Pipe routing on a floor plan

Balancing and pump

Insulation

Routing: the plan is covered by a grid (about 200 steps across, plus every coordinate that matters, so pipes end exactly on their objects). The cost of a step is its length – blocked in a forbidden area, 40 % in a pipe corridor, 15 times in an escape route, stairwell, lift shaft or public space – plus a penalty for every bend. A* search with the direction in the state finds the cheapest right-angle path.

Shared mains: the pipes of a system form a tree (a rectilinear Steiner tree, heuristic): first the unit through the pass-here points in their order, then always the evaporator that is cheapest to reach from the pipes already laid, then one round where every evaporator is joined again where it is cheapest. A new pipe never starts on a terminal, a riser or a tee that already has three pipes, so every tee is a plain 90° tee on the pipe it sits on. Traditional layout (chosen per system): one straight main along the row or column with the lowest cost for the main and the branches, through the middle of the evaporators and spanning all of them and the unit; the unit is piped to the main and every evaporator gets its own branch from it. Pipes of other kinds (another system, the gas cooler/condenser lines) are followed: the grid lines beside an existing route cost less, so new pipes run in the same run on the same supports, side by side. In the traditional layout a branch may become a sub-main for nearby evaporators of the same kind (MT with MT, LT with LT). "Route again" varies the costs and the bend penalty (and, for the traditional main, the row or column) to give other alternatives.

Lines, in the colours of the calculators' flow diagrams (CO2: MT suction green, LT suction blue, high pressure red; HFC/HC: low-pressure side blue, high-pressure side red): liquid and suction (CO2: MT and LT suction; HFC/HC: suction) run along the same route with a fixed distance on the drawing; the hot gas and condensate lines (CO2: to and from the gas cooler) have their own route. A dragged pipe or tee keeps every piece horizontal or vertical; a fixed end gets a short jog.

Sizing: each piece between two tees, terminals or risers gets one size per line, with the physics of the CO2 calculator (R744: the same property tables, velocity sizing, Darcy–Weisbach with Swamee–Jain) or of the HFC/HC calculators (CoolProp tables, superheat counted as cooling effect, gas expanding along the line). Elbows and tees count by their equivalent length (Crane TP-410: elbow 30 D, tee run 20 D, branch 60 D); the allowance covers valves and the like.

Heights: every piece is mounted in/at the ceiling, on a wall, in the floor or in the ground, each at its height above the floor (the line's dash shows which). Where the unit, a piece and the next, or a piece and an evaporator are at different heights, the vertical pipe is added with two elbows, its static head and – for gas going up – the oil return check. A riser marked by hand is a change of storey. Ball valves are listed but not counted in the pressure drop.

Risers: a riser adds its vertical length and two elbows. A liquid riser adds its static head; a gas riser (suction going up to the unit, hot gas going up to the condenser) is checked for oil return with j*g = v·√(ρg/(g·D·(ρl−ρg))) ≥ 0.85 and sized down until it carries the oil, as in the HFC calculator.

Water and brine: the flow of each load is its power / (cp × (supply − return)) at the mean temperature (the Heating & cooling calculator's property tables); each pipe gets the smallest size within the highest velocity and pressure drop (Darcy–Weisbach, Colebrook–White), fittings as a percentage of the length. Every load is balanced to the worst one (at least 3 kPa over its valve, Kv = Q/√Δp); the pump head is the worst path, its valve, the source and a margin. Insulation and heat loss per pipe (EN ISO 12241 model, as the Heating & cooling calculator), with a dew-point check for cold pipes.

Export: each system is written as a project file of its calculator (CO2 copper, HFC or HC): every line as a main with the evaporators tapped on it and further evaporators teed into an evaporator's own branch (from every tee the farthest evaporator owns the branch), the real lengths, and an allowance that gives the same friction length as the counted bends here.