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Revert the water-only heat-network calculator changes (tracked in #1592)
Backs out the WHC-950/951/952 primary-loss (d3c0b9e4) and flat-rate-charging (fecf4f62) changes to cert_to_inputs.py: they fire on ANY cert with those water-heating codes, regressing the gov-API RdSAP corpus (test_api_path_sap_accuracy_on_rdsap_21_0_1_corpus MAE 0.627 -> 0.630), and an Opus audit found the water-only branch has a pre-existing plant-efficiency double count they flow more kWh through. The calculator work + the correct fix (water_eff = 1.0/(DLF*1.05)) + an Elmhurst-worksheet regression are tracked in #1592, isolated from the extractor accuracy PR. The cylinder- insulation MAPPER fix (f5e4814b) is retained. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Khalim Conn-Kowlessar
parent
21674d5ed0
commit
dc271e959a
2 changed files with 6 additions and 94 deletions
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@ -1187,11 +1187,6 @@ _HEAT_NETWORK_DHW_CHARGING_FACTOR_BY_CODE: Final[dict[int, float]] = {
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2306: 1.00, 2308: 1.00, 2309: 1.00, 2310: 1.00, 2312: 1.00, 2314: 1.00,
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}
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# SAP 10.2 Table 4c(3) (PDF p.169) worksheet (305a) flat-rate-charging
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# factor — the RdSAP 10 (spec p.59) default for a water-ONLY heat network
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# (WHC 950/951/952), whose own charging method is never lodged.
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_TABLE_4C3_FLAT_RATE_CHARGING_FACTOR: Final[float] = 1.05
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def _heat_network_space_charging_factor(main: Optional[MainHeatingDetail]) -> float:
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"""SAP 10.2 Table 4c(3) (PDF p.169) worksheet (305) — heat-network
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@ -6590,16 +6585,6 @@ def _primary_loss_applies(
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# kWh/yr — zero before this branch.
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if water_heating_code in _WATER_HEATING_BOILER_CIRCULATOR_CODES:
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return True
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# SAP 10.2 §4 "Heat networks" (PDF p.17 line 1482): "Primary circuit
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# loss for insulated pipework and cylinderstat should be included (see
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# Table 3)." A water-ONLY community scheme (WHC 950/951/952) feeds the
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# dwelling-side cylinder via primary pipework from the network
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# connection whatever the space main is, so the loss applies exactly
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# as for heat-network mains with WHC 901/902/914 (below). Checked off
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# `water_heating_code` before the main-keyed branches so a non-network
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# space main (HP, direct-acting electric) can't zero it out.
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if water_heating_code in _WATER_HEAT_NETWORK_ONLY_CODES:
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return True
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# SAP 10.2 Table 3 (PDF p.160) zero-loss list names "Direct-acting
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# electric boiler" verbatim. RdSAP 10 §12 (p.62) classifies SAP code
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# 191 as the direct-acting electric boiler: its cylinder is immersion-
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@ -7104,20 +7089,13 @@ def _primary_loss_override(
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water_heating_code=epc.sap_heating.water_heating_code,
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):
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return None
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# Heat-network DHW: either the space main is a network (WHC 901/902/914
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# inherit its DHW) or the DHW is its own water-only community scheme
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# (WHC 950/951/952) — the Table 3 heat-network row keys on the DHW
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# source, not on the space main.
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heat_network_dhw = is_heat_network_main(main) or (
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epc.sap_heating.water_heating_code in _WATER_HEAT_NETWORK_ONLY_CODES
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)
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# SAP 10.2 §4 "Heat networks" (PDF p.17 line 1482) pins community-
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# heating primary pipework to "insulated" (p=1.0), overriding the
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# RdSAP §3 age-band default which would otherwise return 0 for
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# pre-2007 stock. See `_HEAT_NETWORK_PIPEWORK_INSULATION_FRACTION`.
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pipework_p = (
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_HEAT_NETWORK_PIPEWORK_INSULATION_FRACTION
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if heat_network_dhw
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if is_heat_network_main(main)
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else _pipework_insulation_fraction_table_3(primary_age)
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)
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base = primary_loss_monthly_kwh(
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@ -7129,7 +7107,7 @@ def _primary_loss_override(
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# row applies regardless of the thermostat / separate-timing
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# lodgement (and so is robust to the community-fuel-as-electric
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# collision that would otherwise route DHW to the h=5 row).
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heat_network=heat_network_dhw,
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heat_network=is_heat_network_main(main),
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)
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# SAP 10.2 §12.4.4 (PDF p.36-37): for back-boiler combos summer DHW
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# comes from an electric immersion, not from the boiler — the boiler
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@ -8029,16 +8007,7 @@ def cert_to_inputs(
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# heating only ... distribution loss"). q_generated = q_useful ×
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# DLF, so delivered-per-fuel efficiency = plant_eff / DLF. Fires
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# on the WHC alone — the HW network is independent of the main.
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# RdSAP 10 (spec p.59, "Heat Network (HN) supplying — water
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# heating only"): a non-PCDB water-only network defaults to
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# "flat-rate charging", so the Table 4c(3) worksheet (305a)
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# factor 1.05 always applies — the scheme's own charging method
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# is never lodged (the dwelling's heating-control code describes
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# the SPACE network's charging, not this one's).
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water_eff = water_eff / (
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_heat_network_dlf(primary_age)
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* _TABLE_4C3_FLAT_RATE_CHARGING_FACTOR
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)
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water_eff = water_eff / _heat_network_dlf(primary_age)
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is_instantaneous = epc.sap_heating.water_heating_code in _INSTANTANEOUS_WATER_CODES
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# §9a Table 11 secondary fraction — pulled forward of §4 so the
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# post-§8 Equation D1 cascade can derive Q_space = (98c)m × (204)
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@ -478,57 +478,6 @@ def test_heat_network_primary_loss_uses_p1_h3_all_months_per_table_3() -> None:
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assert abs(sum(wh_result.primary_loss_monthly_kwh) - expected_primary_kwh) <= 1e-6
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def test_water_only_heat_network_cylinder_accrues_primary_loss() -> None:
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# Arrange — DHW from a water-ONLY community scheme (WHC 950) with a
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# lodged 210 L cylinder, on a heat-network space main (Table 4a 301,
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# cat 6) — fixture 507644414148's shape. SAP 10.2 §4 "Heat networks"
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# (PDF p.17 line 1482): "Primary circuit loss for insulated pipework
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# and cylinderstat should be included (see Table 3)" — the network
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# feeds the dwelling-side cylinder via primary pipework whichever WHC
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# lodges it, so the loss applies to 950/951/952 exactly as to
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# 901/902/914 (pre-fix these fell through to zero). Table 3 heat-
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# network row: p = 1.0 and h = 3 for all months.
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main = MainHeatingDetail(
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has_fghrs=False,
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main_fuel_type=51, # Table 12 community heat (from boilers)
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heat_emitter_type=1,
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emitter_temperature=1,
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main_heating_control=2306,
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main_heating_category=6,
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sap_main_heating_code=301,
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)
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part = make_building_part(construction_age_band="F")
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epc = make_minimal_sap10_epc(
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total_floor_area_m2=_TYPICAL_TFA_M2,
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habitable_rooms_count=4,
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country_code="ENG",
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has_hot_water_cylinder=True,
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sap_building_parts=[part],
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sap_heating=make_sap_heating(
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main_heating_details=[main],
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water_heating_code=950,
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water_heating_fuel=51,
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cylinder_size=4, # Large (>170 litres) → 210 L
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cylinder_insulation_type=1,
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cylinder_insulation_thickness_mm=50,
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),
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)
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# Act
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wh_result, _ = _water_heating_worksheet_and_gains(
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epc=epc,
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water_efficiency_pct=100.0,
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is_instantaneous=False,
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primary_age="F",
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pcdb_record=None,
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)
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# Assert — p=1.0, h=3 all months → 365 × 14 × (0.0091×3 + 0.0263).
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assert wh_result is not None
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expected_primary_kwh = 365.0 * 14.0 * (0.0091 * 3.0 + 0.0263)
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assert abs(sum(wh_result.primary_loss_monthly_kwh) - expected_primary_kwh) <= 1e-6
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def test_dual_main_system_2_costed_at_its_own_fuel_price() -> None:
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# Arrange — SAP 10.2 §10a: main heating system 2's fuel cost (worksheet
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# line (213)) is billed at ITS OWN Table 32 fuel price, separately from
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@ -1460,12 +1409,7 @@ def test_hot_water_only_heat_network_whc_950_applies_table12c_dlf() -> None:
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# gas boiler (NOT a heat network), mirroring cert 9093 (whc 950 + a
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# warm-air main). Compare against a non-heat-network baseline at the
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# same 0.80 water efficiency (whc 901 from the same gas main): the 950
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# HW fuel must exceed it by the DLF (age E → 1.41) × the Table 4c(3)
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# charging factor. RdSAP 10 (spec p.59, "Heat Network (HN) supplying
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# — water heating only"): a non-PCDB water-only network defaults to
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# "flat-rate charging" — worksheet (305a) factor 1.05 — since the
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# scheme's own charging method is never lodged (the dwelling's
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# heating-control code describes the SPACE network, not this one).
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# HW fuel must exceed it by exactly the DLF (age E → 1.41).
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part = make_building_part(construction_age_band="E")
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gas_main = MainHeatingDetail(
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has_fghrs=False,
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@ -1501,9 +1445,8 @@ def test_hot_water_only_heat_network_whc_950_applies_table12c_dlf() -> None:
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hw_network: float = cert_to_inputs(hw_network_epc).hot_water_kwh_per_yr
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baseline: float = cert_to_inputs(baseline_epc).hot_water_kwh_per_yr
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# Assert — the HW-only-heat-network fuel is scaled up by the age-E DLF
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# × the flat-rate-charging default (1.41 × 1.05 = 1.4805).
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assert abs(hw_network / baseline - 1.41 * 1.05) <= 0.02
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# Assert — the HW-only-heat-network fuel is scaled up by the age-E DLF.
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assert abs(hw_network / baseline - 1.41) <= 0.02
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def test_gas_boiler_main_efficiency_unchanged_by_dlf_override() -> None:
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