Four questions get you to the right family: what you are sensing, what you are switching, where you can mount, and what is in the tank. Every configuration is assembled from stock parts — nothing is custom fabricated.
This choice sets the product family. Everything after it is geometry and electrical load.
A float rises and falls with the liquid and actuates a hermetically sealed reed switch. Single point, or two, three and four levels on one assembly.
Series 10 · Series 15 · Series 20 →A poppet moves against a calibrated titanium spring in the flow path. Flow switches, flow indicators, and combined sets.
Series 5 →Bimetallic disc switching, factory-set from 0 °C to 100 °C, close-on-rise or open-on-rise. Switch sets and probe sets.
Series 11 →Solid state relays, latching relays and accessories, for when the sensed signal has to drive something larger — or anything reactive beyond pilot duty.
Series 50 →Two questions, and the first one is not the size of the load — it is the kind. This is also the real difference between Series 10 and Series 20: heavy-duty refers to the switch element's rating, not to tank pressure, temperature or size.
| Family | Switch element | Rating | Switches directly |
|---|---|---|---|
| Series 5 · 10 · 15 | KOFU ORD229 reed | 70 VA / 50 W resistive 1A @ 100V · UL File E70063 |
Resistive pilot duty only — a PLC or controller input, an indicator lamp, a resistive alarm. Wire it in series with your relay or controller. Anything reactive needs suppression or a Series 50 relay. |
| Series 20 | Yaskawa Bestact™ hermetically sealed | 120 VA | Contactors, solenoid valves and motor circuits directly — no relay required |
Most manufacturers force this decision. We do not.
Vertical mounted single point, from a bare 1/8″ NPT switch upward.
Vertical mounted single point →Extended stem sets carrying one, two, three or four floats on a single assembly.
Extended stem sets →Side-mounted single point. Differs from Series 15 in the mounting configurations offered and the slosh shields available.
Side mounted level switches →Material is chosen by chemistry, and it is an independent choice — 102 of our 106 model configurations are offered in all three materials, so your geometry decision above does not restrict it.
General aqueous service, acids and bases. Water, soaps, coolants, dilute solutions.
Solvents, fuels and hydrocarbons.
Aggressive acids, caustics, oxidizers and halogens.
Every model is a building block. Nothing is custom fabricated.
| Family | Senses | Mounting | Switch rating | Typical use |
|---|---|---|---|---|
| Series 5 | Flow | In-line | Pilot duty | Flow switches, indicators and combined sets. Titanium spring in the flow path. |
| Series 10 | Level | Top or side | 70 VA resistive | The modular workhorse. Single point through four-level extended stem sets. |
| Series 11 | Temperature | Top or probe | — | Bimetallic disc, 0–100 °C, close- or open-on-rise. Switch and probe sets. |
| Series 15 | Level | Side, no stem | 70 VA resistive | Low-level and differential sensing through the tank wall. 15-650 installs three ways. |
| Series 20 | Level | Top mount | 120 VA | Switches contactors, solenoid valves and motor circuits directly. |
| Series 50 | — | Panel | — | Solid state relays, latchers and accessories. Required for reactive loads beyond pilot duty — 50-NP-AC5 and 50-LP-AC10. |
Switching capacity. Series 10 uses the KOFU ORD229 reed switch rated 70 VA (1A at 100V), intended for signal-level loads such as a PLC input, an alarm or a small relay coil. Series 20 is built around the Yaskawa Bestact™ hermetically sealed switch element rated 120 VA, which switches contactors, solenoid valves and motor circuits directly with no interposing relay. Heavy-duty refers to the electrical rating, not to tank pressure or temperature.
Side mounting is popular with OEMs for low-level and differential level sensing. Most level switch manufacturers have to custom-fabricate an extended-stem low-level or differential version mounted from the top. ERECTA SWITCH fabricates nothing custom — every configuration comes from stock parts — so the price per level is approximately the same either way. That makes it a free choice: pick whichever is more advantageous for your equipment.
Both sense level through the tank wall and both use the same 70 VA reed switch. They differ in the mounting configurations offered and in the slosh shields available. Series 15 requires no stem and the 15-650 installs three ways.
That depends on the kind of load as much as the size of it. The KOFU reed switch in Series 5, 10 and 15 is rated 70 VA / 50 W resistive — pilot duty. It drives a PLC or controller input or an indicator lamp directly. A reactive load — a solenoid, a contactor coil, a motor, a transformer, another relay's coil — arcs across the contacts as the field collapses, so even within the rating it needs arc suppression circuitry at minimum, and above the rating it needs a relay: the 50-NP-AC5 or the 50-LP-AC10. A Series 20 at 120 VA switches contactors, solenoid valves and motor circuits directly, so no relay is required there.
No. The 70 VA / 50 W figure is a resistive rating. An inductive load stores energy in a magnetic field and dumps it across the contacts as they open; the resulting arc erodes the reed and can eventually weld it closed — a level switch that fails on. Being under the VA number is not on its own permission to switch it directly. Add arc suppression, or isolate the load with a Series 50 relay. If you are not sure which your load is, send us the part number of what you are switching and we will tell you.
Match the material to the media: Polypropylene (PP) for general aqueous service, acids and bases; Acetal (AC) for solvents, fuels and hydrocarbons; PVDF Kynar (KR) for aggressive acids, caustics, oxidizers and halogens. Series 5 flow switches additionally carry a titanium spring in the flow path, so check titanium compatibility as well. Four models — 10-785, 10-786, 10-786-R and 10-787 — are polypropylene only. If your chemistry is borderline, send it to us with the concentration and temperature and we will confirm the material.
Tell us the liquid, the concentration, the temperature and what you need to switch. We will specify it and send a free evaluation sample — no minimums, and every part ships from stock.
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