Hydronic Mechanical Controls

Air Scoop or Air Purge 1. Located in the system (commonly on top of expansion tank 2. Has internal baffles that divert bubble into separate chamber 3. Air rises to air vent and is released 4. Has arrow for direction 5. Another method for removing air is a micro bubble resorber

Back flow Preventer 1. Prevents water for leaving a system and going back into the potable water supply 2. Has inlet markings and also a blow vent A. Inlet connects to domestic water 3. Works when city water drops below boiler pressure 4. Almost all municipal codes require a back flow

Boiler Drain Valve A valve to drain the boiler for necessary repairs Lowest part of the water system

Boiler Fill Valve Feed water pressure regulator Pressure reducing valve Reduces the water pressure because pressure are normally higher than the relief valve A. Pressure will be different for system when more levels of floors must be heated

us Located after backflow preventer Has arrow to show direction Pressure can be changed by rotating the center shaft with a screwdriver, tighten the lock washer us

Check Valve Allows flow in only one direction Types of check valves A. Swing check B. Ball check C. Magnetic check Can be installed in the feed line or water supply line Not needed in the supply line if zone valves are used They are directional and must be installed level

Expansion Tank A tank to store water after it has been heated and expands When water is heated it expands System must have a method of dealing with the expansion Older models are just a compression tank above the boiler

Older tanks: every 5000 BTU’s of output require 1 gallon of expansion tank capacity Some have flexible bladders A. When system is cold bladder pushes down on water B. Warm water will expand into tank C. These tanks will prevent pressure relief valve from permanently releasing D. Advantages of a bladder tank i. Smaller size ii. No need to drain and create a new air cushion

Flow Check Valve Basic type is a swing check which has a weighted gate It will stop thermal siphoning or gravity flow while the circulator is off They are not needed if zone valves are used They are directional and must be installed level

Only required if A. If the boiler produces domestic hot water B. More than one zone and no zone valves are used

Flow Control Valve Set by the GPM of water flow desired Controls the flow of hot water so as not to run out Prevents water from moving through the system during off cycle

Gate or Globe Valve A stop or isolation valve Globe valves must be installed correctly (check the arrows) Used to isolate for maintenance

Tempering Valves Installed on the hot water coming out of the heater coil, and the cold water entering the coil Tempers the water so that when it comes out of the faucet it’s cooler 3 Connections A. Hot water discharge side from boiler or water heater B. Cold water connection C. Hot water supply to the fixtures in the house

If Possible should be installed 8 – 12” below the hot water line A. So they are trapped and to prevent from heat build up when not in use

Purge Valve Valve installed in Return line before the circulator A butterfly valve inside is closed when filling system and a boiler drain before the butterfly valve opened The water is forced through the piping and heat emitters to the boiler drain A. Air is forced out 4. The butterfly valve keeps water from backing up in the return

Pressure Relief Valve Necessary to relieve a closed system from excessive pressure Located on the Domestic Hot Water Side Usually set to relieve at 150 PSI at 210 degrees If pressure is excessive the relief valve will open

Safety Relief Valve Must be installed on all systems A spring holds the seat down to hold pressure in, excess pressure pushed up and the seat relieves pressure Steam and boiler systems have the same design but different pressure ratings

Hot water tanks will have pressure sensors as well Normal settings A. Steam systems are set at 15 PSI B. Boilers are set at 30 PSI C. Hot water heaters are set at 150 PSI and 210 Degrees i. Can be installed on tank less heaters

Test Plug 1. A test port to test water pressure

Ball Valves Stop or isolation valve Straight through valve with little or no restriction A quick close valve Inside the face of the valve is like a ball

Vent Valve Necessary to remove air bubbles from system Bubbles create noises Air can collect and cut off circulation to different parts of the hydronic system Location A. Normally on the air scoop B. Highest part of the system

Automatic bleed valve Permits air to be forced out of the system but closes against water

Feed Water Pressure Regulator Water pressure reducing valve Reduces water pressure because pressures are normally higher than the relief valve Normally set at 12 PSI A. Pressure will be different for a system heating more floors 4. Is a directional valve

Zone Valves Used for multiple zone applications To uniformly heat a building Supplies heat A valve for isolating different sections of the system to only open on a call for heat

Base Board Tees with Air Vents 1. Located where air could accumulate Resembles a standard 90 degree elbow Has an additional vent port Normally located at the end of the base board or the return side

Pumps 1. Two types used in residential systems A. Open B. Cartridge A. The pump has a coupling B. Are serviceable in the field

C. Many have what's called a bearing assembly D. Contains a bearing and a seal for the pump Cartridge A. Pump and motor are in one housing B. The impeller is direct drive C. The pump is cooled by boiler water D. Not serviceable if it leaks it needs to be replaced

Altitude Gauge The gauge on all boilers which indicates temperature and pressure The boiler pressure relates to the height from the boil to the last emitter One PSI will push water up 2.31 feet A. Standard 12 PSI system will support a column of water 27.72 Feet

Coin Vent Mechanical vent that is opened to bleed radiation To bleed system with auto feed A. Start radiation farthest from the boiler and open the vent until air being purged is replaced by a good stream of water

If the boiler does not have an auto feeder the pressure in the boiler will need to be maintained while purging A. Start with boiler pressure at maximum required pressure i. One PSI for every 2.31 feet of head ii. Recommended pressure for a 2 story dwelling is 12 PSI

B. After bleeding the farthest radiator check the system pressure i. Be sure that the pressure is high enough to continue bleeding ii. Add water to keep pressure up