Effects of not running an engine compartment fan?

[lifeofreilly57]

DO you really need an exhaust fan in the engine compartment of a diesel powered boat? No, but.....
If you have a high amperage alternator it's usually a good idea, in fact some manufacturers suggest a ducted cool air supply to the alternator.
In my case I have a center cockpit boat with the engine located under the cockpit, inside the engine compartment there are a fair amount of electronic devices mounted, the box for the SSB, charge controllers, the diesel generator, etc, etc. There's a high amperage alternator on the motor too.
So, in my case and engine compartment blower is a good idea for several reasons. It keeps the fine engine compartment aroma out of the salon, it keeps the engine compartment temperature to a civil level, it keeps the interior temperature of the boat to a more comfortable level.
Even though it seems a minor issue, most motors whether diesel or gas like cool air for the intake, it's denser and makes for more efficient running.
Electronics generally do not like hot temperatures, this includes your smart charge controllers and most radio and control electronics, seems a minor issue until it fails. I know from my industrial background that most electronic devices can get touchy above 140F.
And those humongous house batteries in my boat sure do need a little ventilation when going through a rapid charge cycle with the modern charge controller doing the managing.
Do you have to have one? No, but most engine compartments on modern boats have been made pretty tight to allow for more usable interior space, this just exacerbates the heat issue.
My take on it is, if you have it, and the plumbing is correct, and you find the wiring is correct, why not use it? Just check the wiring first to make sure it's wired correctly and is set up to run when the engines on.

[Jim Cate]

If you read a book on diesel maintenance as, sad person that I am, I was doing the other day, you will be amazed at the roomfulls of air a modern diesel sucks in. Especially a turbo charged one. The fan gets the stuff, and the heat, out.

Umm, no, the fan does not get that stuff (air that the engine has sucked in) out, the engine ingests it and it goes out the exhaust. The fan can only exhaust the remaining air, which can be quite warm, and getting rid of it is a good thing.

And for the chap whose engine overheats if the vent fan goes off: I'd suspect a fault in your engine cooling system, for the amount of heat extracted from the engine into the ambient air, compared to that rejected into a properly operating cooling system must be far smaller.

Jim

[daletournier]

My alternator wont perform well without the blower, therefore its a must. Wish i worked that out 7,000 nm ago!!

[buzzstar]

Was there a gasoline engine option for the vessel in some market or markets, or maybe a gasoline generator? Perhaps a fan was not hooked up unless such an option was selected, the original purchaser requested one, or maybe one was always installed, and some hurried worker failed to connect it? The last seems the most probable.

[LongRange]

Wow! Almost 50 responses in less than 24h. Thank you all. To address some of the points raised:

- To the best of my knowledge there was never a gasoline option for a Dufour 455 GL, or indeed any of the models from that series.

- My boat does not have a generator, and to the best of my knowledge never had one in the past. The factory generator option places the genset in the front 'sail' locker, right at the other end of the boat from where the unconnected fan is located.

- The power leads near the fan are dead - not currently supplying 12V. The schematic in the owner's manual shows that the fan is meant to be powered through a 5A fuse and a relay which is driven off the alternator. In other words, whenever the engine and alternator are on, the relay should be closed and the fan should come on as well. Then again, I have noted several differences between the schematic and reality, and it would not surprise me if the wiring was in fact completely different. I will try to find that relay and fuse.

- The exhaust conduit from the fan comes out in an awkward place - not overboard, but instead under the helmsman's "bench" at the back of the cockpit. In effect, the fan would exhaust air from the engine compartment into the cockpit. That alone makes me reluctant to hook it up until the conduit is rerouted outside.

- Sound insulation and general integrity around the engine are good, but far from airtight. I'm guessing the engine could probably pull in sufficient air through the cracks even if it had no ventilation at all, not that I'm going to try such a thing!

- The three house batteries are located on a plywood shelf right above the engine in the engine compartment - the location cannot get any worse in terms of heat. I would like to move them into an underfloor compartment which is currently underutilized, thus relocating ~100kg about a metre down, but until then activating the blower to cool that compartment a little seems like a good idea.

- I will try to contact Dufour and ask about whether the lack of connection is intentional.

[GordMay]

Originally Posted by LongRange

Wow! Almost 50 responses in less than 24h. Thank you all. To address some of the points raised:..

Especially on such a well (previously) discussed subject.

➥ https://cse.google.com/cse?siteurl=w...ion&gsc.page=1

See also ➥ https://www.proboat.com/2015/06/venting-the-engineroom/

[Dockhead]

Whew, what a lot of passion, unleashed by such a simple question!

Actually EVERYONE who posted here is right, each in his own way, but almost EVERYONE is making far too big a deal out of it.

A well-ventilated engine compartment is a very, very good thing. Internal combustion engines need fresh, cool air, and as others have said, various components in the engine compartments, especially electronics, and especially especially any batteries you might have in there, don't like heat. You already have a ventilation fan installed -- of course, hook it up, and use it. That's a no-brainer. It's a very basic electrical job -- get the polarity right, make sure the wiring is in good condition and heavy enough to carry the current, make sure you have appropriate breaker or fuse in appropriate place, make sure all the connections are good, make sure you've connected to the right power source, and job done. But if you don't have the skills, hire a pro sparky or ask a fellow cruiser who does have the skill. It's not a big job, in fact I doubt if it's a whole hour. It's a one-beer job, tops.

But would I stop using the boat and cancel all sailing until it's done? Heck no. As someone posted, diesel engines are immensely powerful air pumps in and of themselves. Probably most sailboats don't have powered ventilation at all, and I doubt there is so much difference between different boats, what concerns the possibility of natural ventilation -- air is always pulled through the bilges with very little restriction. So just do it when you get around to it.

That's my personal point of view -- obviously you will have to choose yourself, from the variety of views you've been given here. Good luck.

[rwidman]

Originally Posted by LongRange

................... - I will try to contact Dufour and ask about whether the lack of connection is intentional.

(post #2)

[Snore]

Having a fan helps keep the engine room and cabin cooler. All the newer boats have them wired such that when the ignition is on the fan runs. IMHO, I would modify that with a second feed and a diode so you can run the fan manually after a long motoring session to get the heat out of the boat.

My Tartan’s blower exits under the helm seat. This is great for two reasons- first, unless I get pooped, the fan outlet will never flood into the engine area. If I was in conditions where I could be pooped, I have a plug to place over the vent’s outlet. Second, when it is cold.... okay Florida cold, the heat feels good on my hands. In the summer, I never really feel that much hotter with the vented air coming out. Then again, during long periods of motoring the AP is driving. I just keep watch.

[ramblinrod]

Originally Posted by Jim Cate

Umm, no, the fan does not get that stuff (air that the engine has sucked in) out, the engine ingests it and it goes out the exhaust.
Jim

Obviously you have never encountered a vessel with an exhaust leak.

The blower has so many advantages it is surprising to me we have to even discuss it. It is true, many diesel powered sailboats were not equipped with a blower. My 1975 Douglas 32 was. Most boat manufacturers now know better and install one, standard, at the factory.

Another benefit, not yet discussed, is that if the fire suppression system or an extinguisher has to be activated, after the fire is out, the blower will help exhaust the smoke and extinguisher inert gas or chemicals.

And again, the negative pressure created by the blower exhausting air out of the compartment, will help prevent these noxious fumes from entering the cabin.

For this single reason alone, I suggest a blower in the engine compartment of a diesel powered vessel is a terrific idea.

(I inspected a fire on a diesel trawler this summer, where the transmission rear seal blew out, the tranny overheated due to lack of lubrication, and set all kinds of things in the engine compartment room on fire. Two additional consequential fires were started quite some distance away, by the insulation melting, and causing short circuits, in the electrical wiring in the harness over the transmission.)

The owner was quite thankful to have multiple blowers in the engine compartment after the incident, which was about 5 miles offshore.

[CarinaPDX]

Originally Posted by ramblinrod

Another benefit, not yet discussed, is that if the fire suppression system or an extinguisher has to be activated, after the fire is out, the blower will help exhaust the smoke and extinguisher inert gas or chemicals.

I believe we all should have automatic fire extinguishers in our engine compartments. The exhaust fan's ground should be routed through the fire extinguisher's cut-off switch such that when the fire extinguisher goes off the fan is stopped - so as to not pump the extinguishing agent out before the fire is suppressed. Afterwards the cut-off switch would have to be bypassed prior to using the fan to evacuate the smoke. I suppose that could be planned for with a separate emergency ground that could be switched on.

Volvo offers an "auxiliary relay cable" that can be added to the cable from the engine to the EVC system tachometer. This adds a relay which is energized when the engine is running, and is ideal for switching the exhaust fan.

Greg

[fdr14127]

I don't know about the legal requirements, but I have heard of a C&C 34+ that required $10,300 to retab the bulkheads after firing up the engine without the blower. That's why I don't have propane on my boat. I don't think the starting has spark suppression.

[Dockhead]

Originally Posted by CarinaPDX

I believe we all should have automatic fire extinguishers in our engine compartments. The exhaust fan's ground should be routed through the fire extinguisher's cut-off switch such that when the fire extinguisher goes off the fan is stopped - so as to not pump the extinguishing agent out before the fire is suppressed. Afterwards the cut-off switch would have to be bypassed prior to using the fan to evacuate the smoke. I suppose that could be planned for with a separate emergency ground that could be switched on.

Volvo offers an "auxiliary relay cable" that can be added to the cable from the engine to the EVC system tachometer. This adds a relay which is energized when the engine is running, and is ideal for switching the exhaust fan.

Greg

Not only that, but a running blower can fan a small fire into a huge destructive one. Fans should go off in case of fire!!

My boat has a SeaFire system which releases halon, cuts the blowers, and cuts fuel supply, automatically in case of an engine room fire.

OP should make sure he has a way to get the fan off quickly in case of fire.

[ramblinrod]

Originally Posted by Dockhead

Not only that, but a running blower can fan a small fire into a huge destructive one. Fans should go off in case of fire!!

My boat has a SeaFire system which releases halon, cuts the blowers, and cuts fuel supply, automatically in case of an engine room fire.

OP should make sure he has a way to get the fan off quickly in case of fire.

Thank you. Absolutely correct that the blower must be off (manual or auto) during the fire. For boats not equipped with an auto shut off on fire suppression system activation, the blower control is usually (and should be) right be side the engine manual start/stop control. This proximity promotes blower use before engine starting and stopping in the event of an engine compartment fire when the engines are shut down.

Most auto fire suppression systems do have an "auto engine shut down" additional cost option available.

If the blower is auto **** down, it is best to have a manual override or reset, so that after the fire is out, the engine conpartment can be cleared quickly to assess damage. Especially with inert gas fire suppression, where the engine compartment may not have breathable atmosphere after a false trigger, or relatively minor incident.