries

pioneered and developed EPIC Fan Technology

in order to

provide the following primary benefits – Maximized Energy

Savings, Variable Air Volume (VAV) control and factory pre-set

fan airflow.

Why and how do you pre-set fan airflow?

Pre-setting the fan airflow (cfm) has not been an issue with

fan coil manufacturers because these units were either on at

full load or off in normal operating conditions. With EPIC Fan

Technology

, the fan coils can now be run as a VAV device

with all of the requisite savings that VAV brings to other

commercial applications. (See control sequence for further

explanation.)

AC motors are not synchronous machines and the rpm, and

consequently the unit cfm, changes when static pressure

changes. The difficulty in pre-setting the fan lies in estimating

the motor workload required at the job site in actual working

conditions. The fan operated by an AC motor will not produce

the same volume of air as it did at the factory without the duct

work or loaded filter. Because there is no way to accurately

predict the downstream static pressure as it would exist at the

job site, it was impossible to pre-set the fan cfm. The ECM

motors are DC and inherently synchronous machines. The

motors are programmed to calculate the work they are doing

and then compare the work accomplished to the cfm

requirement. The integral microprocessor based controller

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