Dwyer V7-WBS-30N Flotect Vane Operated Flow Switch
The Dwyer V7-WBS-30N is a Flotect vane operated flow switch with a brass process connection, 1 in male NPT, and an SPDT snap switch rated 10 A at 125, 250 and 480 VAC. It proves flow or no-flow in 1 to 4 in liquid lines up to 250 psi (17.2 bar) and -40 to 250°F (-40 to 121°C), inside a die cast aluminum NEMA 4X (IP66) weatherproof housing. The full-length 301 SS vane is field trimmable using the supplied template, allowing selection among the documented set points for the applicable line size.
Specifications on this page were compiled from the Dwyer Series V7 catalog page (Dwyer Instruments, LLC, p.274) and the Series V7 Flotect Vane Operated Flow Switch Specifications - Installation and Operating Instructions, Bulletin F-V7, FR# 82-443693-00 Rev. 3 (2/10). Verified August 2026.
Magnetic actuation is what separates the V7 from a mechanical paddle switch. A magnet on the end of the vane couples through a solid metal wall to a second magnet on a lever arm in the upper housing, which trips the snap switch. The upper and lower housings are separated by solid metal, so no mechanical linkage or seal passes through that separation. The lower body is machined from solid bar stock for the same reason.
Best For
- Proving boiler flow before firing or before enabling downstream equipment
- Shutting down a burner when air flow through a heating coil fails
- Protecting pumps, motors and other rotating equipment against low or no flow
- Stopping liquid cooled engines, machines and process equipment when coolant flow is interrupted
Key Features
Magnetically actuated switching design
A magnet on the vane couples through the solid metal separation to a second magnet on a lever arm that trips the snap switch. No mechanical linkage or seal passes through the separation between the upper and lower housings.
Leak-proof bar stock lower body
The lower body is machined from solid metal bar stock, so there are no leak points regardless of how long the unit stays in service.
Field trimmable vane sets the trip point
The full length 301 SS vane ships with a template. Trim it to the marked position for the pipe size and flow rate you need instead of ordering a different model.
SPDT snap switch rated to 10 A
Three screw terminals provide common, normally open and normally closed connections. The documented rating is 10 A @ 125, 250 and 480 VAC, 1/8 hp @ 125 VAC and 1/4 hp @ 250 VAC.
NEMA 4X weatherproof housing
The die cast aluminum upper body is rated weatherproof to NEMA 4X (IP66). Installation conditions must remain within the documented process and ambient limits.
Covers 1 through 4 in line sizes
One 1 in male NPT body installs in 1 to 4 in pipe through a standard tee or bushing, with published actuation and deactuation rates for each size.
Technical Specifications
| Service | Liquids compatible with wetted materials that are non-coating and non-crystallizing |
| Sensing Element | Vane (paddle), rigid and field trimmable |
| Wetted Materials | Vane: 301 SS; Process connection: brass or 316 SS; Magnet: ceramic; Other: 301, 302 SS |
| Upper Body Material | Die cast aluminum |
| Process Temperature Limits | -40 to 250°F (-40 to 121°C) |
| Maximum Ambient Temperature | 181°F (83°C) |
| Pressure Limits | 250 psi (17.2 bar) |
| Enclosure Rating | Weatherproof, meets NEMA 4X (IP66) |
| Switch Type | SPDT snap switch |
| Electrical Rating | 10 A @ 125, 250, 480 VAC; 1/8 hp @ 125 VAC; 1/4 hp @ 250 VAC |
| Electrical Connections | 3 screw type - common, normally open, normally closed |
| Conduit Connection | 1/2 in NPSM (female) |
| Process Connection | 1 in male NPT (contact factory for optional tees) |
| Pipe Size | 1 to 4 in |
| Mounting Orientation | Horizontal or vertical; actuation flow rates are based on horizontal pipe runs with the switch in the vertical position. Will not work in vertical pipe with down flow |
| Set Point Adjustment | Vane is trimmable - see set point chart |
| Weight | 1 lb 2 oz (500 g) |
| Compliance / Approvals | CE, UL; UL353 |
| Model Code | V7 = V7 Flow Switch / W = Weatherproof / B = Brass (S = 316 SS) / S = SPDT / 3 = 1 in / 0 = Full length vane with template / N = No Tee |
| Pipe Size | Actuate | Deactuate |
|---|---|---|
| 1 in | 7.5 (28.4) | 6.8 (25.7) |
| 1-1/4 in | 8.1 (30.8) | 7.6 (28.9) |
| 1-1/2 in | 11.7 (44.1) | 10.9 (41.3) |
| 2 in | 16.9 (64.0) | 15.6 (59.1) |
| 2-1/2 in | 19.6 (74.2) | 18.1 (68.5) |
| 3 in | 31.6 (120) | 29.6 (112) |
| 4 in | 58.0 (218) | 52.0 (197) |
These catalog summary rates are nominal and are based on horizontal pipe runs. Actual actuation and deactuation rates depend on vane trim and installation. Use the trim-specific set point chart below and contact the factory when a different rate is required.
| Vane Trim | Pipe Size | Actuate | Deactuate |
|---|---|---|---|
| a (full vane) | 2 in | 12.8 [48.5] | 12.1 [45.8] |
| a (full vane) | 3 in | 31.6 [119.6] | 29.6 [112] |
| a (full vane) | 4 in | 58 [218] | 52 [197] |
| b | 1-1/2 in | 7.5 [28.4] | 6.7 [25.4] |
| b | 2 in | 12.7 [48.1] | 12 [45.4] |
| c | 1-1/2 in | 8.3 [31.5] | 7.7 [29.1] |
| c | 2 in | 14 [53] | 13.6 [51.5] |
| d | 1-1/2 in | 8.3 [31.4] | 7.5 [28.4] |
| d | 2 in | 13.7 [51.8] | 13.4 [50.7] |
| e | 1-1/2 in | 9.8 [37.1] | 9.2 [34.8] |
| e | 2 in | 16.9 [64] | 15.6 [59.1] |
| f | 1-1/4 in | 8.13 [30.8] | 7.63 [28.9] |
| f | 1-1/2 in | 11.65 [44.1] | 10.9 [41.3] |
| j | 1 in | 7.5 [28.4] | 6.8 [25.7] |
The vane template is marked a through o. Dwyer publishes flow data only for the trim positions listed above. Chart values are based on installation in standard tees, except the 4 in size, which is based on a 4 in x 1 in pipe saddle.
| Pipe Size | Dim. A |
|---|---|
| 1 in | 1-17/64 in [32.15 mm] |
| 1-1/4 in | 1-19/32 in [40.48 mm] |
| 1-1/2 in | 1-53/64 in [46.43 mm] |
| 2 in | 2-11/64 in [55.17 mm] |
| 3 in | 2-11/64 in [55.17 mm] |
| 4 in | 2-11/64 in [55.17 mm] |
Documentation
Series V7 Catalog Page / DatasheetSpecifications, actuation and deactuation flow rates, model chart and dimensionsSeries V7 Installation and Operating InstructionsBulletin F-V7 - set point chart, mounting, wiring and maintenanceFrequently Asked Questions
What is the difference between the V7-WBS-30N and the V7-WSS-30N?
Lower body material. The Dwyer Series V7 model chart identifies brass for the V7-WBS-30N and 316 SS for the V7-WSS-30N. Confirm material compatibility for the intended liquid before selection.
How do I set the trip point on a V7?
You trim the vane. The switch ships with a full length 301 SS vane marked with a template. The instruction manual's set point chart lists the approximate actuation and deactuation flow rates for each trim position and pipe size, so you cut the vane back to the position that matches your line size and required flow.
Can the V7 be mounted vertically?
The published specifications allow horizontal or vertical mounting. The listed actuation flow rates are based on horizontal pipe runs with the switch in the vertical position, and Dwyer states the switch will not work in a vertical pipe with downward flow.
What flow rate does the V7 actuate at in a 2 in line?
It depends on vane trim. For a 2 in line, the instruction manual lists approximate cold-water actuation/deactuation values of 12.8/12.1 GPM with the full vane, 12.7/12.0 at trim b, 14.0/13.6 at trim c, 13.7/13.4 at trim d and 16.9/15.6 at trim e. These values are based on standard-tee installation.
Is the V7 suitable for air or gas service?
No. Dwyer specifies the Series V7 for liquids that are compatible with the wetted materials and that are non-coating and non-crystallizing. All published flow data is for cold water.
What is the maximum pressure and temperature?
250 psi (17.2 bar) and a process temperature range of -40 to 250°F (-40 to 121°C). Maximum ambient temperature at the housing is 181°F (83°C).
How is the V7 wired?
Three screw terminals: common, normally open and normally closed, plus an internal ground screw. The N.O. contacts close and the N.C. contacts open when flow rises to the actuation point, and return to normal condition when flow falls to the deactuation point. Dwyer specifies 90°C copper conductors.
1 Year Manufacturer Warranty
DwyerOmega warrants that its products are free from defects in material and workmanship under normal use for a period of one year from delivery to the buyer, unless a product-specific warranty supplied with the product states a different period. The supplied Series V7 documents state no product-specific duration, so the standard one year term applies. The Series V7 instructions state that disassembly or modifications by the user void the warranty and could impair continued product safety. For repair, obtain a Return Goods Authorization (RGA) number from Dwyer and return the unit freight prepaid with a detailed description of the problem and operating conditions.
- Product Type:
- Flow Switch
- Series:
- V7 Flotect
- Sensing Method:
- Vane Operated
- Media:
- Liquids
- Switch Type:
- SPDT
- Body Material:
- Brass
- Connection Type:
- NPT
- Connection Size:
- 1 in
- Pipe Size Range:
- 1 to 4 in
- Set Point Adjustment:
- Field Trimmable Vane
- Enclosure Rating:
- NEMA 4X
- Maximum Pressure:
- 250 psi
- Max Process Temperature:
- 250°F
