Upgrading the existing power supply system of a house with a UPS installed for priority consumers

Feb 13, 2022

This project was implemented in three stages. At the first stage, we conducted an inspection of the existing power supply system. At the second stage, we made a list of the minimum quantities of equipment to improve fire safety, electrical safety, and components to protect expensive household appliances from surges, voltage slumps, etc. At this stage, we selected the necessary uninterruptible power supply (UPS), the required UPS run time in the event of voltage loss in the mains and priority loads; At the third stage, we implemented the project. Please see a step-by-step implementation of the project below.

The results of the inspection of the power supply system of the house

The house meter board (MB) (Photo 1):

  1. The incoming circuit breaker with a rating of 16A, the outgoing circuit breaker supplying the house with a rating of 32A – distorted selectivity of the circuit breakers. Therefore, overload or short circuit will actuate a circuit breaker with a lower rating and thereby de-energize all equipment completely;
  2. There is no protection against low and high voltages at the terminal, which can lead to damage to expensive household appliances and electronics;
  3. There is no residual current device at the terminal, so-called “fire alarm RCD”, which responds to current leaks in the line and serves to improve fire safety. Also, the installation of this RCD is required by fire safety regulations;
  4. At the input, there is no protection against pulse overvoltage caused by lightning hitting an overhead power line or switching overvoltage (switching off/on at a transformer substation causes a voltage surge in the line), which can destroy expensive household appliances and electronics;
  5. A grounding circuit is missing;
  6. Poorly made installation;
  7. The electrical circuit of the board is missing;
  8. Cable tags and circuit breaker labels are missing.

Photo 1. The house meter board (MB)

Self-supporting insulated wire (SIW) brought in from the support to the house (Photo 2):

  1. The SIW is brought in through the entrance door of the annex;
  2. Brought in overhead. The wire on one side is attached to the support with special SIW mounting fittings, and on the other side it is screwed with wire to the house annex.

Photo 2. Input from the support into the house

Distribution boards inside the house (Photo 3):

  1. There are three distribution boards in the house, one on each floor;
  2. Selectivity is not complied in the boards, as described above in the MB;
  3. The outgoing lines of wall outlet circuit lack differential protection to protect people from electric shock and from fire. This protection is necessary as required by fire safety regulations and regulations for electrical installations;
  4. The automatic circuit breaker ratings are not selected correctly in relation to the cross section of the outgoing cable lines. The maximum permissible automatic circuit breaker current, in some cases, is higher than the maximum permissible cable current, i.e., if the line is overloaded for a long time, the automatic circuit breaker will not break, but the cable is overheated, and cable insulation can melt or ignite;
  5. The electrical circuit of the board is missing;
  6. Labels on circuit breakers are missing.

Photo 3. Input from the support into the house

General comments and customer’s wishes:

  1. A grounding circuit is missing;
  2. The customer complains about frequent short-term voltage outages, after which it is necessary to restart the gas boiler;
  3. The customer asks to protect the electrical equipment of the house from all kinds of voltage drops and slumps.

Solution

We have selected the optimal solution to address the identified issues, with due regard to the financial capacities of the customer:

  1. We decided to install a circuit breaker with a higher rating at the terminal, a high and low voltage protection device (LVPD), a selective residual current device (RCD-S), a surge protection device (SPD) in the meter board (MB) (see the MB Diagram below);
  2. Provide for the connection of a single-phase UPS to supply A phase of the house circuit breaker in the meter board (MB) (see the MB Diagram below);
  3. Rephase the boards in the house, connect all lighting, a gas boiler, circulation pumps of the heating system, a refrigerator, a TV in the living room, a Wi-Fi router to A phase. Therefore, we connected priority consumers to A phase to be powered from an uninterruptible power supply;
  4. Install an on-line UPS with a capacity of 6KVA, single-phase terminal with external batteries. The run time at 5 kW load is 1 hour, 1.5 kW is 3 hours;
  5. Mount the grounding circuit;
  6. Bring the incoming SIW in again and fasten it;
  7. Align the circuit breaker ratings with the cable sections in all distribution boards;
  8. Start-up and commissioning;
  9. Tests by an electrical laboratory.

MB diagram

For AQTech website

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