HomeDangerous Water Heater Alert
Portable “travel” immersion water heaters are widely available online and are sometimes brought into workplaces, schools and shared accommodation. From a PAT testing perspective, these products present a significant risk. Although they appear simple and effective, their construction allows mains voltage to be present directly in the water, creating a serious electric shock hazard.
This case study underlines the importance of formal visual inspection and shows that where inherent design or construction faults are identified, the item should be failed and not subjected to further testing.
These products should be treated as immediately unsafe and failed on visual inspection during PAT testing.
What To Do If Found During PAT Testing
- Fail on formal visual inspection and record the reason clearly (e.g. “Unsafe live-electrode water heater – exposed mains voltage in water”).
- Remove from service immediately. Do not permit further use.
- Do not proceed with full electrical testing. Where construction is inherently unsafe, further energised testing may expose the person carrying out the inspection to unnecessary risk.
- Report to the duty holder or responsible person. Management must be made aware of the risk and take appropriate action.
- Review workplace policy on personal electrical equipment. Consider whether personal electrical items should be restricted or subject to stricter controls before use.
These types of products highlight the importance of effective management controls. For more information, see our guide to Managing PAT Testing in the Workplace.
Inspection and Electrical Test Results
We've carried out inspection and testing on this example to demonstrate the level of risk involved. However, if these are found during PAT testing, they should be failed on formal visual inspection and immediately removed from service. They should not be subjected to electrical testing, as this could expose the person carrying out the test to unnecessary risk, particularly during a leakage test.
This example was marketed as a “Portable Travel Hot Water Heater Immersion Element”. The listing description included pseudo-technical wording which is often a red flag for poor product compliance.
The heater consists of a plastic housing with two metal plates separated by a gap of approximately 5 mm. The supply cord is two-core 0.5 mm2, fitted with a NEMA-type plug. The metal plates are directly connected to the mains supply, meaning the water effectively becomes part of the live circuit during operation.
The portable heater is extremely effective and very quickly brings a cup of water to a boil.
An insulation resistance test was carried out using a PAT tester. A metal spoon placed in the water was used as the accessible conductive test point. The measured insulation resistance was 0.01 MΩ, the lowest range of the instrument. This extremely low value indicates that the two metal plates inside the plastic housing are effectively acting as exposed electrodes connected to the mains supply.
With insulation resistance at this level, a standard leakage test would be expected to trip a 30 mA RCD. For this reason, a substitute leakage test was performed instead, which produced a reading greater than 19.99 mA, the upper limit of the PAT instrument’s measurement range.
Because the substitute leakage current exceeded the instrument range, touch current was measured directly using a multimeter. A 2 kΩ resistance (2 × 1 kΩ resistors) was connected between the metal spoon and neutral to simulate the impedance of the human body while preventing RCD operation. Although body impedance varies depending on conditions, IEC research indicates that 95% of the population have a body impedance of approximately 2125 Ω at 220 V. The measured touch current at the spoon was 54 mA, well above typical safety limits and capable of causing a severe electric shock.
| Current (mA) | Effects on the body |
|---|---|
| 1.5 | First noticeable sensation |
| 2.5 | Tingling in palms |
| 5 | Cramp starts |
| 7.5 | Hands stiffening, 'let go' still possible |
| 10 - 15 | Cramp increases; limit of 'let go' |
| 25 - 30 | Severe cramp extending to the thoracic region |
| 30 - 50 | Increase in blood pressure; heart irregular |
| 50 - 60 | Respiratory system affected; loss of consciousness |
| 60 - 75 | Lower threshold of heart fibrillation |
For further information on the physiological effects of electric current on the body, see our article on electric shock and current effects.
Similar Live-Electrode Kettle Design
Further research identified a kettle using the same live-electrode water heating method. An example is demonstrated in the video Inside a dodgy Turkish "stinger" kettle by bigclivedotcom.
This type of kettle is available for purchase via online marketplaces. The accompanying instructions include warnings such as: “When the plug is in the socket, do not put your hand in the appliance or in the water remained in the appliance” and “Never use a metal spoon.” The product is also supplied with a plastic spoon, presumably intended to reduce the likelihood of contact with water that may be at mains potential
Touch current was measured using the same method described previously: a clamp meter and a test lead incorporating a 2 kΩ resistance connected to a metal spoon immersed in the water. The measured touch current was 52 mA, comparable to the earlier portable immersion heater and well in excess of accepted safety limits.
Conclusion
These examples demonstrate how non-compliant electrical equipment can find its way into the workplace, particularly in environments such as schools, shared accommodation and offices where individuals may bring in personal items. Products purchased from online marketplaces or overseas suppliers may not meet UK safety standards, even if they appear to function correctly.
Typical warning signs include unbranded or unfamiliar manufacturers, missing or poorly formed conformity markings, absence of a proper rating plate, non-UK plug types used with adaptor plugs, unusually lightweight construction, or unrealistic technical claims in the product description. Extremely low purchase price is often another indicator of potential non-compliance.
Live-electrode water heaters represent an obvious electric shock hazard and should be failed immediately on formal visual inspection. More generally, these examples reinforce an important point: electrical testing alone is not sufficient. A thorough and informed visual inspection remains the most effective way of identifying dangerous or counterfeit equipment during PAT testing.
For further examples of unsafe and non-compliant products encountered during inspection, see our page on counterfeit and dangerous electrical equipment.