Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
AFUE DEFINITION, RATINGS
AGE of AIR CONDITIONERS & HEAT PUMPS
AGE of HEATERS, BOILERS, FURNACES
AIR CONDITIONING & HEAT PUMP SYSTEMS
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER / BLOWER UNITS
AIRBOUND HEAT SYSTEM REPAIRS
ANODES & DIP TUBES on WATER HEATERS
ANTIFREEZE for BOILERS
ANTI SCALD VALVES
APPLIANCE EFFICIENCY RATINGS
ASBESTOS IDENTIFICATION IN buildings
BACKDRAFTING HEATING EQUIPMENT
BACKFLOW PREVENTERS, HEAT
BACKDRAFTING HEATING EQUIPMENT
BACKUP HEAT for HEAT PUMPS
BIOGAS PRODUCTION & USE
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BLUE vs YELLOW COMBUSTION FLAMES
BOILER PRESSURE & TEMPERATURE SETTINGS
BOOKSTORE - InspectAPedia
BTU USAGE MONITORS
BUILDING SAFETY HAZARDS GUIDE
CAPACITORS for HARD STARTING MOTORS
CARBON DIOXIDE - CO2
CARBON MONOXIDE - CO
CHEMICAL TREATMENTS for BOILERS
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CHIMNEYS & Flues - Asbestos Transite Pipe
CHINESE DRYWALL HAZARDS
CIRCULATOR PUMPS & RELAYS
COOL OFF HEAT, Thermostat Switch
COMBUSTION AIR for TIGHT buildings
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
COMPLETE COMBUSTION, Stoichiometric
CREOSOTE FIRE HAZARDS
Curved Brick Chimneys - Sulphation
CONDENSING BOILERS/FURNACES DAMAGE
CONVECTOR HEATERS - HYDRONIC COILS
DEFINITION of Heating & Cooling Terms
DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DIRECTORY of OIL TANK EXPERTS
DRAFT HOODS - gas fired
DRAFT MEASUREMENT, CHIMNEYS & FLUES
DRAFT REGULATORS, DAMPERS, BOOSTERS
DUCT SYSTEM & DUCT DEFECTS
DUST, HVAC CONTAMINATION STUDY
DUST SAMPLING PROCEDURE
ELECTRIC HEAT, DIAGNOSIS, REPAIR
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRICAL POWER SWITCH FOR HEAT
EVAPORATIVE COOLING SYSTEMS
FAN, AIR HANDLER BLOWER UNIT
FAN AUTO ON Thermostat Switch
FAN, COMPRESSOR/CONDENSER UNIT
FAN CONVECTOR HEATERS - HYDRONIC COILS
FAN LIMIT SWITCH
FILTERS, AIR for HVAC SYSTEMS
FILTERS, OIL on HEATING EQUIPMENT
FIRE SAFETY CONTROLS
FIREPLACES & HEARTHS
FLAME COLOR, BLUE vs YELLOW COMBUSTION
FLOODED HEATING EQUIPMENT REPAIR
FLOODED WATER HEATER REPAIR
FLUE SIZE SPECIFICATIONS
FLUE VENT CONNECTORS
FREEZE-PROOF A BUILDING
FUEL OIL TYPES & CHARACTERISTICS
FUEL UNIT, HEATING OIL PUMPS
GALVANIC SCALE & METAL CORROSION
GAS BURNER Flame & Noise Defects
GAS FIRED WATER HEATERS
GAS PIPING, VALVES, CONTROLS
GAUGES ON HEATING EQUIPMENT
GEOTHERMAL HEATING SYSTEMS
HEAT EXCHANGER LEAK TEST
HEAT LOSS in BUILDINGS
HEAT LOSS DETECTION TOOLS
HEAT LOSS INDICATORS
HEAT LOSS PREVENTION PRIORITIES
HEAT LOSS R U & K VALUE CALCULATION
HEAT PUMPS, DIAGNOSIS, REPAIR
HEAT TAPES & CABLES on Roofs for Ice Dams
HEATING COST FUEL & BTU Cost Table
HEATING COST SAVINGS METHODS
HEATING LOSS DIAGNOSIS-BOILERS
HEATING LOSS DIAGNOSIS-FURNACES
HEATING OIL CLOUD WAX GEL POINT
HEATING OIL EXPOSURE HAZARDS, LIMITS
HEATING OIL - OLD, USEABLE?
HEATING OIL PIPING TROUBLES
HEATING OIL SHELF LIFE
HEATING OIL SLUDGE
HEATING OIL USAGE RATE
HEATING SMALL LOADS
HEATING SYSTEM INSPECT DIAGNOSE REPAIR
HEATING SYSTEM INSPECTION DETAILS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
HIGH EFFICIENCY BOILERS/FURNACES
HOT WATER HEATERS
HOT WATER IMPROVEMENT
INSULATION INSPECTION & IMPROVEMENT
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
LP & Natural Gas Safety Hazards
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
MOTOR OVERLOAD RESET SWITCH
Natural Gas Combustion Products
NO HEAT - BOILER
NO HEAT - FURNACE
NOISE / SOUND DIAGNOSIS & CURE
NOISE AIR CONDITIONER / HEAT PUMP
NOISE, DUCT VIBRATION DAMPENERS
NOISE, HEATING SYSTEMS
NOISE, WATER HEATER
ODORS FROM HEATING SYSTEMS
OIL BURNER FUEL UNIT
OIL BURNER INSPECTION & REPAIR
OIL BURNER NOISE SMOKE ODORS
OIL BURNER NOZZLE & ELECTRODES
OIL BURNERS, RETENTION HEAD
OIL BURNER SOOT & PUFFBACKS
OIL FILTERS on HEATING EQUIPMENT
OIL FILTER MISSING
OIL FUEL TYPES & CHARACTERISTICS
OIL HEAT FIRE SAFETY CONTROLS
OIL LINE CLOGGING FIX
OIL LINE QUICK STOP VALVES
OIL LINE SAFETY VALVES
OIL ODORS, LEAKY OIL TANK PIPING
OIL PUMP FUEL UNIT
OIL SPILL CLEANUP / PREVENTION
PLASTIC HEATER VENT
PULSE COMBUSTION HEATERS
PRESSURE REDUCING VALVES
PRESSURE REGULATOR, WATER
PUFFBACKS, OIL BURNER
PUMPS, PONY PUMPS
RADIANT HEAT Floor Mistakes to Avoid
RADIANT HEAT TEMPERATURES
RADIANT SLAB FLOORING CHOICES
RADIANT SLAB TUBING & FLUID CHOICES
REFRIGERANTS & PIPING
RELIEF VALVE LEAKS
RELIEF VALVES - TP Valves on Boilers
RELIEF VALVES - STEAM TP VALVES
RELIEF VALVES - Water Heaters
RELIEF VALVES - Water Tanks
Reset Switch - Heater Primary Control
Reset Switch Broken - Quick Repair
RESET SWITCH - ELECTRIC MOTOR
Reset Switch - Stack Relays
SAFETY HAZARDS & INSPECTIONS
SAFETY HAZARDS GUIDE
SAFETY, HEATING INSPECTION
SAFETY RECALLS, Chimneys, Vents, Heaters
SOLAR HEATING SYSTEM DESIGNS
SOLAR HOT WATER HEATERS
SOOT on OIL FIRED HEATING EQUIPMENT
SPILL SWITCHES - Flue Gas Detection
SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS
STACK RELAY SWITCHES
STAIN DIAGNOSIS on BUILDING INTERIORS
STEAM HEATING SYSTEMS
Thermal Expansion Cracking of Brick
THERMAL EXPANSION of HOT WATER
THERMAL EXPANSION of MATERIALS
THERMAL IMAGING, THERMOGRAPHY
THERMAL IMAGING MOLD SCANS
THERMAL MASS in BUILDINGS
THERMAL TRACKING & HEAT LOSS
THERMOSTATS, HEATING / COOLING
Transite Pipe Chimneys & FlueS
VIDEO GUIDES: Heating System Videos
VIDEO GUIDES - InspectAPedia.com
WATER HEATER SAFETY
WATER HEATERS for HOME HEATING USE?
WATER HEATER NOISES
WATER HEATER SCALE - De-Liming Procedure
WATER HEATER SCALE PREVENTION
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
Here we explain where and how and to what numbers the pressure & temperature are set or controlled on hydronic heating boilers. We also describe where and how the pressure & temperature is controlled on residential steam boilers. We include notes and links to detailed articles about the operation and use of controls on boilers, furnaces, and water heaters.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
What Are the Normal Hot and Cold Operating Pressures of Residential Hydronic (hot water) Heating Boilers?
This website answers most questions about all types of central Heating System r Controls on central heating systems to aid in troubleshooting, inspection, diagnosis, and repairs.
.On a residential heating boiler the automatic water-feeder/pressure reducing valve that automatically provides makeup water to the heating boiler if pressure drops below 12 psi. So 12 psi is the typical "cold" pressure for residential boilers.
12 psi is for typical U.S. / Canadian residential heating systems normal cold temperature starting pressure. U.K. and european heating systems should be pressurized to between 1 and 1.5 bar - cold.
20 psi is typical for U.S. / Canadian residential heating systems normal hot operating temperature, up to just under 30 psi, depending on the high-limit temperature setting on the boiler limit control. If we set the boiler high-limit much over 210, on many residential systems the system pressure will exceed 30 psi and we'll see water leaking from the pressure/temperature relief valve - ultimately an unsafe condition.
If your building is taller than two floors, the installer may have needed to boost the starting "cold" water pressure for your boiler to overcome the hot water distribution piping head pressure - otherwise your heating circulators may not be able to circulate hot water.
Causes of Variation in Pressure in Hydronic Heating Systems
Hot Water Boiler Temperature Settings
Remember that the building THERMOSTATS set the desired temperature in the occupied spaces in building, not the actual temperature in the heating boiler or furnace itself. In most heating systems, turning up the thermostat simply causes the boiler or furnace to turn on.
The temperature at the boiler or furnace is controlled by local safety devices mounted right at that equipment, such as the heating boiler Aquastat shown at left.
Hot water heating boiler normal pressure ranges as read on the pressure gauge, are described in this article, below.
The means by which a hot water heating boiler's pressure is set or controlled are described in this article below at Where do I Set the Heating Boiler Operating Pressure?
Steam Boiler Temperature & Pressure Settings
Steam boiler temperature, pressure setting controls: For details how, to what number, and on what controls the steam boiler pressure settings and pressure readings are set see:>
Warm Air Furnace Temperature Settings
Furnace temperature setting controls: Warm air furnace temperatures are controlled at the FAN LIMIT SWITCH.
See FURNACES, HEATING for a complete discussion of warm air heat.
Additional furnace controls include register and duct dampers - ZONE DAMPER CONTROLS
Pressure and Temperature gauge on hot water or hydronic heating boilers: this gauge displays the heating boiler internal pressure and temperature.
Typical pressure for a residential boiler serving a two story home would show 12 psi cold, and less than 30 psi hot. Over 30 psi boiler pressure will cause the pressure relief valve to open.
Typical operating temperature settings on a boiler call for a Low temperature (boiler cut-in) between 120 and 160 degF.
Typical operating temperatures on a hydronic boiler call for a high temperature (boiler cuts off) of 180-200 degF.
If we set the boiler upper temperature too high over 200 degrees F. we're at risk of spilling at the pressure temperature relief valve. If we set the boiler upper limit too low, there may be no relief valve problem but under some conditions we may reduce the operating efficiency of the boiler and heating system, thus increasing heating costs. See AQUASTAT CONTROL Functionsfor details.
The temperature/pressure gauge may help in checking for normal conditions before and during boiler operation.
However the gauge can be wrong!
This gauge shows a typical in-boiler pressure of under 20 psi, and a temperature of about 190 degF. (The boiler had just cut off on a heating cycle.)
For more diagnostic aid on finding the cause and executing the cure of abnormal heating boiler pressures see
The operating pressure of a heating boiler (hot water or hydronic heat) is read at the pressure and temperature gauge (see above) and controlled by
The building THERMOSTATS do not normally directly control the temperature or pressure in the heating boiler. The thermostat sets the desired temperature in the building, but to the heating boiler it is working as a simple "on" - "off" switch, turning the boiler "on" until the thermostat is satisfied (the building is warm enough), then turning the boiler "off".
You should see similar settings on the pressure gauge (at left in our photograph) and on the steam pressure control switch (the gray box at right in our photo) on your boiler.
Because a steam boiler makes heat by producing steam - by boiling water, at sea level, the temperature at the boiler will be boiling or 212 degF.
The steam boiler pressure is controlled by the Pressure Switch, Steam Boiler - the gray box shown in our photo at left and in closeup at our photo, below.
The controls in this photo are discussed in more detail at STEAM HEATING SYSTEMS
Residential steam heating systems are almost always designed to operate at very low pressures, perhaps around .5 psi - that' s 1/2 of one psi. Click to enlarge and you can see the actual pressure settings on the steam boiler control shown at left.
If your residential steam boiler is operating at higher pressures (take a look at the dial setting on your Pressure Switch, Steam Boiler) , that may be an indication that a service technician or owner was having trouble getting heat distributed through the building. Rather than finding and fixing the problem, someone is trying to "force" the steam around the system.
An experienced steam heat service technician will look at the operating pressure of your steam heating boiler and if it is not set to a normal level, the technician will look for the reason. Examples of problems that can affect the flow of steam heat through the system, leading to attempts to over pressurized the system include
Questions & answers or comments about heating system operating pressures, temperatures, and controls for hot water and hot air heating systems and for warm air furnace systems
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Related Topics, found near the top of this page suggest articles closely related to this one.