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UK electrician-grade temporary HVAC tools
Temporary HVAC electrical calculators for UK sites.
Not another generic load planner. These tools answer the awkward site questions for heaters, drying kit, fans and portable AC: will the 110V transformer hold, will the RCD nuisance-trip, is the cable reel derated, will the generator survive compressor start, and how should loads split across phases?
Project Power Context
- Supply: 110V transformer + 230V 13A sockets
- Loads: heater, dehumidifier, fan, portable AC
- Checks: leakage, voltage drop, kVA, phase balance
- Output: circuit split + NHS equipment categories
Shared context means each tool feeds the next. No duplicated calculator dead-ends.
Built around real site failure modes
The core idea: electrical constraints before equipment selection.
National Electric MFG sits one step before the heater shop. It helps a competent person understand the supply, circuit, cable, RCD and generator limits, then points to the relevant National Heater Shops category: electric heaters, dehumidifiers, air movers, portable AC, drying equipment or ventilation.
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Drying equipment needs a power plan, not guesswork.
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Portable AC checks include start current, ducting and condensate.
Calculator · 110V / site transformer
110V transformer heater check
Check whether a 110V site transformer can realistically power temporary heaters, dehumidifiers, fans or drying kit without overload or ugly voltage drop.
For construction sites, drying contractors and hire desks using 110V heaters or 110V drying equipment.
Calculator · RCD / earth leakage
RCD leakage budget
Estimate cumulative leakage from compressors, dehumidifiers, portable AC, heaters, pumps and long wet leads before stacking everything behind one RCD.
Use it when drying or cooling equipment trips randomly or when several items share one RCD/RCBO.
Calculator · generator / kVA
Generator kVA + start current
Size a generator for portable AC, dehumidifiers, fans and heaters with a start-current allowance rather than only running watts.
For event sites, emergency cooling, flood drying and temporary power jobs.
Calculator · extension lead / cable reel
Heater cable reel derating
Check whether a coiled, partly unwound or long extension reel is a bad match for a 2kW or 3kW temporary heater.
For heater setups using 13A plugs, 16A commando leads or long extension reels.
Calculator · three-phase / phase balance
Three-phase load balancer
Allocate single-phase heaters, dehumidifiers, fans and portable AC units across L1/L2/L3 to reduce imbalance and nuisance trips.
For 32A, 63A and 125A temporary distribution boards with mixed 230V loads.
Calculator · BS 7671 / voltage drop
HVAC voltage drop envelope
Estimate voltage drop over long leads for heaters, air movers, dehumidifiers and portable AC, with compressor start warnings.
A planning aid, not a certification cable design package.
Calculator · PFC / PSCC
PFC / fault current
Estimate PSCC or PEFC from Ze and voltage, compare against device breaking capacity, and draft a quick test-sheet note.
For competent persons checking prospective fault current, breaking capacity and temporary distribution assumptions.
Calculator · max Zs / MCB
Max Zs checker
Check a measured Zs value against an entered device limit, with optional 80% rule headroom and clear pass/check wording.
For reviewing Zs results on MCB/RCBO circuits before recording or investigating a circuit.
Calculator · CPC / adiabatic
CPC adiabatic
Use the adiabatic equation shape to compare fault current, disconnection time, k factor and CPC size as a planning aid.
For competent review of CPC adequacy where final design still needs current BS 7671 tables and site data.
Calculator · cable correction factor / Iz
Cable correction factors
Stack ambient temperature, grouping, insulation and installation correction factors to see whether corrected Iz still covers load current.
For quick cable-capacity sanity checks before final BS 7671 cable selection.
Calculator · RCD / trip time
RCD trip time checker
Review x0.5, x1 and x5 RCD trip-time readings and produce a clear pass/check prompt for the job file.
For checking recorded RCD results before deciding whether to retest, investigate or replace.
Calculator · insulation resistance / IR test
IR test triage
Turn L-N, L-E and N-E insulation-resistance readings into practical next-step notes for damp circuits, appliances and fault finding.
For electricians reviewing low or borderline MΩ readings without treating a web tool as certification.
Site Heating Power Check
A guided flow for answering: can this site supply run the electric heaters without cooking reels, dropping voltage or overloading one phase?
- Select 13A, 16A, 32A, 63A, 110V transformer, generator or three-phase supply.
- Add heater kW or choose equipment presets.
- Run amps, transformer, cable reel derating, voltage drop, RCD leakage and phase balance checks.
Flood Drying Electrical Plan
Turn room size, humidity and available power into a drying stack: dehumidifiers, air movers, heater support, RCD split and daily log.
- Enter room size, RH, temperature, wet materials and target.
- Size dehumidifier capacity and decide refrigerant vs desiccant.
- Add air movers and support heat.
Portable AC Event & Server-Room Power Plan
Estimate cooling, start current, exhaust duct losses, condensate handling and generator demand for temporary cooling.
- Choose server room, event, office, kitchen or workshop.
- Estimate cooling kW/BTU and spot load.
- Check compressor start current and generator kVA.
Warehouse Fan & Heater Balance
Link high-bay heat loss, door ventilation, destratification and temporary electric heater power into one plan.
- Enter warehouse volume, target temperature and door/ventilation conditions.
- Calculate ACH and ventilation heat loss.
- Estimate destratification benefit.
Nuisance RCD Trip Diagnosis
Diagnose why drying, cooling or heating equipment trips protection: leakage budget, start current, panel map, lead condition and visual heat-risk scan.
- Select the symptom: immediate trip, compressor start, damp/random, cable reel or overload.
- Add equipment and circuit details.
- Run RCD leakage and MCB curve checks.
Generator-Powered Temporary HVAC Setup
Build a generator plan for heaters, AC, dehumidifiers and fans with kVA, compressor start, voltage drop, RCD and sequencing checks.
- Add all planned equipment.
- Enter available or target generator kVA.
- Run running kW, surge kVA and start sequence.
AI tools with honest boundaries
Phone photos can flag visual heat-risk clues. They cannot measure real temperature.
Ordinary RGB phone cameras are not LWIR thermal cameras. The AI thermal-style tool therefore creates a risk overlay from visible clues and supports true thermal image upload mode where users have proper thermal-camera data.
AI panel photo mapUpload a board photo and create a draft circuit map, breaker list, RCD group notes and temporary HVAC suitability questions.AI thermal-style risk scanUse a normal phone photo for a thermal-style risk overlay based on visible clues, or upload true thermal imagery when available.AI nameplate readerUpload or type nameplate details from heaters, dehumidifiers, fans or AC units and extract voltage, current, watts, phase and IP hints.AI plug/reel visual checkA photo-led checklist for coiled reels, discolouration, cracked plugs, loose strain relief and overloaded adaptors.AI drying layoutUse a room photo plus measurements to draft dehumidifier and air mover placement notes for drying jobs.