The New Engineer — HVAC MCP Server

Where the upload stands. When `state` is `depose`, `token` is the token to pass to read_ifc_networks.

DETERMINISTIC: networks come from geometry, not from a guess. The same model always gives the same networks, from any AI, on any day. Read the networks of an IFC model already uploaded by the user. WHAT A NETWORK IS. A set of parts that touch each other, cut at equipment: a pump, an air handling unit, a chiller separates two systems, so the tool does not run through them. This is measured on the geometry — you cannot and need not check it. WHAT YOU GET, PER NETWORK state 'homogeneous' — a system exists, some parts were mis-named by the modeller; the tool will correct them. 'undetermined' — no system can be read. THIS is where you are useful. 'assigned' — the user or you already named it. system the dominant name, when there is one part_dominante the share of named parts carrying it equipements_voisins the NAMES of the machines this network is connected to. An undetermined network starting from 'AHU-Supply-L2' names itself — but only you can see it. systemes_existants every system name already in the model WHAT TO DO NEXT. Propose a name for each undetermined network, using the neighbouring equipment, the existing system names, and anything the user told you about the project's naming scheme. Ask the user for their list of planned systems if you do not have it. Then call name_ifc_networks. WHAT NOT TO DO. Do not rename a network the report calls 'homogeneous' unless its name plainly contradicts the equipment it is connected to — and then say why. Do not invent a network: you cannot see the geometry, and the tool already did that work. CALL THIS AGAIN WHENEVER THE STATE MAY HAVE MOVED. The token stays valid for 48 hours and is a key, not a snapshot: every call recomputes and returns the model AS IT IS NOW. The user works in the browser between your messages — renaming networks, assigning parts by hand, accepting or refusing corrections. So the moment they say they have done something, or you are about to state a figure, call this tool again. NEVER ANSWER FROM MEMORY about networks, counts or states. What you read earlier is already out of date the moment the user touches the 3D view, and a stale figure stated confidently is worse than no figure at all.

CALL THIS FIRST, as soon as the user gives you a token - a link thenewengineer.com/ia/XXXX pasted in the conversation - BEFORE you answer anything, even when the user only says they will choose or do something themselves. It answers within seconds, while the network graph is still being built - use that time to think. THE USER WANTS TO CHOOSE THE UNITS THEMSELVES (« let me select », « je vais choisir les centrales »): the place to do it is the control page. Go on through the steps below until trace_duct_circuits (token only) returns 'lien_centrales', and GIVE THEM THAT LINK. Never tell them to select « in the interface » without the link: there is no other place to select. A MODEL ALREADY TREATED: if the answer carries 'designation_existante', an earlier session already designated the units and fans of this model. Reuse it: skip step 2, go straight to trace_duct_circuits, and show the user the designation you reused. Post new rules only if the user asks to start again. THE CIRCUITS OF A MODEL IN FOUR CALLS: 1. read_ifc_overview - this call: the types of the model. 2. apply_ifc_rules - your rules. Give air handling units, monoblocs and ventilation casings the role centrale_de_traitement_d_air, fans the role ventilateur, and smoke exhaust fans (and smoke compensation fans) the role ventilateur_desenfumage, exactly these words - and ONLY to equipment that holds a fan. Coils, heat exchangers, filters, silencers, dampers, VAV boxes are pieces of the network, not units - BUT a family NAMED as a unit (CTA, AHU, UTA, monobloc, caisson, centrale) is one, even when its type names its heat recovery: « BG_CTA_Echangeur à plaques » is an air handling unit. Its answer lists under 'equipements' every unit and fan of the model. 3. trace_duct_circuits with ONLY the token - it computes nothing, walks the networks from every unit and fan, and either returns the COMPLETE list of units and fans with the control page, or says the units could not be connected to the model's networks. 4. trace_duct_circuits again with the units the user wants, or all_networks=true for all of them (offered up to 50 air networks only). The answer of this call repeats these steps under 'marche_a_suivre'. YOU SEE A SAMPLE, THE TOOL SEES EVERYTHING. This overview shows one example per type, not every piece: you cannot count the units, the fans or the networks of the model from it, and you must not believe you have seen them all. The tool applies your rules to every piece and walks every network. So never pick the networks to compute from this overview: trace_duct_circuits gives you the complete list of units and fans first, and you choose from THAT list. WHAT YOU GET. Not 3 000 parts: an INDEX of the model, one line per FAMILY of types (the sizes of one family share its line) - dampers, terminals, equipment, proxies -, each with its IFC class, its number of pieces, an example GUID and the identity fields of its largest type ('identite': object_type, nom_du_type...), which is what rules are written on. Plain ducts and fittings need no role: they are listed in one line each under 'reseau_ordinaire', and 'cotes_exemples' shows the numeric properties of the main duct families - where height, width and diameter are. THE DETAIL, ON DEMAND. When a family's name does not tell you what it is, call this tool again with families=[its 'famille' names] (up to 12 per call): you get every property of an example piece and every type of the family. property_catalogue=true lists every property of the model once. These follow-up calls bill nothing. WHAT TO DO WITH IT. Write RULES, not verdicts. For roles: which words, in which field, identify a fire damper, a silencer, a balancing damper, an air terminal, an air handling unit, a fan, a pump - and which groups are NOT network at all (access zones, plinths, placeholders, damper motors). For sizes: which 'PropertySet.Property' holds height, width, diameter, length. A rule applies to every part, including those you were not shown, and to the user's next models. TRAPS the field 'a_savoir' warns about: values are in the FILE's unit (see metres_par_unite), not millimetres; insulation sizes and hydraulic diameters look like dimensions and are not. The field 'etat_du_graphe' says whether the networks are ready yet: 'pret' means read_ifc_networks will answer now.

Turn what you read in the overview into rules the tool replays on EVERY piece of the model, including the ones you were never shown. NOT NEEDED ON A MODEL ALREADY TREATED: when read_ifc_overview returns 'designation_existante', the units and fans are already designated - reuse them. Posting rules REPLACES that designation entirely: do it only when the user asks to start again, or when the designation plainly contradicts what they say. THIS IS HOW THE TOOL LEARNS A MODEL. read_ifc_overview gives you one line per family of types, not one per piece. You answer with RULES on those groups, and this tool applies them to the three thousand pieces. You never give a verdict piece by piece: the result stays deterministic because a program, not you, does the matching. THEN READ THE ANSWER BACK, AND EXPECT TO POST AGAIN. The answer gives every group with the role your rules gave it and how many pieces that is. A rule that is too wide shows up on one line — « Gaine rectangulaire cadree, 471 pieces, centrale_de_traitement_d_air » is a rule that turned every duct into an air handling unit. Narrow it and post again. Calling this tool costs nothing and may be repeated as often as you need. WHAT NEEDS A ROLE, AND WHAT DOES NOT. Plain ducts and fittings need none: they are network by nature, and the answer marks them segment_ou_raccord so you can see at a glance whether a rule caught them by mistake. What needs a role is everything else — air handling units, fans, fire dampers, balancing dampers, silencers, louvres, diffusers — plus whatever must be kept OUT of the network, such as access zones, equipment plinths or damper motors. THREE ROLE NAMES ARE FIXED, because circuits start from them: give air handling units, monoblocs and ventilation casings the role centrale_de_traitement_d_air, fans the role ventilateur, and SMOKE EXHAUST fans - including fans that bring compensation air for smoke exhaust - the role ventilateur_desenfumage - exactly these words. A smoke fan runs only in a fire, with the ventilation stopped: a duct it shares with an air handling unit is not a plenum shared by two installations, and the tool does not cut the networks there. Read the names, families and types: « désenfumage », « DES », « smoke », « Entrauchung », « RWA ». ONLY EQUIPMENT THAT MOVES THE AIR gets one of them: a unit is a box with a fan in it. Heating and cooling coils, heat exchangers, filters, silencers, dampers, fire dampers, VAV boxes, humidifiers are NOT units: the air runs through them, they are pieces of the network. Give them another role (coil, silencer, damper...) or none - never one of the unit roles. A coil in 'equipements' is a rule that is too wide. BUT A FAMILY WHOSE NAME SAYS IT IS A UNIT IS A UNIT - CTA, AHU, UTA, monobloc, caisson, centrale, Lüftungsgerät - even when its type describes its heat recovery: « BG_CTA_Echangeur à plaques » is an air handling unit with plate heat recovery, not a heat exchanger. A heat exchanger is a network piece only when it is a separate piece in a duct run. The answer lists, under 'equipements', the GUIDs of every piece of the model that got one of these roles: that list is what trace_duct_circuits starts from, and what the pages show as units. Every other role name is yours to choose. A MONOBLOC BUILT FROM MODULES. Many air handling units are modelled as casings set end to end, each its own piece: filter casing, coil casing, heat exchanger or heat recovery casing, humidifier, washer, fan section, damper casing, empty casing. Give every such MODULE the role composant_de_monobloc - exactly these words - and its fan section(s) the unit role as usual. The tool then joins the modules that touch each other face to face (over 0.25 m2 of contact) into ONE unit: every duct on any module becomes one of its branches, and two fans of the same casing become one unit. Only modules of a unit get this role: a coil, a filter or a silencer fitted IN a duct is a piece of the network, and an equipment frame or plinth is not a module. ORDER THE LIST YOURSELF, most specific first, down to the most general. The fire damper rule must come before the balancing damper rule, or « damper » takes everything. Equipment must come before terminals: « VEN_MSF_MONOBLOC_SIMPLE_FLUX_REPRISE » contains « reprise », and a return-diffuser rule placed first would claim the air handling unit. Pieces no rule catches are simply listed, with no warning and no failure: the engineer judges on the 3D view, not on a coverage report. NEXT: once 'equipements' lists the air handling units and fans you expect, call trace_duct_circuits with only the token. It computes nothing yet: it checks that the units are connected to the networks and returns the complete list of units and fans, to choose from - see trace_duct_circuits. 'equipements' counts every piece ('pieces') but lists at most thirty names: the count, not the list, is the model.

DETERMINISTIC: the same inputs always give the same result — from any AI, on any day. Figures come from the standard's tables and formulas, never from a language model's estimate. Every step is auditable. EN 378 applied to BUILDING projects, volume by volume. An installation does not occupy one room but several: the machine, the rooms crossed by refrigerant lines, the rooms served by indoor units. Each volume is classified on its own — access category (a/b/c) and location class (I–IV) — and each classification calls for its own measures. The tool answers per volume, never as a single verdict. It returns, for every volume: its classification and why, the charge limit from Tables C.1 and C.2 of EN 378-1 (with the C.2 formula computed when the table calls for it), whether the charge exceeds it, the EN 378-3 measures that follow, the applicable texts (EN 378-1 to -4, EN IEC 60079-10-1, SUVA 66139 and 2153) and the ventilation flow rates. FOUR CONFIGURATIONS COVER ALMOST EVERY BUILDING PROJECT. Bring the user's case back to one of them wherever possible: machine_en_local_technique chiller or heat pump, all refrigerant inside the machine, standing in a plant room -> c III enceinte_accessible_fermee all refrigerant inside a walk-in ventilated enclosure that stays closed even for maintenance -> the enclosure is c III, the room around it carries no requirement enceintes_inaccessibles one or more units, each in a manufacturer's non-accessible ventilated enclosure -> TWO analyses: the enclosure in operation (class IV, the manufacturer sizes and justifies it, ask him for the enclosure ventilation), and the plant room with the enclosure OPEN for maintenance, which comes back to c III split_traversant split or VRF outdoors, refrigerant lines crossing occupied rooms -> each room on its own; offices and their circulations are b I, and formula C.2 gives the maximum charge for the floor area, or the minimum floor area for the charge THIS TOOL ANSWERS SAFETY IN THE ROOM. It says NOTHING about whether the refrigerant may still be placed on the market or refilled: in Switzerland that is `check_refrigerant_switzerland`. A question that mixes both - « may I use R-32 for 3 kg in a server room, and until when can I refill it » - needs BOTH tools: call this one for the room, and check_refrigerant_switzerland for the dates. Do not answer half the question. NEVER guess. The refrigerant, the configuration and the charge are always needed; a split also needs the floor area and how the indoor unit is mounted (floor, wall, window, ceiling), since C.2 depends on it. Without them the result is `provisional` and carries `questions_to_ask`: ask them, one or two at a time, then call again. Answer from `answer_outline`, volume by volume. In building projects, detection is preferred over treating a plant room as an ATEX zone. C.3 is never used. Say that the practical limit alone proves nothing: the charge limit of Tables C.1 and C.2 is what counts. SCOPE: building services. Cold rooms, food refrigeration and industrial process refrigeration are a different trade.

Apply the names you propose, and get back the updated report. THE NAMES ARE YOURS, THE NETWORKS ARE NOT. You are naming what the tool measured; you are not changing what it measured. Nothing you send here alters a network, a part, or a correction. WHAT COMES BACK. The updated report, a 3D link where the user sees your names in colour, and a link to the corrective Dynamo script that writes the systems back into Revit. ALWAYS GIVE THE USER THE 3D LINK, and say plainly which names are yours. Networks are deterministic; names are a proposal. A user who cannot tell the two apart cannot check your work. AFTER THE USER HAS BEEN IN THE 3D VIEW, call read_ifc_networks again with the same token before saying anything about the model. They may have renamed what you proposed, assigned parts by hand, or refused a correction — and only a fresh read shows it.

Show an upload box in the conversation where the user can drop an IFC file (.ifc) of a building services model (HVAC, plumbing, heating). The file goes straight from the user's browser to thenewengineer.com - you never see it. CALL THIS when the user wants to analyse an IFC model and has not yet given you a link from thenewengineer.com. Then tell the user to drop the file in the box. When the upload is done, the box posts a message with a token. Use that token with read_ifc_networks. If no message arrives and the user says the upload is done, call ifc_upload_result with the upload_token returned here. Prototype: files up to the anonymous size limit of the site.

DETERMINISTIC: the same inputs always give the same result — from any AI, on any day. Figures come from the regulation's annexes and thresholds, never from a language model's estimate. Every step is auditable. Swiss refrigerant regulation check (ORRChim / ChemRRV annex 2.10, OFEV synthesis of May 2026, rules adopted 29.10.2025) plus refrigerant data from EN 378-1 Annex E: GWP (AR4, the ORRChim basis), ODP, LFL, safety class, practical limit. Returns, for a given refrigerant and installation: the date from which machines using it can no longer be placed on the Swiss market (import from 01.01.2027, sale to third parties from 01.07.2027), the date from which filling with virgin refrigerant is banned, the period when only reclaimed refrigerant may be used, and the date from which all filling is banned. SCOPE: heating, air conditioning, building cooling and process cooling, data centres included. NOT food refrigeration, cold rooms or deep freezing: those are a different trade, and the tool declines them instead of answering. Use it whenever the user asks about a refrigerant in Switzerland — its GWP / PRG, flammability, whether a chiller, heat pump, split, VRF or cold room using it may still be sold or refilled — in any language: fluide frigorigène, Kältemittel, refrigerante, refrigerant, R-32, R-410A, R-290, CO2, NH3... The answer depends on the installation. The regulation distinguishes: use (building cooling, food refrigeration medium / low temperature / combined / deep freezing, process cooling, heat pump mainly for heating, ice rink), cooling capacity Q0K or heating capacity Q0H, self-contained (factory-built packaged unit) or not, split, direct expansion (incl. VRF), secondary coolant loop (chilled water / brine), air-cooled condenser and refrigerant charge. THIS TOOL ANSWERS ONE QUESTION ONLY: may the refrigerant still be sold and refilled in Switzerland, and until when. It says NOTHING about safety in the room - charge limits, machine room, detection, ventilation, ATEX. That is `check_en378_zones`. A question that mixes both - « may I use R-32 for 3 kg in a server room, and until when can I refill it » - needs BOTH tools: call this one for the dates, and check_en378_zones for the room. Do not answer half the question. NEVER guess these. Call the tool with what the user gave: it returns `provisional: true`, the possible `scenarios`, and `questions_to_ask` in the order that matters most. Ask them (one or two at a time), then call again. Natural refrigerants need no questions. Build your answer on `answer_outline`; quote exceptions as possible, never as granted.

DETERMINISTIC: the same inputs always give the same result — from any AI, on any day. Figures come from the standard's tables and formulas, never from a language model's estimate. Every step is auditable. Size the expansion vessel and pressurisation of a closed heating or chilled-water circuit to EN 12828: static height, minimum pressure p0, fill pressure pa, final pressure pe, expansion volume, water reserve, nominal vessel volume with the standard vessel to buy, safety valve setting together with the minimum it must not fall below, pressure class of the lowest equipment, intermediate vessel when needed. Heights become pressures through the real density of the fluid, at the temperature that matters for each: the coldest for p0, the design temperature for the valve and the lowest point. Water and glycols therefore give different figures for the same height. Use it whenever the user asks to size or check an expansion vessel, pressurisation unit, pre-charge pressure or safety valve — in any language: vase d'expansion, maintien de pression, Ausdehnungsgefäss, Druckhaltung, vaso di espansione, vaso de expansión. Needs the installation water volume and THREE heights, all measured from the point where the expansion vessel connects to the network: - the highest point of the installation, above it; - the lowest point, usually below it (negative) or level with it; - the safety valve, which always sits on the heat generator or chiller. If the user does not know it, it is assumed 1 m above the vessel connection, and the result says so. Ask the user for the volume and the three heights before calling. NEVER invent a height: if the lowest point or the valve height is unknown, omit it. The result is then marked provisional and lists the questions to ask. Build your answer on `answer_outline`: it carries the assumptions, the questions and the link to the website, which measures all of these on the user's IFC model.

THE CIRCUITS THE FANS OF A MODEL ARE SIZED ON, found without anyone clicking and computed on the pressure-drop page, where the user confirms types and flows and reads the pressure drops. THE USER WANTS TO PICK THE UNITS THEMSELVES: call this tool with ONLY the token right away, and give them 'lien_centrales' - the control page, where a click turns a unit red and 'Send to my AI' sends you their choice. Without that link they have nowhere to select. ONLY UNITS AND FANS ARE EXCHANGED. The tool never sends you system names: it sends the air handling units and fans your rules found, each with what the network walk finds connected to it - geometry, not names. A unit is equipment with a FAN - air handling unit, monobloc, ventilation casing, fan. Coils, heat exchangers, filters, silencers, dampers are network pieces: if one shows up in the list (often as 'dans_le_reseau_de' another unit), your rules are too wide - fix them with apply_ifc_rules before choosing. But a family NAMED as a unit (CTA, AHU, monobloc) is one, whatever its type says. A LOW 'raccordement' MOSTLY MEANS MISSED UNITS: look for families named CTA, AHU, monobloc, caisson that got no unit role, and add them before sending the user anywhere. FIRST THE CHECK AND THE LIST, THEN THE CALCULATION. Called with only the token, once your rules are posted with apply_ifc_rules, it computes NOTHING and bills nothing. It walks the networks from every unit and fan and measures the share of the model's air pieces they reach ('raccordement'). Two answers: - CONNECTED (half of the air pieces or more): the COMPLETE list of units and fans ('centrales_et_ventilateurs', each with its number of connected networks) and 'lien_centrales', the CONTROL PAGE ('Network check' in English, 'Contrôle des réseaux' in French) - not a view-only page: every unit in its colour with its networks, where the user checks and CORRECTS the connections (identify or remove a unit, add a virtual AHU, connect or separate two parts, cross a shared plenum) before anything is computed. Ask them to check it FIRST and wait for their answer. There they can also open the calculation page directly, or CLICK the units to compute: they turn red, and 'Send to my AI' copies a new link carrying that choice. Give the user that link, say nothing is computed yet, and that they can tick there or name the units here. Then: * the answer carries 'choix_de_l_utilisateur' (the user ticked on the page): compute EXACTLY those names with units, as its 'consigne' says - do not ask them again; * the user named units, even loosely: map their words onto the EXACT names of the list, say which you picked, and call again with units; * the user asked for the whole model and the list says 'tous_possible' (50 air networks or fewer): call again with all_networks=true; * otherwise show the user the WHOLE list to tick - every unit and fan, however long; never only the main ones. 'Tous' first when it is offered, then one numbered line per unit with its number of connected networks; mark the units connected to nothing. Filter only on what the user said, and then say which filter and how many lines it left out. Call with what they tick. - NOT CONNECTED ('non_raccorde': less than half, or no unit at all): tell the user the sentence of 'A_DIRE_A_L_UTILISATEUR' - « Nous n'avons pas pu connecter les centrales de traitement d'air aux réseaux de votre modèle », in their language - and suggest the pressure-drop page ('lien_pdc'), where they define each network themselves by a start and an end. Nothing is computed. If your rules missed units, fix them and call again. WHAT IS COMPUTED: for each network connected to a chosen unit or fan, the LONGEST path. Networks connected to no unit are not computed here. BEYOND 50 AIR NETWORKS, THE MODEL IS COMPUTED ONE UNIT AT A TIME. Each call computes ONE unit - unit_name, or units with a single name - or the network of ONE piece - network_guid. The whole model, start_role and several units are refused: nothing is computed, and the answer says why. Ask the user which unit, or which piece: on the control page, hovering a piece shows its GUID, and a click ticks a unit. Units the user ticked on the page ('choix_de_l_utilisateur') are asked for: compute them one per call, one after the other. Never pick the units yourself, never go through them all in a row on your own, and never call in parallel (sub-agents, simultaneous calls): the calls on one model run one after the other on the server, and parallel calls only slow the site down for everyone. Call again for the next one the user asks for; what is computed stays, and is not billed again. YOU SEE A SAMPLE IN THE OVERVIEW, THE WHOLE MODEL HERE. Never choose the units from what read_ifc_overview showed you - one example per type: choose from the list this tool returns. A REQUEST THE TOOL CANNOT MATCH. Names that match nothing come back under 'non_reconnus', each with the closest names; the names that did match are computed. If NOTHING matched - or the GUID or unit_name is unknown - nothing is computed, whatever the size of the model: the list comes back, with the closest names under 'non_reconnus' and what went wrong under 'demande_non_satisfaite'. Correct the names from the list, or ask the user which one they meant, and call again. A PIECE INSTEAD OF A UNIT. When the model has no unit, when the unit the user means was not recognised, or when they simply show a piece: network_guid computes the network of any piece - the tool finds where its air starts; end_guid computes one circuit to that end - from start_guid if given, else from the start the tool finds. A start found by the tool comes back under 'depart_trouve' with what made it chosen: say so, and ask the user to check it on the 3D link. The user gets a GUID by hovering a piece on the control page. These work on complex models too: they designate one network. ONE UNIT BY ITS NAME. unit_name computes the unit or fan of that name, found among all the pieces - units does the same for several. start_guid starts from one part - an air handling unit, a fan, a duct - and computes the network it belongs to, nothing else. The answer says so under 'portee' and lists the model's other units and fans under 'autres_departs': tell the user the result is partial. From each starting part it keeps ONE CIRCUIT PER BRANCH: the longest path in metres of each branch. From an air handling unit, that is one circuit per network connected to it - supply, return, intake, exhaust. EACH OF THESE CIRCUITS IS COMPUTED, and becomes a circuit of the model: it has a name, a COLOUR, and a tab on the website. All the circuits of one unit or fan share THAT UNIT'S colour; on the page, its networks show in a light version of it, and networks connected to no unit in grey. WHAT YOU GET portee what the call covers: the whole model, one role, or one part's network only. circuits one per branch: name, colour, length, its unit, its current type, the flow used at the start and where it came from. NO PRESSURE DROP: see below. autres_arrivees shorter paths, found but NOT computed. lien_3d the calculation page: every unit's networks in its colour, its circuits in a deeper shade. lien_centrales the control page: the units and their networks, where the user checks and corrects the connections and ticks the units to compute. ALWAYS give it, as a full URL, at the top of your answer - also after a calculation: it is the view the user needs most. Never describe it without its link. lien_classeur the Excel workbook of the computed circuits: the supply / return box and the flows are corrected there and everything recalculates. Give it too (a free account is needed to download it). metre the take-off of the whole network. IF A CIRCUIT IS STILL 'calcul', call again with THE SAME ARGUMENTS a moment later. Nothing is recomputed and nothing is billed again: an identical call only reads. A different velocity or flow is applied to the circuits already there, without a new analysis. HOW TO USE IT WELL. Ask the user for the design velocity before calling, or say which one you used. THIS TOOL DOES NOT READ THE FLOW FROM THE MODEL: look for it in the air handling unit's properties with read_ifc_overview and pass it as flow_m3h, one unit at a time - see that argument. Failing that, the flow comes from the design velocity: between two branches, the length-weighted average velocity of the straight ducts equals it, and no duct runs more than 20 % above it. Say which of the two it was. TWO WAYS TO COMPUTE, AND THE USER CHOOSES. Offer them both, in one short sentence each, before computing: - the network AS MODELLED (the default): flows follow the duct sections and never rise along a circuit, as in a sized network. The pressure drops are NOT returned - see below. - a PRELIMINARY network (preliminary_design=true): nothing is sized yet, so each stretch carries what its own ducts carry at the design velocity, the flow may rise along the circuit, and every fitting is computed at that velocity. The pressure drops ARE returned, because they no longer depend on any flow the user must confirm: they say what a correctly sized circuit with these singularities and this length would reach. Quote them only with that sentence attached. Both compute the same circuits, on the same geometry; only the flows differ. The same circuits can be recomputed either way, by calling again with or without preliminary_design. YOU ARE NOT GIVEN THE PRESSURE DROPS, ON PURPOSE - except in the preliminary mode above. Until the user has confirmed on the page each circuit's type (supply, return, outdoor air, exhaust) and its flows, the pressure drop is wrong - the tool cannot know either. Never estimate, quote or compute one yourself, not even roughly: say the pressure drops are on the page, once the type and the flows are confirmed. Every circuit is computed as a SUPPLY circuit until someone says otherwise: the tool cannot tell supply from return. The flow rates do not depend on it - a duct carries what its section allows either way - but the tee coefficients and the design velocity do. If a branch is a return, an intake or an exhaust, SAY SO and tell the user how to set it in the 3D view: hovering the arrow of a circuit shows its type, and each click on that label moves to the next one - supply, return, outdoor air, exhaust. A click on the arrow itself reverses the air direction, which is how the user says at which end the terminal or the louvre sits when the duct has a constant section. Say that each circuit was chosen BY LENGTH. A shorter path loaded with dampers, bends or silencers can lose more pressure. BEFORE THE LINK, SAY WHAT THE USER MUST CONFIRM ON THE PAGE - see 'A_CONFIRMER_PAR_L_UTILISATEUR', circuit by circuit: whether each network is supply, return, outdoor air or exhaust (all are computed as supply until the user says otherwise), and the flows (which are estimates from the velocity, which were given). Never leave it out: the figures mean nothing until both are confirmed. END YOUR ANSWER WITH THE 3D LINK, on its own line, and urge the user to open it - see 'A_DONNER_A_L_UTILISATEUR'. Name each circuit by its unit, its colour and its type - several circuits share a colour. The page is where the calculation is finished: the user sets the flows (a click on the unit, or typed in the table), the velocity, the air direction and the circuit type, deletes a circuit from its tab - its colour goes with it -, adds one by clicking a start and an end part, and downloads the workbook, one editable sheet per circuit. A FLOW THAT LOOKS WRONG IS AN ESTIMATE, NOT A DEFECT. When none was given, flows come from the design velocity. If you point one out, say in the same breath that the user sets it on the page or in the workbook - see 'debits_et_reglages'. THE USER'S CHOICES STAND. A circuit they deleted is not computed again: it comes back under 'retires_par_l_utilisateur', and only they can restore it, by tracing it on the page. A circuit they traced by hand is never replaced. So after they have been on the page, call this again before stating any figure - never answer from memory.

DETERMINISTIC: the same inputs always give the same result — from any AI, on any day. Figures come from the standard's tables and formulas, never from a language model's estimate. Every step is auditable. Deduce the water content of an installation from the expansion vessel already fitted. WHAT THIS IS FOR. Refurbishment, and site visits with no drawings. Sizing a new vessel, a new pump or a new generator needs the water content, and on an existing installation nobody has it: the drawings are lost, or never matched what was built. The vessel on the wall is the one piece of evidence still standing, and it was chosen from that very figure. ASK THE OPERATOR FIRST. Whoever filled or refilled the system knows the real figure — from the meter, the filling station, or the maintenance log — and that figure beats any deduction. This tool is what you use when nobody knows, or to check a number that looks wrong. It gets the conversation moving; it does not close it. HOW. The sizing calculation is run backwards: a trial water content is fed to the EN 12828 sizing, the resulting vessel is compared with the one on site, and the trial is adjusted until they match. The formulas are never rewritten in reverse — the answer cannot contradict the direct calculation, because it is the same code. WHAT THE ANSWER IS WORTH. A vessel is picked from a catalogue range: a 200 L unit covers everything needing between 141 and 200 L. The result is therefore A RANGE, never a single figure. And an oversized vessel — common — will overstate the content. Compare the range with what you see on site; it does not replace looking. It also assumes the vessel was sized correctly in the first place. If it was not, the deduction inherits the mistake — which is itself worth knowing: a range far from what the installation plainly holds means the vessel is wrong, and that is a finding in its own right.