Diesel Fired Coolant Heaters

Hi, as I've been researching heating solutions for boats, I thought I'd share this interesting report that I came across from a 2010 study in NY about utilizing "Diesel Fired Coolant Heaters in School Bus Applications."

Many of you already have hydronic systems and perhaps could add positive factors as well as drawbacks to such systems, for the rest of us.

There may be a case for passenger comfort with diesel fired coolant heating, but I can't see the stated benefits of engine preheating, particularly for us cruisers.

Buses may need preheating to start reliably in harsh climates, but a 250 watt block heater can do it cheaper and more reliably. Yes, you have to invest in power pedestals for the busses to use overnight, but I will bet that is cheaper than installing diesel fired heating. Also common rail injection is allowing diesels to be reliably started in sub zero F temperatures.

Most of us cruisers never operate in conditions that require heat overnight to let our engines start easily.

OTOH passenger heat may be critical for cruisers and diesel fired hot water heater is installed for that purpose and engine starting is just a plus. It does cost more to integrate your diesel's coolant system with the hot water system.

Is diesel fired coolant heating an important consideration for bus passengers? Don't know. School busses operate in a fairly well loaded environment starting and stopping to pick up passengers. Kids are also well dressed for the cold. So whatever heat is available from "bus heaters" may be sufficient.

Don't know hot well Greyhound heats their long distance coaches in harsh climates though where passengers aren't bundled up typically.

David

Nothing complicated here - a business 101 scheme that is thriving. Some "think tank" group presented a proposal to a New York government group stating that a study was needed to evaluate extending engine life, reduce bus emissions and improve fuel economy. Money changed hands and out came a study showing the obvious.

In cold climates, preheating engines via circulating coolant has been standard issue for generators, trucks, off highway equipment and personal vehicles for a long time. Henry Ford said the Model T would start better if kept in an enclosed garage.

The customary alternative, as mentioned by Dave, is an electric cord with some manner of block heating. When no cord available, as evidenced by thousands of truck stop haulers, a hydronic heater is utilized. One of my boat engines is plumbed into the Hurricane heater. Amazing how quickly the engine and ER heat up on a cold winter day.

Mako, suggest you install a well thought out hydronic system for your steel vessel. Not sure if your Chinese yard has that skill set. The Chinese yacht building yards do.

In a city the reduced emissions alone may justify an engine heater. Think black smoke. And since we’re paying for them I would be pleased to know there’s some fairly old busses being used.

A charter fishing boat I worked on had electric coolant heaters/circulators for a pair of 671 Detroits, they improved start up and reduced smoke at start up. Better for the engines and the charter guests as well.

Application is everything.

I do generator work for a living. Every genset comes from the factory with a jwh. Have seen the diesel fired units on some portable units. It's helpful when you don't have anything more than a 120v plug for power. Most all modern diesel engine's will start in cold weather even if they are not happy about it. I've seen old PC camber stuff not light off when cold.

My Jimmies never had problems starting when we lived in Seattle, although I don't remember the winter being too terribly cold. But the next boat will be 4-stroke, which generally don't start up instantaneously like those magical GMs. Since we're planning some occasional high latitude cruising, I'm researching the block heaters.

Q1) So the electric block heaters, how are they installed for a large diesel? Is it glued to the exterior of the block (like a car engine), or inserted in the coolant loop when needed? The ones I see online are $50 or less. Seems too cheap for a boat

Q2) For a hydronic system, with engine-fed closed loop to the hot water tank, do you install a small circulation pump in the loop to back-feed from the hot water tank returning to the engine?

Q3) Regarding to the Chinese shipyard (a commercial yard), I absolutely agree with your comment. I'm learning to let them just do what they do best - which gives me the best value for the money. Try to avoid asking for too much customization. They are not in that business and don't want super-custom projects.

I may be over-thinking this whole thing. The simplest solution might just be a portable engine block heater - install when needed - and a couple of Dickinson bulkhead heaters for cabin heat.

A Wolverine block heater is a semi flexible pad that is designed to be glued to the oil pan. They come in 100, 250, 500 watt sizes.


David

makobuilders said:

My Jimmies never had problems starting when we lived in Seattle, although I don't remember the winter being too terribly cold. But the next boat will be 4-stroke, which generally don't start up instantaneously like those magical GMs. Since we're planning some occasional high latitude cruising, I'm researching the block heaters.

Q1) So the electric block heaters, how are they installed for a large diesel? Is it glued to the exterior of the block (like a car engine), or inserted in the coolant loop when needed? The ones I see online are $50 or less. Seems too cheap for a boat

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As Dave mentioned an oil pan heater is a very simple, inexpensive solution. I have one on my boat and it is plugged in 24/7 when at my home dock. I don't use it due to any cold start issues. I've never had any starting problems with my Cummins QSB engine even in below freezing temperatures. The oil pan heater simply keeps the engine and ER from getting damp and clammy thereby reducing corrosion. Again, I've not noticed any change in cold starts since I started using it. My engine takes less than 5 seconds to start regardless of temperature.


I do have a hydronic heater on board to supply cabin heat and hot water. Since engine heat can also be used to heat hot water, I suppose that when I'm running the diesel furnace overnight, that some heat gets back fed into the engine coolant. To make that efficient, I suppose an auxiliary pump that would circulate the coolant through the engine would work, however I think the oil pan heater is likely much more effective.

The most common practice in cold areas is to either leave them run all night or start them up at 4 or 5AM so the bus is warm when the driver arrives.

A toasty bus with a warm engine from an aux heater might save money , if it was ever used, and maintained..

Unless your boat will be left off and unheated in a very cold climate, say 20F or below, I see no need for any heater. I have construction equipment that sits for months at a time in the winter, then starts with no problem in -10F.

Any boat that is actively cruised is likely to remain heated in the living space. In that case your ER will be warmish too, obviating the need for a heater. We ran in the winter for a few years leaving the boat heat on, and the ER never dropped below 50F. In practice, we found it was just not a problem.

For a new build, incorporating an hydronic heating system would definitely be part of the spec for me. I already had a Webasto unit from the PO, and during refit the overall utility of the system was expanded. As well as the Webasto being able to provide hot water, one engine can also heat water (and the boat) via a heat exchanger, without an additional pump in the engine.

We also incorporated a 'pre-heat' tank (electric element) for boat heating when on shore power in order to eliminate electric fan heater usage. The schematic attached shows configuration.