Flow Switches Made in the U.S.A. · Serving Industry Worldwide
Technical Reference
Flow Switch Cover Types
Not all PEECO covers are the same. The cover design is directly tied to the hazardous location rating of each series — understanding the difference matters for proper installation and code compliance.
PEECO flow switches are built around the same core mechanism across all three series, but the cover — the top enclosure that houses the micro-switch and wiring — differs based on whether the unit is rated for hazardous locations. The N Series uses a slip-on cover suited for general industrial environments. The E and H Series use a threaded cover that is a fundamental requirement of their Class I, Division 1, Group D explosion-proof rating.
Both cover types are machined from heat-treated aluminum alloy 356-T6. The difference is not material — it is mechanical design and the safety standard it satisfies.
N Series
Slip-On Cover
The N Series cover slides onto the housing and is secured with a single fastener. It provides a weatherproof NEMA 4X seal suitable for outdoor and wash-down environments, but it is not rated for use in atmospheres where flammable gases or vapors may be present.
- Heat treated aluminum alloy 356-T6
- Slip-on design — single fastener retention
- NEMA 4X weatherproof rating
- Quick access for wiring and adjustment
- Not rated for hazardous locations
Use the N Series in non-hazardous locations: cooling water, HVAC, general process lines, pump protection.
E & H Series
Threaded Cover
The E and H Series use a threaded cover that screws directly onto the housing. To maintain the Class I, Division 1, Group D explosion-proof rating, the cover must have a minimum of five fully engaged threads at all times. This is not a preference — it is a code requirement. Removing the cover in a live hazardous area requires following proper hot-work and de-energization procedures.
- Heat treated aluminum alloy 356-T6
- Threaded engagement — screws onto housing
- Minimum 5 fully engaged threads required
- Class I, Division 1, Group D rated
- Required for flammable gas / vapor environments
Important: The cover must have five fully engaged threads to maintain the explosion-proof rating. Never operate an E or H Series switch with a partially threaded or missing cover in a hazardous location.
Cover Comparison at a Glance
| Feature | N Series — Slip-On | E & H Series — Threaded |
|---|---|---|
| Attachment method | Slip-on, single fastener | Threaded, screws onto housing |
| Material | Aluminum 356-T6 | Aluminum 356-T6 |
| Enclosure rating | NEMA 4X | Class I, Div 1, Group D (XP) |
| Minimum thread engagement | N/A | 5 fully engaged threads |
| Hazardous location rated | No | Yes |
| Suitable for flammable atmospheres | No | Yes — with cover fully engaged |
| Access for wiring | Quick slip-off | Unscrew (follow hot-work procedures in hazardous areas) |
| Series | N Series | E Series, H Series |
Why the Threaded Cover Matters for XP Rating
Explosion-proof enclosures work by containing any internal ignition — not by preventing it. The threaded cover creates a long, tight flame path. If an internal arc or spark ignites gas that has entered the housing, the flame is quenched as it travels through the thread engagement before it can reach the surrounding atmosphere. Five fully engaged threads is the minimum path length required by NEC and UL standards to reliably quench the flame.
Choosing the Right Series for Your Location
If your installation is in a classified hazardous location — anywhere flammable gases, vapors, or liquids may be present — you must use the E or H Series. The N Series slip-on cover does not satisfy the requirements of NEC Article 500 for Class I locations.
Not sure which series fits your application? Use the Product Selector or contact our engineering team — we will help you specify the right switch for your conditions.
Need Help Selecting the Right Series?
Our engineering team can review your application and confirm whether you need an N, E, or H Series switch — and which cover configuration applies.