650cfm Room Air Filter

**Polie** · 4th January 2012, 04:19 PM

Hi,

I have bought myself a 650cfm room air filter from Carba-Tec

Carba-Tec 650cfm Room Air Filter : CARBA-TEC

I read somewhere that the way to tell if your filter is blocked is to place a piece of A4 paper over the inlet and see how long it takes to fall down after you switch off the unit, it should take 1/2 the amount of time when the filters need changing when compared to new. The problem with this method is I am unlikely to test the system often enough and can't be bothered.

I figure the vacuum inside the unit will increase as the filters block and if I can monitor the vacuum with a gauge then I would know when to clean the filters.
The problem I have is I have no idea what level of vacuum to expect for clean or dirty filters and don't want to buy one and just hope it will cover the range of interest.

Does anyone have an idea what range of vacuum I can expect?

Regards,
Polie

**BobL** · 4th January 2012, 05:55 PM

I wouldn't buy one. I'd make one with a piece of clear PVC made into a U shape and c-clip it to some MDF, inside the tube put some some water and food colouring. You can simulate blocked filters by putting paper or plastic over the intake and that will tell you the maximum pressure difference (actually it's vacuum) that you are likely to get to.

**Polie** · 4th January 2012, 06:23 PM

Originally Posted by BobL

I wouldn't buy one. I'd make one with a piece of clear PVC made into a U shape and c-clip it to some MDF, inside the tube put some some water and food colouring. You can simulate blocked filters by putting paper or plastic over the intake and that will tell you the maximum pressure difference (actually it's vacuum) that you are likely to get to.

Thanks Bob,

Not sure if I am clear on how to make it, how do you stop the water from being sucked into the vacuum or the water drying up?
I am trying to remember back to the days when I had something similar but with mercury for balancing motorcycle carburetors.

Polie

**BobL** · 4th January 2012, 08:48 PM

Originally Posted by Polie

Thanks Bob,

Not sure if I am clear on how to make it, how do you stop the water from being sucked into the vacuum or the water drying up?

I have made dozens of these - the water won't get sucked in.
Water will dry up slowly but if you narrow the entrance and exit to the U-tube to the size of a pin hole it might need topping up once a year.

Even if some water evaporates it doesn't matter as it is the relative water levels that determine the pressure.

**Polie** · 5th January 2012, 11:23 AM

Thanks Bob,

What diameter tube do you suggest and what sort of length should I use?

I was thinking of making it a little too long to see what range it needs.
If I start with clean filters and take a reading then block 50% of the filter with a sheet of newspaper and take a second reading, then I will have an idea of the range required.

Regards,
Polie

**BobL** · 5th January 2012, 12:52 PM

Originally Posted by Polie

Thanks Bob,

What diameter tube do you suggest and what sort of length should I use?

I use something around 1/4" tube ID and a U tube height of say 200 mm.

I was thinking of making it a little too long to see what range it needs.If I start with clean filters and take a reading then block 50% of the filter with a sheet of newspaper and take a second reading, then I will have an idea of the range required.

Yep

Post a pic when you get it working.

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