Dwyer F7-T1 - Manual (Page 2)

Consult your Dwyer 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
).
Definition of Variables Used in Examples
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)
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"
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 ap-
propriate potting may be used to fill the vertical
run to occupy the space in which condensation
will normally form. (Figure 3)
CAUTION
Most of Dwyer 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 mois-
ture 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.
- Figure 3 -
Silicone
Oil
Electrical Data
Standard reed switches in Dwyer level switch units are hermetically-sealed, magnetically
actuated, make-and-break type. Switches are SPST or SPDT and are rated in Volt-Amps (VA).
See the chart below for maximum load characteristics of Dwyer level switches. CAUTION:
Contact protection is required for transient or high in-rush current.
* Not U.L. Recognized ** Limited to 50,000 operations
Amps DC
.13
N.A.
.10
.3
.13
.06
0.5
.4
.2
N.A.
N.A.
Amps AC
.2
.08
N.A.
.4
.17
.08
0.5
.4
.2
.8**
.4
Volts
0-50
120
100
0-30
120
240
0-50
120
240
120
240
VA
10
General Use
20
Pilot Duty
50
General Use
100*
Red
Black
COM
N.C.
N.O.
Orange,
Yellow
or
White
Typical Wiring Diagrams
(Circuit Condition Dry)
SPDT
SPST, Normally Open or Closed
Red
Red
Internally Mounted F7-BB
(Standard Length)
F7-BB 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 F7-C/F7-SS3
(Standard Length)
F7-C/F7-SS3 internally mounted
through a 1/8" NPT hole. To
calculate "L" dimension:
L = L
1
+ (A-T)
L = .63" + (.56" - .27")
L = .92"
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
↑
↓
↓
↑
↓
↑
↓
↓
↑
↓
↓
↑
↓
↓