This article is about the process that should be applied when you plan to work on an underground installation. And it’s written by Patricia, your felllow electrical engineer.
Read and give her your feedback in the comments.
Underground installations are made to replace overhead cables with underground cables. They offer good solution to limit blackouts and outages during wind thunderstorms. They are also very appealing compared to overhead lines which tend to overwhelm the sky.
For this article, I’ll focus on underground installation in houses and residential subdivision which will only be possible after checking the feasibility of such works. It is important for electricians, engineer, and developer to be well prepared for that process.
Let’s look first of all at some important points.
Planning an underground installation: WHEN?
- When the client wants to provide some additional power to its yard or garden.
- When there is a no possibility to process to overhead installation during a transmission line construction: this occurs frequently in area suggest natural obstacles, vulnerable ecosystems or just have an historical heritage.
- When due to health reasons, the client wants to adopt a more environmental option to reduce the emission of magnetic field in the case of leukemia disease for example.
Steps to follow for underground installation
1) Discuss with the client
Let the client understand clearly what is going about; you are the professional but not him, so have a deep exchange with him. Most often, client changes their installations by imitation or to follow the trends. The following points should be considered:
- The type of project: Is it an extension or a complete reinstallation? Depending on what he wants, explain him clearly what is involved in that project and where its own responsibility starts. You should be able also to explain him how you will process and what he can do before starting any underground installation (dig the trenches for example).
- Do telephone cables come from the same pole than the electrical pole? Then he should call the telephone company if there is a possibility of a joint connection, to ask for an authorization to perform such tasks.
- When does he plan to start? This will help you to start planning you work too. He should also know how long it will take to do the work.
2) Visit the site
…In order to determine the best route and trench for your underground installation.
This is of paramount importance since it helps to evaluate the works as well as the feasibility of the project. The terrain conditions and loads will be checked carefully to see if it will be possible to construct and maintain those underground facilities.
In most jurisdiction client needs a permit before digging any trench. As a rule of thumb, the underground meter will be installed in same area as the overhead electrical service, but if the client wants another area, check it with him and ask for the copy of the new proposed location.
3) Choose the cable installation method
Depending on the use, the budget and the project, the cable installation methods are different. Direct buried cable is the most common installation type.
Why? Maybe because it is the cheapest one and present a good economical proposition for house owner. Ducted methods are more expensive but save time during installation, and surface troughs are mostly used where there is no vehicle traffic. The choice depends on the level of project.
4) Determine the required material for the installation
Depending on the project and the type of installation we will have PVC conduits, PVC coupling, etc. for direct burial installations especially, trenching shovel, marker flags , warning underground tapes , meter tape to measure the distances, hammer, etc.
This evaluation is necessary in the project development and avoids any disruption of work which might be caused by bad preparation.
5) Finalize the contract with the client
After sketching the proposed installation route defined by both the client and the utility company’s representative, a contract is written and then signed by the client with the cost and estimation of the material and equipment involved.
6) Process to electrical installations from the meter socket to the control box
The client hires a registered electrician to perform such works. The electrician should therefore explain to the client what he will do exactly. There is no extra works of maintenance than those defined in the agreement after a certain period.
Many clients like such interventions to present their other electrical problems. No, if it is a simple light fixing problem, why not? Tell to client where the works should start and what you will do: install a metal socket, connect it to its control panel and wait for an inspection. That’s it.
7) Arrange for inspection
This is a crucial step before starting any underground installation. Many authorities required a permit to perform those works. An inspection allow you to evaluate some important points in the work like trench and conduits (trench depth, sand bed…), structures (backfills, property pins, access…) and streets lights (base alignment or base grade) and all of them will come at different phases in the process: trenching, structure grounding, duct work… After that the schedule of the final work is determined.
Although this method offers good options and advantages, one of its downside it is the cost of installation which can be up to 14 times more expensive than overhead installations.
Electricians should always checks on the regulations board and policies of each town to see if they authorize any underground installation in their localities and also to learn more about the installation requirements in those places: minimum size of buried conduits, color of ducts, depth allowed for conduit systems installations, etc.
Always take your time and stay calm when working in these projects because they can become hazardous and unsafe at any moment.
Thanks for reading my advices,
What do you think of these 7 steps? Do you agree or do you have more to add?