engine room blower does not suck out but blows air in !

[aerobat]

hey ! today i for first time since having this boat found one strange thing out : my engine room blower does not suck out but forces air in !

i have 4 opening to the engine room via housings and on one of them the blower is attached, the other are forced air supply.

it does not look like anybody would have reversed polarity on this so i,m asking if there is any use to install a engine blower that forces air inside the compartment instead of sucking air out on one side so fresh air comes in the other side.

one more question : its a centrifugal blower, so will it work when i reverse polarity by myself ? i quess not !

thanks much !

 

[robert graham]

Re: engine room blower does not suck out but blows air in !

Maybe the blower was just mounted in there backwards....can you reverse it?...

 

[aerobat]

Re: engine room blower does not suck out but blows air in !

do you mean reverse polarity or the whole blower ?

polarity of course yes, the blower may be a problem since its tightly attached on the one hand to the engine room compartment and on the other hand to the housing for fresh air intake. i may have a closer look tomorrow

do you see any use in installing the engine room blower this way? it does not look like somebody ever screwed on it but that it is designed so by the yard !

and would a centrifugal blower even work when the electric motor would turn the opposite direction but the intake and exhaust housing of the blower would stay in the same direction ?

the blower also significantly reduces engine room temperature on hot days- but for very sure it blows in and not out

 

[JoLin]

Re: engine room blower does not suck out but blows air in !

Hi, aerobat- it's wrong, period. Either polarity is reversed, causing the motor to run 'backward', or the motor was mounted pointing in the wrong direction. It's a simple in-line fan mounted in a tube, so IMO either condition could be the culprit.

The blower is there for one reason- to exhaust gasoline vapor from the bilge to the outside of the hull. That function is critical, so get it straightened out asap.

 

[Another retired guy]

Re: engine room blower does not suck out but blows air in !

The primary function of the blower is to remove fumes from the engine compartment. I don't think it can do that very well blowing in! The whole unit should be disconnected and turned around so that it blows out. Although it may work with reversed polarity it won't operate efficiently.

 

[robert graham]

Re: engine room blower does not suck out but blows air in !

Well, that seems peculiar for sure, but you could try and reverse that polarity and see what it does?.....maybe it was just mounted backwards by the builder? Most engine room blowers are Exhast Fans, for sure!

 

[blouderback]

Re: engine room blower does not suck out but blows air in !

If it's supposed to suck air out instead of blowing it in, why is it called a "blower"?

 

[JoLin]

Re: engine room blower does not suck out but blows air in !

If it's supposed to suck air out instead of blowing it in, why is it called a "blower"?

It doesn't suck air out, it blows air out. Better?

 

[aerobat]

Re: engine room blower does not suck out but blows air in !

thats all interesting i must say. i give you fully right with the fumes and because of that it makes sense to suck air out and not force in. forcing air in may only reduce the concentration but will not be that effective.

i,m thinking in this moment if beyond fumes there is any benefit to force fresh air inside the engine compartment instead of sucking hot air out and letting flow fresh air in via the other openings.

what i can say- this blow-in constellation reduces significantly engine room temperature and the engine has not any problems with fresh air forced in.

nevertheless , i will teach my blower tomorrow to be a sucker !

 

[blouderback]

Re: engine room blower does not suck out but blows air in !

Yeah, it definitely should be sucking it out. The 4" hose that's pulling air out should be as low as possible in the bilge, as that's where the flammable gasses will collect.

 

[robert graham]

Re: engine room blower does not suck out but blows air in !

It doesn't suck air out, it blows air out. Better?

Blowing/Sucking...would all depend on which side of the fan you're standing....

 

[aerobat]

Re: engine room blower does not suck out but blows air in !

Blowing/Sucking...would all depend on which side of the fan you're standing....

a nice blow job barely sucks !

 

[UncleWillie]

Re: engine room blower does not suck out but blows air in !

He has a Centrifugal/Squirrel cage(radial), NOT an in-line(Axial), blower.
Reversing power polarity will make it work poorly, but still In the same direction.
Air comes in the center and out the side.

Blowing air into the bilge will tend to cause the heavily concentrated inflammable fumes to be leaned out enough to become flammable.
You want to blow the full strength fumes overboard without leaning them out.
There should never be any fumes for the blower to move, but that is irrelevant.

As you blow the air out of the engine room it is replaced with cool air from the outside, so as you're blowing it out you are also sucking it in.
You can't do one without the other without creating a vacuum chamber.

Once the engines are started , they pull in way more air than the blower ever did.
A 250 Cubic inch engine pulls in a cubic foot every 14 revolutions. (@WOT)
That is nearly 290 cubic feet a minute at 4000 rpm.
That's a lot of hot air!

Your saving grace its that the blowers job is to remove fume that should never be there in the first place.
The Blower is like a life insurance policy, you never want to have a need to use it!

 

[cribber]

Re: engine room blower does not suck out but blows air in !

It blows air into the the bilge/engine room to force out the flammable fumes thru the other vent. If is sucked the flammable fumes up and over the blower motor it could cause a fire or explosion. Don't reverse the motor... you're just inviting trouble where things could go boom.

 

[UncleWillie]

Re: engine room blower does not suck out but blows air in !

It blows air into the the bilge/engine room to force out the flammable fumes thru the other vent. If is sucked the flammable fumes up and over the blower motor it could cause a fire or explosion. Don't reverse the motor... you're just inviting trouble where things could go boom.

Again, it is a Centrifugal/Squirrel Cage(RADIAL), NOT an in-line(Axial), blower.
The air does not go past, or through, the motor.
Even if it were an Axial motor, the motor would be Sealed/Explosion Proof.

You want to pull the fumes from the bottom of the bilge and dump them overboard.
Gasoline fumes are heavier than air.
Blowing them around will not blow them outside.
You will just be spreading them all over the boat.

It would be like trying to clean up a gas spill with compressed air.
You want use a mop, not an air gun!

 

[eng208]

Re: engine room blower does not suck out but blows air in !

Wow, this controversy will go on forever. Does the blower pull the engine room fumes out? Or, does the blower pull fresh air into the engine room, forcing fumes out the vent. The few inboard/outboard setups I have seen have forced air into the compartment, creating a positive pressure forcing fumes and vapors out of the area through the vent. It is the cheaper way of doing it. In order to have a negative pressure set up, one would have to have a sealed-explosion proof (and labeled/tested) motor capable of moving enough air to decrease pressure and allow atmospheric pressure to be forced into a designed vent to replace air removed. The fumes in the area would then have to pass through the fan(whether it be a squirrel cage set up or an inline fan) and out the exhaust vent. In the fire service, the old way of ventilation was to use negative pressure. The more efficient way is with positive pressure fans replacing gases and fumes with fresh air.

 

[sstone]

Re: engine room blower does not suck out but blows air in !

In engineering school we were always told positive pressure is best for ventilation purposes. Of course this was in cooling applications not bilge blowing. Blowing fuel fumes over an electric motor, spark proofed or not, seems kind of risky though. But then again im not a boat builder

 

[Part-time]

Re: engine room blower does not suck out but blows air in !

The hamster wheel type blower is supposed to blow the air/fumes out. It's wired backwards and will be much more efficient working in the proper direction.

 

[Oshkosh1]

Re: engine room blower does not suck out but blows air in !

There should be an intake and exhaust. The intake should have two static 4" hose(s) which allow fresh air to be drawn in, the exhaust side has one 4" hose under "power" from the exhaust blower, and one static. At least that's how my boat's vent system is set-up...4 seperate tubes total.

Also, the stbd intake side vanes are oriented so that air is "rammed" into it(facing forward) and the exhaust portside is designed to draw a slight vacuum(facing stern). Each assembly has two openings for 4" tubing.

You SHOULD have a sealed unit so if all is well there is very little chance of explosion.

 

[Another retired guy]

Re: engine room blower does not suck out but blows air in !

I'm going to jump in here again! Blowing air into the engine bay ( positive pressure) will NOT displace the heavier-than-air fumes sitting in the bilge. The nice fresh air will just pass through the upper part of the bay and out of the other vents. The fumes will still be there waiting for that spark