Furnas / Siemens / Hubbell · Class 69MB
69MB7LY (and 69MB109xx OEM variants)
For decades the OEM switch on Emglo, Jenny, Champion and Curtis recips. Visible contacts, two ground screws, generous wiring room and non-drifting settings. Siemens has discontinued most 69MB catalog numbers; Lefoo LF10-L1 is the accepted drop-in.
Specifications
- Action
- Standard — contacts open on rising pressure
- Adjustable range
- Builds from roughly 35 to 175 psi depending on catalog number
- Differential
- 30–40 psi on the standard 95/125 build (fixed)
- Factory settings
- Cut-in 95 psi / cut-out 125 psi (most common)
- Ports
- 1/4 in. female NPT single port; four-port versions exist
- Unloader
- Integral unloader on most compressor builds, with 1/4 in. compression fitting for the pilot line
- Lever / disconnect
- Auto/off disconnect lever standard on the LY builds
- Enclosure
- NEMA 1, corrosion-resistant non-metallic cover
- Temperature
- -22 °F to 257 °F
Electrical
- DPST, typically 15 A rated on the standard shop build
- Two ground screws — a small but real advantage over some competitors
- Temperature range -22 °F to 257 °F
Size against motor full-load amps with the motor amperage calculator, and check feeder sizing with the voltage drop calculator.
Adjustment
- Large centre nut sets the range; on adjustable-differential builds a smaller nut sets the gap.
- Bleed to zero and lock out before removing the cover — the terminals are live and exposed.
Before you open the cover
Kill power at the disconnect and lock out. Bleed the tank to 0 psi. Never set cut-out above the tank data-plate MAWP. Verify your numbers first in the cut-in / cut-out calculator.
Best fit
- Emglo, Jenny, Champion, Curtis and similar contractor/shop recips
- Any retrofit where the customer wants the original lever feel
Watch out
- Many listings sell a Lefoo in Furnas packaging. That is fine functionally — just confirm the UL mark.
- The old unloader compression fitting hardens with age; replace the pilot tube whenever you replace the switch.
Cross-references
- Lefoo LF10-L1 (direct replacement, single port, 125 psi)
- Furnas 69JF7LY
- Square D 9013FHG12J52 with lever and unloader