Thread: Moving the DC outside

Originally Posted by Ian Dobson

No room for a second bag in my shed, but I could swap the bag for a PF if that decreases the back pressure?

No room for a other filter in my shed either so I ran a pipe outside into a 200 litre drum with a Thein filter

Ok, I've finally got the DC back into the shed. I had to partially disassemble it to turn it 90 degrees through the door now that I've reduced the space inside with the soundproofing.

I've attached a few photos showing the DC, the baffle box and its exhaust port.

When I fired it up for a few minutes I can see some tiny dust trails starting to appear around the bag ring where it's leaking a bit so I am very glad it's not in the workshop any more!

Last night I cobbled together a U-tube manometer from a few scraps and measured the static pressure (with no flow) at the impeller input as 7.25" WC with the bag ring connected up. It was 7.75" with the impeller output unhooked which surprised me as I thought the bag/filter would be more lossy. (Please tell me if I haven't measured this properly - refer photo.)

I don't have an anemometer to measure the CFM - can it be inferred from the static pressure and 6" duct size or does it need to be measured directly?

Measuring SPL will have to wait until I get the input ducting back through the window - although to my ear with the door closed sufficiently quiet. There does seem to be a small amount of resistance still in the last inch or two of closing the door - hope I've made my baffle output large enough. The exit is about four times the 6" duct area although the dampening material on the walls eats into that a bit on the inside.

Originally Posted by Ian Dobson

When I fired it up for a few minutes I can see some tiny dust trails starting to appear around the bag ring where it's leaking a bit so I am very glad it's not in the workshop any more!

Last night I cobbled together a U-tube manometer from a few scraps and measured the static pressure (with no flow) at the impeller input as 7.25" WC with the bag ring connected up.

That's about right. The most I have seen on a 2HP DC is ~8"

It was 7.75" with the impeller output unhooked which surprised me as I thought the bag/filter would be more lossy. (Please tell me if I haven't measured this properly - refer photo.)

I'm surprised you measure any difference in SP as there is no flow. It's only when there is a decent flow that a pressure difference will develop.

I don't have an anemometer to measure the CFM - can it be inferred from the static pressure and 6" duct size or does it need to be measured directly?

Yep it needs to measured directly.

I've plumbed the intake back to the workshop.

SPL at 1m now measures 63dbA ... a great result as the measure with the door closed before I installed the baffle was comparable, so the baffle is doing its job well.

Glad that's finished!

Next step is to devise an internal duct plan, that's a whole different topic so I will close this thread here. Thanks for all your advise and assistance, especially BobL, MandJ, and Lappa.

Originally Posted by MandJ

Those readings are interesting? I assume that you had the intake ducted into the shed when doing the test above.

Here are my readings for a 3HP 4 bag DE mounted in a timber frame (lots of treated pine to cut down panel resonance) Fibre Cement clad housing - no other lining - no exhaust baffle.

Sorry to but in on thread but was interested in statements around Fibre Cement.
This I realise was used on outside of enclosure. Would it have been 6mm think FC?
Could it be used inside (in same 6mm thickness) an enclosure to successfully reduce sound and as alternative to ply or MDF?

Originally Posted by SuperB15

Sorry to but in on thread but was interested in statements around Fibre Cement.
This I realise was used on outside of enclosure. Would it have been 6mm think FC?
Could it be used inside (in same 6mm thickness) an enclosure to successfully reduce sound and as alternative to ply or MDF?

Yes - anything with a bit of weight and rigidity helps - but it needs to be well supported (eg sturdy wooden frame) so it can't flex otherwise it can act as a drum head and transfer the sound out the other side.

Ok thanks Bob