PsychroView User Manual

PsychroView is a free online tool for psychrometric calculations and for visualizing air treatment processes on the psychrometric chart. It is built for engineers, HVAC designers and students of ventilation and air conditioning.

What PsychroView is and who it is for

PsychroView is a web psychrometric application for professional psychrometric calculations in ventilation and air conditioning. It lets you model and compare air treatment processes — heating, cooling, humidification, energy recovery and more — and plot them on an interactive psychrometric chart in the Carrier layout, or on the European Mollier h-x chart, straight in the browser. The theory behind the field is summarized in the article What is psychrometrics; for a short definition see the glossary entry psychrometrics.

As an online psychrometric calculator it needs no installation. You can run psychrometric calculations from any device at app.psychroview.com. A full overview of what the app calculates — and where the limits of each model are — is on the page What it calculates.

Who PsychroView is for

Calculations follow the ASHRAE Handbook – Fundamentals 2021.

Units: IP and SI side by side

The unit system is switched with the SI and IMP buttons at the right-hand edge of the chart, below the chart-type buttons, or in Preferences → Units, which also sets the flow unit. Switching units changes only what is displayed: internally everything is stored and computed in SI, and IP is a display conversion. Enthalpy is the one place where that is more than arithmetic — PsychroView reports it on the ASHRAE IP datum (0°F for dry air), so the value agrees with your printed chart rather than with a raw unit conversion.

The switch reaches every field, including atmospheric pressure (psi) and altitude (feet). Note that the unit toggle is independent of the interface language — a language sets the initial system, but your explicit choice wins and sticks.

Quick start – your first calculation

This walkthrough takes a new user from opening the application to the first point plotted on the chart. The same walkthrough is available as an interactive guide inside the application: it is offered in the welcome dialog and can be started at any time with the Guide button in the top bar; the guide for a specific process opens from the help icon on its process card.

Step by step

1. Open the application at app.psychroview.com. Free access requires no sign-up but is limited in features. Signing up is recommended to unlock more of them.
2. Once you are signed in, you land on the Projects tab, which gives you an overview of your projects and access to the example projects.
3. Click New project to enter the workspace. On the left is a narrow vertical bar with the process tiles (the palette), and next to it the panel with the process cards of the set.
4. Check the atmospheric pressure — the default is standard atmospheric pressure, 14.696 psi (corresponding to an altitude of 0 ft a.s.l.). For locations at higher elevation, enter the altitude in feet and the application converts it to pressure automatically. Atmospheric pressure affects every psychrometric calculation — at Denver’s elevation the same temperature and relative humidity give a humidity ratio roughly a fifth higher than at sea level. It is set in Project properties (see the chapter Project properties).
5. Add the first process — click the Point tile (air point) in the process palette, or the + button in the empty workspace. A process card with a form opens.
6. Enter the inlet air conditions — temperature $t$ [°F], relative humidity $\varphi$ [%] and volume flow rate $\dot V$ [CFM]. You can type the values in, or take them from the climate data of the selected location in a single click (winter/summer design conditions). The application plots the point on the chart immediately and derives the humidity ratio, the moist-air enthalpy, the dew point and the remaining quantities.
7. Add a treatment process — clicking a tile such as Heating or Cooling appends another step to the chain. The outlet of the preceding process automatically becomes the inlet of the new one.
8. Watch the chart — every process you add appears as a point and an arrow. The whole air treatment sequence is visible at a glance.
9. Export the results — Export PDF in the Export menu of the top bar generates the complete technical output: chart, summary table and detailed results of every process.

Tip: You can build the same chain directly on the chart: press P and click on the chart (air point), then H and click the target temperature (heating). The procedure is described in Working on the chart.

The top bar

The top bar gathers the actions on the project and the application:

Below the top bar are the tabs of the open projects.

Projects

The application organizes work into projects, where one project corresponds to one or more sets of calculations within a single job. You can have several projects open in one window at once — they appear as tabs, much like browser tabs. For signed-in users, projects are saved to the cloud automatically. Closing a project tab only closes the project; it stays ready for further editing in the Projects overview.

Projects overview

The first tab in the bar is always Projects — the home screen of the application. It contains:

• a list of saved projects with the number of sets and processes, opened by clicking,
• example projects — ready-made sample calculations (energy recovery, cooling, humidification…) that can be browsed for free; you open them as your own editable copy,
• creating a new project and opening an .hxp file from disk.

You can return to the overview at any time by clicking its tab; it cannot be closed, as it is the base surface of the application.

Creating a project

Click the + icon to the right of the tabs, use the New project button in the overview, or choose New project from the Projects menu.

Switching between projects

Click the project tab. The active project is underlined in blue.

Renaming a project

Click the pencil icon on the project tab or double-click the tab name. Type the new name and confirm with Enter, or cancel with Escape. You can also use Rename in the Projects menu, or rename the project in the Projects overview.

Closing a project

Click the × icon on the tab, or Close in the Projects menu.

• Signed-in user — data is saved to the cloud continuously; the tab can be closed with no risk of data loss.
• Anonymous user — the application shows a warning, because the data is not stored in the cloud.

Deleting a project

In the Projects overview, click the trash icon next to the project you want to remove, or use Delete project in the Projects menu while the project is open. The project is deleted permanently and cannot be restored.

Saving and loading locally

Save locally downloads the project as an .hxp file; Load locally opens it again. Useful for archiving, or for handing a calculation over without the cloud.

Scrolling the tabs

With a larger number of projects, ‹ / › arrows appear for horizontal scrolling of the tab bar.

Project properties

Whatever applies to the whole project is set in the Project properties dialog, which opens from the right-hand panel or from the icon on the project tab. The settings are stored in the project and travel with it to another computer.

Project properties are available to signed-in users.

Process sets – calculation variants

A set holds one process chain, that is, one set of processes and points. A single project can contain several sets — each set represents one variant of the calculation chain. Sets are color-coded on the chart, so you can compare a variant with and without energy recovery directly on one chart, or a summer and a winter operating state. Sets are also handy for visualizing several operating states side by side.

Set controls

Undo / Redo

The application keeps a change history for the active set. Undo or redo an operation with the Undo / Redo buttons in the top bar or the keyboard shortcuts Ctrl+Z / Ctrl+Y.

Process palette

The palette in the left vertical panel is used to add processes to the active set. Clicking a tile appends that process type to the end of the calculation chain — behind the last process in the set.

With the process panel hidden, a tile does not add the process straight away but switches on the tool for drawing it on the chart; the tooltip of the tile shows the letter of the tool (see Working on the chart).

Inserting a process in the middle of the chain

Processes do not have to go at the end. Hovering between two process cards (or before the first / after the last card) reveals a + circle. Clicking it marks the insertion point; you then pick the process type in the palette — the new process is inserted exactly at the chosen position and the chain is recalculated automatically.

Customizing the palette

The gear at the bottom of the process bar opens Preferences directly at the Process palette section:

• Size of the tiles (XS / S / M / L) and Labels (show the names or not)
• Order & visibility: drag the ⋮⋮ handle to change the order of the processes, and click the eye icon to hide processes you do not need at this stage of the project
• Reset restores the factory palette settings

Tip: Hovering over any tile shows a tooltip with the full process name and a short description — a handy quick psychrometric chart tutorial for new users.

The process card – controls and settings

Every process you add appears as a card in the left-hand process overview panel. Cards are ordered top to bottom following the calculation chain — the outlet (outlet air) of the upper card is the inlet of the card below it. Cards are linked into the calculation chain automatically.

Card header

The card header is colored (the color of the process or of the set) and holds the controls:

Card display (⚙)

The panel opens directly above the card form and applies to that card only. It lets you set:

A custom process name — name the process however you like (e.g. “ERV – plate exchanger 75%”). The name appears in the header, in the summary table and in the exported PDF.

Field visibility by category:

• Inlet air (from chain) — contextual display of the air state coming from the preceding process
• Input parameters — the parameters you enter
• Results — the calculated output values

Extended air properties (inlet / outlet sections) — hidden in the basic view; switch on only those you need for the calculation at hand:

• Dew point $t_d$, wet-bulb temperature $t_{wb}$
• Partial pressure of water vapor $p_w$, saturation vapor pressure $p_{ws}$
• Degree of saturation $\mu$, specific volume v, air density $\rho$, specific heat capacity $c_p$, mass flow rates $\dot m$, $\dot m_{da}$, $\dot m_w$

The default for all cards is set in Preferences → Process property display. A setting made on an individual card overrides that default.

Which quantities you enter

In the air state fields, clicking the symbol of a quantity (for example $\varphi$) changes which pair you enter: alongside the temperature $t$, instead of relative humidity, the wet-bulb temperature, the dew point, the humidity ratio or the enthalpy. The application calculates the rest.

Entering numbers on a tablet or phone

On a touch device, tapping a number field in a card does not open the system keyboard but a small number pad right next to the field (below it, or above it when there is no room): digits, the decimal point, ±, delete ⌫, arrows one step up and down, and confirm ✓. The first digit replaces the original value and further digits are appended; enter a negative value with the number and ±. The chart recalculates while you type, and ✓ or a tap elsewhere saves the value. The ⌨ button in the corner switches to the tablet’s or phone’s own keyboard until you leave the field.

You can also change a value without typing: place your finger on the quantity label to the left of the field (for example $t$ or $\varphi$, marked with a small ↔ icon) and drag right for a higher value, left for a lower one. The value changes in the field’s steps (1 °F, 1 % …), faster the further you drag, and the chart follows. The whole drag is undone with a single Undo; moving your finger vertically still scrolls the panel. A row with two fields (a from–to range) cannot be dragged.

Process description

The text field below the header is for notes — assumptions, data source, reference to a standard. The text appears in the exported PDF in the detail of that process.

Moving a card

Drag the card by the grip handle (⋮⋮) to the left of the header to its new position in the chain. The calculation is recalculated automatically from the point of the move.

Overriding the inlet air (disconnecting from the chain)

Instead of taking the inlet from the preceding process, any process can accept a manually entered inlet air state. Activate the function with the Override switch in the “Inlet air” section of the process card; the From chain option takes you back. The first process in the chain offers the inlet straight away — either typed in, or taken from the climate data in one click.

Typical use: testing different inlet conditions without changing the whole chain; simulating seasonal variation in an HVAC design.

Binding the inlet to a point of another process (branching)

The Point button in the inlet air section binds the process inlet to any earlier point in the chain — not just to its immediate predecessor. Side ports are available too: the Side branch of a Flow Split process, or the Warm air (out) port of an energy recovery unit. This is how you model branched ventilation systems (one branch downstream of a splitter continues to a reheat coil, the other feeds a different zone, for instance). An active binding is marked “in ←” on the card; Remove binding clears it. On the chart, a binding is created with the chain-link button in the point toolbar or by dragging the ＋ handle (see Bindings on the chart). Before you remove a process that other processes are bound to, the application asks for confirmation — their bindings would be removed.

Air treatment processes – detailed description

A total of 13 process types is split into four groups: Inputs, Heat, Moisture and Mixing / Split. The physics of the individual processes and how they run on the chart are covered in the article Moist air processes.

Group: Inputs

Air Point

Defines the inlet air state — the start of the calculation chain. This card is typically the first in every calculation; it corresponds to point A in a classic chart construction.

Inputs: temperature $t$ [°F], relative humidity $\varphi$ [%], volume flow rate $\dot V$ [CFM]. The values can be filled in from the climate data of a location (winter ❄ / summer ☀ design conditions).

If the point is not the first in the chain, the Disconnect button in its input data section plots it as a stand-alone point without an arrow linking it to the preceding process (useful for showing outdoor and exhaust air side by side); Connect links it again.

Group: Heat processes

Air heating

Models air heating calculations — dry heating at constant humidity ratio. On the psychrometric chart this is a move horizontally to the right, toward higher enthalpy.

Input modes (always one; the rest is derived):

• Target temperature $t_{out}$ [°F]
• Heater capacity $\Phi$ [BTU/h]
• Heat loss — the heater sized to cover the specified heat loss of the space

Outputs: heater capacity $\Phi$ [BTU/h], outlet air state. The card also holds the room balance solver for heating (see the Space balance solvers chapter).

Typical use in ventilation design: a heating coil in the supply branch of an air handling unit, an electric or hot-water coil in air conditioning and ventilation system design, warm-air heating.

Air cooling with condensation

Covers full air cooling calculations — including the sensible and latent parts of the capacity and the condensate calculation (the step-by-step cooling coil design procedure is covered in the article Cooling coil in an AHU). It corresponds to the “cooling with condensation” process on a finned cooling coil.

Inputs:

• Target parameter — one of four modes: Temperature $t_{out}$ [°F], Power $\Phi$ [BTU/h], Condensation [lb/h], or Humidity ratio $W_{out}$ [gr/lb] (target dehumidification)
• Coil type — CHW (Chilled Water) with the inlet/outlet temperature of the heat-transfer medium EWT/LWT, or DX (direct expansion) with the saturated suction temperature SST
• Circuit medium (CHW) — water, propylene glycol 30/50%, ethylene glycol 30/50%, custom
• Fin pitch: coarse 3.5–5 mm / medium 2.5–3.5 mm / fine 1.5–2.5 mm (the application states fin spacing in millimeters, as coil manufacturers do)
• Coolant presets — saved temperature pairs for repeated use, which you can edit and extend

Outputs: total capacity $\Phi$ [BTU/h], sensible part $\Phi_s$, latent part $\Phi_{lat}$, SHR (Sensible Heat Ratio), condensate $\dot m_{cond}$ [lb/h], ADP (Apparatus Dew Point — the effective fin surface temperature), the contact factor CF and the bypass factor BF, MTD [°F], the UA coefficient [BTU/(h·°F)], the temperature span of the heat-transfer medium $\Delta T_w$ and its flow rate $\dot V_w$.

The card also carries the space load solver for cooling and a read-only cooling coil check (advisories on the parameters you entered). The thresholds at which the check warns are set in Preferences → Cooling coil – advisory thresholds.

HRV – energy recovery

Calculates energy recovery between the supply and the exhaust air — air-to-air heat exchange through a heat exchanger. It is one of the most used processes in the design of mechanical ventilation systems. For the definition see the glossary entry heat recovery; the calculation of effectiveness and savings is covered in the article Energy recovery (ERV/HRV).

Exchanger types:

Inputs:

• Side e1 (typically the cold supply air) — from the chain, entered manually, or bound to a point
• Side e2 (typically the warm exhaust air): t, $\varphi$, $\dot V$ — or bound to an earlier point in the chain (the exhaust branch)
• Temperature efficiency $\eta_T$ [%]
• Hygroscopic effectiveness $\eta_w$ [%] — enthalpy rotary exchanger only
• Stream designation (outdoor / extract / exhaust / supply air) for the labels

Outputs: actual $\eta_T$, $\eta_w$, enthalpy effectiveness $\eta_{HRV}$, capacity $\Phi_{HRV}$ [BTU/h], mode (pre-heating / pre-cooling), condensate on both sides, exchanger surface temperature, an automatic frost warning ($t_{surf}$ < 32°F) and a warning when the e1/e2 flow rates are markedly unbalanced.

Adiabatic cooling (adiabatic humidification)

Models adiabatic cooling — cooling by water evaporation with no heat added or removed, along the line of constant wet-bulb temperature. The air also takes up the enthalpy of the evaporated water, so the process deviates only slightly from a line of constant enthalpy (adiabatic saturation per ASHRAE). In air conditioning installations it is used as pre-cooling ahead of the cooling coil, or as evaporative cooling. See the glossary entry adiabatic cooling and the article Evaporative cooling.

Calculation modes:

• Adiabatic efficiency $\eta_a$ [%] — 100% corresponds to saturation at $t_{wb}$
• Target temperature $t_{out}$ [°F]
• Target relative humidity $\varphi_{out}$ [%]

Outputs: wet-bulb temperature $t_{wb}$ [°F], actual efficiency $\eta_a$, water consumption [lb/h].

Heat load

Simulates internal heat gains (people, lighting, equipment) — sensible heat added without changing the humidity ratio of the air. It corresponds to the process taking place in the room in an air conditioning design.

Input: heat input $\Phi$ [BTU/h].

Heat loss

Dry heat loss through the building envelope — sensible heat removed without condensation. Input: capacity $\Phi$ [BTU/h]. If the outlet temperature drops below the dew point of the inlet air, the application shows a warning. Condensation in building assemblies and how to prevent it are covered in the article Condensation in buildings.

Group: Moisture processes

Air humidification

Complete humidification calculations — three different ways of humidifying air. Steam, adiabatic and ultrasonic humidification are compared in the article Air humidification in HVAC.

Inputs: target relative humidity $\varphi$ [%] or target humidity ratio $W$ [gr/lb]; steam temperature $t_s$ [°F] and steam quality $q_s$ for the steam variants; water temperature $t_w$ for water humidification. The slope of the process on the chart is set by the quantity dh/dx (the specific enthalpy of the humidifying medium).

Outputs: humidification capacity $\Phi$ [BTU/h], humidification flow rate $\dot m_{evap}$ [lb/h], steam enthalpy $h_s$ [BTU/lb]. Note that steam and water enthalpy use the same datum in both unit systems (liquid water at 32°F), so unlike moist-air enthalpy it converts by a plain factor. The card also holds the combined Heat + humidify solver (see Space balance solvers).

Humidity load

Isothermal moisture addition — models the moisture produced by people, food or wet surfaces. Enter it either as a moisture flow rate [gr/h] or as the required increase in humidity ratio $\Delta W$. Outputs: actual moisture flow rate, $\Delta W$, latent capacity $\Phi_{lat}$ [BTU/h].

Sorption dehumidification

Adsorption of water vapor on a solid desiccant (silica gel, molecular sieves) — see the glossary entry desiccant dehumidification and the article Desiccant dehumidification. The calculation gives the minimum power needed to regenerate the desiccant. Inputs: target $\varphi$ [%] or $W$ [gr/lb]. Outputs: moisture removed [lb/h], adsorption power [BTU/h], regeneration power [BTU/h], outlet temperature (adsorption releases heat).

Group: Mixing and split

Mixing of 2 streams

Mixing of two airstreams — a basic operation in every ventilation and air conditioning calculation (mixing outdoor and recirculated air).

Inputs:

• Stream 1 — automatically from the preceding process, manually (disconnected from the chain), or bound to a point
• Stream 2 — manually: t, $\varphi$, $\dot V$, or bound to an earlier point in the chain (e.g. the side branch of a Flow Split — recirculation)

Outputs: mixed air state (t, $\varphi$, W, h, $\rho$, $\dot V$), condensate when the mixture is subcooled below its dew point [lb/h].

Mixing of 3 streams

Mixing of three airstreams — an extension of the previous process for three-component mixing calculations (e.g. outdoor + recirculated + exhaust air). Inputs: t, $\varphi$, $\dot V$ for each of the three streams. Outputs: mixed state, condensate [lb/h].

Flow split

Splitting one airstream into two branches by a given ratio — typically in ductwork or as a recirculation take-off.

Input: branch 1 fraction.

Outputs:

• Branch 1 — continues as the outlet into the next process in the chain
• Branch 2 — the secondary branch, shown on the chart and in the table; the inlet of another process can be bound to it (binding to a point)
• Flow rates of both branches [CFM] and [$\mathrm{lb_{da}}$/h]

Space balance solvers

The Cooling, Heating and Humidification cards contain integrated deterministic solvers that derive the required processes from the room balance automatically — with no manual iteration.

Space load solver (Cooling)

Enter the target band for the space ($t_{min}$–$t_{max}$, $\varphi_{min}$–$\varphi_{max}$), the heat gain — either as a total or split into sensible + latent parts — the moisture production [gr/h], the permitted $\Delta T$ between supply and space and the coolant temperature range. The solver determines the required supply state, the temperature span of the heat-transfer medium $t_{c,in}$/t_c,out, the cooling capacity, the condensate, the SHR and any reheat needed. The Apply button writes the calculated processes into the chain.

Room balance solver (Heating)

From the heat loss of the space, the moisture production and the target band it determines the required supply state, the heater capacity and any humidification needed (steam or adiabatic), including the steam/water flow rate.

Heat + humidify (Humidification)

A combined calculation: from the target temperature and relative humidity it determines the heater capacity, the steam flow rate and the intermediate point after heating.

The solvers report readable errors whenever the input is physically impossible (saturation exceeded, insufficient flow rate, coolant unable to reach the dew point…), together with a recommendation on what to change.

Climate data – design conditions for a location

The Climate data dialog (at the inlet point, in Project properties or in the Builder) provides design conditions for thousands of locations. You apply the chosen winter ❄ and summer ☀ condition to the inlet point of the chain in one click; at the same time the atmospheric pressure of the project is set from the altitude of the location (or directly from the source). Where design conditions come from and how humidity is measured in the atmosphere is explained in the article Meteorological psychrometrics.

Data sources

The bundled curated datasets cover Central Europe. For a US site, use the Search city tab or upload a TMY3/EPW weather file for the location — that is also the route to ASHRAE-consistent design conditions.

Conditions and percentiles

For every location, winter and summer design conditions are available at several severity levels (design temperature, moderate conditions, extremes), including the coincident humidity/enthalpy wherever the source provides it.

Comparing locations

The Comparison panel lets you place several locations/conditions side by side and compare the design values before making a choice.

The psychrometric chart and the Mollier h-x chart

Chart type

PsychroView supports two kinds of psychrometric chart, switchable with the Carrier and Mollier h-x buttons at the right-hand edge of the chart. For US locales the Carrier layout is selected automatically:

• Carrier (ASHRAE) chart — horizontal axis = dry-bulb temperature $t$ [°F], vertical axis = humidity ratio $W$ [$\mathrm{gr/lb_{da}}$], oblique lines for enthalpy and wet-bulb temperature. The standard across North America.
• Mollier h-x chart — the transposed European layout: horizontal axis = humidity ratio W, oblique enthalpy lines h. Useful when a project is shared with a European partner.

Both charts show identical psychrometric data — they differ only in the orientation of the axes and in their graphical appearance.

Reading the chart in detail, the meaning of the individual isolines and the typical tasks are covered in the guide The psychrometric chart.

Diagram appearance

The Diagram appearance button opens the panel with the graphic settings, which are stored in the project:

• Axes and grid — minimum, maximum and step of the temperature and humidity ratio axes; Reset to defaults restores the standard range. For special calculations (dry air, extreme cooling, high-temperature processes), adjust the range as needed. In IP the axis steps are chosen to land on round numbers of °F, gr/lb and ft³/lb rather than on converted SI values. When a process ends up outside the axes, the axis extends by itself to the next grid line with some margin and a notice offers Undo (it never shrinks on its own); turn this off in Preferences with Automatically extend the diagram axes
• Auxiliary lines — lines with a given slope, SHR (Sensible Heat Ratio) or dh/dx, drawn from a reference point of the chain; useful for the graphical design of a cooling process or for checking the slope of a humidification process
• Comfort layers — thermal comfort zones drawn on the chart
• sections for each family of isolines (temperature, relative humidity, enthalpy, wet bulb, specific volume, dew point) and for the Protractor Δh/Δx and SHR — colors, steps and line widths. In I-P the isotherm, humidity ratio and enthalpy grids sit on round imperial values (2 / 10 °F, 10 / 20 gr/lb, 1 / 5 BTU/lb), so those steps are shown read-only; the relative humidity step stays editable, because percent is the same in both systems
• Layout — the aspect ratio of the chart (auto, A4 landscape, A4 portrait, or a custom ratio), useful for printed output
• Font sizes of the axes and labels
• Processes (in diagram) — arrow type (filled / open / tick / none), line widths, point size and font

Atmospheric pressure

Atmospheric pressure is a project constant: it is set in Project properties, either directly in psi or by entering the altitude in feet, from which the application computes the pressure per the ISA (International Standard Atmosphere). Above the chart the value is only displayed. The pressure can also be taken from the selected climate location. Atmospheric pressure affects every curve on the chart and the results of every psychrometric calculation; changing it triggers an automatic recalculation of the whole project.

Working zones

The Working zones section of the right-hand panel lets you define color-marked areas on the chart (a range of t and $\varphi$), for example the required band for the indoor environment. Add them with Add zone; zones can be named, colored and hidden individually.

Chart legend

The Show legend button above the chart shows/hides the legend of the sets. In Legend display you can set:

• Show name as — the process type / the process label / both
• Process types — pick the process types you do not want to appear in the legend
• Nodes without result — hide processes with no result (error, empty set)
• Sets layout — stacked or side by side

Project info on the chart

The Project info button shows the project name, designation, building and author inside the chart area; Visible fields selects which of them appear. Useful for PDF exports attached to submittal documentation.

Dark mode

The sun/moon toggle in the top bar. The preference is stored in the browser and persists between sessions.

Hover synchronization

Hovering over a row of the summary table or over a process card highlights the corresponding point and arrow on the chart, and the other way round. It makes calculations with a larger number of processes easier to navigate.

Working on the chart

Most of the work can be done directly on the chart: the mouse decides what and where, the keyboard how much. Actions on the chart change the same chain as the cards in the panel — a new process also appears among the cards, and every action is undone by a single Undo step. Everything works in both the Carrier and the Mollier layout. The Working in the diagram guide (the Guide button in the top bar) takes you through it step by step. If you only want to view the chart, turn editing off in Preferences with Mouse and touch control in the diagram: a click on a point then only selects its card, and on a tablet you can scroll over the chart with your finger.

Selecting a point, the toolbar and the menu

Clicking a point on the chart selects it, and its card in the panel expands and is highlighted; clicking a card or a row of the summary table selects the point on the chart in turn. A toolbar of icons appears next to the selected point:

Right-clicking a point opens the menu Edit · Add after ▸ · Insert before ▸ · Duplicate · Link input… · Color · Remove. Duplicate inserts a copy of the process right after it, Color sets the color of the process on the chart. Right-clicking an empty spot offers New point here — an air point with the state under the cursor is appended to the end of the chain as a separate start. In an empty set, double-clicking the chart also creates the first point.

When several points lie on top of each other, a click offers Points here so that you can pick the one you mean. A point of an inactive set offers Switch to set — only the active set can be edited; a locked set and a shared link are read-only. Esc always goes one level back: it closes the menu, cancels the tool, closes the card and finally clears the selection.

Drawing processes

A process is drawn from the selected point, or from the end of the chain when nothing is selected. Switch the tool on with its letter, with Add after in the toolbar or the menu, or — with the process panel hidden — with a palette tile. The letters are the same in every language:

The chart shows the path along which the process may move — heating along $W$ = const toward a higher temperature, cooling along the coil curve, adiabatic cooling along the wet-bulb line, humidification along its own line — and the cursor snaps to it at round values. Live values follow the cursor: the target state and what the process costs (capacity, condensate, water or steam). A click saves the process; it is inserted after the point it starts from and stays selected, so you can draw the next one straight away.

• Exact value — instead of clicking, type a number: a field opens at the cursor, Tab switches the quantity (temperature / capacity for heating, for instance), Enter saves.
• Shift turns snapping off (fine step), Esc goes one step back, a right-click cancels the tool.
• Processes with another stream are drawn in steps. Mixing: the state of the 2nd stream, then the mixing point on the connecting line (it sets the flow rate of the 2nd stream). Three streams: the 2nd and the 3rd stream, then the mixing point inside the triangle. Energy recovery: the exhaust air state, then the effectiveness on the line; for the enthalpy rotary exchanger, a point inside the rectangle (temperature sets $\eta_T$, humidity $\eta_w$).
• Cooling follows the coil curve for the card’s default coolant temperatures; a different coolant is set on the card.
• Where drawing is not possible (Flow split has no path on the chart, an empty set has nothing to start from), the process is added with its card, as from the palette.

Dragging points

Grab a point and drag it: the point moves along the path of its process, snaps as when drawing and is saved when you let go — the application back-calculates the process parameters (capacity, effectiveness, flow rate…). You can drag the outlet of a process, the 2nd and 3rd stream of a mixing and the exhaust air of an energy recovery unit; a bound stream is moved at its source point. Releasing outside the plot area or pressing Esc cancels the drag.

• Axis locks — the padlock button in the toolbar selects the quantities ($t$, $W$, $\varphi$, $h$) that must stay unchanged while dragging; the choice is remembered. It applies to points and streams — processes follow their own path. Two locks fix the point completely, and it will not move.
• Alt while dragging keeps the motion strictly vertical or horizontal, Shift turns snapping off.
• The arrow keys move the selected point to the next round value along its path, with Shift in a coarser step. A series of presses is one Undo step.

The ＋ handle — the next process by dragging

Next to the selected point there is a small ＋ circle in the direction of the process that leads into the point. Pull a line out of it and let go:

• on an empty spot — the New process from here menu lists first the processes whose path runs close to the release point. Hovering over an item shows where the process would end; choosing it saves the process with its target at the release point.
• on the point of a later process — binds its inlet (see Bindings on the chart).

Clicking ＋ without dragging opens the list of types, like Add after. Esc discards the line.

Bindings on the chart

A binding feeds a process with air from an earlier point of the chain instead of its immediate predecessor (see Binding the inlet to a point of another process). On the chart, create one with the chain-link button (Link input to an earlier point) in the toolbar or with Link input… in the menu: the chart highlights the points the inlet can come from, and clicking one of them creates the binding. The ＋ handle released on the point of a later process works the same way — the 2nd or 3rd stream of a mixing and the exhaust air of an energy recovery unit are bound at once; for the outlet of a process, a menu lists its inputs and, for each of them, what the binding will replace.

A bound connecting line carries a small chain mark in its middle. The list of bindings and their removal stay on the process card.

Working with the process panel hidden

The ‹ button (Hide process panel) on the border between the cards and the chart hides the panel and enlarges the chart; the narrow › strip next to the palette brings it back.

• Above the chart there is the chain strip: the set switcher and numbered process chips. Clicking a chip selects the process, a double-click opens its card, a right-click the menu; dragging a chip changes the order. Hovering over the gap between chips reveals a + — clicking it marks the insertion point, and you then pick the type in the palette.
• Edit or a double-click opens the process card right next to the point, placed so that it does not cover the selected process. The pin fixes it to the edge of the chart — it stays open and always shows the selected point.
• A palette tile switches the drawing tool on, a second click switches it off. With the panel shown, the palette adds processes as before and opens the card in the panel.

Setting a value on the chart from the card

Quantities on the card that the chart can set — the target temperature of heating, the coil outlet, the energy recovery effectiveness, the state of the 2nd stream and others — have a ⌖ button (Set in the diagram). Clicking it switches on editing of that quantity on the chart: click the target spot, or type a number and confirm it with Enter.

Results on the chart

The Show results on processes button in the icon column at the bottom right of the chart displays the capacity next to the lines, the condensate for cooling, water or steam for humidification and warnings on the points — frosting of the energy recovery exchanger, fog, condensation. The choice is remembered; results go into an export only when they are switched on.

The hint line

The line below the chart always says what a click, a right-click, typing and Esc will do right now, depending on the active tool. Hide it with the cross; switch it back on in Preferences with Hints below the diagram.

Touch and pen

On a tablet the same works with a finger: a tap = a click, a double tap on a point = edit, a long press = the menu. Points and the ＋ handle are dragged with a finger just like with the mouse. When drawing, place your finger, slide it along the path and lift it to save the process; a long press without moving cancels the tool, and a second finger cancels the dragging of a point. A pen behaves like a mouse. On a phone, processes are added and edited in the cards; on the chart you can select points and open the menu with a long press. Numbers in the cards are entered with the built-in number pad or by dragging the quantity label — see Entering numbers on a tablet or phone.

Results overview table

The table in the right-hand panel lays out the air states (inlet / outlet) of all processes in the active set.

Displayed columns

Extended columns

Add further columns with Customize columns:

• Dew point $t_d$ [°F], wet-bulb temperature $t_{wb}$ [°F]
• Partial pressure of water vapor $p_w$ [psi] and saturation vapor pressure $p_{ws}$ [psi]
• Degree of saturation $\mu$ [–], specific volume $v$ [ft³/lb], air density $\rho$ [lb/ft³], specific heat capacity $c_p$ [BTU/(lb·°F)]

Copy the table to the clipboard with Copy → Copy summary table and paste it into a spreadsheet.

Exporting and printing the results

The exports are in the Export menu of the top bar; the Copy menu copies the chart or the summary table to the clipboard.

Available formats

Format availability depends on development stage.

The availability of the formats depends on the development stage.

PDF header

The PDF header contains:

• Project name, designation, author, date of generation
• Atmospheric pressure [psi] and altitude [ft a.s.l.]

Sharing a project

Signed-in users can share a project through a read-only link.

Creating a share link

1. Click the Share button in the top bar.
2. The application generates a link valid for 7 days.
3. Copy the link with the Copy button.

Revoking a link

In the sharing panel, click Revoke link. Anyone holding the link loses access immediately.

Only projects stored in the cloud can be shared. The recipient can only view the project — the data cannot be edited.

Modules

The icons in the top bar to the right of Guide switch between the chart and the specialized modules that go beyond the basic psychrometric calculation: the HVAC, Energy, Ventilation, Generative and Toolbox groups, and the shortcuts Autopilot, Builder and Thermal Comfort. Back to diagram returns the workspace to the chart.

Builder — visual assembly of an AHU — CURRENTLY IN DEVELOPMENT

An alternative way of building a calculation: you assemble the process chain visually from blocks on a canvas — like an air handling unit schematic — and write the result into the project as a new set.

• Block palette: inputs, heat and moisture processes, mixing + a fan (heat gain from the pressure rise, $\Phi$ = $\Delta p$ · $\dot V$ / 3,600,000 in SI terms) and mechanical parts — filter (class, clean/dirty $\Delta p$), dampers, droplet separator, empty chamber, silencer, weather louver, activated carbon filter, UV-C section. Mechanical parts record their pressure drop for the fan design point.
• Two rows — supply and exhaust: the unit can be built in both directions; energy recovery links the two rows (a plate exchanger crosswise, a wheel inline).
• Mixing chamber (recirculation): connects the exhaust back into the supply — you enter the ratio either as a percentage of return air or directly as the recirculation flow rate; the application keeps an eye on the fresh-air and exhaust balance.
• Operating modes: one unit, several operating modes (summer / winter / night operation…). When writing to the project you choose which modes to write — each becomes a separate set.
• A live preview of the outlet air state behind every block; climate data ❄/☀ can be applied straight into the inlet of the active mode.

Availability of this feature is not guaranteed.

Autopilot — automatic process sequence design — CURRENTLY IN DEVELOPMENT

Enter the start point (outdoor air), the target zone for the supply air/space, the space loads and the permitted processes — Autopilot searches for AHU process sequences automatically that bring the air to its “target”. It ranks the results by configurable weights (simplicity, energy estimate, supply $\Delta T$, sequence logic) and the best sequence can be imported into the chart as a new set in one click. The manual design procedure that Autopilot automates is described in the article Air conditioning design on the psychrometric chart. When no solution is found, it advises what to relax (processes, number of steps, coolant range…).

Availability of this feature is not guaranteed.

Energy flow (Sankey) — CURRENTLY IN DEVELOPMENT

The Sankey diagram visualizes the heat and moisture flow balances across the individual processes of the active set — the band width represents the air flow rate, the side streams show heat exchange and condensate. Preset levels of detail (Clean / Standard / Detailed).

Availability of this feature is not guaranteed.

Heat stress (WBGT) — CURRENTLY IN DEVELOPMENT

Assessment of worker heat stress per ISO 7243 — see the following chapter.

Availability of this feature is not guaranteed.

Toolbox — quick calculators — CURRENTLY IN DEVELOPMENT

Further modules (room air conditioning, cleanrooms, data centers, dryers, energy calculations, ventilation sizing…) are marked “Coming soon”.

Availability of this feature is not guaranteed.

Comfort analysis

Thermal comfort – PMV/PPD (ASHRAE 55, EN 16798-1) — CURRENTLY IN DEVELOPMENT

The Thermal comfort overlay draws comfort zones directly on the chart and computes the thermal comfort indices. The PMV/PPD calculation method per ISO 7730 is covered in the article Thermal comfort and the PMV/PPD index.

• PMV / PPD (Predicted Mean Vote / Predicted Percentage of Dissatisfied) per ASHRAE 55 — inputs: air velocity, activity (met), clothing (clo), radiant temperature; the t and $\varphi$ values can be synchronized from any point of the chain
• PMV ±0.5 comfort zone drawn on the chart, both the standard ASHRAE 55 zones and custom parameters
• Adaptive model (ASHRAE 55 §5.4 / EN 16798-1) with a band based on the outdoor temperature
• SET (Standard Effective Temperature), Heat Index isolines, ankle draft check

WBGT (Wet-Bulb Globe Temperature, ISO 7243) — CURRENTLY IN DEVELOPMENT

A module for assessing worker heat stress per ISO 7243 — indoors and outdoors (solar radiation, wind speed, globe temperature $t_g$). The result is compared with the limits for acclimatized/non-acclimatized workers according to the metabolic rate and returns a verdict of WITHIN LIMITS / CAUTION / EXCEEDED. The t and $\varphi$ values can be taken from a point of the chain.

Availability of this feature is not guaranteed.

Preferences and account

Preferences

The Preferences button in the top bar opens your personal settings, which apply to all your projects and are stored in the browser:

Account

When you are signed in, the user icon in the top bar leads to Account settings:

• Custom branding (white-label) — for companies and design offices: a Company logo and a Company name that appear in the application header and in the exports; the output looks like a company document, with no mention of PsychroView. This is an individual feature that is not commonly available.
• Data export (GDPR Art. 20) — Download my data downloads all your personal data and projects in JSON format, fulfilling the right to data portability.

Physical quantities – overview

An overview of the psychrometric quantities used in the application and their symbols, with the units shown when IP is selected. Familiarity with these concepts is a prerequisite for psychrometrics for engineers — if any of them are new to you, we recommend going through the interactive guide in the application. Definitions, formulas and the normative context of each concept can be found in the glossary.

Tips, keyboard shortcuts and troubleshooting

Keyboard shortcuts

Tips for working efficiently

Automatic recalculation — the application processes every value you enter after a short delay (debounce). There is no Save button to press — psychrometric calculations run continuously.

Calculation variants side by side — duplicate a process set and change a single parameter (the type of energy recovery exchanger or the coolant temperature, for instance). Both variants appear on one chart, so the comparison is immediate.

Climate data instead of typing values — fill the inlet point with the design conditions of a location (city search anywhere in the world, your own TMY3/EPW file or an import) — including the correct atmospheric pressure derived from the altitude.

Lock an approved calculation — once the results have been signed off, lock the set. That prevents accidental edits while presenting the calculation or handing it over to a colleague.

Start from an example — the example projects in the overview show typical arrangements (energy recovery, cooling with reheat, humidification…) and can be opened as the starting point of your own calculation.

Offline access — the core psychrometric application works without an internet connection too (the calculations run in the browser). Cloud storage, climate data and sharing require a connection.

Solving common problems

PsychroView — professional online psychrometrics for HVAC, ventilation and air conditioning designers.

Manual version: 3.0 (September 2026) · psychroview.com