I’m sure I’m not alone in sharing the hatred of having to clean playfield glass every 15-30 days due to dust. It makes you wonder if that level of dust is making it onto the playfield glass, imagine what you’re inhaling into your respiratory system.

I searched for a total basement HEPA filtration solution and was not impressed at the quality of most consumer units. Of the very few good ones that existed, they either used too much electricity to achieve the needed number of air turns, or their filter replacement cost & lifespan ratio was not cost effective to own.
Commercial solutions such as “HEPA Air Scrubbers” were just too expensive and had their own set of drawbacks. This lead me down a path to build my own system completely from scratch, and to tailor it to fit my application.

I began researching Carrier’s Commerical Opticlean Negative Air Machine / Air Scrubber. It is a hospital grade HEPA filtration system used for creating a negative air space during treatment of COVID, and to scrub the infected air before discharging it. For applications where this was not possible, it would continue to recirculate the infected air, essentially “Scrubbing” it, and further reducing the contagious effect. Once again, way too expensive to acquire, and way too loud for a home arcade.

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This thread will be about building a custom version – near clone, on a budget, while making it quieter, and having a lower electrical consumption. For starters I acquired a 2.5 ton Carrier residential base model fan coil. The Opticlean uses the same base cabinet and blower assembly. I will essentially gut the inside of the unit by pulling the A/C Coil, wiring, and 230 volt blower motor. This will allow me to install a factory Parker 16x20x12 HEPA filter, and upgrade the blower motor to a very efficient 120 volt 1/2HP Evergreen IM constant torque ECM. By using a constant torque motor, the airflow will remain similar as the filters begin to load, and the motor will compensate automatically by increasing the wattage.

Here is a photo of the unit I aquired:

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Steps to build the unit:

Figure 1: Once the panels and A/C coil are removed, I began by removing the blower assembly, transformer and all the factory wiring.

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Figure 2: The existing 1/5 HP 230V motor is of no use to me for this build, so out it comes.

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Figure 3: A new 1/2 HP 120V Evergreen IM ECM motor is installed. It will move a lot more air, and is very efficient. It is very versatile as it can be wired in ways that emulate approx 15 different speeds ranging from 1/5HP up to 1/2HP.

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Figure 4: The blower assembly is re-installed with the new motor, and the HEPA filter assembly is temporarily set into the space where the A/C coil used to reside. Measurements are then taken to secure angle pieces to the side of the cabinet to provide an airtight seal to the top gasket of the HEPA filter frame.

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Figure 5: Angle / L- Channel is mounted to the cabinet and care is taken to seal behind with silicon and also that the gasket is able to sit flush to prevent air leakage.

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Figure 6: All thread is cut to length and nuts installed thru the top flange, HEPA is installed and clamped to a lower frame that is not sealed or gasketed to the cabinet. The nuts were tightened to compress the gasket on the top of the HEPA filter. A little clearance is allowed on the lower mounting side rails to allow the filter to slide out of the unit for a change out. (Estimated life is 4 yrs)

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Figure 7: Simple sheet metal “L Brackets” are bent to make a prefilter frame / retainer that can accept 1” thick up to 12” thick prefilters / carbon odor eliminating filter. Or I can sandwich multiple thickness prefilters to protect the expensive HEPA.

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Figure 8: Here is a photo of everything installed and secured prior to the panels being installed. I added a foam tape gasket on the lower hold down to prevent any air whistle, but chose to omit the one on top as the panels have their own gasket already glued to them. At the time of this build I am using a standard MERV 8 16x20x4 pleated pre filter to test static pressure drop, and to see how long the prefilter will last before experimenting with expensive carbon filters.

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Figure 9: With filters installed, panels secured, and with the blower speed on the lowest tap, the unit is only drawing 60 watts. Given the amount of air movement, I consider the electrical consumption to be very good. I will be upgrading the controls and experimenting with different type of pre filters to see what it does to overall electrical consumption. The more resistance, the more watts the blower motor will use.

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Figure 10: Photo of completed unit, standing up. I did not install caster wheels on this as it will be laid down in a horizontal application.

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Figure 11: Unit is in it's final location, under a row of pinballs. I located it in the most central spot where it would draw in air. The dirty air going into the unit is more important than the clean air being discharged. The idea is to calculate the number of “air turns” per hour so essentially the entire space is cleaned several times per hour to reduce the fine micro particles. I am leaving mine open with no duct work or air grilles, but you could easily fabricate sheet metal duct work, and install on the return and supply openings if you have a finished basement arcade / room.

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This post is an official placeholder for the controls part of the build.

This post is an official placeholder for the controls part of the build 2.

Figure 14: Carbon prefilters are excellent at reducing VOCs (volatile-organic-compounds), various gasses, in addition to many different types of common household odors. My intent was to find a low cost, convenient solution to reduce typical basement / game room odors while not creating excess air restriction. After much testing, a regular MERV 8 - 16 x 20 x 4 prefilter would begin to visually load with dust after 3 months and reach end of life in 6 months. This was tested using the machine 24/7. This makes using a carbon based prefilter a very viable and cost-effective solution. Had the prefilter reached end-of-life in a shorter time frame, this would not have been economically feasible.

Due to availability I chose to test first the Tri Dim, Tri-Sorb 50/50 Carbon/Alumina Blend filter. I selected a MERV 7 - 16 x 20 x 4 nominal size and installed it behind a regular MERV 8 prefilter, but prior to the HEPA. This allows the regular prefilter to handle the large dust particles, then the 50/50 carbon/alumina blend filter would handle gasses, odors, and VOCs, leaving the HEPA to handle the micro fine particles.

While any carbon or carbon/alumina filter is absorbing gasses, odors, and VOC’s, it is normal to have a sweet smell often described as a Vanilla or Cake odor. It is very pleasant and is very detectible, immediately after it is installed. This was effective in eliminating 100% of detectible basement odor. I noticed this was present for approx. 1 month, which shortly after faded completely away. As the filter reached its 3rd month a very minor basement odor began to return, and by 5 months the filter reached end of life, with odors returning to full level.

With the carbon or carbon/alumina filter being installed behind the regular MERV 8 prefilter, it appeared visually clean with no dust loading, but is no longer able to absorb anything further. It should be mentioned that this filter should NOT be repurposed as a front line prefilter as you do not want all the gasses, VOC’s, and odors seeping back out. It is best to discard at this point.

Here are the photos of the Tri Sorb 50/50 MERV 7 16 x 20 x 4: (the media is a dark carbon black with specks of pink granular alumina)

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Figure 15: Up next for testing is another carbon filter from Tri Dim that is listed as a MERV 8 gas phase pleated filter. It’s called a Tri-Sorb XL HEAVY DUTY. The model I selected is MERV 8 16 x 20 x 4 and I ordered it as a heavy duty part# so it would contain the maximum amount of carbon. They have it listed at 335 grams per Sq. Ft of filter face. It took some time to arrive as they seem to be build to order. It has the highest carbon in the industry using 32 mesh carbon media. When handling the filter it feels significantly heavier than the 50/50 blend filter. The “XL” (Extended Life) media they utilize is advertised as allowing virtually the entire carbon surface to be available to capture gasses, and maintain the MERV 8 rating.

Upon install it seemed to eliminate all odors and seems to produce the classic clean vanilla smell for about 3 months straight, and by 6 months is still controlling odor. This filter reaches its end of life in approx. 6 – 8 months depending on the humidity. It should be mentioned again that this filter should NOT be repurposed as a front line prefilter as you do not want all the gasses, VOC’s, and odors seeping back out, slowly over time. It is best to discard at this point.

I will push this one a bit more and edit this post again if I can squeeze more life out of it.

Here are the photos of the Tri-Sorb XL HEAVY DUTY MERV 8 16 x 20 x 4: ( Media is a light grey color on both sides)

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This post is an official placeholder for final thoughts, conclusions, and material costs once the project is finished.

My initial thoughts for this project was to find an economical yet effective way of filtering the air in my basement arcade, while also eliminating all household odors. My basement is very dry and in combination with my central A/C, and dehumidifier, the humidity is maintained thru all seasons for optimal aging of pinball machines. What was lacking is the dust control, and the typical "earthy" basement odor, even though the cement floor and block walls were sealed. As stated in the opening post, retail and commercial products did not fit my needs for various reasons. Mostly due to either up-front cost, or operation cost. This build suits my needs and will stay with me for the duration of my ownership of pinball machines. It is fully serviceable and can always be repaired with "off the shelf" parts, and aside from the exact part# HEPA filter, just about any nominal 16 x 20 x 12 filter can be installed in the future availability come into question.

Depending on filter arrangement, and dust loading my typical current draw is between 60 ~ 74 Watts when on low. This is the speed I use for 24/7 constant operation. When doing a project or any construction at which point dust will be generated, I use a higher speed which can be at high as 700 watts.

I will update the controls section of this build once I determine what all I want in terms of electronics, switches, dials, guages, etc....

Material Part# and Cost at time of build:

Carrier Fan Coil Model FB4CNP030L00 $396 (minor dent - sold at bargain price)
Carrier / Parker HEPA Part# 346345-75101 $269
Standard 16x20x4 MERV 8 Filter $5.15 each
Evergreen 6005 IM Motor $100
Tri Dim Tri-Sorb 50/50 Carbon/Alumina Blend MERV 7 - 16 x 20 x 4 Filter Part# 68916204 $38.03 each
Tri Dim Tri-Sorb XL HEAVY DUTY MERV 8 - 16 x 20 x 4 Filter Part# 69216204H $40.47 each
Black 6 ft Extension Cord $7

I updated posts #16 , #17, and #18 with carbon filters, thoughts, and material costs. Controls to come next year.