For another project kick off ... I need to source an electric blower. (220V) Ideally an in-line blower, but would consider axial or similar.
I need around 200 cfm (150m3 hr)
The key thing is that it must not be a brushed motor as I can't have any ozone given off ..... which mean I need an induction motor.
I could use a bathroom in-line extract blower but these are pretty pricey .... anybody know of alternative ?
I did think of the Bilge Blowers as used on boats ... these are in-line duct blowers, but I am assuming as they are 12V then they would probably be permanent magnet brushed motors ? .. which would rule them out (unless you know different)
I have a couple of Vent Axia 150mm duct fans to provide air flow to my server and networking enclosure. These run at 490 m^3/hr when on full power. I run them via electronic speed control using a temperature sensor so that outside air temperature, ambient temperature and electrical power consumption are all taken into account. The result is that the enclosure temperature stabilises to +/- a degree or so.
Most of the time, the fans run quite slowly and are then very quiet.
There is a smaller one at around 130 m^3/hr
Have a look on the RS web site and search by duct fans. Then buy elsewhere.
All that I have come across are straight induction (synchronous) motored or capacitor start types. Brush fitted AC motors are generally not intended for continuous use, their design is more suited to providing high starting torque as is needed for portable drills etc.. A fan load needs little torque to start.
It's vital to have an idea of the head it's working against, i.e. the resistance on both inlet and exhaust sides.
Fan makers use headline figures of huge numbers of cfm, but whereas some may maintain a high proportion of it against a reasonable head, others drop to virtually nothing. Axial flow fans are often particularly poor for this.
Don't forget to allow for wind pressure (positive or negative), grilles, filters, bends, and so on.
They are fairly local to me. A large machine tool I used to work on in the '70s had a couple of their fans for cooling purposes. I thought they might fit the bill as they use induction motors and the web site gives some useful data about flow and back pressure (but a bit unclear)
I'm after a small induction blower though ... those things look meaty enough to fill a Zeppelin, I only need 100 cfm.
Even bathroom extracts are too big (usually)
I thought I had the ideal answer with a Bilge Blower from a boat ... these are used to blow out any petrol vapor before starting ...
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can't get a reply from seller ... and when I contacted Attwood they say they don't make brushless blowers, surprised brushed blower used as that would be fire risk ?
Andy .... a slightly oddball one (again) .. one of my hobbies is scuba diving ... and drying out a drysuit after a days diving takes a long time. I know you would expect a dry suit to remain dry inside, but they get a lot of condensation build up.
Came across this on a US dive forum :-
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and thought if I build the base and main risers out of 40mm abs waste pipe, and then smaller front risers (for gloves & hood) out of 21.5mm abs overflow. I have plenty of the pipe .. collected the fittings today , just need to source a blower ...
While at plumbing merchants - had a mooch around on shelves at extract fans, vent axial etc., but they showed me a catalogue ... for DOMUS
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where they have a 100 or 150mm in-line duct extract, they can give me 100mm one of those at very good price (not sure on
150mm price)
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is the model I thought may be suitable, have asked manufacturer for specs
If one of these is suitable .. I could have it fixed to a box, i.e sucking air from the box, and couple the box to the 40mm pipes, I have no idea how I would calculate the air pressure losses or head required. As these fans are suitable for ducting, I'm guessing that they would be much more suitable than an axial fan, and capable of giving a bit of pressure to overcome the resistance of pipe work.
I have no idea what it would be, just posted details of project - in responses to Andy's Q ... if you have any idea how I would calculate the 'head' for this ... let me know.
Ah... Now I understand and of course why you don't want ozone.
For this application, I would look at a centrifugal rather than an axial fan as long as you don't mind the extra noise. They are noisier. The point is that they will tolerate greater duct resistance without the flow falling as badly.
You would probably find that a 100mm bathroom type would be enough. If you couple it to a framework of 50mm rather than 40mm waste (assuming that will fit the wetsuit - I think it should) then I reckon it would be reasonable.
Since you are going to be restricting the airflow quite a bit, you need something able to overcome the resistance and maintain airflow. Coupling an axial fan will simply mean that the fan will back up and may not deliver the flow you are looking for.
Take a look at the Vent Axia site and under residential fans look at centrifugal and axial in turn. Look at the Solo (centrifugal) and VA100 (axial). Download the PDFs of the catalogue pages and look at the pressure/flow curves and you will see a huge difference between them in terms of maintaining flow at higher back pressure.
I don't think that probably something of Vent Axia quality is necessary for the application, because it's not the end of the world if it fails. I went for in line centrifugal fans and two of them because if there's a failure, the servers will overheat and the automatic shutdown would have to start shutting them down.
Centrifugal in-line fans are available - for example on the Screwfix site look at 98482. Notice that the shape at the sides is fatter than the ducted version you were offered which is axial. The impeller is shaped like a drum with blades around the side rather than a propeller and the air enters enters the centre. Think spinning action of washing machine. Then the oversized housing deflects the air to the exit duct.
You may not need something of this amount of output, although it is easy to hook up. You could perhaps get away with something smaller like 11442, but that's less clear. If you had to double it up through inadequacy then you have spent as much as to get the larger fan.
Are you going to use this in a garage or a spare room? One thing is that centrifugal fans are noisier than axial ones, although the axial ones do get noisier with back pressure.
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