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How do HVO systems work?

The HVO oxygen-generating system turns itself on and off automatically based on the pressure in the oxygen storage tank. It is programmed to keep the tank pressure within a range of “setpoints”. Here’s how it works:

  • When the system turns on for the first time, the tank pressure is at zero PSI. This triggers the “charging” process.
  • Charging consists of running the oxygen concentrators that are attached to the HVO system, compressing the generated oxygen, and storing it in an oxygen-clean tank.
  • Tank pressure is monitored continuously. When the pressure reaches the high threshold (100 PSI for the Standard, 150 PSI for the Mighty Mite and MAX), the system goes into “discharging” mode, at which point the oxygen concentrators and the compressor are turned off. All that can be heard is the quiet hiss of oxygen running through the regulator.
  • Once the pressure drops below the low threshold (30 PSI for the Standard, 100 PSI for the Mighty Mite and MAX), the charging process is triggered again.

If the oxygen generating capacity is well-matched to the output requirements, you’ll receive a continuous supply of oxygen.

HVO supports a wide range of solution scales, from small to very large

Our simplest, lowest-cost system has the following components:

  • (1) Main headbox on a 20-gallon tank
  • (1) 10-LPM PSA Oxygen Concentrator
  • (1) Relay Box

The diagram below shows a system with a Main and six concentrators.

Here’s a diagram of a larger system with a Main & Drone controlling twelve 10 LPM oxygen concentrators:

The photo below shows a system that has all of the components in the HVO product line. Keep in mind that not all systems require a Drone or extra storage tanks.

HVO System with Main, Drone, and 6 Concentrators

A: Main Headbox: Controls the overall system
B: Drone Headbox: Augments the oxygen storage capacity. Is controlled by the Main.
C: Storage Tank: Stores oxygen at up to 150 PSI
D: Relay Box: Electrical outlets controlled by the Main
E: Oxygen Concentrators: Separate oxygen from air. Each is plugged into a relay box. The system may have one or more. Six are shown on two shelves.
F: Oxygen Regulator: Controls the oxygen output pressure

Note: Coaxial cables are used to send a control signal from the Main to the other controlled components (Drones, Relay Boxes).

The system shown has six Philips Respironics M10 (10-LPM) concentrators, yielding 60 LPM of oxygen.

The Main Headbox

The Main Headbox contains a proprietary logic controller that acts as the brain of the system. It may also contain the Seeing Eye™ IoT controller, which stores system metrics (e.g. PSI, O2 %) in the cloud.

The Pro Series™ contains an onboard ultrasonic oxygen sensor and a data display on the front of the box. The display shows system status information such as current PSI and percent full. In addition, there are three LEDs: red for low oxygen percentage, green for normal oxygen percentage, and blue to indicate low tank pressure.

Compressors are used to take inbound oxygen from the concentrator(s) and store it in the tank(s). There are three compressor models offered, and each has slightly different capabilities. See the post entitled ”How to choose the right HVO model”.

The Drone Headbox

The purpose of a Drone is to increase the number of oxygen concentrators that can be attached to a single system, as well as to increase the volume of oxygen that can be stored. The Drone lacks a logic controller because it is turned on and off by the Main via a coaxial signal. A Drone is not usable without a Main.

The Storage Tank

Storage tanks come in multiple sizes. You should match the number of oxygen concentrators to the tank size as follows:

  • 20-gallon: 1 – 3 oxygen concentrators
  • 30-gallon: 2 – 4 oxygen concentrators
  • 60-gallon: 3 – 5 oxygen concentrators
  • 80-gallon: 4 – 5 oxygen concentrators

When there is overlap, consider whether growth is likely, i.e. whether you will add more oxygen concentrators in the future.

HVO storage tanks are oxygen-rated, meaning that they are designed to store oxygen safely.

Storage Tank Interconnection

Storage tanks may be interconnected to expand storage:

The photo below shows a Main (left), Drone (center), and additional storage (right).


A Main connected to a Drone, and three 60-gallon storage tanks, for 180 gallons of storage overall, or 6,952 liters @ 150 psig.

The interconnection hoses are braided-steel lines. Together, the interconnected tanks form a single storage unit with a common tank pressure. Expansion is theoretically unlimited.

The Relay Boxes

Relay Boxes come in two sizes:

  • 3-outlet Relay Box: Can power up to three oxygen concentrators. Requires a 20-amp dedicated circuit.
  • 5-outlet Relay Box: Can power up to five oxygen concentrators. Requires a 30-amp dedicated circuit.


When the Main senses low pressure in the tank, it generates a 24 volt signal that is sent over the coaxial cable. When the relay box receives the signal, it turns on an internal relay switch, causing the power outlets to become energized. There are two coaxial connectors per relay box so you can “daisy chain” the signal to additional components, such as a Drone or another relay box.

The Oxygen Concentrator

The HVO System can accommodate most manufacturers’ 5-10 LPM oxygen concentrators. We carry the following products:

  • Olive, 10 LPM / 9 PSI
  • Philips Respironics M10, 10 LPM / 9 PSI
  • Philips Respironics Everflo, 5 LPM / 9 PSI
  • AirSep Onyx, 10 LPM / 20 PSI

If you know your usage in liters per minute (LPM), you can use this formula to calculate the number of oxygen concentrators needed for continuous output:

  • Determine the constant flow rate* in LPM
  • Add 5 to that number and divide by the LPM rating of the oxygen concentrators you plan to recommend
  • Round up.

For example, to maintain a flow of 30 LPM with Airsep Newlife Intensity concentrators, which produce 10 LPM each:

(30 + 5) / 10 LPM = 35 / 10 = 3.5 rounded up = 4

Four oxygen concentrators are needed, and at least a 30-gallon storage tank (see the Storage Tank section).

This formula works best for Veterinary or Aquaculture Systems where the output is more-or-less continuous. For other applications, the typical and peak usage may vary. We are more than happy to make recommendations that will suit your usage and needs. If you have questions, don’t hesitate to contact us.

* The oxygen flow in LPM that the system should be able to deliver continuously.

The Oxygen Regulator

Most oxygen regulators are designed for high-pressure tanks. We recommend a Harris Low-Pressure, High-Flow Oxygen Regulator, which is designed for the low pressure that is maintained in the HVO tank. This is a critical component that will prevent oxygen flow issues.

Planning for Power

HVO Systems run on standard 110 volt AC power. A household outlet (20 amp dedicated circuit with no other appliances running on it) is required for each headbox (either Main or Drone). In addition, a dedicated circuit is required for each Relay Box:

  • Three outlet Relay Box requires 20 amps
  • Five outlet Relay Box requires 30 amps

See the FAQ for information about calculating your power cost.

The Seeing Eye™ Internet of Things (IoT) Cloud Service

IoT is simply computers incorporated into everyday devices, such as thermostats, refrigerators, doorknobs, and, now, HVO systems. The goal is to make these “things” more useful.

What do these computers do?

Mainly, they interact with sensors to gather actionable data and store it in a database in the cloud. HVO’s Seeing Eye™ IoT service is able to measure the pressure in the storage tank, the percentage of generated oxygen, headbox temperature and humidity, as well as atmospheric pressure. See the graph below.

Notice the purple line, which shows the real-time flow rate in LPM. This data is only available if you purchase the optional Mass Flow Sensor.

A monitor process in the cloud examines the data to see if recent measurements are outside of normal ranges. When a problem is detected, the monitor process notifies a list of interested parties via text, email, or both.

Benefits of the Seeing Eye Cloud Service:

  • Enables customers and support personnel to know instantly about a problem with the oxygen supply, before it becomes a serious issue.
  • Provides a historical record of oxygen availability and percentage.
  • Highlights system over- and underutilization.
  • Tracks usage to indicate when a system upgrade may be needed, such as a Drone, storage tank, or additional oxygen concentrators.

The HVO Seeing Eye™ website has been certified by Qualsys SSL Labs as an A+ rated secure website.

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