Ariston Combi Boiler Air Pressure Switch 60/50 Pa – Huba Control 605.99F22, Compatible with 65100716

The Huba Control 605.99F22 air pressure switch is the safety part that monitors flue draft in Ariston room-sealed combi boilers. It does not close its contact until the fan is running and has created sufficient vacuum in the flue line; the board does not ignite the burner without this confirmation. In other words, this is the part that prevents the appliance from operating with a blocked flue or a stopped fan.

The switching value is 60/50 Pa. The Ariston spare part code is 65100716, and the production code on the device body is 600 10625.

What Does 60/50 Pa Mean?

• 60 Pa — upper switching point. When the fan vacuum reaches this value, the contact closes and the board receives the ignition confirmation.
• 50 Pa — lower point. If the vacuum falls below this value, the contact opens and the boiler shuts off the gas.
• The 10 Pa difference between them (hysteresis) is intentional. It prevents the contact from constantly opening and closing in wind and flue fluctuations, i.e. the appliance repeatedly locking out and resetting.

According to manufacturer data, the switching point repeatability is better than ±1 Pa, and the switching point is set only at the factory — no adjustment can be made on the part. Therefore a pressure switch with a Pa value that is merely "close" will not do the job.

If the Wrong Pa Value Is Fitted

• If a higher value is fitted (for example 80/68 instead of 60/50), the boiler's fan can never produce that vacuum; the contact never closes. Result: the fan turns but there is no ignition, and the appliance goes into flue safety lockout.
• If a lower value is fitted (for example 40/25), the safety margin is lost. Even when the flue is partially blocked or in windy weather, the contact stays closed and the boiler continues to run. This creates a risk of flue gas leaking into the room — the safety function, which is the pressure switch's only job, is disabled.

🚨 60/50 Pa and 65/50 Pa Are Often Confused

On the market these two values are often thought to be the same part, but they are separate parts: 60/50 Pa is Huba 605.99F22, while 65/50 Pa is Huba 605.99A68. In some listings this product is also listed as "65/50 Pa" or just "50 Pa". Before ordering, read the Pa value and Huba code on the body of the removed part — this product reads 60/50 Pa.

Code Change and Difference in Appearance

Ariston has updated the code of this part over time as 65100716 → 65104671 → 65104671-01; all three perform the same function. Because the manufacturer has redesigned the part, it may differ in appearance from the old part you have; the dimensions, connections and operation are the same.

Fault Symptoms

• The fan turns but there is no ignition. The most typical symptom — the board cannot receive the confirmation signal from the pressure switch, and the spark sound of the ignition electrode is never heard.
• Intermittent lockout and reset. The contacts may be oxidized or stuck.
• A "click-click" sound from the relay and flame flickering. The vacuum is at the limit value and the contact is operating unstably.
• Faults in windy weather, no problems in calm weather. This means the diaphragm is fatigued.
• On Ariston this fault usually appears with code 601 / 6P1 (flue gas exhaust problem) or 607; on the Egis without a display, the yellow light comes on, and on the Matis the light with the flue symbol. If a hose has come off, it may also appear as 501 (no flame).

How Is It Tested in the Field?

First the hoses are checked: cracks, hardening, soot or condensate blockage, looseness at the push-fit joints. A blockage at the flue terminal also gives the same symptom. If the hoses are sound, the pressure switch is measured:

1. The multimeter is set to continuity (audible) or ohm mode.
2. With the fan stopped, the probes are held between the common terminal and the open contact — there should be no sound.
3. Suck gently by mouth (do not blow) on the hose port — a "click" should be heard from inside.
4. At the same time the multimeter should beep and the resistance should read close to zero. When the suction is released, the sound should stop immediately.

Result: if there is no "click" at all, the diaphragm is torn. If there is a "click" but the multimeter does not beep, the contacts are burnt. In both cases the part is replaced.

🚨 Do not apply pressurized air with a compressor and do not blow hard — this permanently tears the diaphragm. The test is done only by mouth, with gentle suction.

P1 and P2 Ports — The Hoses Must Not Be Reversed

The part has two hose ports and they are not symmetrical:

• P1 — higher pressure (or less vacuum) side; the atmosphere/reference port on the boiler.
• P2 — lower pressure (higher vacuum) side; connected to the suction side of the fan, the negative port of the venturi.

If the vacuum hose is mistakenly fitted to P1, the diaphragm is pushed in the opposite direction and the contact never pulls in; the appliance does not work. There is no mechanical damage, but this is the most common cause of cases thought to be "the new part arrived faulty". Mark the hoses before removal.

The pressure switch must be fitted in its original mounting orientation; the manufacturer states that at low Pa values the mounting orientation shifts the switching point.

Technical Specifications

Compatible Models

If you do not see your own model in the list, this does not mean the part does not fit; the decision is made by the Pa value and Huba code on the removed part.

Technical document: Huba Control 605 series datasheet (PDF, English)