Planned Maintenance vs Planned Preventative Maintenance

In this article we share our thoughts and experience on the state of Planned Maintenance vs Planned Preventative Maintenance in commercial buildings and the impact it has on system efficiencies and indoor Health and Wellbeing.

Planned Maintenance vs Planned Preventative Maintenance

Aug 3, 2018

Why do clients choose Smart GreenTech Solutions for quality TM44 inspections, ESOS Phase 2 compliance, energy efficiency and maintenance optimisation initiatives?

We love what we do and are passionate about delivering TM44 inspections and improving the energy efficiency and indoor environmental quality of buildings

I have been involved in building services maintenance and its management since early 1980 when I started my HVAC apprenticeship, and firmly believe that the success of a buildings energy efficiency and indoor health and wellbeing agenda is directly related to the way the building systems are operated and maintained.

Fast forward a good couple of years and I am still doing what I love, and spending most of my days visiting plant rooms and commercial buildings to certify and optimise the operation of HVAC systems, and improving the energy efficiency and indoor health and wellbeing.

We work directly with end user clients but also partner with a range of Mechanical and Electrical and FM service providers as well as air conditioning contractors to provide the above services, and the level of maintenance that we find varies significantly, but from my personal experience I do believe that the client and client procurement processes also have a direct impact on this.

The intention of this article is not to come across as a know it all or explore the above maintenance strategies and/or CMMS in detail, but rather to share my personal experience and thoughts on the current state of maintenance on mechanical and electrical systems in commercial buildings.

Maintenance strategies have advanced significantly over the years from predominantly planned (check it) and planned preventative maintenance (fix it before it fails) to predictive maintenance (measure it and fix it) and reliability centred maintenance (dont just fix it, improve it) as well as enterprise maintenance (improve it and sustain it). We have also seen a significant growth in the availability of Computerised Maintenance Management Systems (CMMS) and maintenance scheduling software, so with all this knowledge and state of the art technologies at our disposal its logical to expect that the general level of maintenance would have advanced in line with these developments, but has it?

CIBSE Guide M 2014 Maintenance engineering and management states that building services engineers provide the internal environmental conditions that enable business processes to function at an optimum level while providing a safe, comfortable environment for occupants to achieve their maximum performance potential. Effective maintenance and operation is a key factor in ensuring this continues for the life of the building.

From my experience I hear a lot of talk at senior level about the more advanced maintenance strategies and more specifically predictive/condition-based maintenance, but from what I see daily I think that Planned Maintenance (PM) is still very much the order of the day and that PM is being confused with Planned Preventative Maintenance (PPM).

Lets explore both!

Planned Maintenance - conduct checks at pre-determined intervals

Planned Preventative Maintenance - conduct checks and adjust at pre-determined intervals

You would observe that at face value the actions look very similar, but the key difference is that PM is activity based whereas PPM is outcome based.

To put it differently, PM is knowing what to do and at what frequencies whilst PPM is knowing why you are doing it so that you can fix/adjust it before it fails and/or goes out of parameter!

A major problem with the way that buildings are being maintained, is that that maintenance is approached from an equipment level and each piece of equipment is viewed as a stand-alone piece of kit rather than being part of an integrated systems i.e. chillers vs chilled water system or Air Handling Unit (AHU) vs ventilation system etc.

Maintenance is predominantly being planned from an equipment perspective (plant room) rather than a client/user perspective (indoor environment). I am not talking about statutory maintenance here, but rather the ongoing maintenance of Mech/Elect systems.

The key difference is that when we plan maintenance from the indoor environment, then we start off by agreeing what outputs/minimum acceptable targets the system needs to deliver and sustain i.e. temperature, relative humidity, CO2, fresh air supply/extract rates, airflow rates, particle matter, lighting levels, water quality etc, and we then implement a PPM plan at system and sub-system/equipment level to achieve these.

From my experience boilers, chillers and the BMS are generally maintained by specialist service providers, but the pumps, control valves, fan coil units, AHUs and lighting etc, are maintained by much lower level staff with generally very limited knowledge of how the integrated system functions.

So, lets explore one of many potential definitions of what maintenance is and what we should be aiming to achieve by maintaining equipment/systems;

The activities required or undertaken to conserve as nearly, and as long, as possible the original condition or performance of an asset or resource while compensating for normal wear and tear.

The mistake we make is seeing assets as individual pieces of equipment rather than a system, where each individual piece of equipment contributes to the overall performance of the system!

Lets use a recent example to explain the above.

The supply air fan of the Air Handling Unit regularly broke its belts due to the significant start-up torque. The engineer decided that it would be a good solution to fit an inverter drive as this would alleviate the problem and provide a soft start i.e. gradually ramp up the speed of the fan motor at start-up and chose to set the inverter at 40Hz.

At this point you can see that the focus is on the equipment! The result of this exercise was that it did alleviate the issue with the belts and did save energy, but as the fan now provided 20% less fresh air to a building that already had very high occupant densities it resulted in even high CO2 levels in the indoor environment/office area!

If this problem was approached from the indoor environment and a system perspective, then the first step would have been to determine what the fresh air supply rate/person needed to be to maintain a CO2 level of circa 800ppm, understand the original design intent and then to measure and compare the actual fresh air supply rate.

The next step would be to ensure that when the inverter drive was installed that it was set to deliver the required duty, and to measure and record the flow rates again.

This approach would not only have alleviated the problem with the belts breaking but would also have ensured that the conditioned space was maintained within the CO2 and fresh air supply rates/person parameters.

Although I used an inverter drive and the reduction of the fan speed in the above example, I could also have used the changing of pulley diameters, replacing motors etc, as these all have a direct impact on the airflow and maintenance of the parameters within an indoor environment.


A Clients greatest asset are their staff, so its our duty to provide healthy and efficient indoor environments, which we can achieve by changing our approach from equipment based (input) to systems based (output) maintenance.

You can significantly improve the quality of your maintenance without implementing the more advanced and costly maintenance strategies, by simply moving from an equipment-based PM strategy to a system-based PPM strategy.

To effectively deliver PPM we would require suitably qualified and trained engineers and service providers need to realise that the one size fits all approach to maintenance planning and scheduling just simply is not effective or good enough.

This approach will ensure an aligned, integrated and value focussed maintenance service which is client centred!

High level summary of approach

1) Agree the key indoor environment parameters with the client

2) Understand the original design intent of the systems

3) Measure the current operating parameters

4) Adjust to achieve 1 and/or 2

5) Develop PPM plans at system and equipment level to maintain 4

6) Log operating parameters during PPM routines

7) Analyse results to pick up discrepancies and fix/adjust before it fails!!

8) Before system/equipment modifications are implemented or components/equipment are replaced, repeat steps 1 to 4

We trust that you enjoyed reading this article and if you would like to discuss the above approach in more detail, then please feel free to contact us on 03300 881451.

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