…
_
uw
u
''
,
'
'
”
(
-
‘
'
.
‘
‘La
.f\Li
'
.
@
+…4
;
:
Fig. 17. A typical protective circuit using three thermostats and two heaters to
'
give protection against high and low temperatures
…
‘ _
L1
L2
L3
_
Below 65°F
Below 75°F
’
Below 85°F‘
_
/
On—T1 open-circuited
On-T2 open—circ‘uited ,
On—T3 open-citouited
Off—T1 switched o/n
Off—T2 switched on
Off—T3 switched on
‘
Above 65°F
_
Above 75°F
,
_
Above 85°F
'
,
On-T1 switched off
0n—T2 switched off
On-T3 switched off
Off—T1 short circuited
Off—T2 Short circuited
Off—Ts short—circuited
'
OI
OI
HI \open circuited,
H2 open circuited
_
Many other variations of heater—thermostat systems are
'
Highly complex circuits can be evolved (see, f0r example, Figure 17);
'
incorporating extra units to provide for all sorts of
_
tions, but this back-up idea usually fails because in properly installed ,
'
_, systems
are rare and the extra thermostats deteorate
from not being used. As a result, they often become contaminated—
With damp and dirt so that when the
anses
'
they do not
properly. Most
anything other than very small volumes or very Cold _placcs‘ develop
-slowly and should be spotted by a-Vigilant aquarist early enought0
_…
—
alloW—Æaulty equipment to be substituted. The annual hohdayand
long» weekends away
ôbvious danger p_eriods, but
of trouble is still not enough to outweigh the
complex multi—thermostat systems. No circuit of
,
this type can,off
course, compensate for power failures, Which cause most ofthe
erergencies that are enc‘ounter_ed.
,
,
.
,
Heat losses_ from internally heated aquaria area funct10nofthe;
{surface— area available to radiateand conduct heat…aWayçandnotî
a function of the Volume, As an_ example we canconsrdertwo—
«Containers of « equal
different
rst container be a cube With 2 ft. sides, that
volume .QÏÿ8r cubic 17
.:Αîet,,andï the second container 16 x l x 0.5 ft.ä"i«n;£sizçgÿatlsOa
volume
{__
_î 'p_;0fî fî8
feet. It can, be seen that the total
’
_
uw
u
''
,
'
'
”
(
-
‘
'
.
‘
‘La
.f\Li
'
.
@
+…4
;
:
Fig. 17. A typical protective circuit using three thermostats and two heaters to
'
give protection against high and low temperatures
…
‘ _
L1
L2
L3
_
Below 65°F
Below 75°F
’
Below 85°F‘
_
/
On—T1 open-circuited
On-T2 open—circ‘uited ,
On—T3 open-citouited
Off—T1 switched o/n
Off—T2 switched on
Off—T3 switched on
‘
Above 65°F
_
Above 75°F
,
_
Above 85°F
'
,
On-T1 switched off
0n—T2 switched off
On-T3 switched off
Off—T1 short circuited
Off—T2 Short circuited
Off—Ts short—circuited
'
OI
OI
HI \open circuited,
H2 open circuited
_
Many other variations of heater—thermostat systems are
'
Highly complex circuits can be evolved (see, f0r example, Figure 17);
'
incorporating extra units to provide for all sorts of
_
tions, but this back-up idea usually fails because in properly installed ,
'
_, systems
are rare and the extra thermostats deteorate
from not being used. As a result, they often become contaminated—
With damp and dirt so that when the
anses
'
they do not
properly. Most
anything other than very small volumes or very Cold _placcs‘ develop
-slowly and should be spotted by a-Vigilant aquarist early enought0
_…
—
alloW—Æaulty equipment to be substituted. The annual hohdayand
long» weekends away
ôbvious danger p_eriods, but
of trouble is still not enough to outweigh the
complex multi—thermostat systems. No circuit of
,
this type can,off
course, compensate for power failures, Which cause most ofthe
erergencies that are enc‘ounter_ed.
,
,
.
,
Heat losses_ from internally heated aquaria area funct10nofthe;
{surface— area available to radiateand conduct heat…aWayçandnotî
a function of the Volume, As an_ example we canconsrdertwo—
«Containers of « equal
different
rst container be a cube With 2 ft. sides, that
volume .QÏÿ8r cubic 17
.:Αîet,,andï the second container 16 x l x 0.5 ft.ä"i«n;£sizçgÿatlsOa
volume
{__
_î 'p_;0fî fî8
feet. It can, be seen that the total
’