SECTION 19: E
LECTRICAL
77 of 154
located on the blo
w
er motor. C
u
rrent dra
w
may be
adj
u
sted do
w
n
w
ard by red
u
cing blo
w
er rotations per
min
u
te (RPM) or by increasing external static
press
u
re.
19.5 Control Current Draw
The maxim
u
m c
u
rrent dra
w
for an air handler’s
controls and accessories is 3A.
19.6 Safety Systems
Safety systems are req
u
ired for proper performance
of the air handler. The air handler shall not be
permitted to operate
w
ith any safety system disabled.
If a fa
u
lt is fo
u
nd in any of the safety systems, then
the system shall be repaired only by a contractor
q
u
alified in the installation and ser
v
ice of gas fired
heating eq
u
ipment,
u
sing only components that are
sold and s
u
pplied by Rapid Engineering LLC. Refer
to
Page 81, Table 31
for a brief description of each
safety de
v
ice, its location and its s
w
itching
v
oltage.
Table 30: Safety Systems
19.6.1 Manual Reset Hi
g
h Temperature Limit
Switch
If for any reason, the temperat
u
re of the air at the
discharge of the blo
w
er reaches the limit set point of
160° F (71.1° C), the high temperat
u
re limit s
w
itch
w
ill
open the circ
u
it to the b
u
rner system and discontin
u
e
all b
u
rner f
u
nctions. E
v
ents that co
u
ld res
u
lt in
excessi
v
e discharge air temperat
u
res incl
u
de if the
b
u
rner mod
u
lation amplifier is defecti
v
e (i.e.
temperat
u
re sensor goes open circ
u
it) or if a s
u
rge in
gas press
u
re reaches the b
u
rner. Restarting of the
b
u
rner can only be accomplished after the limit has
cooled do
w
n and the reset b
u
tton on the s
w
itch has
been depressed. This s
w
itch is located on the blo
w
er
ho
u
sing inside the air handler.
19.6.2 Pressure Switches
The lo
w
airflo
w
v
elocity press
u
re s
w
itch monitors the
airflo
w
(differential press
u
re) across the b
u
rner.
When the airflo
w
across the b
u
rner reaches the
proper
v
elocity (
v
ol
u
me) for comb
u
stion, the s
w
itch
closes. When the s
w
itch closes, it permits the flame
safeg
u
ard relay to begin ignition. This s
w
itch is
factory set at 0.32 in
w
c (0.8 mbar). The high
v
elocity
press
u
re s
w
itch
w
ill open if the airflo
w
across the
b
u
rner reaches its maxim
u
m allo
w
able limit. This
s
w
itch is factory set at 1.40 in
w
c (3.5 mbar). The
press
u
re s
w
itch is a safety de
v
ice,
w
hich cannot be
field-adj
u
sted or tampered
w
ith.
19.6.3 Gas Pressure Switches
Gas press
u
re s
w
itches are standard on certain
models (FM compliant gas trains abo
v
e 2,500 MBH
and XL compliant gas trains) and are also a
v
ailable
as an option on the others.
The f
u
nction of the gas press
u
re s
w
itches is to
protect against ins
u
fficient, lack of gas press
u
re and
excessi
v
e press
u
re in the system.
On the lo
w
gas press
u
re s
w
itch side, this s
w
itch
opens its internal s
w
itch
w
hich sh
u
ts the b
u
rner do
w
n
and pre
v
ents its operation d
u
e to ins
u
fficient gas
press
u
re.
On the high gas press
u
re s
w
itch side, its internal
s
w
itch
w
ill open, sh
u
tting do
w
n the b
u
rner d
u
e to
excessi
v
e gas press
u
re passing thro
u
gh the gas
train.
The settings of the gas press
u
re s
w
itches are field
adj
u
stable. The one monitoring the incoming gas
press
u
re is the lo
w
gas press
u
re s
w
itch. The lo
w
gas
press
u
re s
w
itch m
u
st be set to the minim
u
m req
u
ired
gas press
u
re as indicated on the data plate.
The high gas press
u
re s
w
itch m
u
st be set to 1 in
w
.c.
(2.5 mbar) abo
v
e high fire setting established d
u
ring
commissioning.
The s
w
itch
w
ill ha
v
e to be reset man
u
ally, once the
condition has been corrected.
Safety Controls
Location
Volta
g
e
Man
u
al Reset High-
Temp Limit (All Models)
Blo
w
er Discharge
120
Press
u
re S
w
itches
(All Models)
Air Handler Control
Enclos
u
re
120
Flame Control
(2010/2010B/2020/2030)
Air Handler Control
Enclos
u
re
120
Flame Control (2005)
Air Handler Control
Enclos
u
re
24
Discharge Temperat
u
re
Monitor (All Models)
Blo
w
er Discharge
24
AM Resistor
(AM/VAV Style)
Air Handler Control
Enclos
u
re
24
Summary of Contents for 4044
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