Elliot Ajose, Regional Sales and Technical Manager, Chauvin Arnoux UK
A primary school secured government funding to transition away from oil heating and move towards a fully electric system as part of its long-term sustainability strategy. The project included installing electric heaters, along with a proposed rooftop solar PV system, aimed at reducing both energy costs and carbon emissions.
Before progressing, the school needed evidence-based confirmation that its existing electrical infrastructure could support the additional load.
Two main concerns had to be addressed.
First, whether there was sufficient headroom capacity at the main fuse to accommodate the new heating system. Second, whether the addition of solar PV could introduce overvoltage risks on the local network, as electric vehicle chargers were already installed on site and in the area.
Energy Monitoring Approach
Two PEL113 power and energy loggers were installed at the school’s main distribution board. One was installed at the three-phase main incomer, while the other was at a single-phase board.
The loggers were deployed to measure maximum demand and current consumption, to check that the phases were balanced, and to keep close watch on voltage levels. Voltage was a particular area of focus, as readings needed to remain within the statutory band of 216V to 253V.
Monitoring was conducted over a typical school period to ensure accurate load profiling during heating, cleaning, and classroom usage, providing a reliable and comprehensive dataset.
Key Findings
The maximum load recorded was 37.55A. This indicates that there was sufficient spare capacity to support the proposed electric heater installation. So, no upgrade was required from a current demand perspective.
However, voltage readings told a different story. This was marginally above the DNO’s statutory upper threshold of 253V (230V +10%). While the current capacity was adequate, this elevated voltage presented a constraint. Solar PV inverters and EV chargers are designed to shut down when voltage exceeds 253V, which means both would be at risk of disconnection under existing network conditions when voltage levels exceed safe thresholds.
| Name | AVG | MIN | MIN date | MIN time | MAX | MAX date | MAX time | Units |
| V1 (10 min) | 247.4 | 235.3 | 17/03/2025 | 08:00:00 | 255.5 | 15/03/2025 | 14:00:00 | V |
The three-phase system, protected by 100A fuses per phase, also demonstrated considerable spare capacity. Data from the PEL113 loggers confirmed that the additional electrical heating load could be accommodated without risk of overloading.
The voltage readings, however, told a different story. L1 recorded 256.1V, L2 recorded 256.9V, and L3 recorded 254.2V. All three phases exceeded the statutory upper limit of 253V under the Electricity Safety, Quality and Continuity Regulations (ESQCR).
The implication was clear that installing solar PV would push export voltage further beyond acceptable limits. This would trigger inverter shutdowns and render the system ineffective.
As a result, without intervention from the Distribution Network Operator (DNO) or network reinforcement, the installation of solar PV would not be feasible under current conditions.
Conclusion and Recommendations
The installation of two PEL113 power and energy loggers provided data insight into both maximum demand and voltage stability across the site.
On the question of current headroom, the results were positive. The single-phase and three-phase boards had sufficient capacity to support the transition from oil to electric heating. The school can proceed with confidence on that front.
Regarding solar PV, the picture looks more complex. Existing voltage levels already exceed limits, which present a significant barrier to solar PV integration. Any future PV installation will require consultation with the Distribution Network Operator (DNO) and the potential implementation of voltage mitigation measures before it can proceed.
The school can move ahead with its electric heating infrastructure. However, the integration of solar generation will require network amendments to ensure regulatory compliance and long-term operational viability. It is a reminder, once again, that the limiting factor in renewable energy is often the network rather than the solar resource.
Explore the Chauvin Arnoux power and energy logging range on www.cauk.net
This article appeared in the June 2026 issue of Energy Manager magazine. Subscribe here.
