Don't Use Aquarium Pumps To Pump Cold Air

[PistolPatch]

In some of my prior threads I mentioned I was going to use an aquarium pump to pump cold air from my fridge to a fermenting box (esky) to keep it cool. Whatever you do, DON'T DO THIS. The air they pump is warm (20 degrees)!

If you want the details on wasting a lot of hours and $80, then read on...

Firstly, I spent hours trying to find an air pump that would blow 40-60 litres per minute. A thread came up here with the answer a week after all my searching. After finding out from another AHB member that the body of the pump didn't get warm, I immediately bought a 60 litre per hour pump at $80 or so. The day after my purchase, Ross visited the store and posted here how noisy these high volume pumps were. Too right!

Finally had a few hours to spend today to think of how to get this noisy air pump to work most efficiently. Ended up widening existing holes in fridge and esky which is a very unpleasant task using a hole saw as there is no guide for the larger saw. Hooked up the pump and started pumping air at minus 2 degrees via a direct connection to my fermenter box (esky).

End result - absolutely nothing!

Couldn't work this out but finally had a frightening realisation and shoved a thermometer up the outlet air tube and it read 20 degrees! So, if you want to warm air from minus two to twenty then here is your answer!

Seeing as I rarely get time to tool around I stupidly also cut the electrical plug of the pump so as I could put the it in my fridge. I mean, at this stage I had no doubt that the pump would work. My only question had been that I probably had bought too large and noisy a pump - should I swap it for a 40lt? So, now there is no way I can return it.

There's a lot of swear words going through my head right now but hopefully by my posting here, others will not go down the same track.

The pump I bought runs 8 aquariums so I may give up brewing and take up fishing or whatever you call it. Better still, maybe, I can use the ******* as a fan heater in winter?

FOR SALE: 60lt/Min Aquarium Air Pump. Runs 8 tanks. Heavy duty. Hardly used. Reluctant Sale - Going Overseas to a tropical climate!

 

[razz]

Well done PP. Another piece of brewing equipment takes one for the team. Keep the new(ish) pump for aerating starters. You could try the fan from a pc to blow cold air into your esky, just rip one out of your computer. :lol:

 

[goatherder]

All might not be lost - it sounds like it might make a decent wort airator. What do you reckon?

 

[Tony]

yep, airate your wort with it.

cheers

 

[PostModern]

What is the internal diameter of the pump's outlet and the internal diameter at the end of the hose into the fermentation chamber? My guess is that the former is smaller than the latter.

 

[Ducatiboy stu]

If you want to tranfer air from a fridge to a ferment box, why not use the in-line axial bathroom fans. they come with about 3mtr of flexable 150mm duct and would be perfect for the job. You can get them from electrical wholsalers.

 

[PistolPatch]

Yep Razz, I certainly have taken one for the team - LOL!

I already have a small aquarium pump for aeration which is fine. the 60 litre/minute will be way too much for aeration as someone else here found recently with 40lt/minute. I think I will just move from here and brew in 230 litre batches as this pump would be perfect for that amount!

PoMo - Unfortunately the tubing was the same size all the way through - about 10mm ID. I like the way you're thinking though!

Also like Ducati's idea. Hadn't heard that one before but I can't see myself drilling such a large hole in my fridge and esky. Thankfully I still have one card up my sleeve and I'llplay that on the weekend and see how well it works.

Thanks for the feedback.

Cheers
PP

 

[Finite]

try ebay PistolPatch you might at least get half your money back?

 

[Jez]

Pistol,

Why not still use your pump to aerate your wort but use an adjustable valve between the pump & the aeration stone to lessen the flow similar to Zwickels setup. You'll probably never need to have it on full but you can still use it instead of selling it for a lot less than you paid.

If it's magnetic drive it shouldn't burn out by the airflow being restricted right?

Jez

 

[Goat]

could you re-circulate the warm air back through the fridge and then into the fermenter. ie - re-cool the air and then push it to where you need it?

 

[Vangleator]

Was the hose going from a closed fridge to a closed fermenter box?
If so, you will need a return hose to keep the cold air moving around (saves money too). Otherwise 60lt of air a minute is a hell of a lot of holes in the fridge and esky to go through.
Air in pump was hot because
a) at around one fridge volume every three minutes the fridge couldn't cool the air down fast enough, or
B) the air in the hose was still due to blocked inlet from closed fridge, and overheated because it was (stuck) in the pump housing.
Hope that helps. Cheers.

 

[PistolPatch]

Ebay is looking like a good option Finite! The pump is built like a brick and sounds like a cement mixer so Jez, I don't think it's worth my while keeping it as well as my existing smaller pump. Trying to find an adjustor for that size hose would probably chew up even more time which is currently in short supply! Unfortunately Goat, I can't see a way of easily applying your idea with my set-up. I think the energy cost would also add up pretty quickly. Live and learn eh?

And Vangleator - more bad news! The re-circulation bit and all else is fine (pumps in through a 12 mm hose and has a 25mm hole to return to fridge.) I threw a thermometer in the outlet just then to see how long it takes for the pump to start pumping warm air. It pumped warm immediatlely while sucking from the fridge which was at about 4 degrees! I would have thought it would pump cold air for at least a minute but no luck.

So EBay it is!

Thanks again,
PP

 

[Batz]

! The pump is built like a brick and sounds like a cement mixer

[post="124488"][/post]​

I use a high volume aquarium pump,bigger than yours!
And it very quiet,most of the Queensland brewers have seen mine in action.
I think you have a dud brand

Batz

 

[paulc]

Sounds like you were trying to suck the cold air out of the fridge, through the pump, then into the esky.

How about just trying to cool the air coming out of the pump rather than the air going in? try leaving the inlet at room temp (outside the fridge), and running the outlet hose through the fridge, then into the esky? You might need a longer outlet hose that you can coil in the fridge. Maybe even in a container of cool water?

Hope this helps.

 

[Guest Lurker]

Air in pump was hot because
a) at around one fridge volume every three minutes the fridge couldn't cool the air down fast enough, or
B) the air in the hose was still due to blocked inlet from closed fridge, and overheated because it was (stuck) in the pump housing.
Hope that helps. Cheers.

[post="124399"][/post]​

An aquarium pump is a compressor, which is designed to increase air pressure. It didnt work very well because in this application you need a fan, which increases air flow, not pressure, as has been pointed out. The air coming out is hot because of the friction generated when the compressor squeezes air from a larger volume to a smaller volume. A large scale air compressor generating 150 psi can produce air at well over 100 degrees. So a compressor would only ever work if the air was cooled after being compressed.

 

[Batz]

Air in pump was hot because
a) at around one fridge volume every three minutes the fridge couldn't cool the air down fast enough, or
B) the air in the hose was still due to blocked inlet from closed fridge, and overheated because it was (stuck) in the pump housing.
Hope that helps. Cheers.

[post="124399"][/post]​

An aquarium pump is a compressor, which is designed to increase air pressure. It didnt work very well because in this application you need a fan, which increases air flow, not pressure, as has been pointed out. The air coming out is hot because of the friction generated when the compressor squeezes air from a larger volume to a smaller volume. A large scale air compressor generating 150 psi can produce air at well over 100 degrees. So a compressor would only ever work if the air was cooled after being compressed.

[post="124526"][/post]​

Yep,computer fan and some insulated ducting should do the trick

Batz

 

[thunderleg]

Sounds like you were trying to suck the cold air out of the fridge, through the pump, then into the esky.

How about just trying to cool the air coming out of the pump rather than the air going in? try leaving the inlet at room temp (outside the fridge), and running the outlet hose through the fridge, then into the esky? You might need a longer outlet hose that you can coil in the fridge. Maybe even in a container of cool water?

Hope this helps.

[post="124523"][/post]​

Maybe you could use a copper coil in the fridge for air to air heat exchange? 1/4" annealed copper tubing is easy to make coils from without having special bending equipment. See Homedistiller forum

 

[PistolPatch]

Well I won't throw it on EBay just yet. The 4 of you above have me thinking.

Batz, I've probably exagerated the noise a little and it certainly can be resolved. The pump I have is very well built but I'd be fascinated to see yours and am dying to find out what you use it for as 60 litres of air per minute is a lot!

Stupid of me not to explain the limitations I'm dealing with in this thread. I've explained them in other threads and never thought to do so here. In short...

a) I have a direct 25mm hole between my fridge and an esky which sits on top as per the following pic.



B) Putting a computer fan in etc, will require drilling a second hole not only in my fridge but also the esky which will be a major drawback. I really want to work with one 25mm hole.

Guest has shown what the main problem is, (didn't realise that about the compressing versus blowing,) and Thunder and Paul have my brain spinning about another possibility that Goat hinted at before. Many thanks to you all as you may well have solved the problem.

I stupidly said yes to doing a job tomorrow but will think on the above and may even get a chance to test out the idea you have all triggered on Sunday. Pretty sure it will work thanks to you all.

Many thanks,
PP (and will keep you posted)

 

[razz]

PP. Put it on ebay and get a decent digital camera ! :lol:

 

[PistolPatch]

LOL - My digital camera takes accurate pictures of miners 1km underground prior to them being discovered. Unfortunatley all pictures taken with my Fujifilm F700 look like pictures of miners 1 km underground prior to being discovered! Common problem with the F700 but they are fixing it for free. Above pic done with camera phone.