12v Fan 4in Duct

JimMcGee · #1 (**permalink**) 08-17-2011

I installed AC in the boat this spring and with all the twists and turns running the 4" hose the length of the boat I'm losing a bit of air velocity.

I know you can get 110v fans for HVAC installations in your house that have this problem. I'm wondering if anyone knows a source of 12v fans for boats or RVs. I'm concerned about rust if I use a household fan, and a bilge blower is just too loud. Thought about a computer fan but I'm thinking the CFM would be too low.

Thoughts?

Jim

SlowButSteady · #2 (**permalink**) 08-17-2011

You can use a 12V "muffin fan" like the ones used to cool electronics. They are often used to vent battery compartments on boats.

JimMcGee · #3 (**permalink**) 08-17-2011

I thought about using one, but I'm not sure they'll move enough air.

The AC blower is rated for 410 CFM.

pdqaltair · #4 (**permalink**) 08-17-2011

a. Muffin fans have held up well for me on boats. The only wild card is condensation.

b. I doubt anything that can push 400 cfm down 30 feet of corregated hose will be quiet. I'll go further and say you won't find such a thing at all. I think you need to reconsider the design and place additional outlets closer to the sorce or add hoses. Sorry.

c. If there is such a thing it will be in an industrial supluy catalog under "high pressure fans and will burn amps.

I think you need to reconsider the design. This is a common problem with marine air, since the there is little space for ducts.

Tempest · #5 (**permalink**) 08-17-2011

I looked through my Risco RV catalogue and didn't see anything for ducts. You might try calling them they're in the Atlantic Highlands. 732-872-7722

I found this online. Looks like good CFM might be as loud as a bilge blower though?

http://www.walmart.com/catalog/produ...ndingMethod=rr

They can be found on Amazon too

Good luck

MacGyverRI · #6 (**permalink**) 08-17-2011

You didn't say how many outlets but, I would put the #4000 WalMart fan inline 1-2' after the 1st outlet and a 3000 before the last duct. If you have 4 outlets, put it after the 2nd one.

it should balance the system a bit so all ducts are blowing good as long as Amp use isn't critical/too high.

SVAuspicious · #7 (**permalink**) 08-18-2011

How about an engine room blower? Mine is 4" 12VDC.

JimMcGee · #8 (**permalink**) 08-18-2011

OK some clarification on the installation.

It's a 30 foot boat, so space is at a premium. The AC unit is installed under the v-berth. The outlet runs the length of the boat down the port side and I'm still getting pretty good flow when I get to the back of the cabin. But then I go through a bulkhead and come up to a 4" outlet at the back of the galley. That required two 90's and that's where I'm losing air flow.

There's only one 4" outlet in the galley. The inlet is a vent adjacent to the AC unit under the v-berth. Cold air is blown out in the galley and pulled forward through the boat to the inlet. I don't really need separate outlets in the v-berth or aft berth as the cabin on a 30 isn't all that large. Cool the cabin and you bring down the temperature in the berths.

This works well on all but the hottest days, and even then will bring the boat down to a comfortable temp after a while. But if I could improve the flow that last four feet it would bring the temp down much faster. It's my inner engineer trying to make the system more efficient.

I'm shying away from an engine blower as those fans are pretty loud, and most muffin fans I've seen don't have CFM ratings. I checked the Grainger catalog but only found 110v fans. I can run a 110v fan if I have to but a 12v would be easier to install. Also the 110v fans I'm finding have metal blades and I'm concerned they won't hold up in the salt air.

Jim

Cptken · #9 (**permalink**) 08-18-2011

Why are you only looking at 12v fans. Don't you need to be hooked up to shore power/genset to run the AC?

Tempest · #10 (**permalink**) 08-18-2011

Don't know what your clearance is in the galley. It would be great if you could get rid of one of the 90 degree turns, but I'm sure you weighed that option on the install.

If you had enough room at the outlet, perhaps you could simply mount a slim profile fan over the outlet opening, you might have to modify it for power supply and mounting

10 12 Volt or Battery Power Portable Fan RP73002 - $19.99 :

Though it sounds like for the most part, you're cooling well enough.