Engine Block Heaters: Quick Starts for Standby Power

Dealers and genset providers agree that diesel engine block heaters are a must-have for standby power applications and offer critical operating tips most end users never hear about.

Editor’s note: This article originally appeared in the July/August 2005 issue of Business Energy.

Typically they don’t land on the desk of top decision-makers or lend themselves to innovative applications. Andy Rudderham, vice president of sales for Total Systems Ltd. in Mississauga, ON, says equipment dealers and genset packagers are the only ones likely to get fired up about them. But whether you call them block heaters, water jacket heaters, or engine preheaters, they’re essential to getting diesel-fueled gensets up-and-running at full power in the 10 seconds that are standard for emergency power applications.

Wayne Bass, market manager, engine and industrial distributors, for Kim Hotstart—which supplies heaters to Generac Power Systems Inc., Katolight Corp., Detroit Diesel, Caterpillar, and Kohler, among others—reminds us that coming online at an engine’s rated RPMs and assuming a full load within the 10-second window specified in NFPA standard 110 and Canadian CSA 282 requires maintaining engine temperature between 100°F to 120°F. Bass also maintains that, in addition to easier starts, block heaters save engine warmup time and help reduce fuel, plus engine wear—90% of which he attributes to low water jacket temperature.

Scott Phillips, technical communicator for the Power Systems Division of Wagner Equipment Co., a Caterpillar distributor in Albuquerque, NM, agrees. “On large engines, where the pistons may be 6 inches across, starting dry and cold makes for wear. Starting at 100°F to 120°F you’ll have oil pressure, which means less metal to metal.”

All things considered, says Rudderham, block heaters don’t get much attention because they’re standard. Total Systems Ltd. is a dealer for Generac Power Systems—among other land and marine engine manufacturers—and services approximately 3,000 gen set installations nationwide, along with standby equipment it maintains in its own building. “We’re in the generator business,” says Rudderham, “so we wouldn’t dream of having a generator set without a block heater and without proper maintenance to assure that the engine starts when we need it to. When the power goes out, our phones light up like Christmas trees.”

Total Systems’ emergency power is supplied by a Generac model SD080 diesel generator, 60 kW (347/600 V three-phase), which is in a Level 11 sound-attenuated enclosure and equipped with an 1,800-W, 120-V Kim Hotstart block heater, a double walled basetank for 36+ hours of runtime, a battery blanket, and a remote annunciator panel for indoor annunciation of any faults. Manager of technical services Mike August considers the 1,800-W heater standard for the size of the gen set and, although the unit is located outside the headquarters building, because it’s enclosed, no extra block heater fire power was required. “If the unit were sitting out in the middle of a field where it wasn’t sheltered from wind, for example, you certainly would want to beef up the heater or add a second one,” says August.

“An engine block heater is not important until it doesn’t work,” says Mike Dauffenbach, eastern regional manager for Katolight Inc., which uses Kim Hotstart heaters on gen sets it packages. “There are all kinds of people out there operating engine generator sets, and jacket water heaters are not a big issue. Except when they don’t work.”

Bass agrees, “We don’t hear horror stories from clients as much as apprehension. In the fall we start to get calls—from hospitals, for example, where a heater has stopped working and they need us to send a new element right away—it’s a pretty common experience.”

The tank-type block heaters Kim Hotstart manufactures are designed to heat and circulate coolant through the entire engine block by way of thermal siphon action. The heated coolant rises, seeking the path of least resistance, and pushes cold water out to be heated. A thermostat turns the heater on and off to keep the coolant at the right temperature.

“Some people use heaters that are meant for automotive applications,” says Dauffenbach. “These are designed to be plugged in when it’s cold and then unplugged, and when they’re operated in automatic position on a stationary engine, they don’t have the life of an industrial-grade heater. The fact is that any heater that is sized properly will keep the block warm. And the way we size the heaters depends on the application. If we’re sizing for an ambient temperature that doesn’t go below zero, we use one size, but if we’re sizing for something here in Minnesota where it goes 20 below, we use a larger heater. Otherwise the heat will dissipate faster than the heater can make it. In the end, what it boils down to is that the thermodynamics of sizing a heater are based on the amount of water you want to heat, the surface area of the engine, and the temperature differential.”

“A diesel engine is a cold-blooded animal when the outside temperature is extremely cold,” says Bryon Carlson, project manager at Generac Power Systems, which also uses Kim Hotstart heaters. “Not only is the diesel fuel cold, but so is the air coming in from outside. The idea is to heat the block to allow combustion to take place at a faster rate on initial start up. You can’t do a whole lot about the air unless you have air heaters, but you can do something to keep the area around your cylinders warm, which allows your combustion to happen much more reliably. We send gen sets to Puerto Rico and South America without block heaters, places where the temperature is routinely 75°F to 80°F or higher, but we have a lot of customers along the gold coast in Florida and in warm spots in California, and they all have block heaters.

“As most generator manufacturers, we size by cubic inch of engine. Watts per cubic inch is the rule of thumb. We give customers a choice, from what’s called normal heating, which is three watts per cubic inch, up to what’s called an Arctic package, which is five watts per cubic inch, meaning that you get that much more watt per cubic inch of input of heat. If you go with a little bit higher heater, you’ll end up drawing a little more electricity, but you’re going to retain your heat better. Given the same application, a smaller heater is likely to run longer. But the fact is most of our customers are dealers who have been in the market and are quite knowledgeable. We ship the gen sets with the heaters already on, plumbed, and tested.”

“At Katolight, every engine generator that we have in our catalog has a jacket water heater on it as a standard item,” says Dauffenbach. “And this is because we want the installation to work reliably. The single-phase heater is by far the most common heater we install. But if we’re supplying a large engine, where we might have a couple of 5,000-W heaters, it’s best to use 240 V because you can draw less amps with a higher voltage and keep wire size down. If we get into a case where we have a heavy-duty industrial application, a three-phase heater is a better option, a 208 V or 480 V. The big advantage of a three-phase heater is it’s much cheaper to operate.

“If a pump makes circulation more reliable, then we put a pump on—typically on large 12- and 16-cylinder engines [Kim Hotstart recommends forced circulation on engines 20 L or larger]. We also use pumps on engines where the thermal siphon doesn’t work well because of the geometry of the engine. If you have an engine that’s compartmentalized, the thermal siphon doesn’t work very efficiently. Plus you have two heaters, one on each side of the V, and a pump will circulate the water better. This kind of decision-making is specific to the engine manufacturer.”

Phillips says that the Wagner CAT dealership installs valves on larger engines “You can shut the valve on both sides, and when it comes time, all you have to do is drain whatever is in the hoses and the tank of the block heater. Otherwise you’re going to have to drain the entire cooling system.

“There are other applications besides standby situations where block heaters are important,” says Phillips. “We have customers who run aggregate pits where they make gravel and road product. They’ll run a nighttime generator to keep their asphalt warm, and they have jacket water heaters on the engines because they make for less wear and tear on startup.

“Another application is where low emissions are a factor. Diesel engines tends to over-fuel and when the combustion temperature is low the fuel isn’t burned as well, which produces more raw smoke. When the combustion temperature is hotter it lowers your emissions.”

Although engine block heater manufacturers typically issue recommendations that match heater size to the size of an engine, Rudderham says some block heaters still aren’t spec’d properly. “From a practical standpoint, the further north we go the more often we find block heaters undersized. The specs may call for 1,500 watts, but to really keep the block as warm as it needs to be for reliable starting, what’s needed is 2,500 watts. If we discover this upfront, we install a new heater off the shelf before the engine goes onsite. Other times we find out the hard way. We might not know where the generator is ending up, for example, and when we get called for a startup, we’ll discover it’s been installed where the air is colder than normal, and during testing the engine’s hard starting.

“The other thing you’ll find is that sometimes engineers don’t know. They have their standard specs, and sometimes they don’t look as closely as they should at block heaters. They specify, ‘Must have block heater,’ but what does that mean—500 watts or 5,000 watts? Depending on where you are, one would be more appropriate than another. Also it’s logical that people typically bid to minimum specifications because they don’t want to be priced out of the competition. But once the job is awarded the challenge becomes how to make what’s been purchased work. I don’t think people intentionally cut corners. It’s more a function of misapplication and misinformation.”

But if block heaters are such no-nonsense equipment, why does Kim Hotstart routinely get cold-weather calls?

Block heater maintenance, which most gen set manufacturers suggest should be no big deal, turns out to be a culprit. “With proper maintenance and care,” says Rudderham, “these heaters should last indefinitely. But it’s like everything else. If you abuse them—if they’re undersized and they’re running all the time—it’s not uncommon that when we service a gen set we’ll replace the block heater. Which means that while the ultimate end user isn’t involved in the initial selection process, they’re likely to be pulled in if something doesn’t go right. Customers think they’re getting something that works, and they don’t like discovering that they have to pay someone like us to come out and advise them on a better way of doing things.

“It’s like batteries. Just because a generator has batteries doesn’t mean they’re any good. Are they the right size? Do they have enough cold cranking amps? It’s also not uncommon for the heater to be hooked up incorrectly, like a 240-volt block heater hooked up to 120-volt power.”

Not hooking the unit up at all can also be a problem. “In any type of cold weather climate it’s just plain and simple that if a diesel engine is cold, it won’t start,” says Carlson. “So customers shouldn’t try to save power by turning it off.” But they do, says August. “They figure they’re going to save $10 on their summer utility bill. Then we have a quick little power failure and the engine won’t start. They contact us and it ends up costing them $500 for a service call. We remind all of our customers that the generator is a piece of emergency equipment that has to start up as quickly and easily as possible. All it takes is a block heater that hasn’t been installed properly, or a burned-out block heater and a weak set of batteries to equal a no-start situation. Depending on the application there could be lives at risk.”

“At Kim Hotstart we used to issue maintenance manuals,” says Bass. “We advised customers to check their heaters at least once a year, perhaps remove the element and clean out the tank. But we’ve discovered this doesn’t always happen. Once those heaters go on, a lot of people don’t do much to them unless they fail. Why do they fail? Various reasons. Impurities in the cooling systems, bad coolant, and—a big problem—mixing antifreeze incorrectly. And hard water is one of the most common causes of heating element failure. The surface temperature of the heating element causes the minerals in the water to attach to the sheath. The minerals collect to form an insulation layer that increases the internal element temperature. As the insulation layer thickness continues to increase, the element temperature eventually increases to the point of failure—that is, the element burns itself out. If this happens, the cooling system should be completely drained and flushed. But putting a new heater in this environment will not solve the problem. What’s required is using de-ionized water, low-silicate antifreeze, and low-silicate supplemental additives. And don’t over-concentrate. Anything over a 60-40 mix is very hard on our heating elements. Over-concentration of coolant or additives will cause a gel-like slime to accumulate on the element. In severe cases this may burn on the element causing a black sludge to form, which decreases the heater’s efficiency.

“Antifreeze should never be added to an engine without being mixed with water first. If the antifreeze is added before the water, it will sit at the bottom of the engine. Because block heaters are designed to sit at the lowest point of the water jacket and because water pumps will not mix the coolant in the engine, if antifreeze is added without water, the heater will be filled with pure antifreeeze and this will cause a scale to form.” Bass also notes that because engine coolant reaches its hottest temperature inside the block heater, the heater itself is a good diagnostic tool for cooling system conditions that could have detrimental effects on the water pump, the after cooler, the oil cooler and the radiator.

“It’s also important that the coolant level is always up. Because, if you get an air pocket, the heated coolant can’t circulate and the heater will overheat and fail. What you have to do then is thoroughly purge the engine to eliminate any air pockets before the heater is energized. We recommend running the engine up to operating temperature to open the engine thermostat after installation, which insures that no air pockets are left within the cooling system. Also check the outlet hose and make sure there is no point in the line where it flows down. Remember that heat rises, and a downward trend will stop the flow of hot water.

“The same is true with running the engine while the heater is still energized. All of our stationary applications either use an oil pressure switch—so when the engine starts and begins to build oil pressure, it automatically turns off the heater—or the system may be on something like a 24-V or 12-V relay and, when the engine starts, the relay drops the heater off the line. This is because if the heater’s on and the engine starts, the coolant is sucked out, and again the heater is burning in open air and will fail.” All other things being equal, Bass says, drain the cooling system, clean it, and flush it every two years—procedures he recommends be specified in maintenance contracts.

“What we’ve seen,” says August, “is sometimes OEMs use a cheaper coolant and regular tap water, and the block heater element will cake up very quickly. We use a premixed, premium antifreeze and it’s mixed 50-50 with distilled water. Block heaters should be part of a client’s weekly generator checks. It can be as simple as putting your hand on the side of the engine block. Is it stone cold or nice and warm? Fire up the engine for a couple of minutes. If the block heater isn’t working, it’s going to be difficult to start. This puts an extra strain on the batteries, and of course the engine is going to smoke.”

Dauffenbach recommends other block heater items he considers important to check during regular engine service, hoses for example. “Automotive type hoses last about five years. Stainless steel braided hoses lined with silicone last for 20 years. For just a few dollars more you’ll have no maintenance on your jacket water heaters for the life of the engine/generator set.” From his experience at the dealership, Phillips agrees—use a silicone-based hose because the silicone withstands high temperatures better. “Once a year, grab hold of your hoses and make sure they’re pliable.”

Total Systems recommends hoses be changed at a minimum of every three years. “Block heater hoses have heat on them all the time, 24/7,” says August, “as opposed to a radiator hose, for example. They deteriorate much faster, and if they’re not caught early enough, they’ll fail. They’ll burst open, the engine will lose all of its coolant and the heater will burn out. We recommend silicone hoses for more critical applications like hospitals.”

Phillips reports that Caterpillar has begun installing circulation pumps typically used with large engines on all its factory-installed block heaters, including smaller models. “Convection-type heating is not a perfect world,” says Phillips. “The jacket system has all these passages, which sometimes cause the convection to get stuck. Then you get hot spots. I foresee that in the future pumps are going to be standard, and I think it’s a good idea. With pumps you can count on the entire engine being warmed, and with pumps even more heat will be distributed throughout the engine.”

August isn’t so sure and says if everything’s plumbed correctly there should be no need to install pumps on smaller engines. He also recommends that, although block heaters are common on diesel gen sets, natural gas engines should also be equipped with block heaters. “A block heater on a gas engine will function the same and have the same advantages as on a diesel engine. The engine will start quicker, the heater will bring the oil up to temperature quicker, and this will reduce wear. My basic recommendation is that anything that can have a block heater on it should have one.” BE_bug_web


  • Nazeer Ahmed.

    Useful and beneficial information for Energy Projects.


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