Thread: Clearvue CV1800 / Max Impeller Install - Home Garage Workshop

My apologies, I somehow missed the post with the drum details in it. It looks like a neat solution as it is often hard to find a drum to fit the space under the cyclone. I myself used a 205 litre plastic bin that chemicals are often shipped in. The customer making his own can enlarge the footprint to increase the volume if height is a problem.

Decided to take a few measurements this afternoon. Airflow and static pressure. Using a hot-wire anemometer and large manometer.

I took airflow measurements with the table saw connected, measuring across the duct exiting the table saw port about mid-length between the port and vertical bends (not technically a long-enough straight section to get fully-developed flow). I obtained just under 1000 CFM when calculating across 15 measurement points. It was difficult to get stable readings (+-0.5 m/s) at each point and I found that I had a fairly uniform velocity profile with a mild drop-off towards the edges. The flow is clearly very turbulent inside the pipe.
20160403_163532.jpg

Without the table saw connected I measured just under 1100 CFM (measuring across the vertical drop-down duct about 650 mm up from the gate).

I decided to take some static pressure measurements of the various configurations. I measured the static pressure just before the clear entry to the cyclone. In the results, shown below, one column adds an estimated 2.5" of static pressure for the cyclone and exhaust ducting. Clearly the band saw needs another 4" duct if I want to maximize airflow. The thicknesser dust chute also needs some mods as it is clearly adding a heap of static pressure. Amps draws are from the VFD and are "per phase" current not overall current draw (about 18-19 amps with no machine connected).


20160403_172409-1.jpg

			Current	Static (mm)	Static (Inch)	2.5" for Cyclone
No ducts Open			4.7 Amps	383	15.1	17.6
Table Saw Open Port			9.5 Amps	162	6.4	8.9
Table Saw Port with Flex			9.4 Amps	170	6.7	9.2
Table Saw Connected			9.20 Amps	190	7.5	10.0
Thicknesser connected			8.6 Amps	238	9.4	11.9
Far Wall Port Open			9.4 Amps	168	6.6	9.1
Bandsaw 1 Port Open			-	306	12.0	14.5
Bandsaw 2 Ports Open				272	10.7	13.2

The airflow results actually do correlate reasonably well (although a bit lower) with the performance curve posted by Bill Pentz showing CFM vs Static Pressure for the CVMAx and CV1800 (both with 16" impellers), where at 10" of static pressure the CFM is approximately 1000 CFM.

Originally Posted by DomAU

Decided to take a few measurements this afternoon. Airflow and static pressure. Using a hot-wire anemometer and large manometer.

I took airflow measurements with the table saw connected, measuring across the duct exiting the table saw port about mid-length between the port and vertical bends (not technically a long-enough straight section to get fully-developed flow). I obtained just under 1000 CFM when calculating across 15 measurement points. It was difficult to get stable readings (+-0.5 m/s) at each point and I found that I had a fairly uniform velocity profile with a mild drop-off towards the edges. The flow is clearly very turbulent inside the pipe.

The difference between the middle and the wall of the pipe should be around 40%. The readings jumping around by +/- 5 m/s you describe is pretty common. Sometimes the air speed in the same position will track systematically up and down by as much as 30% over 5-10 seconds. These are causes by compressed air spirals like streamers within the moving air. These may be cause by hard edges on/in/around transitions like the 2 x 100 mm Clearvue splitter or a machine port. Interestingly these spirals can propagate both up and down the flow. I have a doozie spiral in the 4m run of 6" ducting across the top of the old part of my shed and there is nothing I can seem to do about it.

The TS cabinet looks like it needs more ventilation as does the thicknesser.

I have a question, does the fan housing come with a direction of rotation sticker on it these days?

Originally Posted by Chris Parks

I have a question, does the fan housing come with a direction of rotation sticker on it these days?

Yes it does. I checked this when i first started up the cyclone .

I think that the only explanation for my slightly less than expected flow rate at my measured static pressure compared with the curve drawn by Bill Pentz is that my exhaust ducting has a larger than expected static pressure (maybe 2" h2O in addition to the 2.25" for the cyclone). Based on the excel calculator from Bill Pentz my static pressure is also about 25-30% higher in my duct runs than his projected values but this has no bearing on the comparative flow rates just on the absolute flow rate.

My only question is; since the bhp required has a fairly linear relationship to flow rate, if I reduce the static pressure, I won't unlock any more flow rate given that I'm already operating at about the Max power I can pull from a 20 amp outlet...

Originally Posted by DomAU

I think that the only explanation for my slightly less than expected flow rate at my measured static pressure compared with the curve drawn by Bill Pentz is that my exhaust ducting has a larger than expected static pressure (maybe 2" h2O in addition to the 2.25" for the cyclone). Based on the excel calculator from Bill Pentz my static pressure is also about 25-30% higher in my duct runs than his projected values but this has no bearing on the comparative flow rates just on the absolute flow rate.

My only question is; since the bhp required has a fairly linear relationship to flow rate, if I reduce the static pressure, I won't unlock any more flow rate given that I'm already operating at about the Max power I can pull from a 20 amp outlet...

I am surprised that you only get 1100 CFM with 6" ducting.
With 15" of pressure the theoretical flow should be 1500 CFM with 6" ducting.

My 3HP with only a 13" impeller system get a true 1250 CFM with clean bags and a 1.5m length of 6" ducting
This was measure using both a Pitot tube, and also using hot wire Anemometer.
This agrees with the theoretical flow of the static pressure measurement of around 10"
The 240V current drawn is around 9.2A
At the end of the longest ducting and junction run (11m of ducting and 4 x 90º bends) and when the filters get conditioned it drops to around 900CFM.
Not all of my junctions are sealed.
Being such a small impeller of course the fan curve will not be as good a that of a bigger impeller so it won't have as much flow.

I would be wary of any pressures measured and conclusions based on when there is flow in the system due to bernoulli effects.
That's why pitot tubes are used to measure flow rather than using single point pressure readings.
BTW these pressures are not "static pressures" because there is flow in the system. That's what "static" means - no movement.

I tell you one thing I thing I didn't like on the standard Clearvue and that is the tiny radius (1R) 90º elbow on the outlet of the impeller - that's why we didn't buy it for the cyclone at the mens shed and I made a 2.5R bend instead.

Originally Posted by BobL

I am surprised that you only get 1100 CFM with 6" ducting.
With 15" of pressure the theoretical flow should be 1500 CFM with 6" ducting.

My 3HP with only a 13" impeller system get a true 1250 CFM with clean bags and a 1.5m length of 6" ducting
This was measure using both a Pitot tube, and also using hot wire Anemometer.
This agrees with the theoretical flow of the static pressure measurement of around 10"
The 240V current drawn is around 9.2A
At the end of the longest ducting and junction run (11m of ducting and 4 x 90º bends) and when the filters get conditioned it drops to around 900CFM.
Not all of my junctions are sealed.
Being such a small impeller of course the fan curve will not be as good a that of a bigger impeller so it won't have as much flow.

I would be wary of any pressures measured and conclusions based on when there is flow in the system due to bernoulli effects.
That's why pitot tubes are used to measure flow rather than using single point pressure readings.
BTW these pressures are not "static pressures" because there is flow in the system. That's what "static" means - no movement.

I tell you one thing I thing I didn't like on the standard Clearvue and that is the tiny radius (1R) 90º elbow on the outlet of the impeller - that's why we didn't buy it for the cyclone at the mens shed and I made a 2.5R bend instead.

Thanks Bob,

My understanding is that when there is no flow you are measuring Total Pressure which also happens at that condition to be the static pressure as there is no dynamic pressure due to the zero velocity condition. I'm measuring perpendicular to the flow which should give me the static pressure whilst air is flowing. A Pitot static tube provides the differential pressure between the stagnation (or total pressure) measured at the end of the tube facing the flow and the static pressure measured perpendicular to the flow. This differential pressure is the dynamic pressure which allows for calculation of velocity.

Is your 10" of total pressure measured with the filter bags in place? That's a heap of flow for 3hp compared with my 5hp system. Maybe my hot wire Anemometer is not reading correctly. Since my motor and PowerPoint are at their limit and the motor is developing close to 4.5hp I can't really gain any more flow by decreasing restrictions (to the table saw) so am at the limit of what the 16" impeller is capable of.

I don't have an elbow on my exhaust so don't need to worry about this but nice job on the larger radius transition!

Dom, I am puzzled why you have effectively restricted the 16" impeller with the smaller impeller housing of the 1800. I have read your reasoning but I still don't get it as the inlet and exhaust are way too small. Using a Max housing it is possible (just) to run three open ports at once but the 1800 won't flow enough to do that no matter what size impeller is in it. My apologies for being obtuse but I just don't follow the reasoning.

Originally Posted by DomAU

Thanks Bob,

My understanding is that when there is no flow you are measuring Total Pressure which also happens at that condition to be the static pressure as there is no dynamic pressure due to the zero velocity condition. I'm measuring perpendicular to the flow which should give me the static pressure whilst air is flowing. A Pitot static tube provides the differential pressure between the stagnation (or total pressure) measured at the end of the tube facing the flow and the static pressure measured perpendicular to the flow. This differential pressure is the dynamic pressure which allows for calculation of velocity.

When I tried doing this a few years ago I could not make any sense of these types of results.
What you are measuring is the pressure due to Bernoulli effect but as the air velocity varies across the duct diameter plus there is turbulence so all I could see wha the pressure varying quite a bit.
Even the size, shape and slight variations of the orientation of the tip of the tube made a big difference and that's why I don't usually use these measurements.
Pitot tubes have a very specific rounded/tapered point to reduce this problem
Some useful relative differences could be obtained if the anemometer tube is is left in exactly the same place all the time but that's about it. Apart from the no flow measurement Because of these differences it's not possible to compare your results with anyone else with any certainty.

Is your 10" of total pressure measured with the filter bags in place?

Yes - that's with clean bags. I have an in line pressure monitor and every now and then I check the the no flow P and when it starts to drop to around 8" then its time to clean the bags.
Having a cyclone this might not interest you but it is MOST interesting to see what wood working activities cause a drop when the pressure. I could for instance fill the collection bags with thicknesser chips without much loss in pressure but half an hour os using a belt or ROS and the bags clog even though they only have a few cm of dust in the bottom

[QUOTE] That's a heap of flow for 3hp compared with my 5hp system. [QUOTE]
Thai's pretty standard for a 3HP system.

The bigger impellers will of course have a better fan curve so it should continue to suck under the added resistance of ducting and machinery etc.

Maybe my hot wire Anemometer is not reading correctly. Since my motor and PowerPoint are at their limit and the motor is developing close to 4.5hp I can't really gain any more flow by decreasing restrictions (to the table saw) so am at the limit of what the 16" impeller is capable of.

If you want to you could post your measured air speeds as a function of radius just in case there is a problem there.

If you can do it easily I would remove the ducting connection to the Cyclone and insert a test duct and perform a flow measurement so that you know what you are starting with.

Originally Posted by Chris Parks

Dom, I am puzzled why you have effectively restricted the 16" impeller with the smaller impeller housing of the 1800. I have read your reasoning but I still don't get it as the inlet and exhaust are way too small. Using a Max housing it is possible (just) to run three open ports at once but the 1800 won't flow enough to do that no matter what size impeller is in it. My apologies for being obtuse but I just don't follow the reasoning.

Hi Chris. I actually I assumed that I was getting the cvmax impeller and housing when I ordered from Stephen. I knew that they offered the 16" impeller in the states with the cv1800 as an upgrade, apparently with good results. I asked stephen for a cv1800 with cvmax impeller/housing. I guess he assumed just the 16" impeller and I didn't know any different before I assembled the unit.

Then I figored it was too late to change and thought that a larger impeller should still generate more static pressure and flow even in a smaller housing. I had no intention of running an 8" main trunk at this stage.

Are you saying you believe that a 15" impeller would develop more pressure with the cv1800 housing that the 16"?

I only run one port open at a time. That is, one machine at a time. I'm not sure what you mean there.

No offense taken. I welcome all advice and criticism.

[QUOTE=BobL;1943274]When I tried doing this a few years ago I could not make any sense of these types of results.
What you are measuring is the pressure due to Bernoulli effect but as the air velocity varies across the duct diameter plus there is turbulence so all I could see wha the pressure varying quite a bit.
Even the size, shape and slight variations of the orientation of the tip of the tube made a big difference and that's why I don't usually use these measurements.
Pitot tubes have a very specific rounded/tapered point to reduce this problem
Some useful relative differences could be obtained if the anemometer tube is is left in exactly the same place all the time but that's about it. Apart from the no flow measurement Because of these differences it's not possible to compare your results with anyone else with any certainty.


Yes - that's with clean bags. I have an in line pressure monitor and every now and then I check the the no flow P and when it starts to drop to around 8" then its time to clean the bags.
Having a cyclone this might not interest you but it is MOST interesting to see what wood working activities cause a drop when the pressure. I could for instance fill the collection bags with thicknesser chips without much loss in pressure but half an hour os using a belt or ROS and the bags clog even though they only have a few cm of dust in the bottom

[QUOTE] That's a heap of flow for 3hp compared with my 5hp system.

Thai's pretty standard for a 3HP system.

The bigger impellers will of course have a better fan curve so it should continue to suck under the added resistance of ducting and machinery etc.



If you want to you could post your measured air speeds as a function of radius just in case there is a problem there.

If you can do it easily I would remove the ducting connection to the Cyclone and insert a test duct and perform a flow measurement so that you know what you are starting with.

Hmmm. I understood that the static pressure component is equal across a cross section and only the velocity pressure changes. I could see that measuring accurately within the cross section would be difficult. I'll need to do some reading to see if my understanding is flawed.

All of my static pressure measurements were conducted at the very wall of the pipe and did not change between measurements.

I'll try to find some time later in the week to remove the intake duct and measure flow rate with a straight test duct about 2-3m in length. I'll do the same with duct connected to try and eliminate measurement errors due to very turbulent flow near junctions. I'll also measure with the exhaust ducting disconnected to eliminate back pressure as a concern.

I still come back to the simple logic that I'm at the limit of what can be achieved with regard to flow rate however, given that I'm at my bhp limit and therefore the impeller must be moving the maximum air it can with that amount of horsepower. Reducing static pressure will simply increase airflow which will overload the motor, requiring a reduction in rpm to reduce motor power below the working limit and will bring me full circle to the starting amount of airflow, just at a lower rpm. Maybe there will be some tiny gains due to impeller and motor efficiency at a lower rpm.

Thinking on it. There may be some benefit to lowering the system resistance. Going back to basics fan laws, cfm is directly proportional to rpm whereas motor power and rpm is a cubic function. Therefore an increase in cfm due to a reduction in system resistance should require a proportionately smaller drop in rpm to lower bhp to the initial value, but at a higher cfm.

Originally Posted by DomAU

Hi Chris. I actually I assumed that I was getting the cvmax impeller and housing when I ordered from Stephen. I knew that they offered the 16" impeller in the states with the cv1800 as an upgrade, apparently with good results. I asked stephen for a cv1800 with cvmax impeller/housing. I guess he assumed just the 16" impeller and I didn't know any different before I assembled the unit.

Then I figured it was too late to change and thought that a larger impeller should still generate more static pressure and flow even in a smaller housing. I had no intention of running an 8" main trunk at this stage.

Are you saying you believe that a 15" impeller would develop more pressure with the cv1800 housing that the 16"?

I only run one port open at a time. That is, one machine at a time. I'm not sure what you mean there.

No offense taken. I welcome all advice and criticism.

Just to follow on from this I found this quote from a USA forum which was quoted from an email from Clearvue USA to a customer regarding 15 vs 16 inch impellers;

"All of this being said, if in fact you only intend to be using one tool at a time, a good compromise for you may be to consider the CV1800LH unit, but upgrading to the larger 16” impeller/blower. This will allow you to save money by not using 8” pipe (and less money for the system too), but will still get you approximately 20-25% more airflow as compared to the stock CV1800 with the 15” impeller."