Direct answer. Suction is the force that holds a window cleaning robot against vertical glass. It is measured in pascals (Pa), not watts, and on our range it runs from 2,800 Pa to 6,000 Pa depending on the model. Below roughly 3,000 Pa, the correct jobs are villas, shopfronts, sunrooms and single-storey glass. For towers, hotels and curtain walls, buy the top of the range — wind load on the glass rises with height, and so does the hold you need.
Why the suction number is not a cleaning number
A commercial window cleaning robot climbs glass by pulling a vacuum between its seal and the pane. Everything it does afterwards — the spray, the pads, the route planning — depends on that vacuum holding. So the rating is a hold-down figure wearing a performance label.
That matters when you shortlist. Two robots with identical cleaning hardware and different suction ratings are not the same product. One of them stays put on the glass you actually sell into, and the other one becomes a warranty claim.
The unit is also a useful filter on suppliers. If a spec sheet quotes suction in watts, the supplier is describing the motor, not the hold. Quietly ignore the number and ask for pascals.
Why 3,000 Pa is right at ground level and wrong at 90 metres
A robot 4 m up is fighting one thing: its own weight. The same robot on the thirtieth floor is fighting two. Wind pressure acting on the facade rises with height and with gusting, and it pushes against the same seal the vacuum is trying to keep seated. The higher the pane, the more of the motor’s work goes into resisting wind rather than holding the machine.
This is the whole reason a single rating cannot serve a category. It is also why specifying down to save a few dollars per unit is a false economy. A 3,000 Pa unit quoted into a wind-loaded curtain wall does not save money; it converts a predictable order into a failed tender or a claim.
The published rating for every model in the range
Read the figure off the individual product page. The range as a whole does not have one suction rating.
| Model | Suction | What it is built for | Anti-fall system |
|---|---|---|---|
| X9 | 2,800–3,200 Pa, variable (brushless BLDC motor) | Homes, apartments, mid-rise, app-controlled channels | UPS hold, 20–30 min |
| S9 | 3,000 Pa | Villas, shopfronts, sunrooms, single-storey glass | UPS protection on power loss |
| F19-02 | 3,000–3,500 Pa | Ultra-thin square body for tight framing and bezel-less glass | Standard fall protection |
| HCR-10 | Commercial specification | Villa, hotel and high-rise glass | Triple anti-drop mechanism, CE certified |
| H7S Pro | 6,000 Pa | Towers, hotels, curtain walls, high-rise exterior glass | 30-minute UPS emergency hold |
Two notes on reading that table. The tiers describe what a machine is built to survive, not what it must cost — a mid-range body with deep customisation can sit at a commercial price. And the highest rating in the range ships with the most redundancy rather than on its own, because suction and anti-fall solve the same problem at two different points of failure.
The number people forget: minimum pane size
Suction is measured against glass, so the glass has to be there. A pane that is small, heavily divided or interrupted by a proud mullion gives the seal less area to seat on. Frosted and deeply textured glass does the same thing from the other direction — the vacuum leaks.
You can see the effect on site. A robot that holds without argument on a full-height panel can start cycling its pump noticeably harder on a small bathroom pane. If your market includes both, check the minimum pane size on the model you are ordering, not just the Pa figure.
How to specify suction for a project
Start from the glass, not from the number.
If the route is villas, shopfronts and single-storey glass, a 3,000 Pa unit is the correct answer and the cheapest one that will hold. Adding headroom here costs margin for nothing.
If the route includes towers, hotels or curtain walls, go to the top of the range and put the requirement in writing. An autonomous window cleaning robot for commercial high rise buildings is bought on its worst pane, not its average one — one wind-loaded section at height sets the specification for the whole machine.
If the market has both, do not average them. Two models with a mixed order is usually cheaper than one model that is over-spec for half the portfolio and under-spec for the other half.
One more thing worth doing regardless of rating: take a sample unit and run it on the frame geometry you actually sell into. No spec sheet will tell you whether the seal holds on your local mullion profile, how the machine behaves when the tank is half empty, or whether the spray reaches a corner. Twenty minutes on a real pane answers all three.
When we would tell you not to buy the high-suction model
We would rather lose a unit sale than ship the wrong specification.
- Your market is villas, shopfronts and low-rise glass. You will pay for wind-load headroom your customers never use, and your retail price point will lose to a 3,000 Pa unit doing the same job.
- Your glass is heavily divided or under the model’s minimum pane size. Extra pascals will not fix a seal that has too little glass to sit on.
- Your channel is price-led e-commerce with no commercial or tender buyers. The S9 entry model, held for ready-to-ship wholesale at a 200-unit MOQ, is the right first order.
FAQ
Is a higher Pa rating always a better window cleaning robot?
No. Higher suction is bought with a larger motor, more mass and a higher unit cost, and on low-rise glass that capability is unused. Match the rating to the glass, not to the largest number in the table.
Can I compare a peak suction rating with a sustained one?
Not directly, and this is where most comparison tables mislead. Check whether the published figure is peak or sustained, then compare like with like. A supplier who quotes only the higher number without labelling it has given you an unverified specification.
Does suction keep the robot safe at height on its own?
No. Suction is the primary hold; the anti-fall system is the redundancy, and it is the part a client’s safety reviewer and insurer ask about. For commercial work, specify a UPS hold that keeps the pump running through a power cut or a triple anti-drop mechanism, plus a load-bearing safety rope — and put the redundancy requirement in the purchase agreement rather than in a brochure. We cover the tender wording in UPS hold vs triple anti-drop.
Does suction affect how clean the glass ends up?
Indirectly, yes. A seal that is working properly keeps the body flat and the pads in even contact with the pane. A seal that is struggling lets the body ride slightly off the glass, and that shows up as missed strips along the edges rather than as a fall.
Ask us for the sample unit and the frame geometry you sell into — we will tell you honestly which rating your glass needs, including the models we would not recommend for it. Contact us →