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Cx Using Temporary Power?

Cx Using Temporary Power?

Quality, Consequences and the Construction Industrial Complex (part 212).     

Should building systems commissioning be undertaken using temporary power? Short answer, No!

Sometimes in certain countries, systems commissioning using temporary power is necessary but you should always:

  • Resist,
  • Get an explicit instruction to do so,
  • Be clear re-testing on permanent power will be subject to additional fees,
  • Obtain agreement that systems witnessing and client acceptance can be done using temporary power.

Unless explicitly instructed to do so, I recommend the CxA position and good engineering practice is to undertake building HVAC and BMS commissioning using permanent power.  

There is a presupposition that building commissioning, particularly systems functional performance testing (FPT) is undertaken when the building is near completion with;

1. Building envelop enclosed/complete,

2. Electrical, power generation tested, and operating in accordance with specified requirements,

3. Lighting equipment and ELV systems tested, and operating in accordance with specified requirements,

4. TAB is complete.

The US DOD, UFGS specifications are very clear regarding items 1 thru 4. Specifically UFGS-01 91 00.15 states that prior to Functional Performance Testing;


 “All electrical, power generation, and lighting equipment and systems have been completed, calibrated, tested, and operate in accordance with contract documents and construction plans and specifications”.

End Quote.

Good Engineering Practice 

Commissioning using temporary power is not recommended due to the unreliability in service and quality of temporary power i.e. voltage stability, imbalance and variation. Further, in many cases, the equipment used in temporary installations is not new and is not rated for the environment it is being used in.

Temporary power is subject to disturbances which effect HVAC equipment and controls. The IEEE define power quality disturbances/issues as follows:

1. Transients (sudden peak events that raise voltage and/ or current)

2. Interruptions

3. Sag (under voltage)

4. Swell (over voltage)

5. Waveform distortion

6. Voltage fluctuations

7. Frequency variations

The “quality” of power effects performance and life span of HVAC motors, VFD’s, ELV systems equipment and can compromise manufactures warranties. This all effects the reliability and repeatability of TAB and Commissioning test results. On some of my past projects, this has resulted in schedule delays and additional costs due to the Design Engineer of Record (DoR) requiring re-testing on permanent power of systems commissioned using temporary power. 

Due to the risks regarding test results repeatability, possible damage to HVAC equipment and controls, it is preferred that good engineering practice be followed and all systems are tested using permanent power. 

IMHO, the CxA or TAB team should only test systems using temporary power on receipt of the  following: 

1. A written instruction from the client to proceed with testing and commissioning using temporary power and also confirming that any re-testing using permanent power would be subject to addition fees. 

2. Agreement in writing from the Engineer of Record that they accept systems commissioning and handover using temporary power. 

To all Cx and TAB team leaders, do your job, manage your risk and cover your ass! 

BlueRithm Brand Ambassador 

Twitter: @BLDWhisperer


Related posts & links:

#187 – Commissioning Industry Chaos 

#198 – FAT 

#202 – Insurance & Commissioning 

Edifice Complex Podcast


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