Maxitrol SC25S Conditioner

For veteran technicians managing direct or indirect-fired gas applications, the Maxitrol SC25S is a precision-engineered signal conditioner designed to bridge the gap between building automation signals and Selectra modulating gas valves. This analog controller is built to convert a selectable 4-20mA or 0-10VDC control input into a robust 0-20VDC output, capable of driving multiple valves like the M411, M511, and MR212 series simultaneously. Unlike basic converters, the SC25S prioritizes system protection by monitoring discharge air temperature limits. Using a TS194Q sensor, it provides active overrides to maintain temperatures between defined minimum and maximum setpoints, ensuring the burner operates within safe thermal parameters. The integrated adjustable low fire start timer allows for a 5 to 30-second delay, fixing the initial output to 0 or 20VDC to ensure stable ignition before atmospheric modulation takes over. This track-mounted unit is the industry-standard solution for achieving high-precision HVAC gas modulation and reliable temperature limit control in commercial heating systems.

• Universal Input Compatibility: 3-position DIP switches allow for seamless switching between 4-20mA or 0-10VDC signals to match any BMS (Building Management System).
• Advanced Thermal Protection: Overrides the control signal if discharge air hits the high or low limit (80°F - 200°F nominal range) to prevent equipment damage.
• Optimized Ignition: The low fire start timer provides an adjustable 5-30 second window to prevent "chattering" or unstable flames during the start-up sequence.
• Multi-Valve Driving Capability: Engineered to provide a 0-20VDC output at up to 1.8A, making it powerful enough for large-scale modulating gas control setups.
• Contractor-Friendly Installation: Snap-track mounting and 1/4" quick-connect tabs facilitate rapid field replacement or new equipment integration.

Can the SC25S replace the older SC20C-B6S2 model?
Yes, the SC25S is the direct functional replacement for the discontinued SC20C-B6S2 series, offering updated circuitry and more reliable signal processing.

What happens if the discharge air sensor fails?
The SC25S requires a functioning TS194Q sensor for temperature limit monitoring; without a valid signal, the limit override logic may not engage, which is why a dedicated 24VAC independent transformer is recommended to avoid signal noise.

How do I adjust the start-up delay?
There is an onboard adjustable dial that allows you to set the nominal start time interval between 5 and 30 seconds to provide the ideal ignition timing for your specific burner configuration.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.