Fuel oil does not "freeze" but rather "gels" or thickens to a soft wax. This begins to occur below 32F when the fuel starts to become "cloudy". As temperatures continue to drop (15F to 20F), wax or paraffin in the fuel crystallizes and separates from the oil. This wax can buildup and can clog filters and lines. Here are some ways to help prevent this from happening.
Step 1
The following steps are presented in order of least expense and level of difficulty to perform or operate, down to most expense and difficulty. Even if properly implemented, none of the steps (except for possibly the last) can be considered "guaranteed to work". If the correct combination of low temperature and length of time were to occur, eventually the cold would penetrate the insulation and cool the oil lines.
Step 2
Explain the problem to your oil dealer. He might be able to solve the problem for you. If he can't, try another dealer to hear any solutions they might have. Ask the home heating fuel dealer if they offer an "antifreeze" additive for sale or better yet, offers the additive already mixed in the fuel delivery vehicle's tank for those customers with outdoor fuel oil tanks.
Step 3
Install the oil filter indoors. The felt filtering media of an oil filter can quickly become clogged with wax crystals when installed outdoors in wintertime. Moving the filter indoors or near the furnace will get it into an area that is warmer than the outdoor temperature. Simply install a new filter and housing in the indoor location and be sure to remove and discard the filter media from the filter housing outside. Leaving the outdoor filter housing in place will do no harm.
Step 4
Wrap fuel lines with insulation that do not absorb moisture. Minimize the amount of pipe exposed to the cold temperatures by insulating or moving them inside when possible. Carefully seal all openings in the insulation to prevent entry of cold air.
Step 5
Install larger fuel lines. A larger diameter fuel line will withstand lower temperatures and longer low temperature exposure times before clogging when compared to the typical flexible copper 3/8" fuel lines.
Step 6
Add K-1 (kerosene) to the home heating fuel tank. This will lower the "freeze" point, as the freeze point for K-1 is about -20F. K-1 will burn successfully in just about any home heating fuel oil furnace, but the downside is the expense (K-1 has a 20% to 30% higher cost than oil) and fewer BTU's than the same amount of home heating fuel oil.
Step 7
Install an adhesive electric heat sheet to the outdoor oil tank. These are often installed on the bottom of the tank to make use of the fact that heat rises. The rising heated oil will thermally "stir" the contents of the tank. The cost of operating this heater will be reflected in your electric bill.
Step 8
Build a room around the tank. While this is the most expensive solution, it will almost always work. Add a small heat source, or if connected to the home, a small amount of airflow between the two to prevent gelling of the fuel.
Tips
- Oil heat dealers are independent. Choose your dealer by weighing his ability to provide oil at a competitive price, tune up service fees, emergency services (if provided) and in this case, if he has fuel additives available to lower the freeze point of the fuel oil.
- Other issues might just happen to arise in cold weather months that may lead homeowners to believe the fuel or lines have frozen are:
- Clogged fuel filters. These should be changed annually.
- Sludge buildup. Add 1 or 2 gallons of denatured alcohol to the fuel tank when full. Denatured alcohol (sometimes called camping stove fuel or marine fuel) will breakdown sludge buildup and prevent its formation if used annually. Denatured alcohol is popular for its solvent properties and as a result is toxic. Because of it's toxicity, it must not be ingested.
- Clogged nozzles, excessive soot buildup, failed pumped, etc. Professionally maintained and tuned oil fired furnaces should not suffer from most of these issues.
Warnings
- Never try to warm any part of a fuel line with an open flame.
- Never disconnect or cut fuel lines, open filter bowls, loosen compression fittings, etc. without first shutting off the fuel supply at the tank.
- Do not allow fuel to spill when working on the tank or lines. Be prepared to capture all fuel that may drain from the lines when opened.
- Check with your oil heat dealer or town before attempting these steps. Local laws and rules may limit what you can do to the heating system.
- Fuels spills are considered hazardous materials (hazmat). They must be prevented at all costs. When spills occur they almost always require professional clean up and may need to be reported. This can be an extremely expensive procedure and may not be covered by insurance.
