[MarkofSeaLife]

Heading into a tropical summer and want to ventilate the battery bank. Its a box under the bed in the aft cabin, no real venting except one 6 x 6 inch hole at one end. Air seepage the other end.

Sooooo is it better to suck in cooler air? Or blow out the hotter air?​

Thanks

Mark

 

[GlanRock]

I probably shouldn't be on a forum this early in the morning. The only thing I thought of reading this was this and I feel bad about myself, a little.

I am curious about the opinions to the question. Seems like most engine areas on sailboats have a large hose which is attached to a blower, the intent to suck the hot air out and full in fresh air from anywhere there is an opening/egress.

 

[marcjsmith]

its a lot like water flow. if you have a pipe. you can push water or suck water. but its got to have someplace to go.

so if you suck cold air into the battery area, the resulting outflow has to go somewhere. and likewise, if you are blowing the air out of the battery area its got to have an intake somewhere.

personally, I'd rather have a flow into an area. and let the positive pressure find its way out.

 

[marcjsmith]

I probably shouldn't be on a forum this early in the morning. The only thing I thought of reading this was this and I feel bad about myself, a little.

View attachment 147001​

Well it is Steak and BJ day... according to the internet

 

[SanderO]

Exhaust and pull fresh air from the cabin... exhausts to the bilge/cockpit lazarettes

 

[Don L]

As long as there isn't a path around the fan it doesn't matter as the air flow is the same. But I normally when having a choice to have the fans blow fresh air in.

 

[SchockT]

If you are ventilating due to potential fumes such as batteries gassing or engine compartment odors then you want to maintain that compartment at a negative pressure. If you blow into it and create a positive pressure you will force those fumes and odors to migrate throughout the boat.

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[SanderO]

If you are ventilating due to potential fumes such as batteries gassing or engine compartment odors then you want to maintain that compartment at a negative pressure. If you blow into it and create a positive pressure you will force those fumes and odors to migrate throughout the boat.

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Depends on boat architecture. My batts sit aft of the engine... above the bilge... I exhaust into the bilge. I have a bilge blower which exhaust bilge air.

 

[capta]

I would rather have any hot air be removed from the aft cabin (and any battery fumes), especially in the summer down there. I'd install the quietest fan I could find. Many A/C fans are really 12 volt D/C fans with a wall converter and much cheaper and quieter than those sold as "boat fans".
Vent to a hose that goes outside the aft cabin to the lazarette, not the cockpit. The cockpit may fill with water one day and the water will have access to the boat's interior.
O2 Cool has a huge variety of fans that are affordable, almost completely silent, and last many years. You can even get them with USB power, or USB charging for its battery. I've run their 12" fans 24/7, and they lasted at least 5 years. It is very important to pick a fan that disassembles for cleaning. I couldn't believe how much dust the blades collected, over a short period of time.

 

[colemj]

Most fans are better at pushing air than pulling air when a restriction is present.

Mark

 

[paulk]

Schock and Capta make a good point that getting the hot air and other gases OUT of the area is the prime consideration. That calls for sucking the air out of the battery compartment using the 6" opening, and directing it all away from the cabin. Blowing air in would make the hot air leak from the compartment into the cabin - not what you want. If Colemj is also right, then you simply need a better fan for sucking air than you do for pushing it. So get a better one.

 

[shoffman57]

I'm on the suck side of the fence. I would not want to force the hot air and fumes into the aft cabin.

 

[SanderO]

My battery compartment has a blower which pushes air in and a 3" diameter hole and several smaller holes which allow the air to exit into assorted bilge areas which ultimate are interconnected... more or less, There are a few outlet louvers... one in the coaming bin and the other on the transom.

 

[OntarioTheLake]

I think it's already been said well enough, but pushing air in depends on air getting out; sucking air out pretty much dictates that new air will come in. I say pull it out.

 

[oldmanmirage]

I have always set the engine compartment to have a negative pressure, so any blower is set up to exhaust. Every boat I've ever worked on has been set up that way also. Typically you have two vents with appropriate hose. One is usually at the top and towards the back of the engine compartment - that is the exhaust. The supply line does not need a blower and usually runs to somewhere near the engine intake to supply as fresh and cool air as possible to the engine.

 

[SHNOOL]

Am I the only one that thought Spaceballs? Megamaid has gone from .. nevermind.
Exhaust out of the compartment, preferably to somewhere other than the living area.

 

[SchockT]

Most fans are better at pushing air than pulling air when a restriction is present.

Mark

That all depends on what style of fan you are using, but the typical tube-axial fan found in many boat engine compartments can handle either discharge static pressure or suction negative pressure. No fan will perform well if there is excessive restriction. Proper ventilation relies on air being free to flow in and out of a space.

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[colemj]

I think it's already been said well enough, but pushing air in depends on air getting out; sucking air out pretty much dictates that new air will come in. I say pull it out.

Um, no - it is a zero-sum game either way.

Mark

 

[colemj]

That all depends on what style of fan you are using, but the typical tube-axial fan found in many boat engine compartments can handle either discharge static pressure or suction negative pressure. No fan will perform well if there is excessive restriction. Proper ventilation relies on air being free to flow in and out of a space.

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Yes, but earlier posts were discussing house and computer fans. I agree that the axial blowers are good either way, as are squirrel fans.

Mark

 

[SchockT]

Yes, but earlier posts were discussing house and computer fans. I agree that the axial blowers are good either way, as are squirrel fans.

Mark

Agreed. Muffin fans are not appropriate for ducted applications at all!

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