100 questions and answers on ETC water scrubbers

Its primary function is the abatement of soot and carbonaceous particulate carried by combustion fumes. The water, the wetted surfaces and the internal geometry progressively separate the particles from the gas flow. The AH/CLINEAR Series is a line of water-based wet scrubbers: it contains no activated carbon filters, electrostatic fields or ozone generators.

The flow meets atomised water, wetted surfaces and several changes of direction. The particles are intercepted, wetted, gain mass and are carried away into the recirculation water. The result depends on the interaction between flow rate, geometry, atomisation, temperature and contact time.

Under the specific conditions of a documented test, the ETC system achieved a particulate abatement efficiency of 95.2%, measured according to UNI EN 13284-1 at MADE HSE S.r.l., ACCREDIA laboratory n. 0656, reports 14LA11644 and 14LA11645 of 09/12/2014. The value refers to those test conditions and is not a universal guarantee valid for any combustion, flow rate or configuration.

No. The test cited concerns total particulate measured with the method adopted. The same results must not be automatically attributed to the individual PM10, PM2.5 or ultrafine fractions without a dedicated measurement.

No. Smoke is a mixture of solid particles, aerosols, vapours and gaseous components. The wet scrubber markedly reduces the particulate component, but water treatment alone is not equivalent to the absolute elimination of every visible or condensable component.

Water can reduce part of the odorous substances, especially when they are associated with particulate or are sufficiently soluble. Residual odour does not by itself indicate a malfunction. Specific odour treatment requirements may call for additional dedicated technologies.

Yes. The fumes are cooled and loaded with moisture during washing. The outlet may therefore show water vapour, especially with cold outside air or during phases of higher thermal load.

On correctly sized wood-fired ovens, ETC often finds outlet temperatures in the order of 45-50 °C. It is not a fixed value: it changes with the heat generator, fuel, flow rate, inlet temperature and operating conditions.

In ETC's experience, inlet temperatures in the order of 120-150 °C do not normally cause problems for the machine when the system is correctly sized, full of water and operating regularly.

An occasional peak is normally absorbed by the washing system and can greatly increase vapour production. If very high temperatures become the ordinary condition, the fuel, heat generator and sizing of the machine must be checked.

The internal path passes through several wet zones and changes of direction. Small occasional sparks are normally wetted and extinguished along the path. This does not mean that the system should be used to intentionally receive large quantities of incandescent material.

The operating fluid is water. Unless ETC gives a specific technical instruction, no detergents, soaps, antifreeze, salts, alcohol, acids or other additives must be added to the recirculation tank.

As an ETC operating reference, the supply pressure should be set at approximately 1.5 to 3.5 bar. If the pressure is excessive, a pressure reducer is used.

With very hard water a water softener must be provided. Limescale can encrust the solenoid valve, nozzles, manifolds, pump, fittings and water passages.

Yes. Softened water is suitable and reduces the risk of limescale deposits.

Yes. ETC allows its use; the absence or strong reduction of limescale does not cause problems for the normal operation of the abatement unit.

No, unless it has been analysed and treated. ETC prohibits the direct use of untreated well water when it has high hardness or a high mineral content. In severe cases limescale can rapidly encrust the entire circuit and seriously compromise the machine, even within a few months.

Yes. Soot visibly dirties the water very quickly. The colour alone cannot be used to determine precisely how much soot the oven produces. When the water is dirty it must be drained and replaced as part of the normal management of the system.

Normally not. Water that has washed the fumes soon takes on a characteristic, slightly acrid smell. The smell alone is not a sign of a fault; as the concentration of contaminants increases, other characteristics of the water, including acidity, may also change.

In ETC's operating experience, the water temperature in the tank has not normally exceeded approximately 80 °C, even in the most severe conditions observed. The ordinary value is generally lower.

Yes, if it is installed under cover and there is no risk of frost. From the point of view of good maintenance, however, ETC still prefers the water to be drained and renewed at the frequency required by the use, normally at the end of the working day.

After operation the machine must be emptied. Stagnant water must be avoided at exposed points of the circuit, because freezing can cause expansion, breakage and damage to components.

The machine can continue temporarily with the water already in the tank. As an indication, it can work for about one hour, depending on evaporation and operating conditions. When the level drops below the minimum, the float switch stops the normal operation of the pump.

Fill the tank and leave the water inside for about 1-2 hours before starting the pump. Then check pressure, noise and atomisation. This procedure helps the pump components that have been idle to return to normal operating conditions.

Check the necessary connections, that the water is turned on, the position of the taps, the drain, the power supply, the earthing, the tightness of the pipes and the absence of leaks. After switching on, observe correct filling, pump start at the intended level and atomisation.

The pump must not start until the water reaches the first level set by the float switch. If water does not enter, the filling circuit must be diagnosed.

Finish the combustion and close the oven mouth. Then switch off the abatement unit. Draining is then carried out manually or automatically depending on the installed configuration.

No. Once rinsing is complete, the machine can be filled immediately and put back into operation. There is no mandatory technical drying time.

An occasional stop does not necessarily require the oven to be switched off immediately, provided the abatement unit remains full of water and the draught is sufficient. The machine must nevertheless be restored as soon as possible and this condition must not become a normal operating mode.

A long checklist is not needed. The user must know the normal behaviour of the machine, make sure the water is managed correctly and pay attention to changes in noise, pressure, level, atomisation, leaks, vibrations and draught.

Check that screws and hose clamps are tight, that there are no leaks and that no visible damage has occurred during transport. If the installation has been correctly restored, no other adjustments are normally necessary.

There is no absolute parameter. The main practical references are the usual washing noise and the pump pressure. If the rushing sound of the water does not change and the pump pressure gauge reads around its usual value, approximately 2 bar in the typical configuration, the system is normally working correctly.

The float switch controls the water levels and manages the conditions set for the filling circuit, including starting the pump at the minimum level and stopping filling at the maximum level.

Normally not. Calibration is carried out in the factory. A correction may be necessary in particular cases, for example with a machine not installed perfectly level, but it is advisable for a technician to carry it out.

When the electrical contacts or the mechanism do not correctly detect the minimum or maximum level. ETC prefers to replace the entire float switch assembly, not a single element, to prevent another worn part from causing a new problem shortly afterwards.

Yes. The filling system is arranged so that the water helps wash the float switch during the filling cycles. With correct maintenance the component can work for a long time without problems.

First check water availability and pressure, then the float switch and its states, then the solenoid valve and the coil. Only after the filling circuit has been restored should the other components be checked. Electrical checks are reserved for qualified personnel.

The main causes are the float switch not interrupting the command or the solenoid valve not closing mechanically. The technician must distinguish between the two conditions with the machine made safe.

A qualified technician, after electrically isolating the circuit, can separate the coil from the valve body and check whether the water passage closes mechanically. If the valve closes, the problem lies in the command/float switch; if it continues to let water through, the valve body is stuck or faulty and must be repaired or replaced.

It shows the pressure of the water available at the inlet and has a diagnostic function. It shows whether the mains supply is present and whether the pressure is excessive. During filling the reading may drop considerably; with the solenoid valve closed it shows the static mains pressure.

As a practical reference, in the typical configuration the pump works at around approximately 2 bar. The value must be interpreted in relation to the model, the configuration and above all the usual behaviour of the machine.

If atomisation decreases at the same time, the nozzles or other water passages are probably partially clogged. The pump generates pressure but the water meets greater resistance at the outlet.

Check the water level, the pump inlet, any presence of air, obstructions in the impellers and the general condition of the pump.

It may indicate irregular suction, the presence of air or cavitation. The first check concerns the water level; if the phenomenon persists, the suction and impellers must be checked.

The pump pressure gauge must return to zero when the pump is stopped and the circuit is not under pressure. The mains pressure gauge, on the other hand, may continue to show the static pressure of the water supply even with the machine switched off.

It is normally glycerine. The pressure gauges are filled with glycerine to stabilise the needle. Leakage can occur if the top cap is removed or if the pressure gauge is damaged. In this case the pressure gauge must be replaced.

No. A new noise must be checked. Causes already encountered include the cooling fan touching its cover, or small hard bodies or agglomerates in the inlet area or in the impellers.

They can obstruct the inlet and cause noise, cavitation or reduced flow rate. The material must be removed and, if necessary, the pump is flushed.

With the machine disconnected from the power supply, the technician disconnects the designated section near the pump/pressure gauge outlet and uses the washing line with the yellow hose to send clean water in the reverse direction, attempting to clear the inlet and impellers. At the end the hose and clamp are refitted and pressure and atomisation are checked again.

In a correct indoor installation they can last as long as the machine. They are selected for pressures much higher than the operating pressures. They are replaced if they become swollen, cracked or deformed, leak or show abnormal deterioration; the spare part must be identified by the hose code or supplied by ETC.

Yes. Tightening the hose clamps is part of the normal commissioning and maintenance checks. If the leak continues after tightening, the condition of the hose must be checked and the hose replaced if deteriorated.

Through the inspection door, check that the jet is regular and consistent with the usual behaviour of the machine. Very weak atomisation combined with high pressure suggests a blockage.

Normally not. If the water is correct and maintenance is regular, the nozzles do not require frequent removal. Work is carried out when atomisation or diagnosis actually indicates a problem.

The nozzle is removed by competent personnel with a suitable spanner. For stubborn limescale it can be treated separately from the machine with a suitable descaling product; ETC also allows muriatic acid on the removed nozzle, with PPE and in compliance with the safety data sheet. After treatment it must be rinsed thoroughly. A thin, rigid tool can clear the passage without deforming the geometry.

Rarely. The nozzles are made of stainless steel and in most cases can be recovered by cleaning. They are replaced if they are actually damaged, deformed or can no longer be restored.

It is a very rare event. The manifolds are stainless steel pipes of approximately 1/2 inch and normally do not become blocked if the water and maintenance are correct.

The external rubber connections are removed and access is gained through the tees and elbows. A suitable flexible probe can be used to clear the passage. If the blockage persists, the sections concerned are dismantled and physically washed with water and brushes.

The material must be removed because it can reach the pump or obstruct the drain. The machine must be switched off and made safe, drained and cleaned.

Yes. A professional vacuum cleaner suitable for liquids and ash is useful for removing coarse residues and agglomerates in the tank after draining.

Normally not. The inspection door gives access to the areas to be cleaned without dismantling the baffles. If they are removed for extraordinary maintenance, it is advisable to mark their position and orientation and to entrust the work to technical personnel.

No. The factory configuration must be maintained. The water manifolds and nozzles are part of the active operation of the system; if they are excluded, the machine no longer works under the intended conditions.

The frequency depends on use and the dirt load. The ETC principle is to drain the water regularly and rinse the inside when necessary to prevent build-up, more frequently in heavy-duty applications. There is no need to dismantle the machine for normal rinsing.

In ordinary ETC management it is preferable to drain the water at the end of the day or according to the frequency defined for the specific use. Very dirty applications may require more frequent water changes.

For programming, changing the parameters and using the controls, refer to the user manual of the timer supplied with the component/machine. The FAQ explains the function of the timer but does not replace the manufacturer's manual. ETC can provide assistance by telephone or video call when necessary.

It may be blocked by impurities, sediment or limescale, or have an actuator/control problem. The diagnosis must be carried out safely, checking both the mechanical part and, by qualified personnel, the electrical part.

The problem may be in the downstream pipe. The movement of the actuator does not prove that the water is actually flowing out. If a normal drain flow cannot be heard, check for obstructions and the route of the pipe.

Check the timer programming and restore the parameters specified in the specific manual of the timer supplied with the machine. Do not set random values.

The most likely cause is in the pipe after the machine, especially if sections smaller than Ø40 mm have been used or if the route encourages build-up. The drain line must be cleaned right up to its end point.

Foam may indicate a high concentration of substances coming from the process. The first solution is to drain, rinse and use clean water; if it reappears quickly, the frequency of water changes must be increased. Do not add antifoam without ETC instructions.

Grease, ash, soot and particulate can agglomerate and form very hard, stone-like deposits. These residues can obstruct the drain, pump and water circuit; consequently draining and cleaning must be more frequent.

For applications planned from the outset, ETC can provide a specific configuration with a double valve and an additional water supply, so that the overflow is used to remove the surface grease. At the same time, draining and manual cleaning are increased.

The discharge destination must be checked according to the system and the applicable local rules. A trap, settling tank, grease separation or other systems may be necessary. ETC supplies the machine; the compliance of the specific discharge must be verified for the installation site.

The untreated section between the heat generator and the abatement unit must be cleaned at least every three months. If the application produces a lot of dirt or the draught deteriorates, cleaning must be brought forward.

The first check concerns the flue section between the oven and the abatement unit, because there the soot is still untreated and can reduce the cross-section. Then check the water, foam, drain and the condition of the machine.

Yes. The outlet air is very humid and generates condensate. The downstream section must therefore be built as a sealed duct, designed to handle water and condensate without leaks.

According to its current specifications, ETC uses AISI 316L stainless steel in the section downstream of the abatement unit, with joints and installation suitable for the presence of condensate.

Avoid downward sections, pockets and stagnation points. Where the route allows, maintain an indicative upward slope of at least 5° and make the joints so that condensate does not leak out.

The terminal must leave the upward discharge free. ETC advises against Chinese hat caps, wind-driven cowls and other restrictive terminals that collect condensate or increase flow resistance; a suitable open/truncated-cone terminal is preferable.

It can be installed near the oven, in an intermediate position or towards the end, provided the system is correctly designed for draught, maintenance, condensate and drainage. When possible, proximity to the heat generator reduces the length of untreated flue.

Yes, when the system has correctly sized forced extraction and the geometry of the installation avoids stagnation and unfavourable routes. In this configuration the movement of the fumes does not depend only on natural draught.

It is necessary or useful when the natural draught is not sufficient, when the route has many pressure losses, when there are several appliances connected or when the project requires a controlled flow rate. Sizing must take the entire system into account.

Downstream of the abatement unit. A fan installed upstream that pushes the fumes into the machine can create overpressure and smoke leaks from doors, joints or the overflow.

No. It must be supported by its own brackets or an independent structure, avoiding transferring weight and vibrations to the casing of the abatement unit.

The fan performance curve is used at the required operating point: the necessary flow rate and the total static pressure of the system. Motor power alone or maximum free-delivery flow rate are not sufficient criteria.

The setting is defined during commissioning based on the required flow rate. In ETC configurations with a 0-50 scale it is advisable not to go normally below about 15, unless a different specific calibration has been made. In ordinary use the user should mainly limit themselves to switching on and off.

It does not normally damage the abatement unit, but it can draw too much heat from the oven. The oven may then struggle to reach or maintain the temperature needed for cooking.

If the oven is already hot and the residual draught is sufficient, it may be possible to finish work temporarily. If smoke appears in the room, reduce fuel and smoke production and restore extraction as soon as possible.

The condensate drain must be managed. The preferred solution is to connect it to a suitable drain; in configurations that allow it, it can be closed so that the condensate flows back towards the abatement unit. No uncontrolled leaks or stagnation must occur.

First check that the knobs are evenly tightened. If the phenomenon persists, check that the machine is not under overpressure because of an incorrectly installed or adjusted fan.

The drain of the abatement unit must be correctly separated from the drainage network by means of a trap or an equivalent solution provided for in the system. Without correct separation, smoke can travel along the pipe and re-enter the room.

Yes, if the model is sized for the total load. An AH250 must not be considered the ordinary solution for two ovens; an AH300 can serve two ovens when the project and flow rates allow it. For larger models the configuration must be sized case by case.

It is not essential for the operation of the abatement unit. If dampers or butterfly valves provided for in the project are present, the unused branch can be closed; leaving the branch open does not in itself cause a problem for the machine.

Rigid, stable, level and able to bear the operating weight. ETC does not consider anti-vibration mounts under the machine to be the ordinary solution: an elastic or unstable base can amplify vibrations through resonance. Anti-vibration joints on the ducting or on the independently bracketed extraction fan are a different matter.

A partial cover is better than no protection and mainly protects the upper electrical parts, but it does not make the machine completely waterproof. With direct exposure to rain and sun, risk of frost, or a marine or aggressive environment, a suitable full cover is preferable. Continuous exposure can damage the solenoid valve coil, motorised valve, connections and external pump components.

In the presence of leakage currents or potential differences, ineffective earthing can contribute to localised corrosion and perforation. The mere visible presence of the earth wire is not enough: the effectiveness of the protection must be verified with instruments by qualified personnel. The internal brass element provides a preferential conductive point, but it does not replace correct earthing.

An electrical fault or a leakage must be looked for. Possible causes include: the solenoid valve coil, water in the motorised drain valve, the pump, wet connections or contacts, damaged wiring. The diagnosis must be carried out by a qualified electrician with the machine made safe.

If the machine is under warranty, ETC must be informed before any work is carried out. ETC can intervene directly or agree to the use of a qualified welder provided by the customer. Out of warranty the customer can arrange the repair, but it is still advisable to inform ETC so it can check that the leak is not caused by vibrations or other external causes.

Draining and changing the water, cleaning the tank, cleaning the overflow, internal rinsing and visual inspection of the nozzles are part of the user's normal management. Work on electrical parts, adjustments, pump, float switch, solenoid valves, welds or faults that cannot be identified with normal checks requires technical personnel. If a maintenance contract has been signed, the work provided for in that contract must be complied with.

No. ETC has found machines working perfectly even after many years. There is no universal interval for replacing the pump, float switch, valves or other components: action is taken when inspection and operation show actual wear, deterioration or a fault.

The most useful signs come from comparison with the usual behaviour: a different pump noise, a changed rushing sound of the water, pressure different from normal, weaker atomisation, slower or more frequent filling, level variations, leaks, vibrations or reduced draught. A persistent change must be checked before it causes the machine to stop.