Thread: Air Extractor setup question

Originally Posted by plantagenon

Will the addition of the fan help lower any dust level in the shed that the DE misses if I keep the sliding doors at the front open?

Yes it should help.

If so how high should I mount it. I have a very heavy metal 3 shelf setup at the back of the shed that will easily take the weight of the fan on any of the shelves.

Higher up is better as you can then take advantage of the thermal convection that drives fine dust up to ceiling level.

What is the best way to finish off the ducting pipe on the outside to stop water or bugs, spiders and snakes getting into the shed through the unit and the best way to insulate around the ducting pipe which is air conditioning pipe?

If you slight angle the pipe downwards and cut the end of the pipe at an angle so the top overhangs the bottom of the pipe that will stop any rain from getting back in. You could put a fine mesh like fly wire insert into the pipe but it will drastically reduce the flow especially when it collects dust and crud. Is the rest of your shed that airtight and ionsect tight Personally I wouldn't worry about using anything - I don't have anything on my welding bay exhaust hood extractor fan. If anything is in the pipe when I turn it on it's sent flying.

I was thinking of a light metal pipe (one I might have to make up) around the pipe and pop riveting it to the outside of the back wall.

Have a look in large hardware stores and see if you can find a short length of 12" galvanized chimney stack - should work alright.

BTW the specified flow rate and power of that fan (60 m3/min. 0.7 HP) will be for a theoretical unrestricted non-turbulent flow. In reality and placed inside even a short duct or opening I would expect about 1/3 of that e.g. 20 m3/min or 560 cfm. That's almost as much as volume of the shed per minute - should work quite well. I'll bet it will be fairly noise though.

You could get away with around half that flow rate, it might be a bit quieter too?

Thanks Bob. Good advice as usual.

I will only need about 1 metre of ducting or maybe even down to 50cm. I will search for the chimney stack. Maybe I can just use that on the outside and dispense with the ducting as I can get the rear of the fan right up against the back wall of the shed and screw it into place to the timber lining so it shouldn't vibrate too much.

The fan was surprisingly quiet when I got them to turn it on at H&F before I bought it. Just the sound of air gushing. I imagine the pipe might increase it a bit but I can get insulated pipe.

Just getting some air con installed in the house and the installer is giving me the ducting, if I end up needing it. I priced is at a couple of places - H&F - $99 for 5m. Another place $164 pm.

I managed to get some 320 aluminium foil ducting on Ebay fairly cheap. I will probably have to treat it with kid gloves but it should do the trick. I now have the small shed to set up on Saturday outside the main shed. So I can put the DE in it and extract dust from the lathe in the main shed via a 100mm ducting pipe fed through holes cut in the walls of both sheds. A further pipe from the DE shed will run 6 metres to the back of the main shed to keep the dust away from the front and only door to the main shed. Thanks again BobL for that advice.

Until I can cut a 320mm hole in the rear of the main shed to put ducting from the H&F exhaust fan outside the shed, I was thinking of a temporary solution as outlined in the attachment. My question is:

If the fan is placed facing the rear of the shed it will suck air out from the rear through the ducting pipe, out the door and most of the way to the rear of the shed. The two front doors of the shed will be open. Will the fan create a vacuum effect in the shed or will air be sucked in through the front doors ensuring a fresh air supply to the shed?

Thanks for your advice

Greg

[ATTACH]258821

The fan will create a vacuum effect.
The extent of the effect will depend upon inverse distance squared, so doubling the distance reduces the effect by the effect by 4 times. The fact that you are going around a corner further adds to reducing the effect.

I have finally got my DE shed built and the DE put inside it. I went to Austral (insulation supplier in Qld) and bought some noise insulation bats, but had them (the glass centre) also lined with aluminium foil on the back side. It comes with perforated alum on the sound resistant side. The second piece of alum foil was to allow me to glue the sheets to the inside of the DE shed. It cost me an extra $10 per 2400 x 1200 sheet but was well worth it. The DE shed is now like a padded cell. Before I put the insulation in, I cut a hole in the side of the shed and fed the power cable and 100mm DE pipe from the main shed to the DE shed. I then sealed the gaps with Sika Boom (expandable foam). A 100mm hole was cut into the back of the DE shed to allow for DE piping to be fitted and let dust build up flow out the pipe. The pipe runs 6 metres to the rear of the main shed.

Apart from the fact that the insulation cuts the noise from the DE to almost zero, it also stops dust escaping from the DE shed. I sealed every joint of insulation with aluminium tape.

Maybe this will solve my DE problems. Now I want a bigger DE

I will post photos shortly.

Thanks for the advice again BobL

Greg