Common questions about boiler controls, low water cutoffs, steam traps, and replacement parts. Need a specific answer? Contact our team or call (901) 458-2000.
What is a low water cutoff (LWCO) and why does my boiler need one?
A low water cutoff (LWCO) monitors the water level in a boiler and shuts off the burner if water drops below a safe minimum level. Without sufficient water a boiler can overheat and suffer catastrophic damage. LWCOs are required by code on virtually all steam and hot water boilers. Common types include float-type LWCOs like the McDonnell & Miller 150S and 157S, and electronic probe-type LWCOs like the Hydrolevel CG400 and HydroStat 3000.
What is the difference between the McDonnell & Miller 150S and 157S?
The 150S is a straight low water cutoff — it monitors water level and shuts off the burner on low water. The 157S adds pump control functionality, combining a low water cutoff with a pump controller that automatically starts and stops a feedwater pump to maintain the correct boiler water level. The 157S is the right choice when you need both functions in one unit.
What is the difference between a float-type and electronic low water cutoff?
Float-type LWCOs like the McDonnell & Miller 150S use a mechanical float inside a chamber connected to the boiler — as water level drops, the float drops and opens a switch to shut off the burner. Electronic probe-type LWCOs like the Hydrolevel CG400 use conductance sensing probes with no moving parts, making them less susceptible to scale buildup and mechanical failure. Electronic LWCOs are increasingly specified on commercial boilers where reliability and reduced maintenance are priorities. Both types meet ASME CSD-1 requirements.
What types of steam traps does Memphis Control Center stock?
We stock the full Hoffman Specialty steam trap line — 1,400+ products. We carry float & thermostatic (F&T) steam traps, inverted bucket traps, thermodynamic traps, balanced pressure traps, and thermostatic steam traps for residential and commercial steam heating systems. We also stock Hoffman radiator air vents, main line vents, and condensate pumps.
Do you stock legacy and discontinued McDonnell & Miller parts?
Yes. Memphis Control Center has stocked McDonnell & Miller controls since 1967 and maintains inventory on both current and legacy M&M parts. We stock replacement floats, gaskets, and repair parts for older M&M series including the Series 63, 64, and 67 that are still in service across thousands of commercial boiler installations. Call us at (901) 458-2000 with your model number and we'll confirm availability.
What are Warrick-Gems conductance controls used for in boiler systems?
Warrick-Gems conductance level controls use probe-type sensing to detect water levels in boiler feedwater systems, condensate receivers, and deaerators. Their relay panels and DFC dual-function controls provide pump start/stop and low-water cutoff signals based on water conductivity. They are a common OEM component on commercial boiler feedwater packages — we stock replacement relays, probes, and complete assemblies.
