HYDRONIC HEATING AQUASTATS

I. TERMS A. HYDRONIC 1. SYSTEMS THAT USE THE CIRCULATION OF HOT WATER THROUGH PIPES TO HEAT CONDITIONED SPACE B. HIGH LIMIT 1. STOPS THE BURNER IF THE TEMPERATURE OR PRESSURE IS TO HIGH 2. MAY BE MANUAL OR AUTO RESET C. CIRCULATOR 1. PUMP USED TO MOVE WATER

D. CIRCULATOR RELAY 1. TURNS THE PUMP ON AND OFF 2. ALLOWS A LOW VOLTAGE THERMOSTAT TO CONTROL THE LINE VOLTAGE PUMP E. LOW LIMIT 1. TURNS THE BURNER ON WHEN THE BOILER TEMPERATURE IS BELOW SET POINT 2. TURNS BOILER OFF WHEN TEMPERATURE INCREASES TO SET POINT

F. CIRCULATOR CONTROL 1. USED IN SYSTEMS WHICH HAVE DOMESTIC COILS 2. PREVENTS THE CIRCULATOR FROM RUNNING IF BURNER IS OUT ON LOW LIMIT a. KEEPS THE BOILER FROM GETTING TO COLD FOR DOMESTIC HOT WATER

II. AQUASTATS A. AQUASTAT RELAY (COMBINATION CONTROL) 1. SENSES WATER TEMPERATURE IN A HYDRONIC BOILER 2. HAS A LIMIT CONTROL, RELAY, AND TRANSFORMER. ALL MOUNTED TOGETHER IN ONE DEVICE 3. HAS CONNECTIONS FOR THERMOSTAT, CIRCULATOR, BURNER AND MAIN POWER 4. ONE TYPE OF AQUASTAT PROVIDES LOW VOLTAGE POWER FOR A GAS BURNER WHILE ANOTHER TYPE OF AQUASTAT PROVIDES HIGH VOLTAGE POWER FOR AN OIL BURNER

5. MAKE SURE YOU HAVE THE CORRECT. AQUASTAT FOR THE TYPE OF BURNER 5. MAKE SURE YOU HAVE THE CORRECT AQUASTAT FOR THE TYPE OF BURNER THAT THE BOILER USES B. SEQUENCE OF OPERATION – COLD START BOILER 1. THERMOSTAT CALLS FOR HEAT, GAS BURNER TURNS ON 2. THE WATER HEATS UP. HIGH LIMIT SETTING KEEPS THE WATER FROM GETTING TO HOT (“BOILING” 180- 200) 3. CIRCULATOR IS ENERGIZED. IF AQUASTAT HAS A LOW LIMIT SETTING CIRCULATOR WILL NOT RUN UNTIL LOW LIMIT SETTING IS REACHED. 160 f

4. WHEN BOILER IS UP TO TEMPERATURE CIRCULATOR RUNS CONSTANTLY. BURNER MAY CYCLE ON AND OFF 5. WHEN THERMOSTAT IS SATISFIED CIRCULATOR STOPS, BURNER SHUTS OFF

C. AQUASTAT ELECTRICAL CONNECTIONS 1. L1 & L2 CONNECTIONS FOR 120 V POWER SUPPLY 2. TV & T ARE 24V THERMOSTAT CONNECTIONS 3. C1 & C2 ARE CIRCULATOR MOTOR CONNECTIONS 4. B1 & B2 ARE BURNER CONNECTIONS 5. VOLTAGE CHECKS CAN BE MADE AT ALL THESE CONNECTIONS D. AQUASTAT VARIATIONS 1. ANOTHER TYPE OF AQUASTAT IS DESIGNED TO MAINTAIN CONSTANT BOILER TEMPERATURE

2. THE BURNER WILL CYCLE ON AND OFF TO 2. THE BURNER WILL CYCLE ON AND OFF TO MAINTAIN 180deg WATER TEMPERATURE EVEN WHEN THERE IS NO CALL FOR HEAT 3. THIS TYPE OF AQUASTAT CAN BE FOUND IF THE BOILER IS ALSO PROVIDING DOMESTIC HOT WATER WITH A TANKLESS COIL LOCATED IN THE BOILER 4. A TANKLESS COIL IS NOTHING MORE THAN A COIL OF COPPER TUBING SITTING IN THE HOT BOILER WATER. THE COLD WATER FROM A COLD WATER LINE GOES IN AND COMES OUT HOT 5. WITH A TANKLESS COIL THERE IS NO LARGE STORAGE CAPACITY OF HOT WATER

III. AQUASTAT CONTROLLERS A. HIGH AND LOW LIMIT CONTROLLERS 1. AS A HIGH LIMIT, THE CONTROLLER WORKS LIKE THE HIGH LIMIT IN A WARM AIR SYSTEM a. A SAFETY DEVICE TO TURN OFF THE BURNER IF TEMPERATURES ARE TO HIGH 2. AS A LOW LIMIT, THE CONTROLLER WILL TURN ON THE BURNER WHEN THE TEMPERATURE DROPS TO LOW a. MAINTAINING A MINIMUM BOILER WATER TEMPERATURE

3. USES A BULB AND CAPILLARY TO SENSE. TEMPERATURE / CHANGES BELLOWS 3. USES A BULB AND CAPILLARY TO SENSE TEMPERATURE / CHANGES BELLOWS POSITION 4. THE BELLOWS EXPANDS AND CONTRACTS, OPENING AND CLOSING A SWITCH B. CIRCULATOR CONTROL 1. WHEN THE WATER TEMPERATURE DROPS THE CIRCULATOR WILL TURN OFF. THIS PREVENTS EXCESS RUN TIME WHILE THE BOILER HEATS UP C. DUAL AQUASTAT CONTROLLER 1. THE FUNCTION OF THE HIGH LIMIT, LOW LIMIT & CIRCULATOR CONTROLLERS ARE COMPLETED WITH ONE CONTROL

2. A SPDT SWITCH IS USED AS THE LOW LIMIT AND CIRCULATOR CONTROL a. WHEN THE BOILER TEMPERATURE IS BELOW THE SET POINT THE R-B CONTACTS ARE CLOSED (LOW LIMIT), THE R-W CONTACTS ARE OPEN (CIRCULATOR) b. WHEN THE TEMPERATURE IS ABOVE THE SET POINT THE CONTACTS CHANGE POSITION D. COMBINATION AQUASTAT CONTROLLER 1. AQUASTAT RELAY 2. TRIPLE AQUASTAT RELAY

E. AQUASTAT RELAY 1. COMBINES THE FUNCTION OF A SWITCHING RELAY FOR CIRCULATOR AND TEMPERATURE CONTROL OF THE SYSTEM 2. USED WITH SYSTEMS THAT “DO NOT” HAVE DOMESTIC HOT WATER COILS 3. CONTAIN: a. TRANSFORMER FOR CONTROL VOLTAGE 24vac b. RELAY TO CONTROL BURNER AND CIRCULATOR c. TEMPERATURE CONTROL FOR HIGH AND LOW LIMIT OPERATIONS 4. THE BOILER DOES NOT RUN WHEN THE SYSTEM HAS NO CALL FOR HEAT

F. TRIPLE AQUASTAT RELAY 1. USED IN SYSTEMS WHICH ARE REQUIRED TO PROVIDE DOMESTIC HOT WATER 2. SOME PROVIDE ZONE CONTROL 3. THERE ARE SINGLE ZONE MODELS FOR GAS, AND OIL-FIRED APPLICATIONS a. A MILLIVOLT MODEL IS AVAILABLE FOR GAS SYSTEMS 4. MULTI ZONE MODELS ARE ALSO AVAILABLE

a. IN THIS SYSTEM THE TRIPLE AQUASTAT CONTROLLER PROVIDES HIGH LIMIT b. LOW LIMIT/CIRCULATOR CONTROL c. RELAY SWITCHING FOR THE OIL PRIMARY OR GAS VALVE (THROUGH THE HIGH LIMIT) d. POWER FOR THE ZONE CIRCULATOR. CONTROL IN ZONE 2 IS PROVIDED BY AN ADDITIONAL RELAY