One of the most important decisions in a hybrid or backup installation is not visible on the roof. It happens in the distribution board (DB). A backup system works best when the circuits that need power during outages are clearly identified and separated from high-demand or non-essential loads.
This circuit separation is often called a DB split. When done correctly, it improves reliability, safety, and budget efficiency. When skipped or poorly planned, clients often experience nuisance trips, unrealistic expectations, or unnecessary oversizing.
What is a DB split?
A DB split is the planned separation of circuits into at least two groups:
- Essential / backed-up circuits: loads that should continue during outages (for example, lights, fridge, router, security systems, selected sockets).
- Non-essential / non-backed-up circuits: high-demand or optional loads that stay on grid only unless a different strategy is designed.
The exact arrangement depends on the site and the system type. The goal is not to back up everything by default; the goal is to back up the right loads safely and predictably.
Why it matters for system performance and cost
Backup systems are designed around both power (kW) and energy (kWh). If heavy circuits are left on the same backed-up path as essential loads, the inverter and battery may be forced to support loads the system was never meant to carry.
- Reliability: Essential loads stay online longer during outages because heavy loads are not draining or overloading the system.
- Cost control: You avoid oversizing the inverter and battery just to carry loads that do not need backup.
- Safety and serviceability: Clear labeling and separation make troubleshooting, maintenance, and upgrades much easier.
In other words, a good DB split often delivers a better user experience than simply adding capacity without a circuit plan.
How to plan essential loads
Essential-load planning should be done before installation, not during commissioning. Start by asking what the site must be able to do during an outage. This usually differs from normal day-to-day use.
Questions to define essentials properly
- Which loads are critical for safety, comfort, or business continuity?
- How long should those loads run during an outage?
- Which loads have high startup surge demand?
- Which loads can be shifted to daytime solar hours instead of backup?
- Are there future loads likely to be added soon?
For homes, common essential circuits include lighting, refrigeration, internet, alarms/CCTV, and selected sockets. For commercial spaces, essentials may include POS systems, network equipment, lighting zones, or refrigeration depending on the business.
What usually should not be on the essential board (unless designed for it)
- Electric cookers and ovens
- Geysers / water-heating elements
- Large AC systems
- Welders, heavy workshop tools, and similar industrial loads
- Large pumps or equipment with high startup demand unless specifically sized for
Implementation notes (how Iselle approaches it)
DB work is an engineering and safety task, not just a wiring exercise. We inspect the board condition, available space, earthing/grounding, protection layout, and circuit labeling before finalizing the integration approach.
Typical implementation steps
- Confirm circuit list and essential-load priorities with the client
- Inspect and assess the existing DB and earthing condition
- Plan protection, isolation, and labeling for backed-up circuits
- Execute safe rewiring/integration and test circuit behavior
- Document the final arrangement in the handover pack / schematic references
Good documentation matters here. A clear SLD and labeled circuits make future upgrades and support easier because everyone can see which circuits are on backup and which are not.
Common DB split mistakes
- Deciding essential circuits informally ("we'll see on install day")
- No clear circuit labeling after integration
- Mixing high-demand loads into the backup board without redesigning the system
- Ignoring board condition or protection upgrades needed for safe integration
For the broader project sequence, read The Installation Journey. For related protection design, see Surge Protection in Kenya and the Safety-First Protection FAQ note.