The NK300S is a (re)filling combination valve that contains an integrated pressure reducing valve, strainer, double check backflow preventer with air vent (to protect potable water supply against back flow of heating water into supply pipe), (2) shut-off ball valves, pressure gauge, and conveniently located test ports for easy inspections and check out. All the needed devices for refilling a heating system are contained.

Honeywell Combination Boiler Feed Valve, Series: NK300S, 1/2 in Nominal, Union Press Connection, 10 - 58 lb/sq-in Pressure, 16 gal/min at 22 lb/sq-in, Brass Body, NBR and EPDM Seal, 33 - 140 deg F Ambient, 180 deg F Fluid, 7.48 in H

• Optimal protection of the potable water supply system
• Pressure reducing valve with inlet pressure balancing-inlet pressure fluctuation does not influence the outlet pressure
• Outlet pressure adjustable and directly visible on the pressure gauge
• Low maintenance effort-cartridge insert and valve insert are completely replaceable
• Connection type includes union press fitting connections
• Valve type-fast fill
• Controlled fluid-water
• Fiber-reinforced EPDM diaphragm
• Stainless steel fine filter mesh filter interior parts

• Specification Sheet https://assets.unilogcorp.com/267/ITEM/DOC/Honeywell_NK300S_100UP_Specification_Sheet.pdf