NATIONAL BUREAU OF STANDARDS REPORT

6159

PERFORMANCE TEST OP A MINNEAPOLIS-HONEYWELL

ELECTRONIC AIR CLEANER, MODEL PC1A2

by

Carl W. Coblent z and Paul R. Achenbach

Report to

General Services Administration

Public Buildings Service

Washington 25j D. C.

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUKEAIJ OF STANDA!{l)S

Functions and Activities

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Impiiries regarding the Bureau’s reports should he addressed, to the Offiee of Technical Information, National Bureau of Standards. Washington 25. I). C.
G~t3

NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT WB8 REPORT

1000-30-4830 6159

September 23j 1958

PERFORMANCE TEST OP A MINNEAPOLIS-HONEYWELL

ELECTRONIC AIR CLEANER, MODEL FC1A2

by

Carl W. Coblentz and Paul R. Achenbach

Air Conditioning, Heating, and Refrigeration Section

Building Technology Division

to

General Services Administration

Public Buildings Service

Washington 25, D. C.

IMPORTANT NOTICE

NATlONAi. BUREAU OF STAf

Intended for use. wjthln the G

To addltlonkf evaidatldn and re listing of thU Report, either In the Office of the Director, Natl however, by the Government a

to reproduce additional copies

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015.

rogress accounting documents

mally published it is subjected

reproduction, or open-literature

Ion Is obtained in writing from Such permission Is not needed,

prepared If that agency wishee

<NBS>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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PERFORMANCE TEST OF A MINNEAPOLIS-HONEYWELL

ELECTRONIC AIR CLEANER, MODEL FCIA2

by

Carl W. Coblentz

and

Paul R. Achenbach

1 . Introduction

At the request of the Public Buildings Service, General

Services Administration, the performance characteristics of

a Minneapolls-Honeywell electrostatic air filter unit were

determined. The scope of this examination included determination of arrestance of atmospheric dust and Cottrell

precipitate, pressure drop, dust-holding capacity and the

cleanabillty of the specimen.

2 . Description of Test Specimen

The cleaner was manufactured and supplied for test purposes by the Minneapolls-Honeywell Regulator Company of

Wabash, Indiana. The collector cell was identified as the

manufacturer's type FC1A2 and the power pack as type FCI6 AI.

The cell was I8 in. long and was enclosed with little

clearance in a housing about 22 in. wide, 24 in. high and

30 in. long which also formed a support for the nominal 20

by 20 by 1 in. afterfilter. This afterfilter was the

Research Products Corporation type MV #9852. The upstream

and downstream faces of the housing were provided with

flanges for Incorporating the unit into the test apparatus.

The gross face area of the cell was 22 1/8" by 24", or

3.69 sq ft. The plates were spaced 0.270 in. on center.

There were 39 energized plates 20 1/2" high and 11 in. long

and 38 grounded plates, all of aluminum sheet 1/32" thick,

providing a total plate area of approximately 122 sq ft,

corresponding to a total surface area of 244 sq ft. The

net face area of the cell after deducting the area taken

up by the plates was computed to be 3.01 sq ft. At the

design air flow rate of 2000 cfm the mean air velocity

between the plates would be 665 ft/mln.

Socony-Vacuum cold water adhesive furnished by

Minneapolls-Honeywell Regulator Co. was sprayed on the collector plates from upstream and downstream and was also sprayed

- 2 -

on the afterfilter In preparation for the test.

The power pack was 23 l/^" hlgh_, 15" deep^ and wide

and was quoted by the manufacturer’s representative to be

able to energize six cells of the size tested. It was connected to the laboratory power supply and the energizing

voltage was adjusted by the manufacturer’ s representative

prior to starting the tests. The power pack was equipped

with an overload breaker In the primary circuit which tripped

repeatedly when the test specimen had been loaded with dust

to about half Its capacity. The original breaker with a

rating of 0.8 amperes was then replaced by the manufacturer

with another one of the same type but with a rating of 5-0

amperes

3 . Test Method and Procedure

Arrestance determinations were made by the NBS ’’DustSpot Method” using the following aerosols: (a) outdoor

air drawn through the laboratory without addition of other

dust or contaminant and (b) Cottrell precipitate. The test

method Is described In the paper_, ”A Test Method for Air

Filters”^ by R. S. Dill (ASHVE Transactions ^ Vol. 44^

p. 379 , 1938).

For these tests^ the unit was Installed In the test

ductj and carefully sealed to prevent Inleakage of air.

The desired rate of air flow through the air cleaner was

established and samples of air were drawn from the center

points of the test duct one foot upstream and eight feet

downstream of the air cleaner assembly at equal rates and

passed through known areas of Whatman No. 4l filter paper.

For the atmospheric air tests, the samples were drawn at

equal rates for one to two hour periods through filter

paper areas of different sizes to obtain a similar Increase of 'Opacity on the upstream and downstream samplers. The upstream filter paper area selected, had a

diameter of I. 85O In. and the downstream diameter was

0.581 In. The resultant arrestance value, then, was

computed by the following formula:

E = 1 /O.58I 2

) X

AU

Where AD and AU are the observed values of the change in

opacity of the downstream and upstream samplers, respectively.

-3-

Under these conditions^ an efficiency of 90-12 percent

would have been indicated if the upstream and downstream

dust-spots on the filter papers had the same change of opacity^ as observed photometrically by the change in the

light transmissions of the dust-spot areas before and after

the sample was drawn. The filter papers used in the upstream

and downstream positions were selected to have the same light

transmission readings when clean. The same sampler .plates

were used for determining the arrpstance with Cottrell precipitate as an aerosol. However^ since the arrestance value

was expected to be considerably higher^ two filter papers

were used successively in the upstream sampler^ each operated for the duration of the Introduction of 10 grams

of dust into the apparatus, whereas only one sampler was

used downstream for the total of 20 grams. This method resulted in more nearly equal discoloration of the individual

upstream and downstream filter papers and consequently a

more accurate measurement of the discoloration and arrestance. For calculating the arrestance value, the sum of

the discolorations of the two upstream sampler papers was

Introduced as AU in the above formula.

The power pack was connected to the 115-volt laboratory power supply through a Variac, the output voltage of

which was maintained at about 120 ±2 volts. The measurements of the ionizer and plate voltages were made with a

sensitive electrostatic kilovolt meter after adjusting

the input to the power pack to 120 ±1/4 volts. The highvoltage current could be observed on a mllllameter mounted

on the front panel of the power pack.

The following procedure was employed in testing the

filter. After the clean and oiled unit had been installed

in the test duct, and all discoverable air leaks into its

housing had been sealed, its input and output voltages

were adjusted to recommended values by a representative of

the manufacturer: (input 120 volts; ionizer 14.55KV; and

plates 7 .O5 KV). Determinations of the arrestance of the

clean unit were made at the rated air flow rate, using

outdoor air drawn into the test duct through a nearby open

window as the aerosol, and also at air flow rates 20 percent greater, and 20 percent less than the rated air flow

rate

Following these initial determinations, two tests were made at

the rated air flow rate, using outdoor air in which was

dispersed Cottrell precipitate at a concentration of one

gram per thousand cubic feet of air as the aerosol. When

these had been obtained, the loading process was begun with

a mixture of 4 percent cotton lint and 96 percent Cottrell

-4-

precipitate, by weighty separately dispersed into the air

stream. The lint used for this purpose was No. 7 cotton

llnters previously ground In a Wiley mill with a fourmllllmeter screen. The lint was dispersed Into the air

stream through an aspirator operating at approximately 35 psl

Inlet air pressure. At selected Intervals, as loading progressed, the arrestance of the unit was determined using

100 percent Cottrell precipitate In the outdoor air. In

these tests, and during the loading process, the rate of

feed of the dispersant was one gram per thousand cubic feet

of air. The pressure drop and the Ionizer and plate voltages of the unit were recorded at Intervals during the tests.

The dlrt-loadlng process was continued until 1340 grams of

the lint and Cottrell precipitate mixture had been fed (l.e.,

2/3 gram per cfm of unit rating).

The filter cell was removed from the test unit and

cleaned by means of a stream of cold water from a high pressure hose nozzle, directed at and Into the cell plates from

both ends of the unit. The cleanablllty of the afterfllter

was determined separately, by the same means.

4 . Test Results

A summary of the test results Is presented In table 1

which shows the air flow rates, cumulative dust loads. Ionizer and plate voltages and currents, the pressure drops

across both cell and afterfllter and the arrestance values

determined with atmospheric dust as well as with Cottrell

precipitate

Throughout the tests with atmospheric air, audible

electrical discharges occurred at a rate of approximately

three times per minute. This rate Increased to about 23

discharges when Cottrell precipitate was Introduced.

After 976 g of dust had been Introduced, the high voltage current reached I.7 MA and the current overload tripped

repeatedly and finally could not be reset. At this time,

the 0.8 ampere circuit breaker was replaced with a 5 ai^pere

breaker furnished by the manufacturer. The high voltage

current was 3.0 MA Immediately after replacing the breaker

but went down to I.9 MA at the conclusion of the test.

-5-

Table 1

Performance of the Minneapolls-Honeywell

Electronic Air Cleaner Model FC1A2

Air

Flow

Rate

Dust

Load

Voltage

Ionizer Plate Current

Pressure

Drop Arrestance Aerosol

cfm grams kv kv ma in. W.C?. 7° Used*

1600 0 14.5 7.05 1.1 0.194 94 .

A

2000 0 14.6 7.05 lol 0.291 90.5 A

2400 0 14.6 7.2 1.1 0.410 84.3 A

2000 10 14.5 7.P 1.2 0.292 98.5 B

2000 30 14.5 7.0 1.2 0.292 98.5 B

2000 373 14.7 7.0 1.2 0.299 99.3 B

2000 747 14.6 7.0 1.3 0.363 98.9 B

2000 850 14.4 6.9 1.5 0.442 93.4 A

2000 1329 14.3 6.8 2.0 0.692 99.0 B

2000 1340 14.4 6 .2.0 0.718 91.5 A

* A- Particulate matter in atmospheric air at NBS

B-Cottrell precipitate in atmospheric air (rate of feed = 1 gram

per 1000 cu ft)

- 6 -

5 . Summary

A. Performiance

At the rated air flow rate of 2000 cfm^ l.e. ft/mln

face velocity, the arrestance of particulate matter in the

atmospheric air was 90.5 percent at the beginning of the

loading period. When the air flow rate was decreased by

20 percent to 1600 cfm, the arrestance value Increased by

4.1^ to 94.6 percent; conversely, an Increase of the air

flow rate through the test specimen by 20^ to 2400 cfm

reduced the arrestance by 6.2^ to 84.3 percent. All subsequent tests were made at the rated air flow rate of 2000

cfm and showed that the arrestance of atmospheric matter

Increased to 93.4 percent when the unit was about half loaded

and then decreased to 91.5 percent at the end of the test.

Four tests made with Cottrell precipitate showed arrestance values between 98-5 percent and 99.3 percent. The

highest arrestance value coincided with the peak ionizer

voltage of 14.7 KV at a dust load of 373 grams although it

was not established that there was a direct relationship

between these two variables.

The power pack furnished for this test was said by

the manufacturer* s representative to be designed to supply

up to six cells of the size tested and its performance on

one cell during the test, with regard to maintaining an

even ionizer and plate voltage with increasing current rates

without making any adjustments, is not believed to be indicative of its performance on six cells. A similar conclusion might be Justified regarding the original circuit

breaker which during the test had to be replaced by one

with a higher rating. Since the circuit breaker was a minor auxiliary component that was easily replaced, the

test was not terminated when its current rating was reached.

During the process of loading, the pressure drop of the

unit increased from 0.291 in. W.G. to O.718 in. W.G. at the

rated air flow rate of 2000 cfm. Thus a dust load of

1340 g (i.e. 2/3 g per 1 cu ft rated air flow rate) produced

an increase in the pressure drop of 0.427 In. W.G.

- 7

-

B. Cleanabillty

The filter was subjected to the cleaning process described under Test Method and Procedure. No difficulty was

experienced in cleaning the collector cell and the afterfilter with a cold water stream, using moderate care.

C. General

On completion of the dust loading test, the unit was

removed from the test apparatus for a visual examination.

All components of the collector cell were coated with dust.

The dust layer of the grounded plates was considerably

lighter than that of the charged plates. The latter were

fairly evenly covered with a layer estimated at 1/32 inch

thickness. Only very small lint particles were noticed

on the surface of the collector cell but the afterfilter

showed a considerable lint deposit on its front side. The

back side of the afterfilter was completely' clean and did

not indicate that dust had been carried through, during

the test. The dust deposits on the collector cell eg well

as on the afterfilter appeared to be well saturated with

oil.

An examination of the test apparatus after the test

revealed that no visible traces of dust could be found in

either the upstream or downstream part of the duct.

U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope o£ activities of the National Bureau of Standards at its headquarters in Washinj^ton, D. C., and its major laboratories in Boulder, Colo., is suggested in the following listing of the

divisions and sections engaged in technical work. In general, each section carries out specialized

research, development, and engineering in the field indicated by its title. A brief description of the activities, and of the resultant publications, appears on the inside front coyer. WASHINGTON, D. C.

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