About Block Heaters
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A block heater is designed to warm an engine to ease and speed starting and vehicle warmup during cold weather. The most common type found is an electric heating element connected through a power cord, which is often routed through the vehicle’s grille. The block heater may replace one of the engine’s core plugs, or may be installed in line with one of the radiator or heater hoses. Block heaters that run on the vehicle’s own gasoline or diesel fuel supply are also available, and these require no external power source. The coolant is heated and circulated, usually by thermosiphon, through the engine and the vehicle’s heater core. Heaters are also available for engine oil so that warm oil can quickly circulate throughout the engine during startup. The easier starting results from warmer, less viscous engine oil and less condensation of fuel on cold metal surfaces inside the engine; thus a block heater reduces a vehicle’s emission of unburned hydrocarbons and carbon monoxide. A secondary benefit is that heat is also available more quickly for the passenger compartment and window defogging.
As a side not block heaters are also sometimes found on permanently installed systems using diesel engines to allow standby generator sets to take up load quickly in an emergency.
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History of Block Heaters
The head bolt heater was invented in around 1940 by Andrew Freeman of Grand Forks, North Dakota who received a patent for it on November 8, 1949. In 1951, Freeman received another patent on an improved head bolt heater. These early heaters replaced one of the engine’s cylinder head bolts with a hollow, threaded shank containing a resistive heating element. Before the block heater was invented, people utilized various means of warming engines before starting them, such as pouring hot water on the engine block or draining the engine’s oil for storage inside overnight. Some people even went as far as to shovel hot coals underneath their vehicle’s engine to achieve the same effect!
During the dawn of aviation in pre-war Northern Canada, aviators flew with flight engineers who were responsible for preparing the radial engines for shutdown and startup in order to mitigate the effects of sub-zero temperatures. The flight engineer was responsible for draining the oil into buckets at night, and pre-heating both the engine and the buckets of oil using a blanket wrapped around the engine and a device known as a blow pot, essentially, a kerosene torpedo heater (salamander heater) used several hours prior to flight.
Usage of Block Heaters
Block heaters are widely used in regions which have cold winter climates such as the northern U.S. as well as parts of Canada and Scandinavia. In colder climates, block heaters are often standard built-in equipment in new vehicles. In extremely cold climates, electrical outlets are often found in public or private parking lots, especially in multi-storey car parks. Some parking lots cycle the power on for 20 minutes and off for 20 minutes, in order to reduce electricity costs.
Research by the Agricultural Engineering Department of the University of Saskatchewan has shown that operating a block heater for longer than four hours prior to starting a vehicle is a waste of energy. It was found that coolant temperature increased by almost 20°C (36.0°F) degrees in that period, regardless of the initial temperature (4 tests were run at ambient temperatures ranging from −11°C/12°F to −29°C/−20°F); continued use of the heater for a further one or two, or more, hours achieved a mere 2 or 3 more degrees Celsius as conditions stabilized. Engine oil temperature was found to increase over these periods by just 5°C (9.00°F).
There are alternatives to a block heater that offer some of the same benefits. These include heaters attached to the engine’s oil pan, usually with magnets. Dipstick heaters can be installed in place of the engine’s oil dipstick. Heated blankets are available for the entire engine area, as well. A timer can be used with any of these heaters, so that it does not have to be left on all the time. This can help lower the electrical costs of using a block heater.
Some cars, such as the second generation Toyota Prius, pump hot coolant from the cooling system into a 3 litre insulated thermos-style reservoir at shutdown, where it stays warm for up to 3 days.
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Types of Block Heater and Engine Heater
Here are the pros and cons of the various different types of block heater, or engine heater.
External Element Block Heater (magnetic)
- Fixing: sticks flat against block/oil pan
- Installation: easy
- Pros: generic; second easiest to install; simple to transfer to another vehicle; medium to large heating element generates lots of heat
- Cons: not as efficient as frost plug style – some energy wasted heating the air around the element; may not be able to find a large enough flat area to place it; can be potentially jolted loose (though could be wire-tied to something to prevent it from falling off completely); block material must be ferromagnetic (won’t stick to aluminium)
External Element Block Heater (bolt on)
- Fixing: attaches flat against block
- Installation: easy to difficult (depending on location)
- Pros: medium to large heater element means lots of heat
- Cons: not as efficient as frost plug style – some energy wasted heating the air around the element; not easily transferable to another vehicle
Inline Heater3 (circulating)
- Fixing: splices into coolant hose (usually heater core hose), uses built-in pump to circulate coolant over its heating element and through the system
- Installation: moderate
- Pros: generic; much more effective than non-circulating inline style; probably best combination of effectiveness vs. difficulty of installation; fastest heater/defroster output
- Cons: larger size; more to go wrong (built in pump, thermostat)
Inline Heater (non-circulating)
- Fixing: splices into the (usually lower) coolant hose
- Installation: easy-moderate
- Pros: generic; can probably transfer to your next car.
- Cons: coolant in the hose gets hot, but the heat may not transfer well to the engine, particularly if there’s a closed thermostat between the heater and the rest of the system
Frost Plug Heater
- Fixing: replaces an existing frost plug; small to medium sized element warms coolant directly inside the block
- Installation: moderate – difficult (depending on location)
- Pros: traditional, proven OEM approach; efficient & effective
- Cons: not easily transferable to your next car if you should want to do that
Dipstick Heater
- Fixing: replaces your regular engine oil dipstick; the long, thin heating element warms your engine oil
- Installation: easy
- Pros: generic; easiest to install; also easiest to transfer to another car should the need arise
- Cons: smaller diameter element means lower heating capacity; probably the least effective of all types for heating (I saw one rated at 60 watts vs. 250-1000+ watts for other styles)
If you have any questions about any type of block heater please feel free to contact us.
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