ventilation question

[kme]

If I install 2 fans, one intake, one extract - both same make / type / size.

The intake will have a filter on it - the extract won`t!

They`re both much bigger than is necessary, so they`ll usually be running quite slowly..................

BUT

I want positive pressure in the building; therefore I want the extract to run slower than the intake.

I know this and be done with ratio`d drives - but I`m wondering if I can fit a "standard" speed controller to BOTH fans; but add something (resistive??) to the extract fan side, so it gets less than 50% of the output from the speed controller - and therefore goes slower than the intake??

KME

 

[Sidewinder]

Does it "have" to be positive pressure?

You could look at a "standard" speed control pot and put an offset in yes I suspect.

VSD's would probably be an overkill for the fans I suspect.

However, please remember that the clearance time MUST be verified once the fans are commissioned!

It depends on the detail of the speed controllers you use.

---------- Post Auto-Merged at 19:10 ---------- Previous post was made at 19:09 ----------

Ah, just re-read the OP, you are looking at one speed controller?

Are you going to monitor the level of contaminant?

If you are what will be the feedback loop?

 

[kme]

Wasn`t going to mate......

The fans I`m looking at have a max clearance ten times what we actually require - so thought was to put `em on a controller, with a physical restriction on the "minimum"; so they couldn`t tern `em down below approx 150-200% of the calculated airflow requirement.

n.b. Do you have the necessary kit to measure the airflow rates? If so, can you send me a quote for doing it.... (cover the time taken for the LEV doc if you want ] ) - and I`ll include it with the quote for install

 

[Sidewinder]

Yes I do have the kit for the clearance time work, I'll look at a quote as soon as I can.

 

[kme]

They`re only 200mm axial fans mate - <2A load.......What would a ballpark figure be????? (If they make `em that small!!!!) :slap

 

[Sidewinder]

He ain't got the fans yet!!!

 

[Evans Electric]

Not sure what you are trying to achieve Martyn, I can only throw in the following example.

Now I thought the vent engineer mentioned negative pressure but it must be positive I guess, anyway , the printer created a new room for a Digital plate maker and the vent guy put some 6" ducting to outside and a speed controlled fan to create positive pressure within the room to keep the paper dust out from the Print Room adjacent.

Only one fan , drawing air from outside though , not two . Used a rotary speed controller about 3A I think.

 

[kme]

Need nameplate current

1300 spin speed (twin tub :slap )

30W

0.22A @230V

single pole induction squirrel cage

for example!!!!!

 

[steptoe]

:slap

place is full of frickin numpties wanting hypothetical problems solved,

do he even have a BGB?

maybe he needs to ask his mentor. :|

 

[Evans Electric]

Not sure what you are trying to achieve Martyn, I can only throw in the following example.Now I thought the vent engineer mentioned negative pressure but it must be positive I guess, anyway , the printer created a new room for a Digital plate maker and the vent guy put some 6" ducting to outside and a speed controlled fan to create positive pressure within the room to keep the paper dust out from the Print Room adjacent.

Only one fan , drawing air from outside though , not two . Used a rotary speed controller about 3A I think.

Just to add that it works a treat . On the other side of the doors is the Print Room and everything in there has a thick layer of paper dust on it but in the Platemaker Room there is no dust .

 

[kme]

Not sure what you are trying to achieve Martyn, I can only throw in the following example.Now I thought the vent engineer mentioned negative pressure but it must be positive I guess, anyway , the printer created a new room for a Digital plate maker and the vent guy put some 6" ducting to outside and a speed controlled fan to create positive pressure within the room to keep the paper dust out from the Print Room adjacent.

Only one fan , drawing air from outside though , not two . Used a rotary speed controller about 3A I think.

Thanks Sandy :x

The building concerned is one room - needs the air to be refreshed due to the (side effect) production of CO2.

Thanks to the snakey-hipped one, we know the fan requirements.

It only NEEDS to be a 5" - but the intake needs to push more air into the room, than the exhaust removes - so only the clean air is being brought in.....

Erm......actually, having just posted that - do we NEED to exhaust; when we have a 2 sq. Metre doorway (with plastic curtain thingies) that is always open during the day ????

HTH

230Volts is no good unless its three phase, I don't do those crappy little single phase output invertersIf you haven't got a fan yet, get a 3 phase one and make sure its 6 wire so we can connect it in delta for 230V 3 phase on the motor and use a single phase supply to the inverter

OK - but see above.

1. Is there a requirement for an exhaust fan?

2. If not, what advantage is there to having a 6 wire on a drive; over a basic speed control? Given the comparative small size of the fans, I don`t think its necessary to relate fan speed to air quality - if they have speed control, with the minimum air movement preset.

3. If I DO need mech. exhaust; could I use a fan slightly smaller then the intake; to provide the differential?

4. What are the cost differences? `cos I`m going to be asked??