Generator Load Calculator

Starting characteristics and pump data: BSRIA BG 70/2017, including the Tables 8 to 10 pump examples, the locked-rotor window held for 75% of the hot burn-out time unless the protective device clearance time is entered, and the 9 to 13 s burn-out band with the Table 6 typical values. Start sequence: sprinkler pumps immediately power is available, the duty wet riser pump 15 s later and the assist 30 s later (BG 70/2017; LPC TB210:2022 Clause 8.2.1). Starting power factor (pf) by load type as rules of thumb: direct on line 0.30; star-delta rising from 0.30 to 0.80 across the star phase, then 0.80 through the changeover; soft start 0.45; variable speed drive (VSD) 0.90; Non-motor 0.95. A pump held in the locked-rotor window of the "Worst case" scenario is taken at 0.30 whatever its load type, as if started direct on line or through a bypass. A manufacturer's figure entered in "Starting pf" takes precedence. Defaults where a figure is left blank: locked rotor at 6 times full load current, a 3 s run-up at locked rotor, a 0.4 s delta re-inrush, soft start limited to 2.5 times and an inverter to 1.5 times full load current. Inputs with stated defaults: changeover time 15 s (BS 9999 37.2.3.3 b, BS 8519 6.3), rated power factor 0.8, structure fire resistance period 120 min, smoke control duration 60 min. Acceptance limits: BS ISO 8528-5:2013 Table 4 performance class G2, with the 70% variable average of a standby rating (ISO 8528-1, BS 8519 6.3); the 80% steady headroom is a PD indicative warning, not a standard limit. Fuel storage: BS 8519:2020 Table 2 with the local service tank of 6.3. 17 typical life safety loads include real project values and start times as a starting point. Manufacturer motor and pump data takes precedence for every input (BS 8519 20.1), and the generator manufacturer's own sizing run is the selection of record.

06/10/2026 (3.12.0): The star-delta starting power factor rises from 0.30 to 0.80. In "Worst case", a locked-rotor pump is taken at 0.30 whatever its load type, with a note on "VSD" and "Non-motor" fire pumps; "Starting pf" takes precedence. The kVA demand is unchanged. Sizes are smaller, or replace "Above the single-set range", in 108 of 2,688 scenarios per tier ("VSD" 48, "Non-motor" 60) and 826 of 2,561 mixes ("VSD" 396, "Non-motor" 430). With a "Fire DB" line of 450 A or more, sizes with 17 "Star-delta" and 33 "Soft start" pumps are one smaller, 2 "Star-delta" and 4 "DOL" one larger. 26/09/2026 (3.11.0): the printed report is now readable, including the secondary supply schematic; in the cases checked, its labels measure 8.2 pt or more, against 4.0 to 5.1 pt in 3.10.0. The design notes are no longer in the PDF export of a report saved to My Projects with version 3.11.0 or later, or in the report emailed to free users; they stay in the tool and the other exports. In the scenario record for a stall held for the entered clearance time, BS 8519:2020 20.1, which is written with "should", is now cited with "recommends", separately from TB210:2022 8.2.1(e). The calculations and every figure, rating, check and limit are unchanged, and, apart from the changes above, so are the wording in the tool, in the printed report, in the report emailed to free users and in the exports, and the drawings in the tool. The automated print check now also checks that every schematic label is 7 pt or more, and a new one checks that the design notes are left out of the PDF export and the emailed report and kept in the other exports; version 3.10.0 fails both. These checks, the check with one item for each point found in the review of 3.9.0, the 2,688 scenarios in each tier, the derived-input, term-of-art, rating basis and wording checks, and a test of the buttons and fields in the tool at 1280 px and 390 px wide were run on 3.11.0 with no findings; verified live after upload. 26/09/2026 (3.10.0): the printed report is now readable, apart from the labels of the secondary supply schematic. Up to 3.9.1, each page of the report was shrunk to fit one A4 sheet, down to half size, and most of its text measured 3.3 to 6.2 pt. The report is no longer shrunk and is printed over 4 or 5 pages in the cases checked; every line of text outside the drawings measures 8.2 pt or more, and the labels of the load profile chart measure 7.0 pt or more. The schematic labels still measure 4.0 to 5.1 pt; a new layout for that drawing is left for a later release. Every result, check line and record shown in the tool is in the printed report, as before, and the design notes are still not printed. When the sizing duty is above the largest standard set listed, the generator size in the printed report, the exports and the report emailed to free users now reads "Required generator: more than the largest standard set listed", as in the tool; before, it read "Add equipment". The fuse requirement now reads "shall not clear" in every line that read "must not clear", because TB210:2022 8.2.1(e) is written with "shall". In the worst-case sentence under "Sizing basis", the check line on a clearance time below 75% of the hot burn-out time and the scenario record for a stall held for 75% of the hot burn-out time, BS 8519:2020 20.1, which is written with "should", is now cited with "recommends", separately from TB210 8.2.1(e). The note on the equipment record, the rating line of the acceptance criteria and the help under "Operating philosophy (fuel)" now use the verb of the clause they cite. In the exports and the report emailed to free users, the design notes are now headed "Design notes for the designer: delete before issuing to the client". The page had no main heading; the tool name in the dark bar at the top of the tool is now that heading, with the same words, look and size as before. The milestone lines and the peak marker of the load profile chart are now a darker amber. The green for a pass, the amber for a point to check or a warning, and the grey for a neutral mark are now darker, so that any white text on them meets the 4.5:1 contrast that the Web Content Accessibility Guidelines 2.2 require at level AA for text of 12 px; this change applies only to the colours, not to any calculation, result, wording or layout. The calculations and every figure, rating, check and limit are unchanged, and, apart from the changes above, so are the wording in the tool, in the printed report, in the report emailed to free users and in the exports, and the drawings in the tool. A new automated check was added for this release. It checks the colours, the size and look of the page heading and the dark bar against 3.9.1 at 1280 px and 390 px wide, and the size and content of the printed text in several cases; version 3.9.1 fails it. That check, the check with one item for each point found in the review of 3.9.0, the 2,688 scenarios in each tier, the derived-input, term-of-art, rating basis and wording checks, and a test of the buttons and fields in the tool at 1280 px and 390 px wide were run on 3.10.0 with no findings; verified live after upload. 26/09/2026 (3.9.1): in a review of version 3.9.0, each of the 447 distinct lines of wording in the tool, the printed report, the report emailed to free users and the exports was read against its source and for plain UK English; the corrections are in 3.9.1. The "Above the single-set range" check line and the design note on paralleling now cite BS 7671 560.6.9 for sources capable of operation in parallel; earlier versions cited, in error, 560.6.8, which is for sources not capable of operation in parallel. The design note also cites 560.6.8.1 and 560.6.9 NOTE 1. Where BS 8519:2020 6.3, 20.2 and 20.4, and BS 9999:2017 G.2.2 were stated as requirements, the lines now read "recommends" or "should", because each of those clauses is written with "should". The Non-motor load type now has one name throughout, the Pressurisation fan category has the UK spelling, and other lines were revised in plain UK English, to remove capitals used for emphasis, hyphens used as dashes, arrows and the "~" sign. In the printed report, the box with the generator size is now coloured by the result: green when a size entered for checking passes, amber when it passes only with conditions, and red when it is undersized; the recommendation stays blue, and the words in the box are unchanged. The calculations and every figure, rating, check and limit are unchanged, and so are the drawings and the layout of the tool and the printed report. A new automated check has one item for each point found in the review, and version 3.9.0 fails it; that check, the 2,688 scenarios in each tier, the derived-input, term-of-art, rating basis, wording and appearance checks, and a test of every button and field in the tool at 1280 px and 390 px wide were run on 3.9.1 with no findings; verified live after upload. 26/09/2026 (3.9.0): the tool now looks like the PD Power Distribution tool, with the same colours, font, buttons, cards and tables, and the "Start again" button is now in a dark bar at the top of the tool, with the tool name and version. The panel for saving and exporting, below the results, keeps its present colours for now. The load profile chart, the secondary supply schematic and the printed report are in the new colours; no text, figure, position or scale in either drawing has changed. The printed reports of three cases were compared with those of 3.8.8 and have the same text in the same places, on two pages, as before. The calculations and every figure, rating, check and limit are unchanged, and so are the wording shown in the tool apart from the new bar, the exports apart from the colours and font of the schematic picture, the report emailed to free users and the saved reports. The 2,688 scenarios in each tier, the derived-input check and the term-of-art check were re-run on 3.9.0 with no findings; verified live after upload. 16/09/2026 (3.8.8): the wording in the tool was revised in plain UK English. The compliance record line now says in the tool. The ratings, the checks, the printed report and the exports are unchanged. The 2,688 scenarios in each tier, the derived-input check and the term-of-art check were re-run on 3.8.8 with no findings; verified live after upload. 15/09/2026 (3.8.7): the notes written inside the program code were rewritten in plain UK English. The calculations, the wording shown in the tool, the printed report and the exports are unchanged. The 2,688 scenarios in each tier were re-run on 3.8.7 with no findings; verified live after upload. 15/09/2026 (3.8.6): the wording in the tool, the report and the reference lines was revised in plain UK English. The fuse requirement now reads: the fuse shall not clear the stalled rotor current before 75% of the period needed for the windings to fail (BS 8519 20.1; TB210 8.2.1(e)), with its meaning unchanged, and the over-range line names the largest standard set listed. A new automated check reads the wording of every program file, in the tool, the report and the printed sheets after all 20 presets, and fails on the 3.8.5 build; the 2,688 scenarios in each tier, the derived-input check and the term-of-art check were re-run on 3.8.6 with no findings; no rating, check or limit changed; verified live after upload. 10/09/2026 (3.8.4) and 11/09/2026 (3.8.5): a check across every PD tool for a control shown to every user that only a minority case reads, and for a default that misdescribes the load. The rating basis choice, standby (ESP) or prime (PRP), applies only to a size entered for checking, yet it was shown in recommend mode where the recommendation is always a standby rating under ISO 8528-1; it now shows only once a size is entered and cannot change a recommendation. A Fire DB or small power line is resistive, yet a custom line defaulted to direct-on-line starting; a line created on, or moved onto, that category now takes the Non-motor load type, and a Fire DB line left on a motor type prints a check line naming it. A new automated check tests both in both tiers and fails on the 3.8.3 build, and its second half fails on the 3.8.4 build; the 2,688 scenarios were re-run in each tier on 3.8.4 and again on 3.8.5 with no findings; no rating, default or check value changed; verified live after upload. 04/09/2026 (3.8.3): the full input range was enumerated, 3,408 scenarios in each tier, free and Toolkit: every category, starting method, full load current, stalled current and burn-out time in both scenarios, every combination of checked size, rating basis, fuel philosophy, changeover time, rated power factor, structure period and smoke duration, duty and standby pairs with a wet riser, and blank or nonsense entries; peak, steady and stalled demand were recomputed from the currents entered, the recommendation was re-derived from the printed figures, and the BS 8519 Table 2 fuel row, the changeover time and every duration were checked line by line. Two minor findings were corrected: the record printed an entered 26.5 A as 27 A, and the burn-out time field was offered on lines where nothing used it. The checks were re-run on 3.8.3 with no findings (2,688 scenarios in each tier once that field is pump-only), and the script on the live site was confirmed identical to the tested build. 04/09/2026 (3.8.2): every numeric input was checked for the figure a reader could enter in its place. The stalled current is now defined as the delta (direct-on-line) locked-rotor value, the star value is named as the trap, and a stalled current below 3.5 times the full load current on a pump or motor line is flagged in the tool; a size entered for checking now states its rating basis, standby (ESP) or prime (PRP), and the checks name it; the normal current, hot burn-out time and rated power factor name the figures they are confused with. No rating, default or check value changed; the check for a figure entered in place of another and the audit checks all passed, and the script on the live site was confirmed identical to the tested build. 04/09/2026 (3.8.1): BS 8519:2020 clause 6.3 was read back word for word; it sets no on-load test regime or interval, so the two light-running notes that cited it now point to the set manufacturer's operating requirements. No rating, default or check changed; the audit checks passed and the script on the live site was confirmed identical to the tested build. 03/09/2026 (3.8.0): a check across every PD tool that every printed value is reached through the input the standard derives it from. The equipment record was found to print the start times as entered rather than as the worst case modelled them, and the stalled-rotor line could print when no pump had been held; both were corrected. The changeover time, rated power factor, structure fire resistance period and smoke control duration, previously fixed figures, are now inputs with their defaults stated, and the protective device clearance time can be entered per pump. The 80% steady headroom is now a labelled PD warning. The full typical building returns the same 500 kVA as 3.7.2 and the BG 70 pump examples the same 1500 kVA; confirmed by the audit checks and verified live after upload. 02/09/2026 (3.7.2): every cited clause was read back against its source; the sizing principle now states BS 8519:2020 6.3 as the recommendation it is, a set sized to maintain the maximum design load and to support the worst-case transient and fault conditions; no rating, default or check changed. 02/09/2026 (3.7.1): the revised wording was checked in the tool against the house style; no rating, default or check changed. July 2026: a compliance audit of 40 checks traced every claim to its clause, and the sizing was verified against BSRIA BG 70/2017 Example 2 and the generator selection of a live project.