Hot Water Heating Systems Flashcards
Hot Water (Or Hydronic) heating systems provide comfort heating by:
Using a central boiler to heat water
The two basic types of hydronic heating systems are
Gravity Systems
Forced Flow Systems
Gravity systems rely on what 2 things to promote movement of water in the system?
Convection currents within the piping system
Density of cold water versus hot water
Forced Flow Systems provide greater flexibility in design and operation by
Using a pump to move the heating water
Why did the hot water heating system become popular?
Safer than the steam systems
What were the drawbacks of gravity hydronic heating systems?
More costly due to larger piping required
Slow response time
Forced Flow Hydronic Heating Systems use a _____ or circulator to move heated water through a piping distribution system.
PUMP
A _____ system is NOT open to the atmosphere.
CLOSED
Boiler temperature is controlled by the
High and low limits of the temperature controller.
Microprocessors can control ______ lights that show the operational state of motors, valves, pumps, and temperatures.
INDICATOR LIGHTS
Digital Controllers increase energy efficiency and provide
diverse control strategies, safety interlocks, and other options requested by customers.
What device transfers heat energy to the surrounding air or space from the hot water?
Heat Transfer Unit
Power circuits for boilers must have a
DISCONNECT SWITCH
Boilers are the heart of every hydronic heating system. They use ______ to heat the water that in turn heats the building.
FUEL
Boilers with cast iron sectional heat exchangers are
Heavy and hold a large volume of water compared to other boilers of the same capacity.
(High-Mass Boilers)
May be used with gravity heating systems
Direct Vent continuous flow heat exchangers may be made of
stainless steel, steel, cast iron, or copper
Larger Projects like apartment buildings use multiple:
Direct vent Boilers.
Can be combined to produce input values up to 1000 Mega BTU per hour
Standing pilot flame ignition has a pilot flame that burns constantly and is in direct contact with the:
Thermocouple near the main burner
Direct Spark ignition uses a high voltage source to create :
A hot spark across a spark plug
(10,000V Transformers)
Significant shock hazard.
Hot Surface Ignitions are _______ ignition devices similar to the heating element in a toaster.
Resistive
A pyrostat AKA a stack switch is a :
Bimetal coil incorporated inro a probe.
A cad cell is:
A light sensitive cell mounted so light from the flame strikes it directly
With no light the cad cell has very high resistance. When it sees light from the flame, the resistance drops to between ______ and ____ ohms and allows current flow.
300-1000ohms
Circulating pumps typically have a power rating up to ____ hp and operate at speeds between ____rpm and ______ rpm
1 hp
1750 RPM - 3450 RPM
Recommended safety and control devices include:
Low water cut-outs
Temperature Control Devices
Aquastats
Flow Switches
High Limit Control Devices
What does the low water cut out do?
Shuts off the fuel supply to the burner if the water in the boilers falls below acceptable levels
The most common type of Low water cut out is a
float operated device
What are the two basic parts of temperature controls?
Zone Air Temperature, which is controlled by a TSTAT in that zone
Boiler Temperature, which is controlled by an AQUASTAT on the boiler.
Aquastats are ________ devices that react to water temperature.
Switching.
Define Reverse acting control
A strategy which prevents the start up of the circulating pump until the boiler water reaches a minimum temperature.
TRUE OR FALSE
The relief valve is a last resort to ensure the boiler does not exceed maximum working pressure.
TRUE
Safety Flow Controller Limits sense:
The velocity of the water in hydronic heating systems and interrupt the heating circuit if the velocity is too slow.
Mechanical controls use _____ or ________ action in the system to operate.
PRESSURES
MECHANICAL ACTION
The two types of expansion tanks are:
Compression Tanks
Diaphragm Expansion Tanks
What is the difference between a compression and diaphragm expansion tank?
Compression tank is physically much larger and has no internal diaphragm
The point where the expansion tank connects to the hydronic system is called the
Point of no pressure change
Line air scoops remove:
Air bubbles from the hydronic system
Automatic Air Vent Valves are:
Devices that allow air bubbles trapped in a hydronic heating system to bleed to atmosphere while maintaining pressure and preventing water from escaping.
An Automatic Air Vent Valve is a
Mechanical float valve
Pressure relief Valves prevent:
Unsafe internal water pressure in hydronic boilers.
Checking the valve mechanism is called a
POP TEST
or
TRY TEST
Pressure Reducing Valves feed ____________ city water into the hydronic heating system
Reduced-Pressure
City water supply pressure is between ____ PSIG and _____ PSIG
50-70 (350-480 kPA)
Normal hydronic heating operational range is
15 PSI to 30 PSI
What are the 3 basic types of gauges found in commercial hydronic heating installations?
Temperature Gauges
Pressure Gauges
Combination Temperature and pressure gauges.
Chemical treatment feed pots allow the operator to
introduce liquid chemicals while it is operating and under pressure.
