Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
Ask a Question or Search InspectAPedia
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 PREVENTER VALVE, HEATING SYS
BACKFLOW PREVENTER, HEATER WATER FEEDER
BACKUP HEAT for HEAT PUMPS
BANGING HEATING PIPES RADIATORS
BIOGAS PRODUCTION & USE
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BLUE vs YELLOW COMBUSTION FLAMES
BOILER CHEMICAL TREATMENTS
BOILER COMPONENTS & PARTS
BOILER CONTROLS & SWITCHES
BOILER LEAKS CORROSION STAINS
BOILER LEAKS, HOW TO LOCATE
BOILER NOISE SMOKE ODORS
BOILER OPERATING PROBLEMS
BOILER OPERATION DETAILS
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
DUCT SYSTEM & DUCT DEFECTS
DUCT INSULATION - Asbestos Paper
DUCTS - Asbestos Transite Pipe
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
FURNACE CONTROLS & SWITCHES
FURNACE EFFICIENCY, HIGH vs MID
FURNACE HEAT EXCHANGER LEAKS
FURNACE OPERATION DETAILS
FURNACE OPERATING TEMPERATURES
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 - 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
HOT WATER IMPROVEMENT
INSULATION INSPECTION & IMPROVEMENT
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
LP & Natural Gas Safety Hazards
MANUALS & PARTS GUIDES - HVAC
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 GASES SMELLS, DIAGNOSIS & CURE
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
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
SAFETY, HEATING INSPECTION
SAFETY,HOME HEATING TIPS
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
THERMOSTATIC EXPANSION VALVES
Transite Pipe Chimneys & Flues
VIDEO GUIDES: Heating System Videos
VIDEO GUIDES - InspectAPedia.com
WATER SOFTENERS & CONDITIONERS
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
Waxing or jelling heating oil: Here we define and explain heating oil waxing, gelling, or pour point problems which can lead to loss of heat when oil tanks are located outdoors in freezing climates.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Heating Oil Waxing, Gelling, or Clouding: a cause of oil piping or filter clogs and loss of heat - diagnosis and prevention of heating oil problems
Also see OIL FUEL TYPES & CHARACTERISTICS where we describe and compare the properties of heating oil, diesel oil, kerosene, and other petroleum products. This website answers most questions about all types of heating systems and gives important inspection, safety, and repair advice. Criticism and content suggestions are invited from heating service technicians, home inspectors, and home owners.
When heating oil does begin to gel, and before it has become actually too viscous to flow at all in the heating system oil piping, wax particles (wax platelets or little spheres of wax or in some articles, alkane "wax crystals") have already begun to form in the fuel.
The wax platelets form first from the long hydrocarbon chains which are a component in the heating oil (or diesel fuel). It is these waxy particles that can clog an oil line or even a oil fired heating boiler, furnace, or water heater.
Our photo (above left) shows an outdoor heating oil storage tank at a Maine home - certainly in an area where heating oil waxing in an outdoor tank would be a real risk.
At what temperature point does home heating oil or No. 2 heating oil begin to cloud, wax or gel?
A Definition of the Pour Point for Home Heating Oil - No. 2 Heating Oil?
The pour point for heating oil is the lowest temperature at which the oil or fuel will continue to flow, that is it's viscosity has not increased or it has not become clogged with waxy particles. (Products sold as additives for home heating oil are called "pour point depressants" because they push the pour point temperature lower - that is, you can continue to use the treated heating oil or diesel fuel down to lower temperatures than otherwise.
An alternative to using pour point depressants is to purchase a cold-weather mix of fuel such as a mix of No. 2 diesel combined with less viscous Kerosene, or one can purchase a fuel or heating oil which has already been treated.)
A Definition of The Cloud Point for Home Heating Oil - No. 2 heating oil:
Heating oil or diesel fuel waxing or clouding or gelling begins to occur at about -9 degC or about 16 degF.
The cloud point for heating oil is defined as the temperature at which a cloud of wax crystals first appears in a fuel sample that is cooled following the procedure in ASTM Standard D2500. In more practical words, home heating oil will probably flow through the oil piping, filter, and oil burner without an operating problem down to about -9 degrees Centigrade or 16 degrees Fahrenheit.
A Definition of the Wax Point or Gel Point for Home Heating Oil - No. 2 Heating Oil (or diesel fuels)
The gel point for home heating oil (No. 2 Heating Oil or Diesel Fuel) refers to the fuel or heating oil becoming so viscous that it "gels" and will no longer flow at all by gravity nor by pumping through the oil lines or heating equipment. What we call the gel point or wax point of home heating oil is either a temperature lower than the cloud point for heating oil, or it may occur at a higher temperature if the oil is exposed to that temperature long enough.
The wax point or gel point of heating oil means that there has been sufficient formation of wax platelets or crystals that heating oil piping lines or oil filters will become clogged.
Here are the gel point temperatures for heating oil or diesel fuel: Heating oil or diesel fuel gelling or waxing to the point at which the fuel will no longer flow is 5? to 10?F below the cloud point.
The pour point, cloud point, gel point or wax point temperatures given for No. 2 home heating oil, which is similar to diesel fuel used in vehicles, are estimates. The actual gelling or waxing of home heating oil will occur as a function of not only the temperature to which the heating oil (and oil tank) are exposed, but the duration of that exposure. That is to say, if temperature dips below freezing for a few hours and then rises, you may not see any troublesome waxing or gelling.
We have observed that an outdoor home heating oil storage tank exposed to about 10 degrees F for several hours or more may produce gelling or waxing in the heating oil which can stop the heating system from working.
Where in the oil tank, storage, piping, and filter does waxing or gelling first occur and how does this lead to a loss of heat in a building?
The clouding and then waxing of the heating oil will occur where the oil has the least thermal mass and is most exposed to cold conditions. Often this is at the oil piping line exiting at the bottom of an outdoor heating oil tank since this small diameter pipe has much less volume and mass than the larger and perhaps mostly full tank of heating oil.
All petroleum distillate products contain waxy materials, which, at low temperatures, can crystallize and plug fuel filters. So a heating system may go out of service because it's filter has become clogged with waxy particles even though there was still oil flow in the heating oil lines.
At longer exposure to cold temperatures or exposure to lower temperatures the amount of wax forming inside the heating oil in the oil tank can prevent heating oil from flowing out of the tank. Some writers refer to the observation that waxes settle to the bottom of the oil storage tank.
How oil line piping design affects cold weather operation of outdoor heating oil storage tanks
If the oil piping is connected to the bottom of the oil tank it will certainly be blocked by oil waxes settling at the tank bottom. The oil piping in this location is also easily blocked by sludge in the oil tank - see OIL TANK SLUDGE.
If oil piping is taken off of a tapping at the top of the oil tank, as is good practice with outdoor installations in freezing climates, the piping may still include a "low loop" or bend down towards the tank bottom, depending on where the heating equipment is located with respect to the oil tank position and elevation. A low loop in the oil line may accumulate waxes pulled out of the heating oil tank.
Alternatively, oil in the oil piping may gel and cause a blockage because of the line's exposure to very cold conditions because the oil piping has less thermal mass than the oil tank itself.
Wax settlement in heating oil tanks: Even if the oil line itself is not fully blocked by waxed or gelled heating oil, if enough wax sphericules or platelets flow into the heating oil filter the filter may become blocked by waxes and thus starve the oil burner for oil until it goes off on reset. This can be a tricky problem to diagnose since with the heat off for a while but with the oil filter canister sitting indoors in a location that is still much warmer than outdoor temperatures, it's possible that the service technician will arrive and successfully simply re-start the oil burner since the waxes in the filter canister may have returned to their liquid state.
Waxing causes change in heating fuel BTU's: Waxing of fuels in an oil storage tank (or in a vehicle fuel tank) also causes an operating difference in the boiler, furnace, water heater, or vehicle, since the chemistry and thus the energy capacity of the remaining liquid fuel will have been changed by loss of the longer hydrocarbon molecules which have left it to form settled wax spheres.
How does Biodiesel differ from Petroleum Based Fuel with respect to gelling and waxing?
Biodeisels have a higher gel point than petroleum-based diesel because they contain molecules that form large spheres or crystals of wax at temperatures below 40 degF.
Anti-gel additives (also called pour point depressants) have not been shown to be effective with biodiesel fuel. Therefore oil companies in areas where biodiesel is sold recommend that biodiesel (B100) should not be used at temperatures below 40 Deg. For that a blend of B100 biodiesel and 50% petroleum-based diesel be used in the vehicle's fuel tank.
Portions of this article paraphrase a biodiesel article at http://www.staroilco.net/BIODIESEL_07.html]
How pour point depressants work:
How pour point depressant and anti wax-settling additives work is not clear, but some writers including in patent applications for pour point depressant and anti-waxing heating oil and diesel fuel additives have argued that they work by matching alkanes in the heating oil or vehicle fuel fuel to alkyl or alkylene chains in the pour point depressant additive in order to affect the formation of wax particles.
[Paraphrasing patent description for a pour point depressant at http://www.freepatentsonline.com/5906663.html
What are the Different Petroleum-based Fuels and What are their Characteristics?
The differences among these fuels, arranged in our list from "lightest" to "heaviest" are in the types of hydrocarbon chains that are distilled out of the crude oil during refining (and also that some of these fuels may contain other additives.
What this all means is that the heavier petroleum based fuels (higher numbers) have longer hydrocarbon chains than the lower number fuels, they have more BTUs per gallon, they will be more viscous (and often dirtier or will contain more contaminants including environment-polluting sulphur).
It is not helpful to order and burn Kerosene #1 over #2 fuel oil except in outdoor aboveground oil tanks in areas subject to temperatures below 16 degF.
[From the following reference, edited: http://www.impalassforum.com/vBulletin/showthread.php?t=184909]
Problems With Heating System Reliability When Heating Oil Additives are Used or Low-Level Oil Tanks are Filled
When we serviced and installed heating equipment we often recommended use of heating oil additives to remove small amounts of water or sludge (OIL TANK SLUDGE) in oil storage tanks, or to act as a pour point depressant for outdoor aboveground oil storage tanks. But while these are good products, things didn't always go well.
We have seen problems with rapid clogging of heating oil filters and thus loss of heat from sludge that was brought out of an old oil tank and into the filter when we added a pour point depressant to our heating oil. The product also claimed to break up sludge - which sounds good if the oil lines are old and perhaps partly blocked with sludge.
But in this case the combination of use of a heating oil additive with a "de-sludger" combined with the sludge agitation up from the bottom of the oil tank during filling of a nearly empty oil tank led to loss of heat from filter clogging. Oil companies may recommend that if you have to fill an old maybe sludgy oil tank that was nearly empty, turn off the boiler or furnace for a few hours to let the sludge return to the bottom of the tank (and be sure your heating equipment is fed fuel from the tank top tappings not from the tank bottom tapping.
In emergency when no home heating oil is available, one can use diesel fuel or kerosene to run the boiler or furnace.
An example of an oil additive to prevent gelling is at http://www.ezoil.com/Products/Hot_Shot.html
OR you can purchase a kerosene/heating oil mix (more costly) to lower the waxing temperature of your heating oil
Frequently Asked Questions (FAQs) about the waxing or gelling of home heating oil, fuel oil, or diesel oil & the use of pour point depressants
Interesting information. My furnace has been cutting out and each time the service techs replaced the filters and nozzle. The filters came out of the canister looking like balls of wax.
Waxy stuff in the oil filter canister may be telling us that your oil tank has a sludge problem. I agree that an indoor oil storage tank ought not to be seeing actual heating oil waxing.
I have an indoor ( basement ) Oil tank. It is about 30 years old and I'm getting a lot of sludge in bottom of filter canister. Can I use diesel fuel watger remover additives without harming my burners and nozzle? - Charles Lucas 1/2/13
Question: we installed Scully Snorkels but keep having air bubbles and loss of prime in the oil tank piping
WE REPLACED OUR TWO 275 GAL OIL TANKS WITH NEW SCULLY SNORKELS BECAUSE WE HAD BEEN LOOSING THE PRIME,KEPT GETTING AIR BUBBLES, SO OUR SERVICE GUY REPLACED THEM. RUN GOOD FOR A FEW DAYS AND LAST NIGHT SAME PROBLEM. I MIGHT ADD I DID ADD AN ADDITIVE BEFORE GETTING OIL LAST WEEK. I PRIMED ABOUT A 1/4 OF A GALLON AND IT RAN UNTIL REACHING TEMPERATURE BUT WHEN IT CAME TIME TO IGNITE AGAIN SAME PROBLEM. PRIMED ABOUT ANOTHER QUART AND IT SEEMS TO BE RUNNING. I MIGHT ADD THE TEMPERATURE DID GO DOWN TO THE 20S VS, THE 30S WHEN IT RAN FINE. ANY SUGGESTIONS. THANKS YOUR ARTICLES ARE GREAT.
Details about the Scully Snorkel and company contact information are at OIL TANK SLUDGE.
Questions & answers or comments about the gelling, clouding, or waxing properties of No. 2 home heating oil.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.