Xylem MM 277G Model RB-24E-S , Model RB-24E-A , Model RB-24E-L , Conductance Type LowWater Cut-Off - Manual (Page 6)

For all Application:
1. Make sure probe is installed above minimum
safe water line as determined by the boiler
manufacturer.
2. Make sure that ends and side of the probe
are at least 1/4 (6.4mm) from all internal
metal surfaces.
A
1/4"
(6mm)
1/4"
(6mm)
1
E
"