Introduction
In my post last month about my self-induced fiasco with the HEPA filter on my dust collector, I mentioned that I would be installing a pressure gauge on the system to monitor the performance of the filter. I received the Efficiency Gauge Kit from Oneida along with a new filter a few weeks ago and shortly thereafter installed them both. Read on to hear about the installation of both.
Efficiency Gauge Kit Installation
The filter and gauge came quicker than initially estimated which was a nice surprise.
I decided to install the gauge first before changing the filter so that I could get a reading from the gauge before and after installing the new filter. The installation was straightforward. The gauge kit is not specific to a particular model of dust collector so the instructions are written to cover various installation scenarios. The gist is that you install the pressure probe in the plenum just before the filter and mount the gauge nearby in a convenient location based on your particular setup. Lastly, you connect the gauge to the probe by an 8-foot clear plastic tube supplied in the kit.
The instructions call for drilling a 13/32″ hole in the plenum for mounting the static tube. This seems to be a rather uncommon drill bit size and one I don’t have. Since it is only 1/32″ bigger than 3/8″, that is what I used. The plenum on my dust collector is plastic, I was able to work the bit in the hole until the hole was just large enough to allow the tube to fit. On a metal plenum, I imagine the same technique or a little work with a small round file would do the trick.
With the probe inserted into the hole, it is important to ensure that the tip of the probe is pointing into the flow of air that is coming from the separator. I tightened a small nut provided in the kit onto the probe from the outside and then sealed around the penetration inside and out with silicone to ensure there would be no air leaks.
Next, I needed to decide on a location for the gauge. I probably could have attached the gauge to the wall mounting brack for the dust collector but this would have been a little awkward of a location for reading the gauge. Also, the instruction that came in the box for the gauge said to choose a location that avoids vibration. So I found a scrap of wood and chose the mounting location shown above.
With the gauge mounted, I attached and routed the plastic tube and proceeded to test out the installation.
New Filter and Gauge Readings
I fired up the dust collector and checked for any obvious signs of leaks or other problems with the installation. Using a stick of incense, I then thoroughly checked over the system looking for any signs of air leaks. Unfortunately, I had to buy 120 incense sticks but luckily they are cheap. On the bright side, I now have them for future air leak tests or if I decide to get into burning incense regularly, which I doubt. Satisfied that the system was tight, I was ready to take some readings.
The initial reading on the gauge was a complete surprise. Given how dirty I knew the filter was, I expected the reading to be high. However, as you can see above, the reading was pretty low on the scale.
A Note About Reading the Pressure Gauge: The pressure gauge in this setup is showing the backpressure on the filter. The idea is that as the filter builds up more and more dust, the pressure required to push air through the filter will increase. Therefore, the absolute value is not as important as the change in the backpressure reading over time. With a known blast gate configuration, you take a reading with a new clean filter. You can then monitor the pressure as you use the system using the same blast gate configuration. As the dust load in the filter increases, the pressure reading will increase. Cleaning the filter will reduce the pressure. Once you can no longer get the pressure to decrease significantly after cleaning, you know it is time to replace the filter.
I next installed the new filter, restarted the system, and took another pressure reading. As you can see above, the pressure went down but not significantly.
Explaining the Readings and Wrapping Up
While I cannot be sure why the reading with the old filter was so low, I have a theory. I know that the old filter was still really dirty. My theory is that either the large amount of chips and shavings that had gone into the filter, my efforts to clean all of that out, or both caused some significant damage to the filter media itself. If true, that would mean that even though the filter was still dirty, there would be enough significant holes in the filter to allow air through and keep the back pressure down.
With the new filter installed, I can tell that I am getting really good airflow again at the various tool locations. It is also good to know that I have an objective measure of the filter performance. That along with the window I installed in the dust bin should do a lot to ensure that I keep the system running at peak efficiency.