150 - float chamber body with one 2 wire switch (pump) and one 3 wire switch (burner/alarm)

157 - water column body with one 2 wire switch (pump) and one 3 wire switch (burner/alarm)

158 - float chamber body with two 3 wire switches

159 - float chamber body with two 2 wire switches

‘S’ - denotes models with snap switches

‘M’ - denotes models with manual reset switch

‘MD’ - denotes models with maximum differential between pump off and burner off

‘RBP’ - denotes 157 model with two integral probes for additional pump level control utilizing a PCH-G-A-2 control

‘R’ ‘RL’ ‘P’ ‘RB’ - denotes 157 models with different locations and sizes for gauge glass and tri-cock tappings

‘J’ - denotes units with BSPT threads for equalizing line tappings

‘B’ - denotes units with float block tapping

‘A’ - denotes 157 models with side outlet lower equalizing line tappings

Descriptions and dimensions for specific units can be found in the McDonnell & Miller General Catalog MM-825 or on our website. http://www.mcdonnellmiller.com