This page explains the Air + Hydro + Hydro Foot Therapeutic Massage + Heated Seat & Back component diagram, the schematic Ella's Bubbles publishes for tubs that pair the three-pump massage package with electric surface heater pads under the seat and backrest. The primary copy is air-hydro-hydro-heat.pdf in the walk-in-tub schematics folder (revision 01-16-26), and an earlier copy is served as Air-Hydro-Independent-Foot-Massage-System-heated-seat.pdf in the 2024/06 uploads folder (revision 04-29-24). Below you will find which families the diagram lists, the nine numbered components, why the controller is called a Master Box, how the surface heater pads differ from the in-line water heater, the printed electrical requirements, and how to tell a seat-warmth issue from a water-warmth issue.

Two Uploads of This Configuration

Both files show the same nine components and the same three massage systems. The 2024/06 copy carries revision 04-29-24; its drawing labels the box "Master Control Box" with a "Heat Keypad" drawn beside it, while its legend prints "Master Box" for the controller. The schematics-folder copy carries revision 01-16-26 and calls the same component the "Master Box". Either sheet is a valid reference for a tub with this package; the newer 01-16-26 copy is the one linked at the bottom of this page.

Which Families It Lists

Rather than naming individual models, the 01-16-26 copy prints "Available With: Stainless Steel, Outward Door". That means the package is available across the stainless steel inward-swing door family and the outward-swing door family of Ella walk-in tubs. If your order lists Air + Hydro + Hydro Independent Foot Massage with the Heated Seat and Backrest option, this is your diagram regardless of which model in those families you own. For the heated-seat option itself, see heated seat and backrest.

The Nine Numbered Components

The legend along the bottom of the sheet lists nine items. They are reproduced below as printed on the 01-16-26 copy, with the 04-29-24 wording noted where it differs.

Items 1 through 7 are the same three massage systems and supporting electronics found on the plain Air + Hydro + Hydro Foot diagram. Items 8 and 9 are what the heated seat option adds: the pads themselves and the keypad that switches them.

Master Box Versus Control Box

On the diagrams without heated seating, the Electronic Component Controller is printed simply as the Control Box. On this sheet it becomes the Master Box (or Master Control Box) because it carries more: Load 1 for the Air Pump and its "Air Out to Jets" line, Load 2 for the Ozone Generator and its "Ozone Out to Hydro System" line, the deck push controls for Hydro Massage, LED Light, and Air Massage, and the wiring for the Surface Heater Pads and the Heat Keypad. The two hydro pumps are still started by their own relays from their own ON/OFF controls, with independent Air Flow Hydro Massage Intensity Dial Controls for the seat jets and the foot jets. See independent foot massage explained for how the two hydro pumps work together, and cords, control boxes, and connections after install for locating the box under the apron.

Surface Heater Pads Are Not the Water Heater

This diagram contains two very different heaters, and keeping them straight solves most confusion about "the heater".

1. The In-Line Water Heater (item 6) is a plumbing component. On the 01-16-26 copy it is drawn in the foot hydro loop, so it maintains the temperature of water circulating through the jets while that pump runs. It does nothing until water is moving through it. Read how the in-line water heater maintains temperature for details.
2. The Surface Heater Pads (item 8) are electric pads mounted beneath the seat and backrest. They warm the surface you sit against, and they are switched by the Surface Key Pad (item 9), a dedicated ON/OFF push button drawn as the Heat Keypad beside the Master Box. They have nothing to do with the jets or the pumps.

In short, the water heater warms the bath while a hydro pump circulates, and the heater pads warm the seat and back through the shell.

Electrical Printed on the Diagram

Component branches are marked "Electrical 110V", and the footer reads "Please View Specifications for Electrical Amperage (A), Voltage (V) and Wattage (W)." The heated seat option does not add a third outlet on this drawing; the pads and keypad are wired through the Master Box. Your electrician should still confirm each component's amperage on your model's spec sheet.

Diagnosing Seat Warmth Versus Water Warmth

Use the two-heater distinction to describe your concern precisely.

1. If the seat or backrest feels cold, press the Surface Key Pad (the Heat Keypad) once and give the pads 10 to 15 minutes to warm the shell. The pads switch themselves off after about 20 minutes, which is normal; press the keypad again to restart them.
2. If the bath water cools while you soak, make sure the foot hydro pump is running, since the In-Line Water Heater only works while water circulates through it.
3. If neither the pads nor the air pump respond, check both GFCI outlets, because the Master Box that serves the pads, the air pump, and the ozone generator needs power.
4. If a single system still does not respond, note which one and contact your Ella dealer or the team at ellasbubbles.com/support or (800) 480-6850 with your model and serial number.

As on every Ella air massage system, the air pump's Auto Purge starts about 20 minutes after you turn the air massage off and runs for 120 seconds to clear the air lines. That is normal and unrelated to either heater.

Download the official document: Air + Hydro + Hydro Foot Therapeutic Massage + Heated Seat & Back Component Diagram

Common Questions