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Spare capacity calculator

Tingnan kung kakasya ang bagong load sa main switch ng supply.

AS/NZS 3000 Cl 2.2.2

Reads AS/NZS 3000:2018. Tables checked 1 Oct 2026.

Subukan ang isang job 4

Nilalagyan ng halimbawang value ang bawat job. Palitan ang mga ito ng sarili mong value.

Mga input

Worked example gamit ang mga default na input.

Mga phase
Single phase
Phase voltage
230 V
Rating ng main switch
63 A
Maximum demand ayon sa
Pagsukat, Cl 2.2.2(c)
Naitalang demand, L1
38 A
Kalkuladong demand bawat phase
0 A
Bagong load sa
Amps
Bagong load
20

Natitira pagkatapos ng bagong load

5A

Maximum demand
38A
Spare capacity
25A
Bagong load kada phase
20A

Design aid lang ang resultang ito. I-verify ito laban sa kasalukuyang standard.

Mga hakbang ng kalkulasyon

  1. ParaanPagsukat, ang pinakamataas na demand sa loob ng 30 minuto

    AS/NZS 3000:2018 Cl 2.2.2(c)

  2. Naitalang demand ng L138A

    AS/NZS 3000:2018 Cl 2.2.2(c)

  3. Rating ng main switch kada phase63A
  4. Spare capacity ng L125A
  5. Natitira sa L1 pagkatapos ng bagong loadResulta5A

Tungkol sa calculator na ito

How this is calculated

The tool finds the maximum demand of an existing supply. It then finds the spare capacity against the main switch, per phase. It also checks whether a new load fits. It reads AS/NZS 3000:2018 Cl 2.2.2.

  1. Maximum demand by measurement. You enter the highest demand recorded over 30 minutes on each phase (Cl 2.2.2(c)).
  2. Calculated demand. You can also enter a calculated demand per phase. The tool uses the larger of the two, because a measured demand above the calculated one is the maximum demand (Cl 2.2.2).
  3. Maximum demand by limitation. The tool takes one fixed or adjustable circuit-breaker setting as the demand on every phase (Cl 2.2.2(d)). For mains and submains, you can enter the breakers they feed. The tool adds their settings per phase. A three‑pole breaker counts on each phase.
  4. Spare capacity. It subtracts the maximum demand from the main switch rating, per phase.
  5. New load. A load in kW becomes amps at its power factor and the phase voltage. A three‑phase load splits equally across the phases. A single‑phase load goes on the phase you choose.
  6. Fit. It adds the new load to the maximum demand on each phase. The load fits when every phase stays at or below the main switch rating.
StepTable or clauseWhat it decides
MeasurementCl 2.2.2(c)The highest demand over the recording period
Measured above calculatedCl 2.2.2Which of the two figures is the maximum demand
LimitationCl 2.2.2(d)The demand from breaker settings
Spare capacityCl 2.2.2The room left on each phase

Worked example

Limits

  • The tool takes the main switch rating as the capacity. The supply fuse or the network agreement can be lower. Check both.
  • A recording is only as good as the day you take it. Record when the demand is at its highest.
  • The sum of breaker settings takes no diversity. It is the largest of the methods and is often above the main switch.
  • The tool does not size the cable or the protection for the new load. Use the cable size calculator and the RCD selection tool.

See also: Maximum demand by measurement and limitation, Will a heat pump fit a 63 A supply?, EV charger spare capacity on a 63 A main switch, EV charging load and spare capacity and the EV charger calculator.

Mga tanong

Design aid ang resulta. I-verify ito laban sa kasalukuyang standard.

Paano ko hahanapin ang maximum demand ng umiiral na bahay?

Pinapayagan ng AS/NZS 3000 Cl 2.2.2 ang kalkulasyon, assessment, pagsukat o limitasyon. Para sa umiiral na supply, itala ang demand at kunin ang pinakamataas sa loob ng 30 minuto kapag pinakamaraming gamit ang bahay. Puwede rin itong manggaling sa smart meter interval data.

Paano kung mas mataas ang kinalkulang demand kaysa sa naitalang demand?

I-enter ang dalawa. Kinukuha ng tool ang mas malaki sa bawat phase. Ginagawa ng Cl 2.2.2 na maximum demand ang naitalang demand kapag mas mataas ito sa kinalkula, kaya hindi natatago ng mababang reading ang kinalkulang load.

Ano ang maximum demand by limitation?

Puwedeng magtakda ng demand ang circuit-breaker: ang fixed rating nito, o ang load setting ng adjustable na breaker. Para sa mains at submains, kasama rin sa bilang ang kabuuan ng settings ng mga breaker na sinusuplayan nila. Walang diversity ang kabuuang iyon, kaya mataas ito.

Sa aling phase dapat ilagay ang single‑phase load?

Ilagay ito sa phase na may pinakamaraming spare capacity. Ipinapakita ng tool kung ano ang natitira sa bawat phase, at binabagsak ang anumang phase na lumampas sa rating ng main switch.

Ang main switch ba ang tunay na limit?

Kinukuha ng tool ang rating ng main switch bilang capacity. Puwedeng mas mababa ang supply fuse, ang service cable, at ang network agreement. Suriin ang mga ito bago mo idagdag ang load.

Mga clause at table na binabasa ng tool na ito

Bawat clause at table, kasama kung paano ito na-verify

Huling na-check ang mga table noong 1 Oct 2026.

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