Ashcroft LT User Manual
Installation and Maintenance Instructions
(105)
2.25
(57)
2.50
(64)
0.25
(6)
3.47
(88)
2.06
(52)
1.21
(31)
0.38
(
10)
3.94
(100)
1
.31
(33)
“S”
Ø 0 . 3 7
(
9 )
2
. 3 1
ACTIVE BULB
LENGTH
( 5 9 )
3 . 2 6
(
8 3 )
6 . 0 9
( 1 5 5 )
3 /4 NPT
7/8 HEX
1 /2 NPT MALE
4 . 1 2
2.31
ACTIVE BULB
LENGTH
(59)
2.06
(52)
0
.38
(10)
3.94
(100)
3.26
(83)
“L”
3 . 0 0
( 76 )
2 . 5 0
(
6 4 )
Ø 0 . 3 7
( 9 )
1 . 2 1
( 3 1 )
6 . 0 9
( 1 5 5 )
3
/4 NPT
4
. 1 2
( 1 0 5 )
0 . 2 5
( 6 )
2 . 2 5
( 5 7)
2 . 5 0
( 6 4 )
for ASHCROFT®L-Series Snap Action
Switches for Temperature Control
irect Mount
D
3.5 lbs.
TEM LENGTH (S)
S
IN.
23⁄
4 4 6 9 12
MM
(70) (102) (152) (229) (305)
Remote Mount
OPERATION
The ASHCROFT®temperature control is a precision device
which features a snap action switch. Fixed deadband is available
with single or dual SPDT independently adjustable switches
with various electrical ratings. Adjustable deadband is available
with a SPDT switch with various electrical ratings. Bulb material
is stainless steel.
Series LT-S switches have a fixed deadband which will be
within the limits noted on the nameplate.
Series LT-D switches may be set to operate simultaneously or
up to 85 percent of the range apart. The deadband of each
switch will be within the limits noted on the nameplate.
Series LT-A switches may be set to operate with any deadband within the limits sho
wn on the nameplate.
MOUNTING
The “L” Series ASHCROFT®snap action temperature switch has a
NEMA-4 enclosure which is an epoxy coated aluminum casting.
Two holes in the integral bracket are used to surface mount
the control. Location of these holes is shown on the general
wings. An optional pipe mounting bracket is also
dimension dr
a
available. Mount on a vibration free surface or pipe in any
orientation.
Good piping pr
actice requires the use of a well f
where pressure ma
y be applied to the ther
or installation,
mal system, f
or protection against physical damage as well as corrosive effects of
media flow. Use of a well also facilitates removal of the bulb
from the process line without disturbing the process. Standard
well materials include brass, and stainless steel; other materials
are available on application. Selection should be based on corrosion resistance requirements and process pressure.
4.5 lbs.
LINE LENGTH
FT.
5 10 15 20 25
B. REMOTE MOUNTED CONTROLS
Two types of union bushings are available to install a
ell or other
remote-
mounted control bulb into a ther
NPT threaded
A non-pressure-tight type consists of a
.
hole
mow
bushing, split grom-met and compression nut. To use this, the
bulb is inserted through the nut and the split grommet is
slipped into the capillary between the compression nut and
the bushings. After positioning the bulb as desired, tighten
the compression n
ut to the b
ushing. This will lock the capillary at the desired location. The pressure-tight type is
clamped to the bulb after insertion by tightening a compres-
ut. T
sion n
threaded hole
NPT
o use this, the union b
. The compression nut and sleeve are
ushing is screwed into the
slipped onto the bulb which is then inserted into the union
bushing. Bulb is then positioned and compression nut is
hand tightened plus 2
1
⁄
2 turns. This will lock the bulb at the
desired location.
1
⁄
2
1
⁄
2
STEM MOUNTED CONTR
A.
These controls ha
attached directly (or indirectly by means of a thermowell) to
e a
v
equipment to be controlled.
REMOVING CONTROL ALWAYS USE THE WRENCH
FLATS OR HEX ABOVE THE THREADS. DO NOT TWIST
2007 Ashcroft Inc., 250 East Main Street, Str
©
All sales subject to standard ter
THE HOUSING.
ms and conditions of sale
OLS
1
⁄
2 NPT threaded adapter and ma
ALLING OR
I&M009-10018-10/00 (250-2873) AMR 12/-07
.
WHEN INST
ord, CT 06614-5145, USA,
atf
203-378-8281, F
el:
T
y be
CONDUIT CONNECTIONS
One 3⁄
4 NPT hole fitted with a shipping plug, and two additional
k outs are pro
knoc
placing a scre
wdr
The knoc
vided.
iver in the slot and rapping sharply with a
kouts may be removed by
hammer. It is recommended that Teflon tape or other sealant be
used on conduit b
ushing or plug threads to ensure integ
the enclosure.
203-385-0499, www
ax:
.ashcroft.com
ity of
r
Installation and Maintenance Instructions
1 2 3
1 2 3
LEFT SWITCH
TERMINAL BLOCK
RIGHT SWITCH
T
ERMINAL BLOCK
SERVICE LEADS TO THESE TERMINALS
NC
NO
C
A
B
0
20
40
60
0
20
40
60
for ASHCROFT®L-Series Snap Action
Switches for Temperature Control
ELECTRICAL CONNECTION
Remove cover, held in place by two screws.
On all units except one with terminal blocks – wire directly to
the switch according to circuit requirements. Units with terminal
blocks – wire directly to terminal blocks as required. Terminals
are marked common (C), normally open (NO) and normally
closed (NC).
SETPOINT ADJUSTMENTS
Setpoints are changed by means of the setpoint adjusters. The
LT-S single switch has one adjuster and the LT-A adjustable
deadband and LT-D dual switch each have two adjusters. On
switches with two adjusters, the one on the left is referred to as
“A” and the right one is referred to as “B”; see illustration. setpoints can be adjusted from 20 to 100 percent of full range on
increasing temperature.
When adjusting temperature controls optimum performance
will be obtained if the bulb is fully immersed. After initially inserting a bulb into a controlled bath, allow five minutes for stabilization. Whenever setpoint adjustment requires a bath temperature
to be varied (such as to observe setpoint and re-setpoint values) the rate of change in temperature should not exceed 1°F
per minute. Switch operation should be monitored with a suitable light or meter.
SERIES LT-S SINGLE SWITCH
Remove cover. For setpoint adjustment on either increasing or
decreasing temperature, the bulb of the control should be immersed in a bath at the desired setpoint temperature. Optimum
erformance will be obtained if bulb is fully immersed. Allow five
p
minutes for initial stabilization. Monitor switch with a light or meter.
If setpoint is on increasing temperature, turn adjuster so that
switch operates (if common-normally closed circuit is being
monitored light goes off). If setpoint is on decreasing temperature, turn adjuster so that switch resets (if common-normally
closed circuit is being monitored light comes on). When the
setpoint has been achieved, raise and lower the temperature to
ensure that the setpoint is correct.
The deadband (difference between the operate and reset
temperatures) may be verified at this time to be between the
values noted on the nameplate label.
SERIES LT-D DUAL SWITCH
Remove cover. Immerse the bulb and monitor the switch as
described under Series LT-S Single Switch. Also see discussion
of increasing or decreasing setpoints and deadband verification.
The initial bath temperature should be the higher setpoint. Turn
adjuster “B” until the switch operates or resets as required.
When the setpoint has been achieved, raise and lower the bath
temperature to ensure that the setpoint is correct. Then reduce
the bath temperature to the lower setpoint and turn adjuster “A”
until the switch operates or resets as required. Verify this setpoint by raising and lowering bath temperature. Now increase
the temperature to the higher setpoint and make final adjustment on “B.”
SERIES LT-A ADJUSTABLE DEADBAND SWITCH
Remove cover. Adjuster “B” controls the operating point of the
switch on increasing temperature. Adjuster “A” controls the resetpoint of the switch on decreasing temperature.
Immerse the bulb and monitor the switch as described under
single switch setpoint adjustment. With the bath at the required
setpoint temperature, turn adjuster “B” until switch operates.
Then lower the bath temperature to the re-setpoint and turn
adjuster “A” until the switch resets. Now increase the temperature to the operating point and make final adjustment on “B.”
er temperature to ensure that the setpoint and
Raise and lo
w
re-setpoint are correct.
© 2007 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: 203-378-8281, Fax: 203-385-0499, www.ashcroft.com
All sales subject to standard ter
ms and conditions of sale. I&M009-10018-10/00 (250-2873) AMR 12/-07
SOME PRECAUTIONS TO OBSERVE
Do not loosen the screws holding the precision switch element(s) or mounting bracket in place.
Nameplate PROOF temper
ature should not be e
xceeded.
Intermittent operation up to proof temperature is permissible,
however, some change of setpoint may be noted.
ation and correct setpoint actuation should be routinely
Oper
tested.
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