Before you start
Most of this install is straightforward: a magnet, a few connectors and some tape. Two parts of it are not, and they are worth reading before you open the box.
Line voltage
The power supply lands on a contactor that sees roughly 240 volts. A condenser disconnect is not a wall switch, and the terminals stay live until you prove otherwise with a meter. Pull the disconnect first, every time, and test before you touch.
Refrigerant under pressure
The pressure sensors thread onto a sealed circuit that can sit above 400 psi, and seating one briefly opens the service port. Wear gloves and eye protection — escaping refrigerant is cold enough to burn skin on contact. Keep the system off while you work on the ports, do not let a wrench put torque into the line, and leak-check both joints before you call it done.
Work the steps in order. They are sequenced so the unit is never powered while an unterminated connector is open, and so nothing is torqued while the circuit is still under pressure at the port.
Does your system qualify
The monitor reads the refrigerant circuit directly, so the test is simple: is there a reachable direct-expansion circuit with service ports on both lines? If yes, it fits. Split systems, heat pumps, packaged rooftop units, mini-splits with accessible ports and most commercial refrigeration all qualify.
Good to go
- Schrader service ports you can reach on both the liquid and the suction line
- R-410A, R-22, R-454B, R-134a and similar — the sensors read 0–40 bar (0–580 psi)
- Line-voltage power at the condenser
- A mobile signal at the condenser — any carrier, the SIM is built in
- Packaged rooftop units. The question is the refrigerant circuit, never the cabinet shape
Stop and reschedule
- No service ports, or ports that are buried, seized or non-standard
- Chilled-water or water-source systems with no DX circuit to tap
- A system that is already failing — repair it first, then monitor it
- No power source within reach of the 2 m supply lead
- A condenser in a pit or a metal enclosure with no signal
A bad install is worse than no install. If something on the right-hand list is true, stop. Nothing about this product is improved by forcing it onto equipment that cannot carry it.
What's in the box
Already built into the unit
- The monitor, sealed, with a 25 mm magnet on the back face
- Three green indicators and the logo on the top face, marked Power, Status and Cellular
- Two connectors on the angled lower face, marked Splitter and Antenna
- A serial and QR label on the side
Loose in the box
- 1 antenna
- 1 splitter harness — one plug in, five labelled branches out
- 2 pressure sensors — identical and unmarked; the cable decides which is which
- 2 temperature probes — labelled Liquid side and Vapor side
- 1 power supply, 100–240 VAC in, 5 VDC out
- 2 insulation patches — one per temperature probe
- 4 zip ties
Lay it all out on the pad before you start and check it against this list. The one thing you cannot improvise on a roof is a missing sensor.
Tools you need
- One adjustable open-end wrench. That is the only wrench the job needs
- Nut driver or screwdriver, for the disconnect and the electrical compartment cover
- Gloves and eye protection — the pressure sensors are the reason
- Multimeter, or a non-contact voltage tester
- Bubble solution, for leak-checking both sensor joints
- Scissors or snips
- Your phone, for the app and the install photographs
Optional. A torque wrench, if you would rather take the fitting to a specified torque than judge it by feel. An electronic leak detector, if you carry one — it finds a slow leak sooner than bubbles do.
Nothing else is needed. No gauges, no recovery equipment, no nitrogen, no valve-core tool: the circuit is never opened, only tapped at ports that are built to be tapped.
The unit itself
- 1Three indicators, all greenMarked Power, Status and Cellular on the case. All three are the same green — the colour tells you nothing, the blink pattern is the message.
- 2SplitterThe six-pin connector. Everything except the antenna arrives here through one harness.
- 3AntennaFinger-tight only, no wrench, and never power the unit up with this port empty.
Status is the one worth learning — it blinks a code, and step 10 has the chart. There is no SIM to fit, no Wi-Fi to join and no configuration to enter: the cellular connection is built in and already paid for.
Where everything goes
- 1The monitorMagnet-mounted flat on the side panel, level and square, and beside the manufacturer's labels rather than over them.
- 2Splitter and antennaBoth on the underside, pointing down. Fit them before the unit goes on the cabinet — they are far easier to reach in your hand.
- 3Down to the sensorsOne cable down the panel to the splitter, then out to the two pressure sensors and the two probes. Coil and tie the slack rather than leaving it hanging.
Telling the two lines apart
This is the one identification everything else depends on. Get it backwards and every pressure, every temperature and every alert the unit produces will be wrong — and it will look plausible, which is worse.
| Vapor / suction line | Liquid line | |
|---|---|---|
| Which side | The low side | The high side |
| Size | The larger of the two pipes | The smaller |
| Covering | Black foam insulation | Bare copper |
| Feel, while cooling | Cold, often sweating | Warm to hot — do not grab it |
| Gets | Vapor pressure sensor + vapor probe | Liquid pressure sensor + liquid probe |
On a heat pump in heating mode the temperatures swap over. The line identity does not: the large insulated pipe is still the suction line and still takes the vapor sensor. Identify by pipe size and insulation, never by which one feels cold today.
The twelve steps
Turn the power off and prove it dead
- 1The pull-out is outEmpty jaws. This is what the disconnect looks like when it is actually open, rather than just switched.
- 2Keep the block with youIn your pocket or on the pad in sight — not balanced on the cabinet where someone walking past can push it back in.
Pull the disconnect beside the condenser. If the property has a breaker for the condenser, switch that off too. Then check with a tester at the terminals before your hands go anywhere near them.
Do not skip the meter. A pulled disconnect that turns out to be wired backwards is exactly the surprise this step exists to catch.
Identify the two lines and mark them
Ten seconds, and it saves you from the only mistake on this page that does not announce itself. Bigger pipe with black foam on it is the vapor line. Smaller bare copper is the liquid line. Put a strip of tape on each and write on it.
While you are there, photograph the equipment nameplate. Make, model, serial and refrigerant type all go into the app at the end.
Open the electrical compartment and land the power supply
- 1On the contactorThe two AC leads land on the line-side terminals. Follow the thick service conductors coming in from the disconnect — the two screws they are already clamped under are the ones. There is no polarity.
- 2Up into the compartmentRun the pair up from the supply, dressed clear of the contactor's moving parts and away from any sharp edge.
- 3The supply itselfA flat black block with a mounting flange at each end. It sits low and out of the way, with its output cable running on to the splitter.
Take off the side cover over the electrical connections — two to four screws. The power supply's two bare AC leads go onto the two terminals that feed the contactor on the line side. Not the load side.
- One thick conductor and one thin lead per screw. That is the whole test for the line side.
- Tighten the terminal screws down firmly, then tug each lead. If it moves, it is not in properly.
Line side, not load side. The load terminals are only live while the compressor runs. A monitor wired there goes dark between cycles and reports nothing at all about the system at rest — which is half of what it is for.
Stow the supply and close the cover
The power supply box stays inside the electrical compartment. Tuck it into a corner where it is not touching the contactor or anything that moves.
- Feed 12 to 24 inches of the output cable out of the compartment — through an existing hole in the bottom of it, or wedged between the cabinet and the cover.
- Put the cover back on with its two to four screws.
- Leave enough cable outside to reach the harness comfortably, with a little slack. Not taut.
From here on the compartment is closed, and the only thing of ours inside it is the supply.
Fit both pressure sensors
- 1The pressure sensorA short brass body that threads straight onto the service port. Both sensors in the box are identical and unmarked — either one fits either port.
- 2One per lineThe second sensor on the other service port. Nothing goes between the port and the sensor: no adapter and no tee.
- 3The cable carries the labelThis is what makes one sensor the liquid sensor and the other the vapor sensor. Read the label before you plug it in — the sensor body says nothing.
Take the caps off both service ports. A sensor threads straight onto each port — there is no adapter and nothing else in between.
- Start every thread by hand. Then one adjustable open-end wrench to snug it down — that is the only wrench this job needs.
- Snug, not savage. You are sealing a flare face, not fighting it, and you do not want torque travelling into the line.
Leak-check both joints
Two joints, one per port. Bubble solution on each, then watch it for thirty seconds — a slow leak does not show in five. If you carry an electronic leak detector, use that as well.
This is the step that decides whether the charge is still there in two years, and it is the one nobody can verify for you afterwards.
Tape on both temperature probes
- 1Under the insulationOpen the foam and lay the probe tip flat against the bare copper. Not on foam, not on tape, not in air — contact is the entire measurement.
- 2Closed back over itBring the foam back over the probe and cinch it either side, so no outdoor air can reach the tip and pull the reading toward ambient.
- 3One per lineSame again on the other line. Liquid side on the small bare line, vapor side on the big insulated one.
Work about a foot downstream of the service port, and seal the opening with the insulation patch when the foam goes back. Bring the lead out along the line and secure it, so nothing pulls on the tip.
Fit the antenna and splitter, then mount the unit
- Screw the antenna on finger-tight — no wrench.
- Push the splitter plug into the six-pin connector, keyway lined up, then hand-tighten the collar.
- Now magnet-mount the unit on a flat steel panel on the side of the condenser cabinet. Wipe the panel first — dust under a magnet is the difference between holding for ten years and sliding down the cabinet in August.
- Level, square to the cabinet edge, and beside the manufacturer's labels rather than over them.
Fit the antenna and the splitter before the unit goes on the cabinet. Both connectors face down, and they are far easier to reach with the unit still in your hand.
Connect the five branches — the labels decide
Five branches come out of the splitter, and each one has exactly one place to go:
- Power → the output cable you pulled out of the electrical compartment
- Vapor temperature → the probe marked Vapor side, on the big insulated line
- Liquid temperature → the probe marked Liquid side, on the small bare line
- Vapor pressure → whichever sensor is sitting on the big insulated line
- Liquid pressure → whichever sensor is sitting on the small bare line
This is the step to get right
The pressure sensors are identical and unmarked. The cable is what makes one of them the liquid sensor and the other the vapor sensor — so the branch marked Liquid side has to run to the sensor physically sitting on the liquid line.
Get those two the wrong way round and nothing fails. It reports. Every superheat and subcooling figure comes out inverted, the unit looks healthy while the system starves, and nothing in the data announces the error. Trace both cables with your finger before you move on.
Push each connector fully home and hand-tighten the collar. None of them needs force. Leave a drip loop before each sensor so water runs off the cable rather than into it, and tidy the slack with the zip ties.
Turn the power back on and read the lights
Push the disconnect back in. The left light comes on solid straight away. The middle one starts blinking within a few seconds, and what it blinks tells you how far the unit has got. All three lights are the same green — the pattern is the message, never the colour.
| Middle light | What it means | What to do |
|---|---|---|
| One flash every 3 s | Healthy — connected and reporting | Nothing. This is the one you are waiting for. |
| Even 1 Hz blink | Bringing up the cellular link | Normal for the first few minutes. Wait. |
| Two flashes, then a pause | On the network, but cannot reach the cloud | Usually clears itself. If it persists past ten minutes, call us. |
| Three fast, then a pause | No cellular registration after five minutes | Check the antenna is fitted. Move the unit higher on the cabinet. |
| Four fast, then a pause | Modem unresponsive | Pull power for thirty seconds and restore it. If it repeats, the unit needs swapping. |
| Five fast, then a pause | Sensor fault — a probe or sensor is not reading | Re-seat every branch connector. Check the probe tip is on copper. |
| One long pulse | An HVAC alarm is active | The unit is fine; the system it is watching is out of range. Read the alert. |
| Fast flicker | Firmware updating | Do not cut power. It will finish on its own. |
Only one pattern shows at a time — the most serious condition always wins. A sensor fault outranks an alarm on purpose, because an alarm calculated from a faulty probe is not worth chasing.
Commission it before you walk away
This is the step that decides whether anybody has to come back. Do all of it standing at the condenser.
- Register the unit to the property — scan the QR code on the side label, or type the serial.
- Enter the equipment details you photographed in step 2.
- Run the system in cooling for ten minutes, then open the live view on your phone.
- Confirm all four channels are reading, and that the numbers are plausible — see below.
- Confirm the pressures are not the wrong way round. Liquid should read far higher than vapor. If it does not, swap the two pressure cables over at the sensors.
- Send yourself a test alert and confirm it arrives.
If the unit is not reporting, do not leave. Diagnose it now. Checking on it remotely later turns into a second trip, and a second trip costs more than the first one earned.
Finish it properly
Clear the base of the unit, take the packaging away with you, wipe the enclosure face, and take the photographs listed further down this page. Then show the owner the live data on their own system — two minutes on that is worth more than anything written here.
What good readings look like
A sanity check, not a diagnosis. These are the figures you would expect from a healthy system running in cooling on a warm afternoon, roughly ten minutes into a cycle. If what you see is in a different world from this, something is wrong with the install or with the equipment — and either way you want to know before you leave.
| Channel | The general rule | R-410A at ~95 °F outdoor | R-22 at ~95 °F outdoor |
|---|---|---|---|
| Vapor pressure | Saturation around 35–50 °F | ~105–145 psi | ~60–85 psi |
| Liquid pressure | Saturation roughly 20–30 °F above outdoor air | ~340–420 psi | ~210–260 psi |
| Vapor line temp | Saturation plus 8–15 °F of superheat | ~50–65 °F | ~50–65 °F |
| Liquid line temp | Condensing temperature minus 8–12 °F of subcooling | ~95–115 °F | ~95–115 °F |
- Liquid pressure below vapor pressure means the two pressure cables are on the wrong sensors. Swap them at the sensors — step 9.
- Two pressures reading nearly the same on a system that has been off for hours is normal — the circuit has equalised. Run it and look again.
- A line temperature sitting at outdoor air temperature means the probe is not touching copper.
- A channel at its extreme — dead zero, or pinned at full scale — is a wiring or sensor fault, not a refrigerant fault.
Troubleshooting
| Symptom | Most likely cause | Fix |
|---|---|---|
| No lights at all | No power reaching the unit, or the harness power branch is not seated | Confirm the disconnect is in. Check the supply's AC leads at the contactor. Re-seat the power branch. |
| Powered, but nothing in the app | Still registering, or a weak signal where it is mounted | Give it ten minutes. Then move the unit higher on the cabinet, or onto a panel with a clearer view of the sky. |
| Three flashes that never clear | Poor cellular coverage at that spot | Reposition the antenna and the unit. Repeated power cycling will not fix a signal problem — send us the address and we will look at coverage. |
| Five flashes — sensor fault | A branch connector not fully home, or a probe not on copper | Unplug and re-seat all five branches. Re-tape the probe with the tip flat on the pipe. |
| One channel dead, the others fine | That sensor, or its lead | Swap that branch with its partner and see whether the fault follows the sensor or stays with the branch. That tells you which part to replace. |
| Pressures look inverted | The two pressure cables are on the wrong sensors | Swap the two cables over at the sensors. The sensors themselves are identical, so nothing has to come off the ports. Do not try to correct it in software. |
| Readings jump around | Cable strain at a connector, or a probe working loose | Add a drip loop and secure the cable. Re-tape the probe. |
Finishing standard
Every install ends the same way, whether it is your own house or the thirtieth one this month. It costs about five minutes and it is the cheapest quality control there is.
Before you leave
- Every wire secured; nothing touching the ground
- Antenna lead routed along an edge, not across a panel
- Unit level, beside the OEM labels rather than over them
- No field tape showing; insulation repaired neatly
- Base of the condenser clear — weeds, offcuts, packaging gone
- Enclosure face wiped clean
- Nothing leaning on the condenser or within 18 inches of the coil
Photographs to take
- The mounted unit, three-quarter angle
- Each pressure sensor on its port, with its cable label readable
- Each temperature probe before you tape it
- The power supply leads on the contactor, before the cover goes back
- The equipment nameplate
- Your phone showing live data, held in front of the unit
Keep the photographs with the serial number. They are the warranty record, and they are the only thing that will tell you what was actually done here when somebody asks in three years.
Printable checklist
The short version, for the truck or the clipboard. Use the print button at the top of the page.
Install
- Power off at the disconnect, proved dead with a meter
- Both lines identified and marked; nameplate photographed
- Power supply leads on the contactor LINE side, both tugged
- Supply stowed inside the compartment, 12–24 in of cable out, cover back on
- Both pressure sensors on the service ports, snug
- Both sensor joints leak-checked with bubbles
- Both probes taped, metal on copper, patch sealed all round
- Antenna and splitter fitted before mounting; unit level on a wiped panel
- All five branches seated and collars tightened
- Liquid-labelled cable on the sensor on the liquid line — traced by hand
- Drip loops in, slack tied, ties trimmed
Commission
- Power restored; middle light at one flash every three seconds
- Unit registered to the property, serial recorded
- Equipment details entered
- All four channels reading live
- Readings plausible; pressures not inverted
- Test alert received on a phone
- Site left clean; photographs taken
- Owner shown their own live data
Stuck on something?
Call (940) 222-8333 or email sales@vetralis.com with the serial number from the side of the unit. If it is powered and talking to us, we can usually see what is wrong from here.