Effects of not running an engine compartment fan?

[rwidman]

Originally Posted by David M

ABYC requires it for Diesels as does federal law require it for all USCG inspected vessels, gas or Diesel.

Keep in mind that it is possible to have other dangerous or flammable sources of vapors in a bilge, even on a Diesel boat.

So you feel lucky?

It's on the Internet so it must be true.

Seriously, this is the first time I've read this claim and I have been around for may years. I do know that my boat is not equipped with any sort of bilge vapor evacuation system.

[Ferrari]

An air fan has no effect on the operational temperature of the engine. But can draw cooler air into the space around the engine, inside the engine compartment. This will have no noticeable effect on the temps surrounding the compartment if well insulated.
My fan is noiser than my Yanmar, so rarely used!
This is contrary to a battery compartment blower/fan which should be operating when ever the batteries are being charged. IE most of the time!

[S/V Alchemy]

Originally Posted by Pete7

Some times we run ours, some times we forget. Actually if you put your hand in front of it, there isn't much of a breeze given the 4 amps it uses never mind the noise it makes. Also our diesel is quite capable of pulling in air through the bilges etc. Far more important are there use if you have an inboard petrol engine to remove fumes before starting.

Pete

Pretty much this. That said, it certainly doesn't hurt and with the engine running, isn't going to draw down the batteries much. Also, depending on your setup, if you ever have some magic smoke in that area, drawing it out the stern might be your first hint of a problem.

[Cadence]

Originally Posted by rwidman

There is no fan in my boat's engine compartment and no indication that there was supposed to be one. The engine runs fine.

If you can contact the boat's manufacturer, do that. If not, try to contact other owners and see what they have in their boats.

Your boat has been running this way for twelve years with no problems so I wouldn't be in a big rush to change anything without a good reason.

If it ain't broke don't fix it.

[ramblinrod]

Originally Posted by boatpoker

The ABYC part of your statement is not true.
1. Attached photo is a snip from ABYC H32 Ventilation of Boats Using Diesel Fuel.

2. CFR. Title 46, subpart K (uninspected vessels) specifies powered ventilation for gasoline powered boats only. I do not have the"inspected vessel" standards but I'd love to see the reference.

Not technically correct.

ABYC requires one to follow diesel engine manufacturers recommendations for ventilation. (I do not know of one diesel engine manufacturer who does not specify ventilation requirements.)

Also ABYC requires ventilation of the battery compartment...

10.7.9
A vent system or other means shall be provided to permit the discharge from the boat of hydrogen gas released by the battery.

Many boats are non-compliant, having battery compartments under cabin settees, that for all intents and purposes are sealed spaces.

While a sealed battery is better than a vented FLA under normal circumstances, it still isn't compliant, because even sealed batteries can gas out.

[rwidman]

Most our boats are designed by qualified designers and naval architects who know more about this stuff than we do. Pretty much, if you don't have a fan it's because you don't need a fan. If you have a fan, it's because you need a fan.

Soo - Leave well enough alone and go boating.

[kas_1611]

Originally Posted by ramblinrod

Proper engine compartment ventilation is important for the following reasons:

1. Prevent carbon monoxide poisoning. The blower is installed to create a negative pressure in the engine compartment. Passive air vents supply make-up air to the compartment. This negative pressure ensures any air leaks between the engine compartment and occupied living space, flow into the engine compartment. If the engine exhaust system develops a leak, the carbon monoxide by-product of combustion (also known as "the silent killer") can fill the engine compartment. Without proper ventilation, this can enter the living space and kill the occupants. This may sound over-dramatic, but this is very, very, serious stuff.

If my 4in fan can create a negative pressure in the vast volume of the engine bay/transom area of my boat I'd be incredibly surprised. It can't possibly suck that much air out with an equal diameter inlet hose to reduce the internal air pressure by even an attopascal.

I work in an industry that requires positive pressure air flows and to achieve this requires massive blowers pumping hundreds of cubic meters of air a minute to produce even a 1psi pressure differential. A 4in blower fan is never going to move enough air to make any difference. If CO is a worry then invest in a CO detector and forget trying to get a negative pressure differential in your engine bay.


Now there was something in the EU Recreational Craft Directive that was supposed to mean all engine bays had to have a blower fan to ensure sufficient air flow into the engine bay to ensure proper combustion. I've never actually been able to find this in writing mind. As I've already said I have a 4in diameter inlet hose (no fan) and a 4in diameter exhaust hose with the fan. Without the fan running this means I have 2 inlet hoses for my D2-40 to suck air through along with the volume of air in the engine bay and through into the transom. I think the engine is more than capable of sucking sufficient air.

When I swapped my diode based charge splitter for a Sterling ProSplitR I found the fan would not work with the engine so had to wire it up to a spare switch in the instrument panel. Whilst figuring this out I tested the theory that the fan might help keep the engine bay cooler by putting a thermometer high up on the rear wall. With the fan the temp was 40ºC, without it and after several hours of motoring the temp was 45ºC. Is the noise worth 5ºC? Will my alternator or electrics pack in because of 5ºC? In both cases probably not. We do tend to run the fan if we are going to be motoring for more than an hour but I'm not going to worry if I forget.

Just my 2p worth based on my experience

Keiron

[boatpoker]

Originally Posted by Sailmonkey

Been on many sailboats lately? show me more than one that excludes engine spaces from accommodations. Our 40 year old boat has a door in front of the engine, but for all intents the engine is sitting in the same hull that is occupied by the humans, as are thousands out there.

It's really simple. In the old days that's the way they built them. We know better now and have standards against that sort of thing.

[boatpoker]

Originally Posted by ramblinrod

Not technically correct.

ABYC requires one to follow diesel engine manufacturers recommendations for ventilation. (I do not know of one diesel engine manufacturer who does not specify ventilation requirements.)

Also ABYC requires ventilation of the battery compartment...

10.7.9
A vent system or other means shall be provided to permit the discharge from the boat of hydrogen gas released by the battery.

1. I made no reference to "battery compartments" but again on point ... they do not require powered ventilation.

2. What post did you read ? No reference was made to engine manufacturers and that's not what we were talking about. Of course any fool knows the manufacturers have ventilation requirements. Too bad that's not what we were talking about.

We are talking about "powered ventilation" and the fact that ABYC has no such requirement in their Standards for powered ventilation in a diesel compartment as the previous poster stated they did and that is what I was disputing. So yes, I am "technically correct" as the ABYC snippet I posted clearly shows.

[Cadence]

Had anyone considered from the OP, maybe the fan was installed for a different power option. If it hasn't been a problem and looks as though the wires have never been spliced and you need to be Houdini to get a pic I would leave it be.

[ramblinrod]

Originally Posted by boatpoker

1. I made no reference to "battery compartments" but again on point ... they do not require powered ventilation.

2. What post did you read ? No reference was made to engine manufacturers and that's not what we were talking about. Of course any fool knows the manufacturers have ventilation requirements. Too bad that's not what we were talking about.

We are talking about "powered ventilation" and the fact that ABYC has no such requirement in their Standards for powered ventilation in a diesel compartment as the previous poster stated they did and that is what I was disputing. So yes, I am "technically correct" as the ABYC snippet I posted clearly shows.

The engine manufacturer specifies a certain CFM of ventilation be provided.

If the vessel manufacturer's solution was to install a blower to achieve it, the blower needs to be connected for the vessel to be compliant with the engine manufacturer's ventilation requirements and by association ;-), ABYC compliant.

[hellosailor]

ABYC and the CFR are all well and good, but they never have applied to a French-built privately owned yacht cruising the Med. Other than that...

Even diesel fuel can ignite rather explosively, if you get a fine mist spraying out of a pinhole leak in the high pressure side. Rare but memorable. So the more cautious folks run the blower in case there's been some other leak (propane?) into the bilge as well.

On a more practical level, running the blower will cool down the engine compartment after it has run, and that will cool down the whole boat faster, which may be something you'd be interested in during the summer months.

And, when any engine is shut down and the normal cooling systems shut along with it, the engine block temperature RISES. The oil circulation stops. That combination means the oil left in the valve covers and other places cokes and turns into tar, so your oil is breaking down and your oil passages may be blocking up. These are not good things, and running the blower until the engine has cooled back down can minimize them.

So, cooler required? Or course not. You can get away without many things. But seeing that this one probably just requires you to connect two wires to get real benefits, why not?

[ramblinrod]

Originally Posted by kas_1611

If my 4in fan can create a negative pressure in the vast volume of the engine bay/transom area of my boat I'd be incredibly surprised. It can't possibly suck that much air out with an equal diameter inlet hose to reduce the internal air pressure by even an attopascal.

I work in an industry that requires positive pressure air flows and to achieve this requires massive blowers pumping hundreds of cubic meters of air a minute to produce even a 1psi pressure differential. A 4in blower fan is never going to move enough air to make any difference. If CO is a worry then invest in a CO detector and forget trying to get a negative pressure differential in your engine bay.


Now there was something in the EU Recreational Craft Directive that was supposed to mean all engine bays had to have a blower fan to ensure sufficient air flow into the engine bay to ensure proper combustion. I've never actually been able to find this in writing mind. As I've already said I have a 4in diameter inlet hose (no fan) and a 4in diameter exhaust hose with the fan. Without the fan running this means I have 2 inlet hoses for my D2-40 to suck air through along with the volume of air in the engine bay and through into the transom. I think the engine is more than capable of sucking sufficient air.

When I swapped my diode based charge splitter for a Sterling ProSplitR I found the fan would not work with the engine so had to wire it up to a spare switch in the instrument panel. Whilst figuring this out I tested the theory that the fan might help keep the engine bay cooler by putting a thermometer high up on the rear wall. With the fan the temp was 40ºC, without it and after several hours of motoring the temp was 45ºC. Is the noise worth 5ºC? Will my alternator or electrics pack in because of 5ºC? In both cases probably not. We do tend to run the fan if we are going to be motoring for more than an hour but I'm not going to worry if I forget.

Just my 2p worth based on my experience

Keiron

Question: If a discharge fan of any description cannot produce any negative pressure, what causes the air to flow?

Answer: For air flow to occur, there has to be a negative pressure on the suction side and a positive pressure on the discharge side.

Every operating fan has a differential pressure between inlet and outlet, (unless either is completely blocked), else, no air would ever move.

[ramblinrod]

Originally Posted by ramblinrod

The engine manufacturer specifies a certain CFM of ventilation be provided.

If the vessel manufacturer's solution was to install a blower to achieve it, the blower needs to be connected for the vessel to be compliant with the engine manufacturer's ventilation requirements and by association ;-), ABYC compliant.

Just checked the Yanmar engine installation manual. There is a formula for calculating required ventilation based on engine displacement.

For a 4JHTE (75 HP) it is 4.15 m^3 / min or ~ 150 cfm

This means that a single Rule 3" electric blower (rated 135 CFM, open suction and discharge) would not be anywhere near sufficient.

[Sea Angel1]

the 2 large dia tubes are the fresh air inlet from the transom, next to each other. 2 Grids od appr. 100 mm dia
The other tube has a fan installed and draws the warm engine compartment air out of the engine compartment, to the transom (outlet is a smaller grid (about 75 mm), what I recommend to do. I have the original electric circuitry onboard and do not have it on hand. I will first go onboard in coming february. You can connect it at the on/off button, if installed, on the Volvo control panel. to Start the engine you press the start button. However this may be different in your boat.
Also you can contact any Volvo Dealer, they will advise you surely how to wire up.