Compass Software Technology - Newsletter 03 - August 2012

welcome to the latest Compass Software newsletter. Continuing on with our 'heating season' theme, this newsletter is going to look at another main source of heat, air handling units (AHU's).

I have always been amazed by, the care or lack of care, that AHU's receive, especially when outdoors. Often this is due to access difficulties, but when you consider the replacement cost, one would think a high level of priority would be given to their maintenance. This is an image of where it has gone badly wrong Click here

Don't forget the benefits and abilities of our Regional Pro2 EAM software package will allow you to track and monitor your AHIU servicing and build up a lifespan picture of the ongoing health of your AHU plant.

Dominic Murnane

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The AHU is a large metal box containing separate ventilators for supply and exhaust, heating coil, cooling coil, heating/cooling recovery system, air filter racks or chambers, sound attenuators, mixing chamber, and dampers. AHU's connect to ductwork that distributes the conditioned air through the building, and returns it to the AHU. A heat/cooling recovery exchanger may be fitted to the AHU for energy savings and increasing capacity.

1. Filters
The most regular interaction with your AHU will be to change the filters. These are normally replaced 2 to 4 times annually. Dirty filters will increase the static pressure across the coil, increasing fan system energy use in addition to reducing the heat transfer coefficient of the coil, forcing the system to move more air over the coil for the same heating/cooling effects. Standard filters for most commercial usage are either panels or bags with a varied price difference depending on quality. When filters are being replaced, it is worh checking their condition before they are disposed of. Some things to look out for are:
1. Not too dirty - you may be changing too frequently
2. Heavily soiled - Change more frequently, check for external environmental reasons for the dirt buildup. If a source is found (i.e. building works), check the impact on other systems. Once clogged, germs grows profusely in a dirty environment, creating another health hazard.
3. Damaged - If the filter cases are damaged, then you may need to improve the quality purchased.

The filter on the LHS shows an average level of dirt between replacements.

Sick Building Syndrome is attributed to a building where a significant number of the occupants are suffering respiratory illness symptoms and or nausea. Typically 1 in 5 or greater. These symptoms are more usually associated with larger buildings where there is an ahu / air conditioning system that is not properly maintained.

Click here for images showing causes of poor air quality.

2. Dampers
"The dampers are seized (in various positions), and need to be replaced." How many times have we heard this statement. Yes, dampers can seize, but they are simple mechanical devices and in most cases can be unseized in a couple of hours. Considering replacements can cost hundreds, this is a viable option. Non-function dampers can dramatically reduce the efficiency of your AHU by leaving uncontrolled external air into the system. See above RHS.

3. Corrosion
With in many cases AHU's being outdoors and exposed to the elements, corrosion as the plant gets older can become a big issue.
Roof and side panels are often the main cause of deterioration of an expensive AHU and can be treated or replaced. On units with high suction pressures, water is often drawn in through gaps in roof joints causing interior rusting. There is no reason for corrosion not be be spotted at a very early stage during maintenance cycles. Pictures 2 & 3 below are extreme cases and should never happen. Corrosion could easily reduce the lifespan of an AHU by 10 years.

Picture 1. External Corrosion at an early stage.
This should have been rectified up to 1 year previously.

Picture 2. Extreme corrosion of exterior roof panels.

Picture 3. How can this be explained when an AHU is typically serviced 2 to 4 times per year?

4. Ducts & Access Panels
These also have to be well maintained for your AHU to perform efficiently. This image shows extensive damage to ductwork and damage to access doors. Click here This photo was shown to an engineer who specialises in AHU maintenance, who estimated the energy loss alone was costing over 500 Euros per week. These issues could have been easily spotted with a simple walk about and repaired with minimal cost, instead of the estimate from the photo of many thousands.
5. Cable Trays
Cable trays and pipe support brackets have a specific purpose, certainly not as walkways. If you see signs that they are being used as steps or pathways, warning signs and "step-overs" can reduce the potential for costly damage.

6. Visual Inspection
Many potential problems can be detected at an early stage by simply having a good look around your plant. The most obvious can be staining from rust, vibration or unusual sounds. Check filters when changed and your BMS for faults and when in doubt as we always say get it checked out.
Also always ensure whoever is maintaining your plant is both competent and certified to carry out the work.

The Regional Pro2 EAM software package can monitor and track over 40 different checks that apply to standard AHU maintenance (Over 100 when an AHU needs to be maintained to HTM 03-01 standards).

Contact us today for more information and see how we can reduce costs and improve the efficiency of your plant maintenance. As ever we appreciate your comments on the newsletter.

Further Reading...
1. Commercial building checklists.pdf
2. Commercial building assessment guideline.pdf
3. Trane ENL Air-Handling Systems Energy.pdf
4. IAQ Building Education and Assessment Model

You want to change how you operate your Plant & Facilities Maintenance.
We want to help you do it.

Compass Software Technology Ltd.

Head Office: Killarney Road, Macroom, Co. Cork, Ireland

Rubicon Centre, CIT Campus, Bishopstown, Cork, Ireland

Tel: Ireland: 026 23616 / 087 607 6565
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Compass AFM is a trading name of Compass Software Technology Ltd.