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HFC/HFO Pipe Sizing

Suction, liquid and hot gas lines for a refrigeration system with an HFC or HFO refrigerant: compressor, condenser, filter drier, sight glass, expansion valve and evaporators connected in parallel. Drag the evaporators into place and click a line to set its length, size or riser.
R448A · -10.0 °C / 40.0 °C · 18.00 kW

System Data

In brackets the safety class per EN 378/ASHRAE 34 (A2L = mildly flammable). Changing the refrigerant resets the design pressures.
Room or product temperature, used for the country rules. Empty: evaporating temperature + 10 K.
Safety standard: ASHRAE 15 and ASHRAE 34, equipment UL 60335-2-89 / -40; local mechanical codes. The EN 378 charge limit above is shown for comparison only. Bans: Technology Transitions rule, 40 CFR 84 subpart B, as amended on 26 May 2026.
⚠ USA from 1 January 2032 (supermarket systems, remote condensing units and cold storage warehouses): banned with GWP 150 or more at a charge of 200 lb or more, and with GWP 300 or more below 200 lb or on the high-temperature side of a cascade. This system: limit 300 (R448A: GWP 1386).
Source: 40 CFR 84.54(c)(9)–(12), eCFR 2026-10-22 (checked 2026-10-28)
Evaporating and condensing temperatures are dew points (relevant for zeotropic blends with glide). The liquid temperature is the bubble point at the condensing pressure minus the subcooling; it sets the flash gas share and so the mass flow.
R448A (A1) · glide at evaporation 6.2 K · at condensing 5.2 K · liquid temperature 32.8 °C.
Useful superheat at the evaporator outlet. It counts as refrigerating effect, and the suction lines are sized for the lower density of the superheated gas.
Installed compressor capacity for comparison with connected evaporator loads. Enter compressor power for total heat rejection.
Directly controls pipe sizing — higher velocity yields smaller pipes.

Hot gas line

From the compressors to the condenser, carrying the whole circulated mass flow. Length 0 = no hot gas line. Tick Riser if the line runs upwards and its oil return is checked.

Refrigerant charge

USA: the charge is entered and shown in lb. The national limit (ASHRAE 15, UL 60335-2-89) is not calculated – the EN 378 value is shown for comparison only.
Bans for R448A in this region and application: 0 in force, 1 coming or conditional – see Regulations under System data.
→ I – evaporators in occupied rooms
Pipes 6.8 lb (3.1 kg) + other 0.0 lb (0.0 kg) = 6.8 lb (3.1 kg). R448A (A1) is not flammable – no flammability limit.
The pipes are calculated automatically: the liquid line full of liquid, the suction and hot gas lines full of gas. Take the other charge from the manufacturers' data. The limit for flammable refrigerants (A2L) follows EN 378-1:2016+A1:2020 annex C, table C.2, which applies in the EU/EEA, the UK, Switzerland and Turkey; ISO 5149-1 (e.g. China GB/T 9237, Australia AS/NZS 5149, India, Korea) uses the same limits. USA: ASHRAE 15 and UL 60335-2-89. Canada: CSA B52:23 (adopted e.g. in Ontario and Manitoba). Japan: High Pressure Gas Safety Act (refrigeration safety regulations) and JRA GL-20. National rules may be stricter – the check is a guide.
Other countries – safety standards and rules
South Africa – SANS 10147:2014 (ed. 5): safety standard for refrigerating systems with more than 150 g of refrigerant. Work with refrigerants must be done by an Authorised Refrigeration Practitioner registered with SAQCC Gas. The charge limit above follows EN 378/ISO 5149 – check against SANS 10147.
Chile – NCh3241:2017: Chilean standard (INN) for good practice in the design, assembly, installation and maintenance of refrigeration and air-conditioning systems. The charge limit above follows EN 378/ISO 5149 – check against NCh3241.
Source: INN – NCh3241:2017 (checked 2026-10-07)
Colombia – NTC 6228-1:2019 (ICONTEC): Colombian series of standards (ICONTEC, parts 1–4, 2019–2021) on safety and environmental requirements for refrigerating systems, adopted from ISO 5149. The charge limit is calculated as in ISO 5149-1 annex A, the same method as above.
Source: Minambiente – NTC 6228-1 · Dialnet – NTC 6228 (checked 2026-10-07)
Other Latin America – ISO 5149-1:2014: where the country has no adopted standard of its own. The charge limits are in annex A and are calculated with the same method as above.
Source: ISO 5149-1:2014 (checked 2026-10-07)
Singapore – EPMA Part 10A (NEA): GWP limits for new equipment (GWP per IPCC AR5, mass-weighted for blends): household AC ≤ 750, household refrigerators ≤ 15 and water-cooled chillers ≤ 15 since 1 October 2022. From 1 July 2027: centralised commercial refrigeration systems (multipack and semi-plug-in with a water loop) GWP ≤ 150, registration with NEA as a GHG entity and recovery of refrigerants with GWP above 15 (EPMA 1999 Part 10A Div 2); AC in new cars and light goods vehicles from 1 July 2028.
⚠ R448A has GWP 1273 (AR5), above 150: not allowed in new centralised commercial refrigeration systems in Singapore from 1 July 2027.
Advanced – Margins & Pipe Material
Increases the length in the pressure-drop calculation — shows up in the Δp column in the “Main Headers”/“Evaporator Branch Connections” tables below, not in the pipe size or the cards at the top.
Adds ordering margin to the Bill of Materials and Insulation Schedule totals only (offcuts, mistakes) — a different thing from “Extra length for fittings” above, and does not affect the pipe size or Δp.
Standard refrigeration tube (ACR). Enough for most HFC/HFO refrigerants; with R410A, R32 and R454B the largest sizes cannot take the high-side pressure — see the ⛔ mark.
Pipes that cannot take this pressure are marked ⛔ and never chosen automatically. The defaults follow from the refrigerant per EN 378-2 (ambient up to 32 °C): the saturation pressure at 55 °C on the high side (liquid and hot gas) and at 32 °C on the low side, as gauge pressure. They are reset when you change refrigerant. Adjust them to your own system.
Optional. Risers are sized for oil return with the criterion j*g ≥ 0.85; here you can set your own lower limit, e.g. the manufacturer's recommendation. The higher of the two is used. Empty = the criterion only.
Pipes smaller than this threshold will never be selected automatically.
Select insulation specification (thickness/color) per header for the material bill.

Evaporators

NamekW
A pipe stub contains only ONE line (liquid or suction). A suction stub can be converted to an evaporator by assigning a kW load.
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Options · Units

Changes how values are shown and entered — all calculations still run in the background as before.

Flow Diagram

Suction line Liquid Hot gas Expansion valve Tapped off another pipe
100% 100%
Drag an evaporator freely to position it. Click any pipe segment to set its length or manually override size.
Click here, then on a pipe run, to place a power meter.
— m Size:
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Bill of Materials

Lengths include the waste allowance above, but not the fitting length allowance (which only affects Δp).

Insulation Schedule

Insulation types are selected under 'Advanced' in System Data.

Evaporator Branch Connections

"Own Load" is the evaporator's own kW value. "Load in Pipe" is the accumulated flow through that specific pipe — larger if other evaporators/pipes are tapped onto it. Never sum the "Load in Pipe" columns for a grand total; use "Own Load" instead.
Show calculation

Calculation per pipe piece

PipeMass flow [kg/s]Density [kg/m³]Inner diameter [mm]Velocity [m/s]ReFriction factorLength (+ fittings) [m]Δp [kPa]Δp per metre [Pa/m]Note
Liquid: Condenser → Cold Room 10.11521,06214.10.69583,8000.01916 (+1.8)2.713475/8"
Liquid: Cold Room 1 → Cold Room 20.064011,06211.10.62659,3000.02066 (+1.8)3.023871/2"
Liquid: Cold Room 2 → Display Case0.02561,0626.310.77141,6000.02256 (+1.8)8.781,1305/16"
Suction line: Compressor → Cold Room 10.115214.7932.19.61405,0000.01426 (+1.8)2.363031-3/8"
Suction line: Cold Room 1 → Cold Room 20.0640114.79268.13278,0000.01526 (+1.8)2.232861-1/8"
Suction line: Cold Room 2 → Display Case0.025614.7917.37.39168,0000.01686 (+1.8)3.073943/4"
Hot gas: Compressor → Condenser0.115259.0317.38.33607,0000.01410 (+3)21.71,6703/4"
Cold Room 1 · Liquid0.05121,06211.10.50147,4000.02155 (+1.5)1.692591/2"
Cold Room 1 · Suction line0.051214.79266.5222,0000.01585 (+1.5)1.231891-1/8"
Cold Room 2 · Liquid0.03841,0627.90.73849,9000.02155 (+1.5)5.127883/8"
Cold Room 2 · Suction line0.038414.7919.98.32218,0000.0165 (+1.5)2.674117/8"
Display Case · Liquid0.02561,0626.310.77141,6000.02255 (+1.5)7.311,1305/16"
Display Case · Suction line0.025614.7917.37.39168,0000.01685 (+1.5)2.563933/4"

Basis of the calculation

Method
Darcy–Weisbach for every pipe piece. Mass flow from the cooling capacity and the enthalpy difference between the evaporator outlet (dew point + useful superheat) and the liquid (bubble point at the condensing pressure − subcooling). Gas lines (suction, hot gas) are calculated in 50 steps with the density following the local pressure (isothermal); the density in the table is at the inlet. Risers add the weight of the fluid column. The length includes the extra length for fittings (x).
Equations
  • ṁ = Q / (h″(t₀ + Δt_sh) − h′(t_liq))
  • G = ṁ / A, v = G / ρ, Re = G·d / µ
  • f = 0.25 / [log₁₀(ε / (3.7·d) + 5.74 / Re^0.9)]² (Re ≥ 2300); f = 64 / Re (Re < 2300)
  • Δp = f · (L·(1 + x) / d) · ρ·v² / 2 (gas: 50 steps, ρ ∝ p)
  • Δp_static = ρ · g · h (riser)
Friction factor
Swamee–Jain (explicit form of Colebrook–White), roughness ε = 0.0015 mm (drawn copper)
Refrigerant data
CoolProp 8.0 (reference equations of state; blends as CoolProp mixtures with the ASHRAE 34 composition), 2 K table −60…+70 °C
Standards
EN 378-1:2016+A1:2020 (annex C) · EN 378-2:2016+A1:2020 · ASTM B280 (ACR copper tube)
Notes
  • Compared with Danfoss Coolselector 2 in 15 cases with over 60 pipe sizes: mass flow within 2.5 %, Δp within 5 % (8 % at very large pressure drops).
  • Oil return in risers: j*g ≥ 0.85 (or the minimum velocity you enter). Not compared with a manufacturer's program.
  • Pressure drop is also shown as a fall in saturation temperature (dew line for suction and hot gas, bubble line for liquid).

Main Headers

Refrigerant pipe sizing – frequently asked questions

How do you size refrigerant lines for HFC and HFO refrigerants?

The calculator works out the mass flow from each evaporator's capacity and the refrigerant properties (CoolProp), then picks the smallest pipe that keeps the velocity below the target. Pressure drop is calculated with Darcy–Weisbach and shown in kPa and as saturation temperature drop (K). The results have been checked against Danfoss Coolselector 2.

Calculate it in the tool above

What velocity should suction, liquid and hot gas lines have?

The defaults are 10 m/s in the suction line, 0.8 m/s in the liquid line and 12 m/s in the hot gas line. A higher velocity gives smaller pipes but more pressure drop, and suction risers also need enough velocity for oil return.

Calculate it in the tool above

How much pressure drop is acceptable in a refrigerant line?

Common guide values are about 1 K saturation temperature drop in the suction line and 0.5–1 K in the liquid and hot gas lines. The calculator converts every pressure drop to K and warns of flash gas when the liquid line drop exceeds the subcooling.

Calculate it in the tool above

How do I make sure oil returns up a suction riser?

Mark the line as a riser. The calculator then picks a size in which the gas is fast enough to carry the oil upwards (criterion j*g ≥ 0.85) and shows the minimum velocity. If even the smallest allowed size is too large, a double suction riser is suggested.

Calculate it in the tool above

Which refrigerants are included, and how is glide handled?

R134a, R404A, R407C, R407F, R410A, R32, R448A, R449A, R452A, R454B, R454C, R455A, R513A, R1234yf and R1234ze(E). Temperatures are entered as dew points; for zeotropic blends the glide, bubble point and liquid temperature are worked out automatically.

Calculate it in the tool aboveGWP, ODP & CO2e of a refrigerant chargeRefrigerant retrofit: find alternatives

Assumptions: Refrigerant data from CoolProp (reference equations of state, blends with the ASHRAE 34 composition). Evaporating −50…+15 °C and condensing +15…+65 °C, temperatures as dew points. Pressure drop by Darcy–Weisbach, also converted to a saturation temperature drop (K). Oil return in risers is checked with the criterion j*g ≥ 0.85. Pipe sizes are nominal ACR inch sizes. Verify wall thickness and design pressure against EN 378/PED before installation. The mass flow is based on the refrigerating effect: the enthalpy after the evaporator (evaporation plus useful superheat) minus h′ at the liquid temperature. Flash gas at the expansion is included and the useful superheat counts as refrigerating effect. The hot gas line carries the whole circulated mass flow.

Disclaimer: This tool does not guarantee correct results. Always verify pipe wall thickness, pressure rating, and other values manually before installation.

Help – how to use the calculator

The calculator sizes the pipes of a refrigeration system with an HFC or HFO refrigerant: suction line, liquid line and hot gas line. The system is drawn as one circuit: compressor → hot gas → condenser → filter drier → sight glass → expansion valve → evaporators (in parallel) → suction line back to the compressor. Choose the refrigerant, fill in the system data, build the plant in the flow diagram and read off pipe sizes, pressure drops (also as saturation temperature drop, K) and the bill of materials. Each evaporator's capacity sets the flow in the pipe runs, and the pipes are chosen so the velocity does not exceed the target velocity.

1. System data

  • Choose the refrigerant. Enter the evaporating and condensing temperatures, both as dew points, and the subcooling. The liquid temperature is the bubble point at the condensing pressure minus the subcooling. The superheat affects the mass flow and the sizing of the suction line.
  • Set a separate target velocity for the suction line and the liquid line. A higher target velocity gives smaller pipes; a lower one gives larger pipes and lower pressure drop.
  • The installed rack capacity and compressor power are optional. They are used to compare with the evaporator loads and to show the total heat rejection.
  • Under “Advanced – Margins & Pipe Material”: extra length for fittings (affects only the pressure drop, not the pipe size), pipe type, minimum allowed pipe size, and insulation per header (used in the bill of materials).
  • Pipe type and design pressure together decide which sizes are allowed — ⛔ in the tables means that size doesn't meet the pressure you entered.

2. Evaporators and pipe stubs

  • Add an evaporator with “+ Add Evaporator” and enter its name and load. All evaporators are connected in parallel between the liquid line and the suction line. Use ▲ ▼ to change the order and × to remove a row.
  • A pipe stub is a single line (liquid or suction) that other evaporators can be tapped onto. Give a suction stub a load if it should become an evaporator.
  • One calculation = one refrigeration system (one compressor or rack and one condenser). A freezer and a cold room on separate systems never share a liquid line – calculate them separately.

3. The flow diagram

  • Drag an evaporator to move it. Click its name to rename it and its load value to change it.
  • The diagram is drawn as a standard refrigeration flow diagram: the compressor sends hot gas up to the condenser, the liquid line runs along the top through the filter drier and the sight glass, each evaporator has its own expansion valve, and the suction line runs along the bottom back to the compressor.
  • The liquid line and the suction line can be dragged up and down – grab the line, the condenser, the filter drier, the sight glass or the compressor. The condenser follows the liquid line and the compressor the suction line; the evaporators stay where they are and their pipes follow. A click (without dragging) opens the line's length and size as usual.
  • The buttons “Lines closer” and “Lines apart” change the distance between the liquid line and the suction line; the evaporators move with them. The lines can also be dragged one at a time.
  • Click a pipe to set its length, lock the length or choose the pipe size manually. A ✎ in the tables shows that the size was chosen manually.
  • Right-click a pipe to add an evaporator or a pipe stub at that spot.
  • The round handle at an evaporator's pipe can be dragged and dropped onto another evaporator's pipe of the same kind to tap into it, or onto empty space to connect straight to the header. The small squares are dragged along the evaporator's edge to change where the pipe enters it.
  • Select an evaporator or pipe and press Delete to remove it. Undo with “Undo” or Ctrl/Cmd+Z.

4. Navigating the drawing

  • Drag the background to pan. Zoom with the buttons, with Ctrl/Cmd + mouse wheel, or by pinching on a trackpad. A− and A+ change the text size in the drawing.
  • “Re-render” redraws the drawing. “Print Drawing” prints the flow diagram together with a summary.
  • Tick “Force 90° Bends” to route every pipe in clean right angles; untick it to connect and drag pipes freely, however you like.
  • Tick “Force Parallel Lines” so that pipes running directly from a stem connect in line with the evaporator's connection and become one straight line with no bend. The tap point on the stem then follows along when you move the evaporator or its connection.

5. Power meter

  • Click “Add Power Meter” and then a pipe. The meter shows how many kW flow on each side of the point.
  • Drag the dot to measure at another place, drag the box to move the readout, and click × to remove the meter.

6. Reading the results

  • The cards at the top show total cooling load, total mass flow and the pipe size of the three main headers.
  • The tables list, for each evaporator and pipe run, the load, chosen pipe size, velocity and pressure drop (Δp). The program picks the smallest pipe size that stays within the target velocity.
  • ⚠ means the flow needs a larger pipe than the largest size in the table. 🚩 means two pipes or evaporators have the same name.
  • The bill of materials and the insulation list add up pipe lengths per size, without the fitting allowance. Use them as a basis when ordering.

7. Saving and opening

  • “Save” and “Save As…” store the whole plant as a file, and “Open Project” loads it again.
  • In Chrome and Edge, “Save” and autosave (every 5 minutes) write to the same file once you have saved once. Other browsers download a new file each time.

8. Units

  • Under “Options · Units” you choose the unit for temperature, superheat, pressure, velocity, length, power and mass flow separately. This only changes how values are shown and entered, not the calculations.

9. HFC/HFO: glide, pressure drop in K, risers and hot gas

  • Zeotropic blends (e.g. R407C, R448A, R449A, R454C, R455A) have glide: at the same pressure the bubble point is lower than the dew point. Temperatures are entered as dew points; the glide and the liquid temperature are shown below the temperature fields.
  • The pressure drop is shown both as Δp and as ΔT, the drop in saturation temperature: on the dew line for suction and hot gas lines and on the bubble line for the liquid line. Common guide values are about 1 K for the suction line and 0.5–1 K for the liquid and hot gas lines.
  • Click a suction line and tick “Riser” if it runs upwards. The program then picks a size that gives the gas enough velocity to carry the oil (dimensionless gas velocity j*g ≥ 0.85) and shows the minimum velocity in brackets. ⇡🛢 means that even the smallest allowed size is not enough — consider a double riser.
  • The hot gas line runs from the compressors to the condenser and carries the whole mass flow. Enter its length, target velocity and discharge temperature (the gas density is taken at the condensing pressure and that temperature), and tick “Riser” if it runs upwards.
  • The design pressures are set automatically from the refrigerant (EN 378-2, ambient up to 32 °C) but can be changed under “Advanced – Margins & Pipe Material”.
  • A line marked as a riser (the flow goes upwards over its whole length) gets the weight of the liquid or gas column added to its pressure drop, about 10 kPa per metre for liquid. An evaporator above the plant room gives a liquid riser, one below it a suction riser. The check boxes are in the panel that opens when you click a line.
  • If the pressure drop of the liquid line to an evaporator is worth more than the subcooling, the liquid starts to boil before the expansion valve (flash gas). The calculator then warns with ⚠; increase the subcooling or choose larger pipes.
  • Gas lines are calculated with the gas expanding as the pressure falls, so even large pressure drops come out right. The calculation has been compared with Danfoss Coolselector 2 and agrees within 1–3 %.
  • The “Extra length for fittings (%)” allowance is meant to cover bends and valves. A 90° bend is worth about 0.2 m of pipe, so the default 30 % covers many bends.
  • Refrigerant charge: the pipes are calculated automatically; enter the other charge (unit, condenser, receiver, evaporators). For flammable A2L refrigerants (R32, R454B, R454C, R455A, R1234yf, R1234ze(E)) the charge is checked against EN 378-1:2016+A1:2020 annex C, table C.2, from the location class, access category and the volume of the smallest room. Up to m1 × 1.5 (= 6 m³ × LFL) is always allowed. The check is a guide – national rules may be stricter.
Disclaimer: This tool does not guarantee correct results. Always verify pipe wall thickness, pressure rating, and other values manually before installation.