User Manual

Installation
A standard NPT female boss in tank top, bot-
tom or side is all that is required. Units oper-
ate in any attitude - from the vertical to a 30°
inclination - with lead wires up or down. Stan-
dard IPS pipe extends units to any intermedi-
ate level in the tank. (Figure 1)
Moisture Protection: When moisture exists
in conduit and extension pipes, the potential for
this moisture to "wick" down the wire leads and
into the switch assembly exists. Should this
happen, the switch will appear to be closed due
to a high resistance path through the moisture.
The following suggestions may help to prevent
this from happening:
1. Pitch conduit away from the level switch
when possible, so that condensation will drip
away from the level switch assembly.
(Figure 2)
2. When a vertical run of extension pipe is used
to extend a level switch down from the top of
the tank, a non-conductive silicone oil should
be used to fill the vertical run. Alternatively, an
appropriate potting may be used to fill the ver-
tical run to occupy the space in which conden-
sation will normally form. (Figure 3)
CAUTION
Most of GEMS level products incorporate a pot-
ting cap or are fully potted. Due to the bonding
characteristics of the potting to the wire leads,
there is no way of assuring a water-tight seal
at the potting joint. Our potting cap will resist
moisture to some degree, but the precautions
mentioned above should be used to assure
moisture doesn't enter the switch and cause a
short.
Thread Treatment
1.
Sealing: When threading metal threads into a metal coupling, pipe sealant or
Teflon
®
tape is recommended. Due to potential compatibility problems, when
sealing plastic threaded units, a compatible pipe sealant such as No More
Leaks
TM
from Permatex
®
is recommended.
2.
Tightening: When threading a plastic level switch into a metal coupling, the
installer should use a suitable wrench and tighten the threads one to one and one-
half additional turns past hand-tight. Over-torquing of the threads will result in
damage to the plastic mounting plug.
Consult your GEMS representative for more
suggestions on how to lessen the effects of moisture.
No More Leaks is a trademark of Permatex
®
Industrial Corp., a subsidiary
of Loctite Corporation. Teflon is a registered trademark of DuPont Corporation
3. The Effect of Thread Engagement on Actuation Points
The length of mounting threads engaged at installation is important in calculating
switch actuation points and the actual length of stem extending into the tank. Use
the chart below to find the thread engagement length (T) for a given NPT size.
Factor the dimension into any calculation of switch actuation levels (L) and overall
length (L
0
).
- See Examples Below -
Definition of Variables Used in Examples Below
A = Mounting Length
T = Thread Engagement
P = Distance from coupling (bung) top to inside surface of tank or bracket
L
0
= Overall length from bottom of mounting
L = Switch actuation level as measured from inside surface of tank or
bracket to fluid surface
L
1
= Switch actuation level, nominal, as measured from bottom of
mounting (based on a liquid specific gravity of 1.0)
Internally Mounted LS-1900
(Standard Length)
LS-1900 Series internally mounted
through a 1/4" NPT hole. To
calculate "L" dimension:
L = L
1
+ (A-T)
L = 1-3/16" + (21/32" - .39")
L = 1.46"
Internally Mounted LS-1700/1750
(Standard Length)
LS-1700/1750 internally mounted
through a 1/8" NPT hole. To
calculate "L" dimension:
L = L
1
+ (A-T)
L = .63" + (.56" - .27")
L = .92"
- Figure 1 -
- Figure 2 -
- Figure 3 -
30°
Max.
Conduit
Silicone
Oil
T Dim.
NPT
1/2"
.53"
3/4"
.55"
1"
.68"
1-1/4"
.71"
2"
.76"
3"
1.20"
1/4"
.39"
1/8"
.27"
1/4” NPT
A
21/32”
Fluid
Level
1-3/16”
L
0
T
Actual
Tank
Intrusion
L
1/8” NPT
A
9/16”
Fluid
Level
L
1
=5/8”
L
0
T
Actual
Tank
Intrusion
L
↑
↓
↓
↑
↓
↑
↓
↓
↑
↓
↓
↑
↓
↓