Series PS-801
for Steam Boilers
Series PS-851
for Hot Water Boilers
Probe Type Low Water Cut-Offs
Applications:
Residential and Commercial
PS-851 models can be used as secondary low water cut-offs
on steam boilers with pressures up to 15 psi
®
• Before using this product read and understand instructions.
• Save these instructions for future reference.
• All work must be performed by qualified personnel trained in the proper application,
installation, and maintenance of plumbing, steam, and electrical equipment and/or systems
in accordance with all applicable codes and ordinances.
• To prevent flooding, do not use manual reset models with electric automatic water feeders.
• To prevent electrical shock, turn off the electrical power before making electrical connections.
• This low water cut-off must be installed in series with all other limit and operating controls
installed on the boiler. After installation, check for proper operation of all of the limit and
operating controls, before leaving the site.
• We recommend that secondary (redundant) Low Water Cut-Off controls be installed on all
steam boilers with heat input greater than 400,000 BTU/hour or operating above 15 psi of
steam pressure. At least two controls should be connected in series with the burner control
circuit to provide safety redundancy protection should the boiler experience a low water
condition. Moreover, at each annual outage, the low water cut-offs should be dismantled,
inspected, cleaned, and checked for proper calibration and performance.
• When installing jumper wire make sure you are not introducing a second voltage source
into the burner circuit and thereby bypassing other safety, limit, and operating controls.
• When using mixed voltages, remove the factory installed jumper wire between terminal (H)
and (C), or between (1) and (2) on old Model PS-801-120.
Failure to follow this warning could cause property damage, personal injury or death.
WARNING
CAUTION
!
WARNING
U.S. Pat. No. 6,571,625
McDonnell & Miller
Installation & Maintenance
Instructions
MM-202(N)
