Computer fan at front of boat. A revelation.

[cheesegas]

Only my 2nd winter living aboard so I may be late to the party with this...but maybe it'll help someone out!

 

I've got a 45ft conventional layout, cruiser stern boat with the stove at the front and a diesel hot air heater at the back. Coming back to a cold boat, I usually have to run the diesel heater for a couple of hours to get the bed reasonably warm whilst the stove makes the front a sauna. The front of the boat otherwise ends up being 37C at the ceiling and 15-20C near the floor. Quite a differential.

 

Did a very crude installation of two cheap 120mm PC fans mounted either side of the front door, aiming at the floor at an angle. Running these at half speed whilst the stove is running reduces the roof temp to 29C and the floor is a much more foot friendly 25C. And the bedroom got warm without having to run the diesel heater! Convection currents must be carrying all the cold air to the front.

 

With a PWM controller on a 4 pin fan, reducing the speed also reduces the power they need, which is only 300mA each anyway.

[GUMPY]

Much the same as a stove top fan 😉

[cheesegas]

4 minutes ago, Loddon said:

Much the same as a stove top fan 😉

Got one of those too, it only moves air around at stove height and made little difference in my situation. Pretty sure that the pitch on those two blades is so shallow it barely moves any air at all compared to a PC fan; after all, the Peltier is putting out only a little bit of current and it's made worse by being placed in front of the hot stove pipe.

[blackrose]

The alternative is to buy a boat with the stove located in the middle (fore to aft) and then you won't have these issues in the first place. Most narrowboats are fitted with stoves by the bow doors. It's completely wrong from a heating efficiency perspective. They just do it because fitting it there is easy, it's out of the way and they don't need to put any thought into the fit out 

Edited November 8, 2021 by blackrose

[TheBiscuits]

8 minutes ago, cheesegas said:

it's made worse by being placed in front of the hot stove pipe.

 

That's why the fan instructions say don't place it in front of the hot stove pipe ...

[cheesegas]

1 minute ago, blackrose said:

The alternative is to buy a boat with the stove located in the middle (fore to aft) and then you won't have these issues in the first place. Most narrowboats are fitted with stoves by the bow doors. It's completely wrong from a heating efficiency perspective. They just do it because fitting it there is easy.

Agreed, but a couple of fans and a PWM controller are cheaper and easier than swapping boats or moving the stove... Spent a few months boat searching, and this one was the only one which ticked all the boxes apart from stove location.

 

 

Just now, TheBiscuits said:

That's why the fan instructions say don't place it in front of the hot stove pipe ...

I have a narrow stove (Villager something), and with a 5" top exit flue, wherever the fan sits, it'll pull air over the stove pipe and over the 'cold side' heatsink. Ideally, stove fans should be made with the Peltier and fan separate with a giant passive heatsink on the cold side, and the fan clamped to the top of the stove pipe.

[ditchcrawler]

4 minutes ago, cheesegas said:

Agreed, but a couple of fans and a PWM controller are cheaper and easier than swapping boats or moving the stove... Spent a few months boat searching, and this one was the only one which ticked all the boxes apart from stove location.

 

 

I have a narrow stove (Villager something), and with a 5" top exit flue, wherever the fan sits, it'll pull air over the stove pipe and over the 'cold side' heatsink. Ideally, stove fans should be made with the Peltier and fan separate with a giant passive heatsink on the cold side, and the fan clamped to the top of the stove pipe.

Is it possible to blow it across the stove.

[TheBiscuits]

4 minutes ago, cheesegas said:

I have a narrow stove (Villager something), and with a 5" top exit flue, wherever the fan sits, it'll pull air over the stove pipe and over the 'cold side' heatsink

 

Rotate the fan a half turn so it's blowing towards the flue.  It'll still circulate the air in the cabin just as well.

 

Or a quarter turn as Brian suggested.

[blackrose]

6 minutes ago, cheesegas said:

Agreed, but a couple of fans and a PWM controller are cheaper and easier than swapping boats or moving the stove...

 

I agree it's cheaper and easier, but it's also a workaround because of a bad boat fit-out design. 

[Cheshire cat]

Can you point us to the computer fan supplier please?

[ditchcrawler]

13 minutes ago, Cheshire cat said:

Can you point us to the computer fan supplier please?

computer fan 120mm | eBay

[JRT]

You could always try one of the USB powered desk top fans. (There are loads on Amazon). I have one on my boat and it works a treat.

[cheesegas]

23 minutes ago, Cheshire cat said:

Can you point us to the computer fan supplier please?

Try and get the 4 pin versions as you can use a 4 pin fan speed controller like this https://www.amazon.co.uk/Noctua-NA-FC1-4-Pin-PWM-Controller/dp/B072M2HKSN/

 

These have pulse width modulation fan speed control, which is far more efficient than the 3 pin controllers which just reduce the voltage.

[matty40s]

2 hours ago, cheesegas said:

Try and get the 4 pin versions as you can use a 4 pin fan speed controller like this https://www.amazon.co.uk/Noctua-NA-FC1-4-Pin-PWM-Controller/dp/B072M2HKSN/

 

These have pulse width modulation fan speed control, which is far more efficient than the 3 pin controllers which just reduce the voltage.

I've used 2 of these for my kitchen extractor

[Bee]

Blackrose has got it. Stove in the middle. Or, if its possible, get a backboiler for your stove or swap the stove and run a gravity system and radiators down to the cold, dark end. Heat goes upwards nor sideways which is inconvenient in a long boat.

[cheesegas]

19 minutes ago, Bee said:

Blackrose has got it. Stove in the middle. Or, if its possible, get a backboiler for your stove or swap the stove and run a gravity system and radiators down to the cold, dark end. Heat goes upwards nor sideways which is inconvenient in a long boat.

All those solutions seem quite a lot more expensive and difficult than £10 worth of fans and 10 minutes of my time. 😛

 

Looked at the back boiler option but my Villager stove is old and the back boiler is impossible to get hold of, and I have something on all my walls below the gunnels…

[GUMPY]

If I need more warmth down the back of the boat I just put the eberspacher on