Posted by & filed under Engineer Talk.

by Burt Smith, Product Engineer at AJ Manufacturing Co., Inc.

There is a dizzying array of control options and possible control schemes out there for HVAC systems and adding a clean room creates even more complexity. With new requirements like USP 800 firms previously unexposed to these types of systems are now being thrust right into the deep end of complex cleanroom scenarios.

The most difficult situations are those where 100% fresh air is required to the space and you have strict pressure requirements that are significantly different for adjoining rooms. An example of this is a compounding pharmacy which includes exhaust hoods that add to the issues.

Attempting to control incoming and outgoing CFM to maintain the narrow window of pressure requirements is the conventional thinking of balanced system. Balancing a system to achieve this can be very time consuming and there are always unexpected conditions on site that require fine tuning to meet the room requirements further adding to the complexity and frailty of the balance.

There is was to reduce this time consuming process and make the system more robust. Modern controls allow for not just monitoring and controlling to these indirect CFM methods but directly to the requirements themselves.

Modern EC motor fans, like those in our Criti-Clean products, can be directly controlled by a sensor or building management system to maintain the required differential pressures, particle counts, or other critical criteria directly. Using a direct control method often simplifies balancing and ensures that the requirements of the room are more likely to be met even when there is a component failure, inadvertent flow change, or even something as simple as an anteroom door being opened.

Identifying the most critical requirements and prioritizing them will allow you to design a more robust system with better reliability and more useful reporting data. Let us help you ensure your projects success now and in years to come by working with our engineers early in the design process to help find your best solution.

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A-J Manufacturing was featured in the “What’s Hot in Innovation” section of Pharmaceutical Processing/ Controlled Environment s digital magazine.

The piece focuses on A-J Manufacturing’s Fan Filter Unit.

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HEPA Filters

Filter Change Criteria

There are 3 basic reasons to replace HEPA filters:

  1. The filter is too clogged to meet the required air flow for the system.
  2. The filter fails a required filtration test.
  3. To reduce operating costs.

The first reason is a fairly extreme example and the filter would have to be extremely dirty or the system designed on the edge of its capacity for this to be the reason to change a filter. Not just neglect but changing requirements in an area can trigger a filter change.

The second reason is fairly self-explanatory but there are some misconceptions about filtration. The filters actually get better at trapping particles as they get dirty. This means that filtration efficiency is not generally a consideration in replacing a filter. However, it can still fail to filter sufficiently if the media or seal fail due to damage.

The third reason is by far the most common and can be approached several ways but you need to consider more than just electricity and filter costs.

Determining Thresholds

The first two reasons are determined by the facility needs so these are normally dictated. We will concentrate on minimizing operating costs since it is the criteria we have the most control over.

A common rule of thumb is once filters are 150% of initial pressure drop it is cost effective to change them, but the reality is that it is very much influenced by system design and fan efficiency. It is a trade-off between capital expenditures to improve initial efficiency and recurring costs of power, down-time, and filters. If you are not fortunate enough to be able to influence the initial design and budget then you have to spend your time on the back end optimizing filter changes.

The ideal is to monitor power consumption/cost and replace at the breaking point where filter replacement gets you sufficient power savings to justify the cost. Many clean rooms the major cost is availability so it is common to have scheduled filter changes every 6 months to a year and then they are all changed together to minimize down time. Even in these situations you may be able to calculate less arbitrary intervals and be able to realize significant savings.

Some facilities and applications are more flexible where monitoring power and replacing the filters at the tipping point is the more cost-effective method. Many systems will not allow you to monitor power directly so criteria such as fan speed can be substituted but it will take a little more effort to find the threshold.

Considerations During System Design

If you are fortunate enough to have influence at the design stages specifying you can create a major reduction in operating costs. Several avenues are by specifying thicker media packs in filters, more (or larger) filter units, and higher efficiency motors. AJ Manufacturing’s Lighted units can allow more filter area in the same ceiling space by eliminating the need for separate lighting. The Criticlean Ultra line of fan filter units has some of the highest efficiency motors available to reduce power consumption.

Reducing Operating Costs of Existing Systems

Using deeper filter media will also extend the time between filter changes and reduce power consumption. We have a “High Flow” filter option for our units that can accommodate more dirt and can be specified to reduce the down time and power consumption of a fan filter unit or HEPA diffuser. They are backward compatible with most AJ Manufacturing HEPA products.

Rebalance the system with minimum damping is another way to reduce operating costs. If the system is dampened at every duct then the supply system is over-worked. Ideally the system should be balanced so that at least one damper is full open and the supply fan run at the minimum power to provide the required CFM. Depending on the variability of the supply fan this is not always possible. Upgrading to an EC motor that can be variably controlled will improve efficiency.

Similar with smaller fan powered devices such as fan filter units. Upgrading to an EC motor unit like the Criticlean series may reduce operating costs sufficiently to justify their expense.

ASHREA has many resources available to help guide engineers through system design and maintenance scheduling as well as provide specific formulas and calculations to use.

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planning for passing IEST leak tests

Trying to consistently pass IEST leak tests

The Details Matter

With new regulations making IEST-RP-CC034 HEPA and ULPA Filter Leak Tests required in many more facilities than ever before there are considerations for passing these tests initially and in the future that are easily overlooked.


Keeping out the challenge gas is much more difficult than simply not having a “leaky” ceiling by normal HVAC standards. Being truly sealed from gas penetration is much more difficult than it may first appear. Keeping it that way harder still. You have to assume everything above the ceiling level is contaminated and cannot be allowed to pass through.

Gaskets just aren’t good enough in most cases. All devices must be airtight and leak free in both positive and negative pressure differential conditions. Penetrations need to be kept to a minimum. Every possible leak path must be effectively blocked with a sealant that will stay effective for years to come, with the settling of buildings, the vibrations of construction, and everyday use.

Hard ceilings with good rigid support that will stay in place under changing pressure conditions (like every time someone opens a door). Good caulks that remain flexible, regular inspections and maintenance, as well as ensuring any new work is just as carefully done will help ensure the room will keep passing tests for years to come.

Testing Considerations

Who is doing the testing? What equipment do they have? What are their preferred challenge methods? You can save a lot of time and effort later by doing some footwork ahead of time.

Do they want challenge ports at each unit? At the face or remotely mounted? What size and type of fittings do they need? Are the units ducted or share a plenum? Finding out what your testing company needs at the design phase will prevent you from having costly delays and modifications at the last minute when you are trying to get that new facility online.


AJ Manufacturing has heard these hardships from our customers and created solutions for them. We have reduced ceiling penetrations by offering integrating lighting. We have challenge manifolds that meet the IEST requires with data to back them up. We have optimized our knife edge seals to work under the widest variety of conditions to minimize leakage opportunities. We have knowledgeable staff that can help you from planning through certification to make sure your project is done right the first time.

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Tax Incentives Image

Businesses Can Continue To Deduct Up to $1 Million in Qualifying Nonresidential HVAC Equipment Purchases for the 2019 Tax Year.

The expansion of the Section 179 tax deduction in the 2017 Tax Cuts and Jobs Act has been extended for the 2019 tax year. This means businesses can still take a 100% deduction for up to $1 million in qualifying nonresidential HVAC equipment purchases for the 2019 tax year, which obviously helps justify replacement costs vs. repair costs.

The Tax Cuts and Jobs Act that was signed into law in December 2017 contains the expansion of Section 179 – a real benefit for the HVAC industry. Created in 1958, Section 179 allows companies to take depreciation deductions for certain assets in one year rather than depreciating those items over the useful life of the product – historically, over a 39-year period for HVAC equipment. The tax reform bill incorporated HVAC products in Section 179 for the first time, and offered important savings for both small and large projects.

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Forecast Image

Experts Predict Average Growth of More Than 4%.

We recently came across some positive news for many of our customers that serve the healthcare industry. According to a recent Consensus Construction Forecast from the American Institute of Architects (AIA), the industry experts they sampled see continued growth in the healthcare building sector, with many predicting 4%–5% growth for 2019.

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The Criti-Clean Ultra’s Low Profile – Plus High CFM Output and Energy Efficiency – Makes Retrofitting Pharmacy Areas Easier.

The December 1, 2019, deadline for meeting USP 800 regulations in pharmacies handling hazardous pharmaceuticals is right around the corner. AJ Manufacturing can make it easy to create or retrofit pharmacy spaces to meet these new guidelines with our powerful, adaptable Criti-Clean Ultra FFU.

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The Criti-Clean Ultra’s Low Profile – Plus High CFM Output and Energy Efficiency – Makes
Retrofitting Pharmacy Areas Easier.

The December 1, 2019, deadline for meeting USP 800 compliance regulations in pharmacies handling hazardous pharmaceuticals is right around the corner. But AJ Manufacturing can make it easy to create or retrofit pharmacy spaces to meet these new guidelines with our powerful,
adaptable Criti-Clean Ultra FFU.

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Our new room-side constant flow/constant torque toggle switch helps smart components work more efficiently.

Is it possible to be too smart? Sometimes it is, like when you have an FFU such as the Criti-Clean Ultra with a smart ECM motor trying to work downstream from a smart VAV in the same system – and both smart motors are simultaneously trying to adjust to maintain constant airflow. So we came up with a solution.

To help offset this fairly common problem, AJ Manufacturing will soon be introducing a new option for our Criti-Clean Ultra fan powered laminar flow HEPA filter diffusers – a new room side toggle switch that lets you easily change from constant flow to constant torque, thereby allowing the VAV box to control airflow. We think that’s a solution so simple that it’s really pretty smart, too!

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New swirl face options available an all our HEPA diffusers and FFUs!

As we’ve often said, our customers’ ideas and opinions mean a lot to us here at AJ Manufacturing. So when we started getting more and more requests for swirl face HEPA diffusers to provide turbulent airflow for hospitals, laboratories and other clean environments, we responded!

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Thank you for another wonderful year…and we look forward to serving you in 2019!

From all of us at AJ Manufacturing, happy holidays – and thank you for allowing us to help you meet your critical environment air handling needs throughout 2018!

Looking back over the last year, we’ve been very pleased – and truly excited – by all the new and different ways we’ve been able to make things a little easier for our valued customers. Perhaps our best moment came last spring with the long awaited introduction of our Criti-Clean Ultra FFU, the completely re-designed and re-engineered powerhouse FFU that maximizes both CFM and energy efficiency, while still offering all the same great features of our past Criti-Clean units.

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New built-in probes in our laminar flow products will measure and report CFM with 100% accuracy.

In 2016, we introduced a new digital readout on the face of our Criti-Clean FFUs that displays and adjusts the current CFM output. This makes room-side visual verification and adjustment of the needed airflow quick and easy, with just a glance up at the ceiling.

However, at AJ Manufacturing we feel that there’s always room for improvement. So in the coming months we’ll be introducing a new feature to improve that functionality – a built-in probe in the air inlet that more accurately measures CFM.

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Take a virtual tour of our new facility, equipment and systems in less than five minutes.

The positive reviews have been unanimous for our new capabilities video, so if you haven’t had a chance to see it yet, we encourage you to take a look and learn a little bit more about our new 70,000-square-foot facilities and our enhanced production capabilities.

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Take a look inside our new facility

We’ve been in our new 70,000-square-foot, state-of-the-art manufacturing and headquarters building for about a year now. So we thought it was time to let everyone see exactly how our new facility is helping us better meet our customers’ needs.

In less than five minutes, our new capabilities video lets you see how orders are processed, designed and manufactured – from start to finish – thanks to our experienced staff, as well as our new, streamlined systems and top-of-the-line equipment.

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Section 179 expansion allows businesses to immediately deduct up to $1 million in nonresidential HVAC equipment

Here’s some great – and potentially very profitable – news for our customers. The Tax Cuts and Jobs Act that was signed into law in December of 2017 contains a hidden jewel for the HVAC industry: the expansion of Section 179. This expansion allows businesses to immediately deduct up to $1 million in qualifying nonresidential HVAC equipment purchases for the 2018 tax year.

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