# Panaflo Fan - Which Way Is The Right Way Round



## Pete77 (Aug 1, 2006)

I took my Panaflo fan out of my Tivo to clean it but now I'm not sure which way round is the correct way to put it back?

If I put it back with the Panaflo label clearly showing and pointing towards the inside of the Tivo and the unlabelled side towards the exterior outside wall of the Tivo and grill on the Tivo this seems to make sense as the Flo arrow on the Panaflo then shows it is drawing cold air from outside the Tivo in to the Tivo to cool it down. Whereas if the Panaflo was the other way round it would actually be trying to pull hot air out of the inside Tivo, which as far as I know is not a very effective cooling technique.

However the only picture I can find of the orientation of a Tivo fan in a UK Thomson Tivo PVR10UK at www.steveconrad.co.uk/tivo/cachecard.html shows the Panaflo fan the other way round from the one that seems logical with the unlabelled side towards the interior of the Tivo trying to pull hot air out and not blow cool air in.

Unless of course Panaflo were not consistent about the Flo direction in relation to the labelled side of the fan between different batches of the fan.

Which way round do most of you think the Panaflo should be as once you take it out there is no way to be sure as it will fit back in to the Tivo either way round.


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## PaulWilkinsUK (Mar 20, 2006)

Pete77 said:


> I took my Panaflo fan out of my Tivo to clean it but now I'm not sure which way round is the correct way to put it back?
> 
> If I put it back with the Panaflo label clearly showing and pointing towards the inside of the Tivo and the unlabelled side towards the exterior outside wall of the Tivo and grill on the Tivo this seems to make sense as the Flo arrow on the Panaflo then shows it is drawing cold air from outside the Tivo in to the Tivo to cool it down. Whereas if the Panaflo was the other way round it would actually be trying to pull hot air out of the inside Tivo, which as far as I know is not a very effective cooling technique.
> 
> ...


To suck or to blow... that is the question 

Personally, I'd suck...


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## bhedge (Mar 20, 2005)

I had the lid off mine the other day, I've never touched the fan so I investigated it for future reference and it appears to suck air out of the TiVo. It also had the sticker facing outwards.


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## blindlemon (May 12, 2002)

bhedge said:


> It appears to suck air out of the TiVo. It also had the sticker facing outwards.


Correct.


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## SilkMan (Feb 13, 2007)

Given the basic knowledge that hot air is at a higher pressure than cool air, and therefore rises to the top of a sealed container, if you have nowhere for the hot air to escape to, then pushing in more air is only going to raise the pressure and may make things worse. Since the Tivo has no vents on the top of the box, it therefore makes sense to pull the hot air out, allowing cooler air to be pulled in from the vents in the bottom of the case.

For PCs, normally it makes sense for the rear fans at the top of a tower case to pull the hot air out, while the ones lower down, preferably at the front, pull cool air in.

Having said that, if you've ever followed some of the debates on cooling high-end computers, things are not always that simple!


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## 6022tivo (Oct 29, 2002)

99% of fans have a arrow showing the direction of the flow, normally a risen area of the plastic, on one side. The tivo fan blows out.


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## Pete77 (Aug 1, 2006)

But has anyone tried running a Tivo with the Panaflo fan the other way round blowing air in and observed what happened to the Tivo's temperature level as a result?

I think to get the Tivo fan to suck you can't then have the Panaflo label facing outwards the right way up due to the position of the wiring connector.


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## aitcheff (Mar 23, 2003)

SilkMan said:


> Given the basic knowledge that hot air is at a higher pressure than cool air, and therefore rises to the top of a sealed container ....


I'm sorry that I'm going to be pedantic, but I would have had my ear twisted at school for saying this  .

While it's true that if you heat air in a sealed container, the pressure will rise, in this case where air can escape from the Tivo, the hot air will be at the same pressure as the rest of the air (apart from a very minor pressure variation from bottom to top - and ignoring minor changes in pressure due to the motion of the air). However, the hot air will have a lower density than the cooler air and you are quite correct that it will therefore tend to rise to the top.


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## blindlemon (May 12, 2002)

The wire slots into the notches in the bottom of the fan and emerges on the "back" - ie. inside the TiVo


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## Pete77 (Aug 1, 2006)

blindlemon said:


> The wire slots into the notches in the bottom of the fan and emerges on the "back" - ie. inside the TiVo


Yes but this is clearly a standard Panaflo fan so it doesn't necessarily imply that the notch for the wires in the bottom of the fan surround must be utilised in this particular application.

I suppose an interesting test would be both to reverse the direction of the fan and then to also run the Tivo with the fan disconnected and see what difference it actually made to the Tivo's operating temperature in the same ambient room temperature.

Of course all of this is better tested in the dark days of mid winter than in the height of the summer, except that with the wintry summer weather we have forecast for the next few days one might still be able to get away with it......


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## SilkMan (Feb 13, 2007)

aitcheff said:


> I'm sorry that I'm going to be pedantic, but I would have had my ear twisted at school for saying this  .
> 
> While it's true that if you heat air in a sealed container, the pressure will rise, in this case where air can escape from the Tivo, the hot air will be at the same pressure as the rest of the air (apart from a very minor pressure variation from bottom to top - and ignoring minor changes in pressure due to the motion of the air). However, the hot air will have a lower density than the cooler air and you are quite correct that it will therefore tend to rise to the top.


Oh bother  . Ok you're correct (although in my defence, I did say sealed  ) but the important thing is that when you introduce a fan to push air in, you are no longer dealing with a static situation, and things start to get complicated. Throw in the specifics of the case design, component layout (heat sources and obstructions to air flow) and fan position and it all begins to get so dynamic that the simple state solutions no longer apply. If you were to ask me what would happen if you turned the fan around I'd say try it and see 

BTW those "minor" pressure differences from bottom to top are why the less dense air rises, rather than just sitting there, but no more physics lessons - it's making my head hurt (and reminding me of all those tweaked ears at school  ).


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## blindlemon (May 12, 2002)

Pete77 said:


> Yes but this is clearly a standard Panaflo fan so it doesn't necessarily imply that the notch for the wires in the bottom of the fan surround must be utilised in this particular application.


That's how it was shipped from the factory, so I guess that's how it should be


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## Pete77 (Aug 1, 2006)

blindlemon said:


> That's how it was shipped from the factory, so I guess that's how it should be


OK but you have to have the fan with the Panaflo sign on its side to achieve this as otherwise the wires groove isn't in the right place in terms of the length of the wires bundle, unless you cut the cable ties.................


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## blindlemon (May 12, 2002)

Yes, that's correct. The bar where the wires emerges from the centre of the fan should be aligned with the blanked out bar in the fan cutout on the rear panel.


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## Pete77 (Aug 1, 2006)

blindlemon said:


> Yes, that's correct. The bar where the wires emerges from the centre of the fan should be aligned with the blanked out bar in the fan cutout on the rear panel.


Must say I didn't notice the blanked out bar in the fan cutout but found it was the only way round it would fit. You must have been shining a strong torch down there.


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## PaulWilkinsUK (Mar 20, 2006)

Pete77 said:


> But has anyone tried running a Tivo with the Panaflo fan the other way round blowing air in and observed what happened to the Tivo's temperature level as a result?
> 
> I think to get the Tivo fan to suck you can't then have the Panaflo label facing outwards the right way up due to the position of the wiring connector.


Pete77, you worry about far too much in life... Chill


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## Pete77 (Aug 1, 2006)

PaulWilkinsUK said:


> Pete77, you worry about far too much in life... Chill


But those of. us who are anally retentive about such matters cannot but help be interested.....


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## TCM2007 (Dec 25, 2006)

I think all PC-type cooling fans expel hot air rather then drawing in cool air.


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## iankb (Oct 9, 2000)

I think PC fans tend to draw cool air in at the front of the case (i.e. over the disk drives), and expel hot air out the back from the motherboard and the PSU. If you only have one fan (as in the TiVo) it should always expel hot air. Better to create a slight pressure drop within the case than a slight pressure increase.


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## mjk (Mar 13, 2002)

PaulWilkinsUK said:


> Pete77, you worry about far too much in life... Chill


It is a lot easier to chill when your fan is blowing in the right direction!!


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## blindlemon (May 12, 2002)

Yeah, otherwise it just sucks....


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## PaulWilkinsUK (Mar 20, 2006)

Fans should suck, not blow - just like women


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## Pete77 (Aug 1, 2006)

PaulWilkinsUK said:


> Fans should suck, not blow - just like women


I note the time.

Were these comments made shortly after receiving a practical demonstration of the phemonenon you describe?


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## PaulWilkinsUK (Mar 20, 2006)

Pete77 said:


> I note the time.
> 
> Were these comments made shortly after receiving a practical demonstration of the phemonenon you describe?


I wish! 
Sometimes I wake early  . My alarm goes off at 0530 normally anyway. Things to do, cars to build etc etc

Anyway, I digress off topic...


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