How many amps Can I pull safely???

[Big_Spark]

Smitty, why are you thinking of using multiple motors?

Is this practicality, or to ensure you move enough air?

Have you considered something like this..

http://rswww.com/cgi-bin/bv/browse/...D=ukie&3258960855=3258960855&catoid=-85025071

I have a 200mm version, and that sucks air from the computer room so efficiently that no aircon is needed unless the ambient (outside) air temp rises above 23C.

You can increase the air pressure on the output side by reducing the diameter of the outflow duct.

 

[ban-all-sheds]

I thought this was a diy forum not 'expert'.

It is indeed a DIY forum - not sure what information you've been given here that you consider irrelevant to your needs (apart from FLW's condescending comment about the design of the motors).

It doesn't matter whether you are a DIY-er or expert electrical engineer with a lifetime's experience, the capacities of cables, the design rules for electrical circuits, the startup surge of motors, the characteristics of protective devices etc etc etc are the same, and you can't proceed in ignorance of these factors just because you don't do it for a living.

 

[jsmith]

It's several things, but cost and availability is the main (I got my motors off ebay £8 each).

They need to pull 200CFM at a test pressure of 10" of water. I would like to try one as they look very neat but they are expensive.

I need about 200cfm (cubic feet per minute), so the 150mm duct fan would be ok @270CFM and the 200mm great @500CFM.
I wonder if it would create the required test pressure I need though (10"H2O).

 

[Big_Spark]

(apart from FLW's condescending comment about the design of the motors).

Ban, do you wish to justify that comment as nothing I have said is condescending.

 

[Big_Spark]

They need to pull 200CFM at a test pressure of 10" of water. I would like to try one as they look very neat but they are expensive.

I need about 200cfm (cubic feet per minute), so the 150mm duct fan would be ok @270CFM and the 200mm great @500CFM.
I wonder if it would create the required test pressure I need though (10"H2O).

I am certainly not too up on airmovement etc, usually leave such things to AirCon design engineers, however you can increase the pressure of the output of the fan by reducing the size of the bore that it is being passed through, just as with water.

The fan will have a constant input pressure, if you reduce the output by bore by half, then you will (I think) double the pressure..I cannot remember whether the ratio is linear or not, one of the others may know.

Not sure if this will be any use to you, but it may be.

http://www.ventaxia.co.uk/sharing/requirements.asp

 

[ban-all-sheds]

Ban, do you wish to justify that comment as nothing I have said is condescending.

Well - it's ironic that I'm replying to this immediately after the post that I made about how people should take care about how they write things and how they read things, but..

..they will be Squirrel Cage Induction Motors..means b****r all to you..

It just seemed to me that to throw in the name of a particular design of motor and immediately say "means b****r all to you" was condescending. I apologise for my mistake, but I think it's one that others might also make.

Mike.

 

[Big_Spark]

Mike, I added the "means bugger all to you" as to me it was obvious his technical knowledge of motors was severally lacking. If it was not the case he would probably not be asking the question he did.

Without that technical knowledge the chances of him knowing what is meant by a SQIM would be very slim..hence my comment.

I suppose a bit presumtive on my part..certainly not meant ot be condescending at all .

 

[jsmith]

Steady on guys - It's easter after all!!!

How about a comment on post 9. Better way to spend our time than having a pop at each other!

 

[Big_Spark]

Steady on guys - It's easter after all!!!

How about a comment on post 9. Better way to spend our time than having a pop at each other!

Nah, it's OK..Ban commented on what I wrote, I had not really explained it properly in the original post, but my question to Ban was because I read my posts different to Ban, I knew how I meant it, but Ban wasn't sure.

I hope he now understands what I meant, but it's not a big issue...

Unless you wanna make it one Ban

Joke OK!!

 

[Grizzly]

lol i dont no how i posted that i had the page open and wen out ( 6 others in the house at the time lol)

It was something of a triumph for your first post here.

 

[JBR]

If the dyson pulls 15.27A on start up, how come it doesn't blow the fuse every time?

The 13A BS1363 fuses in plugs are slow blow to a certain degree. They will stand up to about 8 times their maximum rating for very short periods, just like any type of fuse for MCB

Presumably, that's why our lights dim slightly and briefly when I turn on our vacuum cleaner (that's a Dyson too)?

I'm hoping that's normal!

 

[ericmark]

Clearly from 2004 he will have cured the problem but I looked at it and thought we had 110 volt vacuum cleaners with three motors which ran on three phase 16A or single phase 32A plugs in Sizewell during the building.

I seem to remember one can draw around 10A per phase with a 16A three phase plug before it will exceed the 16A total.

Oddly Sizewell was the only site I remember having three phase 110 volt transformers. We had four core cable feeding four way distribution boxes stopping one plugging one distribution box into another.

We also had 32A distribution boxes three phase to reduce the wire armoured temps required.

Wonder what people did with those vacuum cleaners with three phase 16A plugs on?

 

[Porque223]

There must be breakers available with trip curves that accommodate motor starting without nuisance tripping, but reading those curves can be tedious because they may use logarithmic and not linear scales.

 

[Taylortwocities]

Yes, we know.

And it is not tedious.

 

[JohnW2]

...but reading those curves can be tedious because they may use logarithmic and not linear scales.

Reading those curves would probably be even more difficult if they used linear scales, unless they were the size of a swimming pool! Tediousness is in the eye of the beholder.

Kind Regards, John