header bg

Mold/Bacteria Protection of an Air Conditioner Coil

Mold/Bacteria Protection of an

Air Conditioner Coil

By Ronald G. Fink

The Problem:

g

r

o

u

n

d

f

o

r

m

o

l

d

a

n

d

Cold

gas

is

pumped

through

an

air

conditioner

coil.

A

coil

is

b

a

c

t

e

r

i

a

)

.

A

s

t

h

e

a

i

r

made

up

of

copper

tubing

with

aluminum

fins.

The

cold

gas

c

o

n

d

i

t

i

o

n

e

r

s

y

s

t

e

m

c

y

-

travels

through

the

copper

coil

transmitting

its

low

tempera-

c

l

e

s

o

n

a

n

d

o

f

f

,

t

h

e

a

i

r

ture

to

the

aluminum

fins,

which

are

c

o

n

d

i

t

i

o

n

e

r

g

e

t

s

d

a

m

p

,

now chilled.

cold

and

warm,

this

wet

Aluminum fins transfer cold

d

a

r

k

e

n

v

i

r

o

n

m

e

n

t

i

s

a

p

e

r

f

e

c

t

b

r

e

e

d

i

n

g

g

r

o

u

n

d

f

o

r

m

o

l

d

a

n

d

b

a

c

t

e

r

i

a

.

M

a

n

y

f

o

r

m

s

o

f

m

o

l

d

Mold and bacteria

Copper tubes carry

love

this

atmosphere

in

chilled gas

addition

Listeria,

a

bacterium

that

loves

ice

bins

and

air

con-

d

i

t

i

o

n

e

r

s

y

s

t

e

m

s

.

L

i

s

t

e

r

i

a

i

s

k

n

o

w

n

f

o

r

i

t

s

a

b

i

l

i

t

y

t

o

c

a

u

s

e

l

a

r

g

e

outbreaks of food poisoning in restaurants.

Cross section of a clean

AC coil

Mold

and

bacteria

build

up

on

an

air

conditioner

coil

will

give

you the following indoor air and other problems:

Mold Odors

Airborne Mold

Increased

Allergy Risks

Coil

Increased mold colonization of equipment

Condensate pan

Fan/ blower

Filter

Increase in

Airborne Bacteria

and associated risk

Return air

Return air from the house is filtered and blown through the

air

conditioner

coil

fins,

which

are

chilled. The

filtered

return

air

is

chilled

by

passing

over

,

under

and

around

the

chilled

Decrease in

Air Conditioner

Air Flow

aluminum fins and copper tubing.

D

e

c

r

e

a

s

e

i

n

A

i

r

C

o

n

d

i

t

i

o

n

e

r

E

f

c

i

e

n

c

y

Reduced equipment lifespan

Cross section of 5 year old Florida ac coil with-

out mold/bacteria protection. 50% air blockage

T

h

e

c

h

i

l

l

e

d

n

s

c

o

n

d

e

n

s

e

t

h

e

m

o

i

s

-

t

u

r

e

o

u

t

o

f

t

h

e

r

e

t

u

r

n

a

i

r

,

m

u

c

h

t

h

e

same

as

a

chilled

glass

of

water

.

The

Higher Electric Bills

$

m

o

i

s

t

u

r

e

d

r

i

p

s

o

f

f

t

h

e

n

s

d

o

w

n

t

o

a

collector

or

drip

pan

where

it

is

drained

away as condensate wastewater

.

The UV

-C Solution:

UV

-C Germicidal Lamps

These

are

rapidly

becoming

very

popular

as

an

easy

fix

for

the

air

conditioner

coil

mold

problem.

This

is

one

of

the

most

prevalent

causes

of

the

mold

smell

you

get

when

you

enter

an

air

conditioned

sick

building.

UV

-C

(254nm)

lamps

are

ba-

The

problem

comes

to

play

when

the

filtered,

often

not

so

sically

similar

to

sun

lamps

and

are

typically

only

ef

fective

on

filtered,

return

air

deposits

mold

spores

and

bacteria

on

the

m

i

c

r

o

b

i

a

l

s

t

h

a

t

p

a

s

s

b

y

w

i

t

h

i

n

a

f

e

w

i

n

c

h

e

s

o

f

t

h

e

l

a

m

p

o

r

moist

coil

surfaces

(most

air

conditioner

filters

will

not

filter

areas

where

the

light

is

shining

directly

on

for

extended

pe-

m

o

l

d

s

p

o

r

e

s

a

n

d

b

a

c

t

e

r

i

a

a

n

d

a

c

t

u

a

l

l

y

a

c

t

a

s

a

b

r

e

e

d

i

n

g

Page 1

riods

of

time,

such

as

the

air

conditioner

coil

(see

article

in

tle

to

no

ef

fect

on

airborne

bacteria,

viruses,

odors

or

VOCs

H

V

A

C

N

e

w

s

J

u

n

e

3

0

,

2

0

0

3

a

n

d

A

s

s

o

c

i

a

t

e

d

P

r

e

s

s

unless

very

large

commercial,

heavy-duty

UV

systems

are

1

1/24/03).

Excerpt

from

article:

utilized.

“The

biggest

questions

from

The

key

to

good

UV/air

conditioner

coil

mold

control

is

the

c

o

n

t

r

a

c

t

o

r

s

a

r

e

o

n

p

l

a

c

e

m

e

n

t

,

P

h

a

r

o

s

a

i

d

.

F

o

r

i

n

s

t

a

n

c

e

,

installation.

A

small

air

conditioner

coil

will

require

a

minimum

s

h

o

u

l

d

U

V

G

I

s

b

e

i

n

s

t

a

l

l

e

d

i

n

t

h

e

r

e

t

u

r

n

o

r

s

u

p

p

l

y

?

F

o

r

a

i

r

of

three

UV

lights.

The

geometry

of

the

light

and

the

intensity

s

t

r

e

a

m

c

o

v

e

r

a

g

e

,

t

h

e

s

t

u

d

y

D

e

n

i

n

g

t

h

e

E

f

f

e

c

t

i

v

e

n

e

s

s

o

f

U

V

w

i

l

l

d

i

c

t

a

t

e

t

h

e

e

f

f

e

c

t

i

v

e

n

e

s

s

.

R

e

m

e

m

b

e

r

,

o

n

l

y

t

h

e

s

u

r

f

a

c

e

t

h

e

L

a

m

p

s

i

n

s

t

a

l

l

e

d

i

n

C

i

r

c

u

l

a

t

i

n

g

A

i

r

D

u

c

t

w

o

r

k

,

f

r

o

m

t

h

e

A

i

r

C

o

n

d

i

t

i

o

n

i

n

g

a

n

d

&

R

e

f

r

i

g

e

r

a

t

i

o

n

T

e

c

h

n

o

l

o

g

y

I

n

s

t

i

t

u

t

e

(

A

R

T

I

)

,

l

i

g

h

t

i

s

s

h

i

n

i

n

g

o

n

w

i

l

l

b

e

t

r

e

a

t

e

d

,

a

n

d

o

n

l

y

u

p

t

o

6

t

o

8

i

n

d

i

s

-

tance

from

the

bulb.

The

following

are

examples

of

installa-

recommends

placement

in

the

return

side,

with

six

lamps

for

tion:

optimum

effectiveness,

Pharo

pointed

out.

Due

to

space

and

n

a

n

c

i

a

l

c

o

n

s

t

r

a

i

n

t

s

,

h

o

w

e

v

e

r

,

M

o

s

t

h

o

m

e

o

w

n

e

r

s

w

o

n

t

:

An

eight-year

old

air

conditioner

coil

with

have

that

many

lamps

installed.

So

we

recommend

the

con-

Example

No.

1

t

w

o

b

u

l

b

s

p

r

o

p

e

r

l

y

i

n

s

t

a

l

l

e

d

o

n

t

h

e

i

n

s

i

d

e

,

o

n

e

b

u

l

b

w

a

s

d

e

a

d

.

cu

rre

n

t

i

n

sta

l

l

a

ti

o

n

o

f

a

re

a

l

l

y

g

o

o

d

fil

te

r

,

w

i

th

th

e

U

V

l

a

mp

Note

growth

next

to

the

dead

bulb.

The

other

side

is

clean.

p

l

a

c

e

d

o

v

e

r

t

h

e

i

n

d

o

o

r

c

o

i

l

,

P

h

a

r

o

s

a

i

d

.

A

i

r

c

o

n

d

i

t

i

o

n

i

n

g

s

y

s

-

N

o

b

u

l

b

s

w

e

r

e

i

n

s

t

a

l

l

e

d

o

n

t

h

e

o

u

t

s

i

d

e

.

A

c

c

o

r

d

i

n

g

l

y

,

o

n

l

y

o

n

e

-

tems are great inventions, but the moist environment (at the

half

of

this

air

conditioner

coil

was

treated.

The

outside

of

the

c

o

i

l

s

)

c

r

e

a

t

e

s

a

m

i

c

r

o

b

i

a

l

b

r

e

e

d

i

n

g

g

r

o

u

n

d

.

A

d

d

i

t

i

o

n

a

l

l

y

,

air

conditioner

coil

was

full

of

mold

and

bacteria

blocking

air

when

UV

lamps

are

shining

directly

on

the

coils,

they

are

hit-

o

w

a

n

d

c

r

e

a

t

i

n

g

I

A

Q

p

r

o

b

l

e

m

s

.

T

h

i

s

i

n

s

t

a

l

l

a

t

i

o

n

i

s

o

f

m

i

n

i

m

a

l

ting

a

stationary

target.

When

moving

targets

(VOCs

and

mi-

crobes)

pass

UV

lights,

the

more

sensitive

microbes

may

be

value to the customer

.

d

a

m

a

g

e

d

,

b

u

t

t

h

e

h

a

r

d

i

e

r

o

n

e

s

w

i

l

l

p

a

s

s

u

n

h

a

r

m

e

d

.

U

V

lights,

for

instance,

have

been

found

to

be

better

applied

to

s

h

i

n

e

o

n

t

h

e

i

n

d

o

o

r

c

o

i

l

,

n

o

t

t

o

t

r

y

t

o

c

l

e

a

n

t

h

e

a

i

r

s

t

r

e

a

m

,

p

a

r

-

ticularly

in

residential

and

light

commercial

applications;

air

UV

-C

lights

on

stream

use

requires

intense

UV

saturation.”

an

air

conditioner

coil

are

like

the

sun

shining

on

a

rock

by

a

stream.

No

mold

or

mildew

will

grow

on

the

sunny

rock,

un-

like a shaded rock.

A

ten-year

old

air

conditioner

coil

with

a

UV

Example

No.

2:

b

u

l

b

p

l

a

c

e

d

t

o

o

c

l

o

s

e

t

o

t

h

e

e

n

d

c

o

i

l

.

M

o

s

t

o

f

t

h

e

c

o

i

l

w

a

s

Direct sun - No mold growth

clean,

but

the

25%

over

8”

away

grew

mold

and

bacteria

ac-

tually blocking air flow of 25%.

This installation was of some

value to the client, but not 100%.

UV lamp

No sun - Extensive mold growth

The

main

advantages

to

UV

-C

lights

are

low

cost,

easy

in-

s

t

a

l

l

a

t

i

o

n

a

n

d

e

f

f

e

c

t

i

v

e

n

e

s

s

o

n

s

u

p

p

r

e

s

s

i

n

g

m

o

l

d

/

b

a

c

t

e

r

i

a

growth on the coil that has the light shining on it.

UV

-C

lights

installed

correctly

can

ef

fectively

control

mold

a

n

d

b

a

c

t

e

r

i

a

g

r

o

w

t

h

s

o

n

t

h

e

a

i

r

c

o

n

d

i

t

i

o

n

e

r

c

o

i

l

.

T

h

e

y

h

a

v

e

l

i

t

-

Page 2

A

small

air

conditioner

coil

with

one

UV

bulb

Example

No.

3:

mounted

in

the

center

.

Only

one-half

of

this

coil

has

UV

pro-

t

e

c

t

i

o

n

a

s

t

h

e

o

u

t

e

r

s

e

c

t

i

o

n

s

h

a

v

e

n

o

U

V

b

u

l

b

s

.

E

x

h

i

b

i

t

3

s

h

o

w

s

h

o

w

t

h

e

l

i

g

h

t

d

o

e

s

n

o

t

g

o

t

h

r

o

u

g

h

t

h

e

c

o

i

l

a

s

t

h

e

geometry of the fins will not permit it.

UV light

A

large residential

AC coil will require 6

Example No. 5:

lamps for a good coverage.

This is an example of an excel-

lent installation.

U

V

-

C

G

e

r

m

i

c

i

d

a

l

L

a

m

p

s

O

n

A

i

r

b

o

r

n

e

M

i

c

r

o

b

e

s

UV

has

the

ability

to

kill

surface

bacteria

that

the

bulb

is

shin-

ing

directly

on

at

a

distance

of

usually

less

than

six

to

eight

inches.

Some

UV

-C

light

companies

state

their

UV

systems

can

kill

99.9%

of

MRSA

bacteria

on

a

single

pass

and

then

reference

an

EP

A

study

.

This

is

very

misleading

as

the

test

was

conducted

on

a

test

unit

of

five

UV

high-energy

lamps,

each

50”

long

in

a

reflective

tunnel,

which

burns

1,100

watts

Light will not pass through coils

of

electricity

. This

is

the

equivalent

of

running

a

hair

dryer

in

your

air

conditioner

24

hours

a

day

.

This

obviously

generates

A

Example

No.

4:

a

lot

of

heat

in

addition

to

burning

a

lot

of

electricity

,

and

the

l

a

r

g

e

r

e

s

i

d

e

n

t

i

a

l

units

cost

thousands

of

dollars.

This

system

is

not

something

c

o

i

l

c

o

u

l

d

r

e

q

u

i

r

e

t

h

e

h

o

m

e

o

w

n

e

r

w

o

u

l

d

i

n

s

t

a

l

l

.

T

h

i

s

i

s

a

n

i

n

d

u

s

t

r

i

a

l

U

V

s

y

s

-

n

i

n

e

U

V

b

u

l

b

s

t

o

t

e

m

;

v

e

r

y

e

x

p

e

n

s

i

v

e

,

h

e

a

v

y

d

u

t

y

s

y

s

t

e

m

s

f

o

r

f

o

o

d

p

r

o

c

e

s

s

i

n

g

p

r

o

v

i

d

e

g

o

o

d

U

V

o

r

m

e

d

i

c

a

l

a

p

p

l

i

c

a

t

i

o

n

s

.

T

h

e

E

P

A

s

t

u

d

y

s

p

e

c

i

c

a

l

l

y

d

i

s

t

i

n

-

p

r

o

t

e

c

t

i

o

n

f

o

r

guishes

this

from

UV

devices

that

are

designed

to

treat

spe-

m

o

l

d

/

b

a

c

t

e

r

i

a

c

i

c

s

u

r

f

a

c

e

s

w

i

t

h

i

n

t

h

e

H

V

A

C

s

y

s

t

e

m

;

i

n

p

a

r

t

i

c

u

l

a

r

,

t

h

e

g

r

o

w

t

h

.

T

h

i

s

w

i

l

l

cooling

coils

and

the

condensate

drain

pan

to

prevent

bio-

add

approximately

l

o

g

i

c

a

l

g

r

o

w

t

h

o

n

t

h

o

s

e

s

u

r

f

a

c

e

s

.

A

s

t

a

n

d

a

r

d

1

2

t

o

2

4

H

V

A

C

3

0

0

w

a

t

t

s

o

f

h

e

a

t

UV

light

system

installed

in

an

air

conditioner

coil

will

destroy

e

n

e

r

g

y

t

o

t

h

e

a

i

r

mold

and

bacteria

growth

on

the

coil

surface

that

the

UV

light

c

o

n

d

i

t

i

o

n

e

r

s

y

s

-

shines

on.

What

sections

of

the

coil

the

light

does

not

hit

will

tem.

However

,

the

grow

mold

and

bacteria.

The

UV

-C

lights

used

on

an

air

con-

m

o

l

d

/

b

a

c

t

e

r

i

a

p

r

o

-

ditioner

coil

will

provide

little,

if

any

,

airborne

microbial

kill

as

tection

and

subse-

t

h

e

U

V

e

n

e

r

g

y

a

n

d

d

w

e

l

l

o

r

e

x

p

o

s

u

r

e

t

i

m

e

i

s

n

o

t

n

e

a

r

l

y

q

u

e

n

t

a

i

r

o

w

enough

to

kill

fast

moving

airborne

microbials.

UV

technol-

s

a

v

i

n

g

s

w

o

u

l

d

ogy

is

very

simple:

take

a

known

quantity

of

UV

light

and

ex-

m

a

k

e

t

h

i

s

i

n

s

t

a

l

l

a

-

pose

a

surface

or

substance

to

the

light

for

a

specified

period

tion worthwhile.

o

f

t

i

m

e

,

a

n

d

a

p

e

r

c

e

n

t

a

g

e

o

f

t

h

e

m

i

c

r

o

b

i

a

l

s

a

r

e

k

i

l

l

e

d

.

T

h

e

product

of

the

UV

light

intensity

,

multiplied

by

the

time

at

that

i

n

t

e

n

s

i

t

y

,

i

s

t

e

r

m

e

d

C

T

V

a

l

u

e

.

T

a

b

l

e

s

o

f

C

T

V

a

l

u

e

s

h

a

v

e

AC coils

been

published,

and

are

well

known.

T

o

properly

determine

what

values

to

use,

look

in

one

of

these

tables

and

pick

a

mi-

c

r

o

b

e

,

t

h

e

n

r

e

a

d

t

h

e

c

o

r

r

e

s

p

o

n

d

i

n

g

C

T

V

a

l

u

e

,

a

n

d

d

e

s

i

g

n

t

h

e

N

o

t

e

o

f

c

a

u

t

i

o

n

:

U

n

p

r

o

t

e

c

t

e

d

U

V

-

C

l

a

m

p

s

w

e

r

e

u

s

e

d

f

o

r

this

article.

In

practice,

protected

lamps

should

always

be

u

s

e

d

a

s

U

V

l

a

m

p

s

c

o

n

t

a

i

n

m

e

r

c

u

r

y

,

a

h

a

z

a

r

d

o

u

s

h

e

a

v

y

m

e

t

a

l

k

n

o

w

n

t

o

c

a

u

s

e

h

e

a

l

t

h

p

r

o

b

l

e

m

s

.

A

b

r

o

k

e

n

l

a

m

p

i

n

a

n

UV lamps

HV

AC

system

could

permanently

contaminate

the

system.

Page 3

Ozone

system

around

that

CT

V

alue.

T

ypical

HV

AC

home

systems

operate

around

2000

cfm

for

a

2,000

sq.

ft.

home.

For

ex-

C

o

n

c

e

r

n

a

b

o

u

t

o

z

o

n

e

a

n

d

H

V

A

C

a

i

r

c

l

e

a

n

i

n

g

d

e

v

i

c

e

s

i

s

o

f

t

e

n

ample,

2,000

cfm

will

have

an

exit

velocity

of

500ft/min,

or

exaggerated.

All

UV

light

lamps

emit

some

ozone.

UV

-C

ger-

8.33

ft/sec.

From

this

value,

the

proper

residence

time

can

micidal

lamps

emit

very

low

levels

way

below

federal

safety

be

evaluated

for

specific

CT

values.

T

ypical

molds

found

in

limits. Many every day items emit ozone such as

h

o

u

s

e

h

o

l

d

s

a

r

e

i

n

th

e

fa

m

i

l

y

.

h

a

s

A

s

p

e

r

g

i

l

l

i

u

s

A

s

p

e

r

g

i

l

l

i

u

s

Fluorescent lamps

CT

values

for

a

90%

kill

ranging

from

44,000

to

132,000

uW

-

Electric motors

sec/cm

.

spores,

a

common

bacteria,

has

a

Bacillus

subtilis

2

Copy machines

CT

value

of

1

1,600

uW

-sec/cm2.

For

example,

we

will

use

Electro static air cleaners

the

number

,

because

as

we

will

see,

that

relatively

Bacillus

All

are

within

federal

safety

limits

.

T

o

pass

a

UL,

ETL

or

TUV

l

o

w

n

u

m

b

e

r

w

i

l

l

m

e

a

n

a

r

e

l

a

t

i

v

e

l

y

h

i

g

h

r

e

s

i

d

e

n

c

e

t

i

m

e

.

C

T

t

est

t

hey

m

ust

be

below

.

04

ppm

of

ozone.

O

ut

s

ide

air

is

usu-

values

higher

than

will

require

an

even

longer

resi-

Bacillus

ally higher than this. Example

dence

time.

The

lamps

can

be

placed

at

the

outlet

or

inlet

of

.01 ppm ozone becomes detectable to humans

the coils, however

, at this flow rate, you will only have a res-

.04 ppm Federal indoor safety limit

i

d

e

n

c

e

t

i

m

e

o

f

0

.

2

4

s

e

c

o

n

d

s

.

T

h

a

t

i

s

o

n

l

y

1

.

7

%

o

f

t

h

e

r

e

-

.12 EP

A city safe air limit

quired

14.5

seconds

for

90%

kill.

This

is

not

even

close

to

the

.50 ppm smog alert #1

r

e

q

u

i

r

e

d

C

T

V

a

l

u

e

t

o

k

i

l

l

.

I

n

f

a

c

t

,

t

h

i

s

v

a

l

u

e

i

s

s

o

B

a

c

i

l

l

u

s

1.0 ppm smog alert #2

s

m

a

l

l

,

t

h

e

U

V

w

i

l

l

h

a

v

e

n

e

x

t

t

o

n

o

e

f

f

e

c

t

o

n

a

n

y

a

i

r

b

o

r

n

e

pathogen.

The

Advanced Oxidation Solution

T

h

e

A

d

v

a

n

c

e

d

O

x

i

d

a

t

i

o

n

P

l

a

s

m

a

w

i

l

l

d

e

s

t

r

o

y

m

o

l

d

a

n

d

b

a

c

t

e

r

i

a

g

r

o

w

t

h

o

n

a

n

a

i

r

c

o

n

d

i

t

i

o

n

e

r

c

o

i

l

a

n

d

t

h

e

a

i

r

l

t

e

r

.

T

h

e

p

l

a

s

m

a

,

being a gas primarily made up of ionized hydro-peroxides, will achieve full coverage as it moves in and around the air con-

ditioner coil fins and through the air filter

, controlling mold and bacteria growth.

Advanced Oxidation

Generator

AC Coils

Ionized

Advanced

Oxidation Plasma

A

c

l

e

a

n

9

E

x

a

m

p

l

e

N

o

.

6

:

y

e

a

r

o

l

d

c

o

i

l

f

r

o

m

a

F

l

o

r

i

d

a

h

o

m

e

t

h

a

t

s

u

r

v

i

v

e

d

3

h

u

r

r

i

-

canes

with

a

total

of

30

days

o

f

p

o

w

e

r

o

u

t

a

g

e

.

A

n

a

d

-

v

a

n

c

e

d

o

x

i

d

a

t

i

o

n

c

e

l

l

w

a

s

p

r

o

p

e

r

l

y

a

n

d

p

r

o

f

e

s

s

i

o

n

a

l

l

y

Fan

Filter

installed.

Silver Nano Coatings

A

new

technology

is

a

silver

nano

coating

on

the

AC

coil

and

drip

pan

to

prevent

microbial

growth.

Copper

and

silver

are

both

good

controllers

of

bacteria

and

mold.

Silver

has

been

u

s

e

d

f

o

r

c

e

n

t

u

r

i

e

s

f

o

r

b

a

c

t

e

r

i

a

c

o

n

t

r

o

l

.

I

n

m

e

d

i

e

v

a

l

t

i

m

e

s

wealthy

families

would

put

a

silver

spoon

in

the

mouth

of

ba-

bies

after

feeding

to

kill

bacteria

and

prevent

food

poisoning.

Hence

the

phrase

“silver

spoon

baby”.

Silver

nano

is

a

prom-

ising

new

possibility

for

low

cost

control

of

bacteria

and

mold.

Silver

Copper

About the author: Ronald G. Fink - President and CEO RGF Environmental Group, Inc.

Mr

. Fink holds a BSME and has been active in UV and Nuclear Energy since the 1960s. He holds numerous patents and authored over

70 articles.

RGF Environmental Group, Inc. founded in 1985 manufactures over 500 products involving UV

,

Advanced Oxidation and Silver Nano C

oatings.

Copyright © RGF 2007

Page 4

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