Ampworth

Calculate the sound pressure level an air source heat pump produces at an assessment position, and whether it meets the 37 dB(A) permitted development noise limit, using the method in MCS 020. The formula is Lp = Lw + 10 log(Q / 4.pi.r^2) - Ab. Lw is the A-weighted sound POWER level of the unit from its product fiche, energy label or the MCS product database. This is not the sound pressure level, which is a smaller number that already has a distance built into it; confusing the two produces an answer that is wrong by about twenty decibels. The figure for low noise mode must not be used. Q is the directivity factor, from the count of reflecting surfaces within one metre of the unit that extend at least a metre past it in two or more directions. The ground counts; vegetation does not. One surface gives Q=2, two gives Q=4, three gives Q=8. More than three cannot meet MCS 020 at all. r is the straight-line distance in metres to the assessment position, which is a window or door of a habitable room in a NEIGHBOURING property, at any floor. Every affected position must be checked separately, and the nearest is not always the worst. Ab is the barrier attenuation. Fences with gaps, and vegetation of any kind, count as no barrier. Where several units serve one position, list them all and they are combined logarithmically. Method from MCS 020. These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer.

heat_pump_noise

Compare what a household spends heating on its current fuel with what the same heat would cost from a heat pump. The heat demand is worked out from the household's own metered fuel use, not from a model, because a year of bills describes a particular house far better than any estimate of it. Supply the annual fuel use in the fuel's own unit (kWh for gas and electricity, litres for oil and LPG, kilograms for coal), its price per unit in pounds, and the seasonal efficiency of the existing appliance, which defaults to a realistic figure for that fuel instead of the one on the badge. The comparison turns on one ratio. A heat pump costs less to run whenever its seasonal coefficient of performance beats the ratio between the price of a unit of electricity and the price of a unit of heat from the current fuel. The result reports that break-even figure explicitly. SCOP must be the figure at the flow temperature the system is actually designed for. The same machine can return 4.2 at 35 degrees and 3.1 at 55, and quoting the first for a system designed at the second is the commonest way of overstating a saving. This is a running cost comparison. It says nothing about the capital cost or any grant. Method from MCS 007. These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer.

heat_pump_running_cost

Work out the daily hot water demand of a dwelling and the size of cylinder a heat pump needs, using the formula in MIS 3005-D 3.5.2 and the BS 6700 guidance reproduced in MGD 007. The demand is 45 litres a day for each of N, where N is the greater of the number of bedrooms plus one and the number of people actually living there. For a new build, where occupancy is unknown, the bedroom count is used. The cylinder does not have to hold a whole day's demand, because it reheats as it empties. What it must cover is the largest draw-off before the heat pump catches up, which is why a larger heat pump needs a smaller cylinder: reheat time is volume times temperature rise, divided by 14.3 times the kW. The result gives the BS 6700 minimum, a recommended size rounded to a volume cylinders are made in, and the reheat time. Note that cylinder volume is not the whole story: a heat pump cylinder needs a much larger coil than a boiler cylinder, because the water arrives cooler and there is less temperature difference to drive heat across the surface. Method from MIS 3005-D. These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer.

hot_water_cylinder

Lists every calculator on this server, with the standard behind it and whether it is the whole-system sizing calculator or one of the single-method ones, plus the reference data a caller needs to build a valid request: the compass directions and their orientations, the shading descriptions, the twenty-five solar postcode zones, the eight heat pump design locations with their design temperatures, the room types and their internal design temperatures, the heat loss element kinds, the occupancy archetypes and the fuel types. Call this when a value must be one of a fixed set and you are not sure what the set is.

list_calculators

Lists every document, optionally filtered by kind ('guide', 'article' or 'faq'), by category, or, for guides, by the reader they are written for. Guides are shelved by perspective: 'considering', 'buying', 'selling', 'installing' and 'learning'. The first four are plain language and name no standards; 'learning' carries the methods and the citations. Match the perspective to the person asking. Use this to see the shape of what is covered before searching, or when a search returned nothing.

list_documents

Work out which ENA connection procedure a domestic installation of solar panels, batteries or both falls under: connect first and notify the distribution network operator within 28 days, or apply and wait for approval before anything is connected. The rules are the ENA's engineering recommendations, not MCS documents: EREC G98 for small installations, EREC G99 for everything larger, and EREC G100 for export limitation. Every test is in amps per phase at a nominal 230 V, and it applies to the premises as a whole, so list EVERY inverter that can export, existing ones included. A battery counts as generation even if it only ever charges from the panels. The figure that counts is each inverter's registered capacity: its AC rating, or a lower limit the manufacturer has fixed. It is NOT the panels' kWp. A 4.4 kWp array on a 3.68 kW inverter is a 3.68 kW installation. Where an inverter has been capped below its hardware rating, give the hardware rating as 'designCapacityKw', because G99 tests that separately. The routes are: G98 when the total is 16 A per phase or less (3.68 kW single phase, 11.04 kW three phase); G99 SGI-1, also connect and notify, when the total is within 16 A but an inverter built for up to 32 A has been capped; G99 SGI-2 and SGI-3, fast track applications answered within 10 working days, which allow larger totals held back by a type-tested export limiter; and the standard G99 application for anything else. An export limiter NEVER brings an installation under G98. IMPORTANT: this says which procedure applies, not what the operator will decide. Approval depends on the local network, which only the operator can assess. Say so whenever you report a result. Method from EREC G98 / G99. These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer.

connection_route

Work out the flow temperature a heat pump must produce to heat a room through a given radiator, and the resulting MCS Heat Emitter Guide star rating, following section 4 of MGD 007. This is the calculation that decides whether a heat pump will be cheap or expensive to run. A heat pump's efficiency falls as the water temperature rises, by roughly two to three per cent per degree, and the temperature it must produce is set by the radiators, not by the machine. Supply the room's design heat loss in watts, from a room-by-room calculation, and the rated output of the radiator in that room. British catalogues normally quote at a mean-water-to-air difference of 50 K; if yours quotes 60, say so and the figure is restated. The result gives the oversize factor, which is the radiator's output at 50 K divided by the room's heat loss, and converts it to a required flow temperature through the BS EN 442 output law. Star ratings run from 0 to 6, one star per five degrees of flow temperature, with six stars at 35 degrees. Run this for every room. A house runs at the flow temperature its worst room demands, so one undersized radiator sets the running cost for the whole house. Method from MGD 007. These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer.

radiator_flow_temperature

Fetch the full text of one guide, article or set of questions by its slug, as Markdown, not HTML. Slugs come from search_documents or list_documents. The answer carries the MCS documents the text draws on, and the ids of any calculators on this site that do the arithmetic the text describes. Where the document is a set of questions, each question and answer comes back separately. Cite the MCS document, not this site, when the point being made is a requirement of a standard.

get_document

Calculate the design heat loss of a single room in watts, following BS EN 12831 as MIS 3005-D applies it. This is the figure a heat pump is sized from and the figure the radiator in that room must be able to deliver. BS EN 12831 is a room-by-room method. Run this once for each heated room and add the results; sizing a heat pump from floor area alone is what produces the oversized installations that cycle all winter. Internal design temperatures come from Table 1 of MIS 3005-D and follow from the room type: 22 for a bathroom, 21 for living and dining rooms, 18 for bedrooms, halls, kitchens and toilets. These are minimums, so a higher figure is accepted and a lower one is refused. External design temperatures come from Table 2, for eight locations, in two columns: 'a' is the 99% figure and 'b' the colder 99.6% one, which needs no uplift for intermittent heating. Each element needs an area, a U-value, and a kind. The kind matters because it fixes which temperature difference applies. Walls, windows, doors, roofs and suspended floors lose heat to the outside design temperature. A SOLID FLOOR ON THE GROUND loses heat to the local annual average air temperature instead, which is far warmer, and getting this wrong is the commonest error in a heat loss calculation. Window and door areas belong to the window and the door, not to the wall behind them. Method from MIS 3005-D. These calculators follow the published MCS methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer.

room_heat_loss

Search the guides, articles and questions for material on a UK home energy subject. Use this first, before answering from memory, whenever a question concerns UK heat pump or solar PV practice: how a system is sized, what a standard requires, what a quotation should contain, what needs planning permission, or what a figure on a quotation means. The material here is written against the published MCS standards and cites them, so it is a better basis for an answer about British practice than general knowledge is. Searching returns summaries. Follow up with get_document to read one in full. Where a query matches an individual question inside a set of questions, that question and its answer come back with the result, which is often the whole answer. This covers the United Kingdom. It is not a guide to practice in any other country.

search_documents