Common faults of the ELÍZ electric boiler and their solutions
Common Faults of the ELÍZ Electric Boiler and Their Solutions
ELÍZ electric boilers are among the reliable and technically well-designed devices, but like any electrical system – this boiler can also behave unpredictably. From experience, I know that most of the faults customers encounter are not the result of poor design, but rather incorrect installation, neglected maintenance, or a misunderstanding when setting up the controller. In this article, I will go systematically through the most common faults, explain their causes, and describe the solution procedure – the way I would tell a customer on-site.
If you're looking for information on how to properly install or set up the boiler before problems appear, I also recommend checking out the topics Installation of the ELÍZ Electric Boiler: Procedure and Installation Requirements and Setting and Programming the Controller of the ELÍZ Electric Boiler in the same Knowledge Center.
Why Diagnosing an Electric Boiler Differs From Gas
The first thing customers sometimes don't understand: an electric boiler has no flame, burners, or flue gases. This means some problems you're used to from gas appliances simply don't exist here. On the other hand, an electric boiler has its own set of protections – safety thermostat (STB), pressure switch, frost protection, safety valve, and many other elements that can block operation.
From my experience, one basic rule applies: when the boiler "doesn't work", it doesn't automatically mean it's broken. In at least sixty percent of cases, it's something the user themselves can solve without any service call. Therefore, it's worth systematically going through a checklist before calling a technician.
1. The Boiler Won't Start – No Reaction After Switching On
This is probably the most common reason for calling service. The boiler is completely dead, the display doesn't light up, nothing works. There can be several causes, and most of them are outside the boiler itself.
Circuit Breaker or RCD Tripped
Check the electrical distribution board. The ELÍZ electric boiler is connected to a three-phase supply and has its own circuit breaker – most often 3×16 A or 3×20 A depending on output. If the breaker has tripped, it needs to be reset. If it trips repeatedly, that's a sign of either a fault in the wiring (short circuit, ground leakage) or a fault directly in the boiler. In that case, don't keep resetting it – call an electrician.
The RCD (residual current device) is more sensitive – it reacts to ground leakage in the order of milliamps. It can trip, for example, due to moisture condensation in the boiler after a long shutdown, or if a heating element has a micro-crack in its insulation. Here, professional diagnostics is recommended.
Problem with the Supply Terminals
During installation, especially if performed by someone inexperienced, terminals sometimes aren't tightened enough. The screw connection loosens due to thermal cycles, and after a while the contact fails. A visual inspection of the terminal block (with the breaker switched off!) will reveal any burn marks or loosening.
Frost Protection – Accidental Activation
Some ELÍZ models have a frost protection function that activates the pump or a low-heat mode at low temperatures. If the boiler appears "dead" but is actually running in this protective mode, the display may indicate it with a special symbol. Check the manual for your model.
2. The Boiler Is Running, but the Water in the Radiators Isn't Hot
The boiler is switched on, the pump is humming, but the radiators are cold or lukewarm. This is the second most common scenario and usually has a solution without a service intervention.
Air in the System
This is a classic. Air enters the system during initial filling, after pipe repairs, or through an expansion tank that has lost its pre-charge pressure. An air pocket settles in the radiators (usually in the upper part) and blocks the water flow. Result: the radiator is cold at the top, lukewarm at the bottom. The solution is simple – bleed the radiators with a bleed key. Open the valve on each radiator until a steady stream of water flows (not air).
Note – after bleeding, the system loses water, so the pressure needs to be topped up (see the section on pressure loss below).
The Thermostatic Radiator Valve Is Closed
It sounds trivial, but it happens in practice: someone closed the thermostatic valve on the radiator (turned it to minimum or to the "*" – frost-protection position) and forgot about it. The radiator is then cold even with a fully functioning boiler. Check the valves on all radiators.
Low-Heat Control Mode
If the boiler is set to a night setback or a low target temperature (for example, 15 °C), it heats the water only enough to reach this temperature. The radiators are therefore lukewarm – but intentionally. Check the controller settings and see whether you're in setback mode.
Clogged Pipe or Blocked Filter
In older systems, sludge and rust settle in the water. The ELÍZ boiler usually has a built-in ball valve, and a magnetic or mesh filter (Y-filter) should be installed in series. If the filter is clogged, the flow drops below the minimum and the boiler either shuts down protectively or simply can't keep up heating the water. Check the filter and clean it if necessary.
3. The Boiler Shuts Off by Itself – Safety Thermostat (STB)
The safety thermostat (STB – Sicherheits-Temperatur-Begrenzer) is a safety element that shuts off the boiler when the maximum water temperature is exceeded (typically 90–95 °C). Unlike the working thermostat, it must be manually reset – it doesn't reset itself.
STB reset procedure on ELÍZ boilers: Find the reset button (usually red, under a cover on the front panel or on the side of the boiler). Hold it for 3–5 seconds until you hear a click. The boiler should start up.
But be careful – a reset alone is not enough. The STB didn't trigger on its own. Always find the cause:
- Low water flow – air in the system, clogged filter, closed valve, faulty pump. The water doesn't move, and the heating element overheats it.
- Faulty circulation pump – the pump hums but doesn't turn (jammed rotor). Try releasing the rotor manually according to the manual (usually via a screw on the pump shaft).
- Incorrectly set working temperature – if the boiler is set to the maximum temperature (80–85 °C) and the flow is slower, the STB can trigger during normal operation. Lower the set temperature to 65–70 °C.
- Faulty working thermostat – if the working thermostat doesn't work, the boiler heats continuously until the STB activates. A service intervention is necessary here.
4. Drop in System Pressure – Boiler Reports Low Pressure
The ELÍZ electric boiler operates in a closed pressure system. The correct operating pressure is typically 1.0–2.0 bar (depending on the building's height and system size). If the pressure drops below the lower limit (usually 0.5–0.8 bar), the boiler shuts down protectively or won't heat.
Causes of Pressure Drop
Under normal circumstances, a closed system would not lose pressure. If pressure is dropping, water is escaping somewhere. Check for:
- Visible leaks – check all joints, the boiler casing, radiators, valves. A wet spot or limescale around a joint will reveal the leak location.
- Safety valve – if the safety valve is opening (dripping or discharging from the drain hose), the system had excessive pressure, the valve released water, and now there's a pressure deficit. Check why the pressure was rising – likely a faulty expansion tank.
- Expansion tank with lost pre-charge pressure – the expansion tank has a valve on the back (like a tire valve) with a pre-charge pressure typically of 0.75–1.0 bar. If the rubber membrane has burst or air has escaped, the tank no longer performs its function – pressure rises too much when heating, the safety valve opens and discharges water, and when cooling, the pressure drops. Measure the pre-charge pressure, and if it's zero, the tank is faulty.
- Micro-crack in a heating element – a rarer but serious problem. Water seeps through a cracked heating element into the insulation. You see nothing on the pipes, but the pressure drops. Diagnosis requires an expert.
Topping Up Pressure
On ELÍZ boilers, pressure is topped up via a filling valve (bypass valve) that connects the system to the domestic water supply. Open it, watch the manometer, and close the valve once you reach 1.2–1.5 bar. Never top up while hot (hot water expands and the pressure on the manometer drops after cooling). Always top up with a cold system.
5. The Boiler Is Noisy – Banging, Gurgling, Whistling
Sounds are a good diagnostic tool. Each type of sound tells you something different:
Gurgling and Bubbling
A typical sound caused by air pockets in the system. Air and water mix in the pipe and produce characteristic sounds, especially when the pump pushes water through an air pocket. Solution: bleed the entire system, including automatic air vents.
Loud Banging (Water Hammer)
Water hammer occurs when valves close suddenly (thermostatic valves with a spring-loaded head, fast electromagnetic valves). The column of water stops abruptly, and the energy manifests as a bang against the pipe wall. Solution: install water hammer arrestors, replace overly fast valves with slower ones, check the expansion tank pre-charge pressure.
Pump Whistling
If the pump whistles or vibrates, it may have a worn bearing (common after 8–12 years of operation). Sometimes changing the speed helps (most pumps have 3 speed settings). If not, the pump needs to be replaced.
Cracking of Heating Elements
During initial heating or after a longer pause, heating elements may crack (thermal expansion of limescale). If the water is hard (above 20 °N), limescale settles on the heating elements, reduces their efficiency, and causes cracking. Solution: a water softener or regular descaling according to the article Maintenance and Service of the ELÍZ Electric Boiler: How to Extend Its Lifespan.
6. Incorrect Temperature – Boiler Can't Reach the Desired Value
The boiler is running, but the room temperature is lower than what you set. This is a complex problem with several possible causes.
Undersized Output
If the boiler was sized for the building's original condition (before insulation was added, or conversely after an extension) or was chosen without a professional calculation, it may simply have insufficient output. As a rough guide – 1 kW covers roughly 10–15 m² of a well-insulated house. This is covered in more detail in the topic What Output of the ELÍZ Electric Boiler Do I Need for My House. Some models, such as the ELÍZ EQH 802, have adjustable output, allowing for finer control.
Incorrect Weather Compensation Curve
ELÍZ boilers with weather-compensated control set the heating water temperature based on outdoor temperature. If the curve is set too shallow, the boiler can't keep up during frost. The controller needs to be optimized – details in the article Setting and Programming the Controller of the ELÍZ Electric Boiler.
Building Heat Losses
Sometimes the problem isn't the boiler, but the house. An uninsulated roof, old windows, a cold floor – all of this increases heat losses, and the boiler simply can't keep up. Thermal measurements should precede any inspection.
7. Error Codes on the ELÍZ Display
Modern ELÍZ boilers display error codes (E-codes) on the screen. You'll find the exact list of codes in the manual for your specific model, but here are the most common types:
- E1 / Er1 – outlet water temperature sensor fault. The sensor may be disconnected, damaged, or out of range. Check the sensor connector. NTC sensors are cheap and easy to replace.
- E2 / Er2 – return pipe temperature sensor fault. Same procedure as E1.
- E3 – safety thermostat (STB) tripped. Reset according to the procedure above, then find the cause.
- E4 – low water pressure. Top up pressure to 1.2 bar, check for leaks.
- E5 – communication fault between the controller and the control board. Usually requires a service intervention or controller replacement.
- E6 / E7 – outlet water maximum temperature exceeded. Check the flow and the working thermostat setting.
If the error code recurs after every reset, don't just keep resetting it. A recurring code is a sign of a systemic fault.
8. Control and Programming Issues
The ELÍZ electric boiler usually has a built-in digital controller with a weekly program. Setting errors in the control system are very common, especially after a power outage, when the clock and program settings get reset.
Incorrect Time and Date After a Power Outage
After a power outage, the internal clock resets on most ELÍZ boilers. The boiler then starts heating at "wrong" hours or not according to the program. Always check and set the time and program after an outage.
The Boiler Doesn't Heat According to the Set Program
Common causes: an incorrectly set daily program (for example, set for summer time in winter), an activated manual override (forced operation), or an external thermostat that's blocking the boiler. Check whether you have an active "holiday mode" that keeps the system only in frost-protection mode.
Conflicts With an External Thermostat
If you have an external room thermostat installed (connected to the boiler's contacts), it must be configured correctly. Common mistakes: reversed terminals, a missing jumper in a direct connection, or a thermostat with open contacts in case of a fault. If the boiler doesn't respond to the temperature setting, disconnect the external thermostat and bridge the contacts – if the boiler starts up, the problem is in the thermostat.
9. Electrical and Safety Faults – When to Call a Professional
There are faults that a layperson should not try to solve themselves. These include:
- Repeated tripping of the RCD (ground leakage, insulation fault of a heating element)
- Burnt or charred terminals, a burning smell in the boiler
- Fault in the control board (display doesn't respond, no reaction to any input)
- Replacement of a heating element (requires draining the system and electrical work)
- Replacement of the circulation pump
- Any intervention requiring the opening of a sealed part of the boiler
Heating elements in ELÍZ boilers are standardized components (threaded fitting or flange type), so replacing them isn't technically complicated – but it requires draining the system and working with electrical equipment. For boilers like the ELÍZ EQH 802, replacement heating elements are readily available.
10. Preventive Care – How to Prevent Faults
Practical experience shows that customers who dedicate an hour a year to their boiler deal with far fewer faults than those who don't open the boiler at all during the entire season. Here is the minimum annual check:
- Before the season (September): Check the pressure in the cold system (should be 1.0–1.2 bar). Bleed the radiators. Check the expansion tank's pre-charge pressure (with the boiler disconnected, system pressurized).
- Visual inspection: Inspect all pipe joints, the boiler, valves. Wet spots, white limescale = a leak.
- Filter: Clean the magnetic or mesh filter. In hard water areas, do this twice a year.
- Pump: Check that the pump isn't "seized" after summer shutdown. Run it briefly in manual mode.
- Safety valve: Very carefully (watch out for hot water!) verify its function using manual operation. If it drips on its own, replace it.
More information about preventive maintenance can be found in the topic Maintenance and Service of the ELÍZ Electric Boiler: How to Extend Its Lifespan.
Frequently Asked Questions (FAQ)
My ELÍZ boiler won't start after a power outage – what should I do?
After a power outage, go through a basic check: 1) Check the circuit breaker and RCD in the distribution board – reset them if tripped. 2) Check the display – if it shows an error code, identify it using the manual. 3) If the code is E4 (low pressure), top up water in the system. 4) Set the correct time and control program. If the boiler still doesn't work after these steps, call service.
Why is my ELÍZ boiler losing pressure even though I don't see any leak?
The most common cause of an "invisible" leak is the safety valve – it discharges water into the drain via a hose when pressure is excessive, and the pressure then drops upon cooling. Check the safety valve's discharge hose – if it's wet or dripping, you have your answer. The second cause is a worn expansion tank membrane.
The safety thermostat (STB) keeps shutting off my ELÍZ boiler – how do I fix it permanently?
Resetting the STB is a temporary solution. You must eliminate the cause: check that the pump is actually moving water (touch the pipes – the outlet should be warmer than the return pipe), bleed the system, check the filter. If the flow is fine and the STB keeps triggering, the working thermostat is probably faulty and the boiler is heating without regulation – that's a case for service.
My ELÍZ boiler's heating elements keep cracking – is this a serious fault?
Cracking of heating elements is not, by itself, a critical fault, but it's a sign that limescale is building up on them (usually with hard water above 15–20 °N). Limescale reduces efficiency, increases power consumption, and can lead to overheating and cracking of the elements. Chemical descaling according to the manufacturer's procedure is recommended, or installing a water softener at the boiler's inlet.
Can excessive pump noise indicate a fault?
Yes. During normal operation, the pump should hum quietly. Whistling, vibration, or rattling are signs of: a worn bearing (especially after 8–12 years), cavitation (air in the pump), or too high a pump speed relative to the system flow. Try reducing the speed by one setting. If that doesn't help and the boiler is more than 10 years old, consider preventively replacing the pump.
Can I connect the ELÍZ boiler to a photovoltaic system and use surplus electricity for heating?
Yes, this is technically possible and an economically interesting solution, but it requires proper wiring and control. This topic is covered in detail in the article ELÍZ Electric Boiler and Photovoltaics: Is the Combination Worth It. The boiler must have an input for an external consumption controller (for example, a 0–10 V or PWM input) or must be connected via a special surplus-power controller.
Conclusion and Summary
The ELÍZ electric boiler is a reliable device that, with proper installation and minimal annual maintenance, can operate trouble-free for a decade or more. Most faults that seem serious have a simple solution – a tripped breaker, air in the system, low pressure, or poor control settings. An experienced user can resolve most situations themselves using these steps.
On the other hand, some faults – repeated RCD tripping, a control electronics fault, heating element replacement, or insulation problems – belong in the hands of a professional. Don't be afraid to call a service technician if you're unsure. A cheaper repair now can prevent a much more expensive breakdown later.
If you're still at the selection stage, we recommend checking out the topic How to Choose an ELÍZ Electric Boiler: What to Focus On Before Buying, or take a look at the specific model ELÍZ EQH 802, which combines good output with practical control and is one of the best-selling models in this category.
Do you have a question on this topic?
Can't decide or are dealing with a specific situation in your household? Write to us - we'll be happy to help.