Without safe, reliable electrical distribution at your jobsite, your construction project is seriously threatened from the start. You need electricity to power your job trailers, tower cranes, elevators, lighting, distribution tools and everything in between.
It makes every stage in the building process possible.
But how do you design electrical distribution effectively for a temporary site? What sources of power should you use? And how do you make sure it’s safe?
Why Is it So Important to Get This Right?
Nothing happens without power. Not construction work, not maintenance - nothing. If you don’t set up your electrical distribution properly, you won’t have access to the electricity needed to get the work done on time. You may lose power in the middle of vital operations. You may experience equipment failures.
Any of these outcomes will play havoc with your schedule and may push you over budget. Some of these problems could take days or even weeks to fix or require you to bring in emergency power sources that cost more than if you’d planned ahead.
Worse, if you don’t take care to set this up properly, you could put workers at risk of harm. It’s absolutely vital that you don’t let things get to that point.
How Do You Get Distribution Into the Site?
Electricity on a jobsite can come either from diesel or natural gas-fueled generators (or temporary power stations created by stacking generators) or from a permanent utility power source - like the temporary pole connected to the existing utility or from an existing facility’s main distribution panel.
This is only the beginning of the story, though. As we’ll see in a moment, you need to take extreme care in calculating demand, designing generator specs, power access points and distribution setup.
Before you start, you need to get a clear idea of exactly what kinds of equipment you’ll be using that need temporary power and the loads they require. If you’re working with contractors, you need to get their input here.
These estimated power loads will help you assess the size of generators or the capacity of the temporary power station you need.
If you plan to connect to an existing, permanent power source, it will help you to figure out what supporting equipment you need - for example, if you need to use enclosed, temporary high-voltage substations that sit between the building’s high-voltage loop and the distribution panels that feed the jobsite.
Designing Your Site Power Distribution
You’re now in a position to design how electricity will be distributed around your site (in line with local rules and regulations!).
In addition to the main power supply considerations described above, this design should take into account exactly how each piece fits together, as well as finer details like input and output connections, corrosion protection, the capacity of current-carrying parts, overcurrent protection, grounding, bonding, electrical insulation materials, enclosures and enclosure performance.
You should also think about factors such as the temperature range that your equipment and electrical setup can work within, strain relief, icing and gaskets, exposure to the elements including waterproofing and rain-resistance, the thickness you need for metallic coating and clamped joint temperature. Run dielectric voltage withstand tests, too.
Coordinating with Local Utilities or Temporary Power Providers
Once you have this design in place, consult with the utility provider you’re using and provide temporary power load summaries so that they can incorporate this into their planning. They should then send you preliminary drawings and arrange pre-construction meetings with you before work gets underway.
Temporary power providers will often be able to meet with you immediately and conduct a job walk, working through different scenarios with power demands and distribution placement. Their experience can help you avoid any unnecessary delays, and uncover unique solutions and setups to your power needs.
Making It Safe
A lot can go wrong with temporary electrical equipment. Bad wiring and connections can lead to severe electric shocks, burns and falls, as well as fines, delays and equipment damage. Never take safety considerations lightly!
Common, preventable errors range from overloading normal-duty extension cords that are connected to temporary power through to failing to mark buried cables and positioning extension cords where they’re able to get wet.
Some of these are common-sense issues that you should be able to counter by laying out clear, strict rules for your team (and enforcing them). Others take a little more care on your part.
Start by ensuring that any temporary cables that you use to power lighting, tools or power distribution are protected with shock-resistant barriers. Use cable protectors to make sure passersby aren’t tripped up or injured by dangerous voltages. Check that settings are correct on your circuit breakers. Make sure that any pressure gauges on liquid-filled transformers are positive.
Finally, don’t shirk on predictive maintenance. Test critical parts of your distribution system before work begins and consider running ultrasonic analysis or thermography for peace of mind. Check voltages are correct. Test wiring and connections. Have a plan in place to deal with any unexpected power outages.
Prevention is much better, safer and cheaper than cure!
Perfecting the temporary power and electrical distribution setup on your jobsite is both complex and incredibly important. Don’t shrug it off and presume it will work out just fine - the risks to your team and to the success of your project are far too great for that!
If you’re in any doubt over your distribution design, consult an expert. Talk to your rental utilities’ provider. Schedule that extra pre-construction meeting with your local utility company. Sure, these things might push back your start date a tiny bit, but you’ll be glad of your caution when the project goes off without a hitch. Having things break down once work is underway will be far more costly, stressful and potentially dangerous in the long run.