National Electric MFGTemporary power • HVAC load tools
Methodology

Electrical calculator · RCD / earth leakage / tripping / dehumidifiers

RCD Leakage Budget & Nuisance Trip Calculator

Estimate cumulative leakage from compressors, dehumidifiers, portable AC, heaters, pumps and long wet leads before stacking everything behind one RCD.

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Use it when drying or cooling equipment trips randomly or when several items share one RCD/RCBO.

Field notes

Field notes for RCD leakage budget

Practical checks to run before this calculator result turns into a site decision.

Site check

Leakage stacks quietly

Multiple dehumidifiers, AC units, pumps and filters can each look harmless alone but become unstable behind one RCD or RCBO.

Site check

Wet leads make intermittent faults harder

A random trip during drying work is often a mixture of normal leakage, damp connections and compressor starts. Split and isolate before blaming one machine.

Site check

Design for serviceability

Separate critical drying or cooling equipment so one nuisance trip does not stop the entire job overnight.

FAQ

RCD leakage budget FAQ

Short answers for UK temporary electrical and HVAC planning.

What is the RCD leakage budget used for?

Estimate cumulative leakage from compressors, dehumidifiers, portable AC, heaters, pumps and long wet leads before stacking everything behind one RCD. It is mainly for temporary HVAC, drying, cooling and site-power planning, especially where a quick pre-check is needed before selecting equipment or changing a temporary setup.

Can this replace BS 7671 design, inspection or testing?

No. Treat it as a pre-check for the conversation or job file. Final decisions still need current BS 7671 requirements, manufacturer data, inspection, testing, risk assessment and the actual site conditions.

What should I verify before acting on the result?

Check supply rating, protective device rating, cable length, voltage drop, start current, phase balance and the condition of temporary leads or distribution boards. If any assumption is uncertain, use the result as a prompt to investigate rather than as clearance to switch on.

What does an amber or red result usually mean?

It normally means the margin is weak, an assumption is missing, or the load should be split, staged, moved closer to the supply, reduced or checked by a qualified electrician before use.

Next tools in this workflow

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