L597BA – ADJUSTABLE HIGH LIMIT SWITCH (7″, 120-250)

Universal replacement high-limit control from SUPCO’s CAMSTAT L59 series, with a 7 in bimetal element extension. It is a safety limit: the SPDT snap switch opens the burner circuit on its normally closed terminals when plenum temperature reaches the setting, then resets automatically as the furnace cools. An adjustable bracket lets you match the cut-out to the control you removed – set that exact temperature, since a higher setting defeats the furnace’s overheat protection.

Specifications published by the manufacturer. Source: manufacturer documentation.

Specs

• ManufacturerSUPCO / CAMSTAT, L59 Series
• TypeUniversal adjustable high limit control
• Element extension7 in
• Adjustable cut-out range150-250 F per the installation sheet (line catalog lists 120-250 F - verify on the control)
• Differential20-40 F
• Switch actionSPDT, silver-plated contacts
• ResetAutomatic
• Pilot duty (N.C.)40 VA @ 30, 120 and 240 VAC
• Full load amps (N.C.)5.8 A @ 120 VAC / 2.9 A @ 240 VAC

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• FF569
• L59-7B-A
• L597B
• L597A

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

What does L200-40 mean on a furnace limit switch?

L is limit, 200 is the temperature in F where the contacts open on a rise, and 40 is the differential, so it closes back around 160F. That is an auto-reset disc. Manual-reset limits have a button and stay open until somebody pushes it. Bring the old one in so we can match the temperature, the mounting hole pattern, and the probe length together.

My limit keeps tripping. Is the switch bad?

Usually not. A limit is a safety reading real heat, and most repeat trips we hear about trace back to airflow - a loaded filter, closed or blocked registers, an undersized return, a dirty blower wheel, or a plugged evaporator coil sitting above the heat exchanger. Check temperature rise against the nameplate range, often 40-70F or 45-75F. Rise above the top number means airflow, not a bad switch.

Can I use a hotter limit if that is what is in stock?

No. L200, L230, L250 and L290 differ only by trip temperature and by base or probe size, and they are not interchangeable. Dropping a hotter limit into a furnace that specced a cooler one lets the heat exchanger run past the temperature it was tested to. That is defeating the safety, not fixing it.

Does insertion length matter?

Yes. A 3 inch probe where 5 inch was called for sits in the wrong part of the airstream, reads low, and trips late or never. Measure the old probe from the back of the mounting plate to the tip.