Dwyer F7-T1 User Manual

MAINTENANCE/REPAIR

Regular maintenance of the total system is recommended to assure sustained
optimum performance. These devices are not field repairable and should be
returned to the factory if recalibration or other service is required. After first
obtaining a Returned Goods Authorization (RGA) number, send the unit freight
prepaid to the following. Please include a clear description of the problem plus
any application information available.

Dwyer Instruments, Inc.
Attn: Repair Department
102 Highway 212
Michigan City, IN 46360

Important Points!

Product must be maintained and installed in strict accordance with the Na­tional Electrical Code and Dwyer product catalog and instruction bulletin. Failure
to observe this warning could result in serious injuries or damages.
An appropriate explosion-proof enclosure or intrinsically safe interface device
must be used for hazardous area applications involving such things as (but not
limited to) ignitable mixtures, combustible dust and flammable materials.
Pressure and temperature limitations shown on individual catalog pages and
drawings for the specified level switches must not be exceeded. These pres­sures and temperatures take into consideration possible system surge pres­sures/temperatures and their frequencies.
Selection of materials for compatibility with the media is critical to the life and
operation of Dwyer level switches. Take care in the proper selection of materials
of construction; particularly wetted materials.
Life expectancy of switch contacts varies with applications. Contact Dwyer if
life cycle testing is required.
Ambient temperature changes do affect switch set points, since the specific
gravity of a liquid can vary with temperature.
Level switches have been designed to resist shock and vibration; however,
shock and vibration should be minimized.
Liquid media containing particulate and/or debris should be filtered to ensure
proper operation of Dwyer products.
Electrical entries and mounting points may require liquid/vapor sealing if lo­cated in an enclosed tank.
Level switches must not be field repaired.
Physical damaged sustained by the product may render it unserviceable.

DWYER INSTRUMENTS,INC.

P .O.BOX 373 MICHIGAN CITY, INDIANA 46361, U.S.A.

Phone: [phone] www.dwyer-inst.com
Fax: [phone] e-mail: [e-mail]
Lit-By Fax: [phone]

Single-Station Level Switches

Instruction Bulletin No. 202503

Series Mounting HEX Size

F7-C**

F7-SS3**

F7-BB**

F7-T*

F7-ST**

F7*

F7-PS*

F7-PVC*

F7-SS6**

* Plastics ** Alloys

Installation

A standard NPT female boss in tank top, bot­tom or side is all that is required. Units operate
in any attitude - from the vertical to a 30° incli­nation - with lead wires up or down. Standard
IPS pipe extends units to any intermediate 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)

1/8" NPT
1/8" NPT
1/4" NPT
1/4" NPT
1/4" NPT
1/8" NPT

1/8" NPT 1/2”
1/8” NPT

1/4" NPT
1/4” NPT
1/8" NPT

3/8" - 24 Str. Thd.

21/32"

1/2"
1/2"
5/8"

5/8"
1/2"

1/2"
5/8"
5/8”
1/2"
3/4"

Float

Diameter

1"

1-1/32"

1-7/8"
2-1/8"

2-1/16"

1"

1-1/4"

(Slosh Shield Version)

1-7/8" (P/N F7-LL)

1-7/8"
1-1/2”

1"

1-1/2"

30°

Max.

- Figure 1 -

Conduit

- 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 ap-

Silicone

Oil

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 pot­ting 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

- Figure 3 -

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.

Consult your Dwyer representative for more
suggestions on how to lessen the effects of moisture.

Thread Treatment

1. Sealing: When threading metal threads into a metal coupling, pipe sealant or

®

Teflon
sealing plastic threaded units, a compatible pipe sealant such as No More Leaks
from Permatex

2.

tape is recommended. Due to potential compatibility problems, when

®

is recommended.

Tightening: When threading a plastic level switch into a metal coupling, the

TM

installer should use a suitable wrench and tighten the threads one to one and one­half additional turns past hand-tight. Over-torquing of the threads will result in
damage to the plastic mounting plug.

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 (L0).

1/8"
.27"

1/4"
.39"

NPT 1/2"

T Dim.

.53"

3/4"
.55"

1"

.68"

1-1/4"

.71"

2"

.76"3"1.20"

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

= Overall length from bottom of mounting

L

0

L = Switch actuation level as measured from inside surface of tank or

bracket to fluid surface
L1 = Switch actuation level, nominal, as measured from bottom of

mounting (based on a liquid specific gravity of 1.0)

1/4” NPT

Internally Mounted F7-BB

L

↓

T

↑

Actual

Tank

Intrusion

↓

↓

T

↑

Actual

Tank

Intrusion

↓

(Standard Length)

F7-BB Series internally mounted
through a 1/4" NPT hole. To
calculate "L" dimension:

L = L
L = 1-3/16" + (21/32" - .39")

+ (A-T)

1

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

+ (A-T)

1

L = .63" + (.56" - .27")
L = .92"

L

0

Fluid
Level

21/32”

1-3/16”

Fluid
Level

L

0

↓

A

↑
↓

9/16”

L

1

↑

L

↓

1/8” NPT

↓

A

↑

=5/8”

↓

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 V olt-Amps (V A).
See the chart below for maximum load characteristics of Dwyer level switches. CAUTION:
Contact protection is required for transient or high in-rush current.

VA

10

General Use

20

Pilot Duty

50

General Use

100*

* Not U.L. Recognized ** Limited to 50,000 operations

Volts

0-50

120
100

0-30

120
240

0-50

120
240
120
240

Amps AC

.2

.08

N.A.

.4
.17
.08

0.5

.4

.2

.8**

.4

Amps DC

.13

N.A.

.10

.3
.13
.06

0.5

.4

.2

N.A.
N.A.

Typical Wiring Diagrams

(Circuit Condition Dry)

SPST, Normally Open or Closed

SPDT

COM

N.O.

N.C.

Red
Red

Orange,

Y ellow

or

White

Red
Black