Performance of 60% of Electric Storage Water Heaters Lower than Labelled – Product Quality in Need of Improvement

15 October 2018
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Performance of 60% of Electric Storage Water Heaters  Lower than Labelled – Product Quality in Need of Improvement

Electric storage water heaters are common in household, their safety and stable supply of hot water are of utter importance.  The Consumer Council, in collaboration with the Electrical and Mechanical Services Department (EMSD), have put to test 12 models of household electric storage water heaters to compare their safety and performance.  All models passed their principal safety test items.  But among the 10 models participating in the EMSD’s Voluntary Energy Efficiency Labelling Scheme (VEELS), 6 were measured with grading lower than the marked energy efficiency grading label, and the discrepancy found in 3 of the models exceeded the permissible limit.  The disappointing test results have been referred to the EMSD for follow-up.  Furthermore, their performance in preheating time and maximum time of hot water delivery also varied considerably among the models.  The variations on the average temperature of hot water delivery reached as much as 20°C.   In particular the Council is deeply concerned about the energy efficiency was lower than the grade displayed on the product energy label.  This could effectively result in consumers making a wrong purchase decision based on inaccurate information. In addition, the Council strongly urges manufacturers to enhance their product performance and quality to meet consumers’ expectations.

Included in the 12 test models, rated power input of 3,000 watts priced between $2,580 and $6,130 with basic installation service inclusive, 6 unvented type models with possible multiple water outlets connections including 3 water heaters with rated water capacity of 22.7 to 25L, and the rest with 38L; and 6 others were of the shower type which can connect to shower head only without other water outlet connection including 3 models with rated capacity of 18L and the remainders of 23 to 25L.  Among the models 11 were single-tank models (with 1 heating element) and 1 double-tank model (2 water tanks connected by an internal water pipe). 

The performance test for the models was conducted in reference to IEC 60379 and the current Voluntary Energy Efficiency Labelling Scheme.  Excluding 1 single-tank model which did not participate in the labelling scheme and 1 double-tank model, 6 in the remaining 10 single-tank models were found with the calculated energy efficiency grading lower than the grade marked on the energy label, and among them 3 had standby power consumption higher than the value marked on the label by 30% or more, far exceeding the scheme’s permissible limit of 10%, the situation is of utmost concern.

In accordance with the third phase of Voluntary Energy Efficiency Labelling Scheme grading standard, only 1 model out of the 11 single-tank models achieved Grade 1 energy rating.  4 models were measured with the lowest energy rating of Grade 5. EMSD has included electric storage water heaters in the third phase of the Mandatory Energy Efficiency Labelling Scheme effective from 1 June this year. The regulations on energy efficiency performance have been strengthened and tightened in terms of standby power consumption and water capacity, in line with market development. Manufacturers are required to submit necessary certificates and test reports to the EMSD, and after the grace period of 18 months, mandatory energy label must be displayed on the models to assist consumers to compare the energy efficiency between models.

When using electric storage water heaters, the power supply must be turned on in advance, so as to enjoy a hot water bath after stored water was preheated, and if there are quite a few family members in need of taking bath during the same time period, special attention should be paid to the length of preheating time. The test measured the time required to heat up stored water from 15°C to 65°C, in which only the 18L shower type water heaters, used 15 minutes while for those of bigger capacity of 23L or above, the preheating time was between 18 and 20 minutes.   For the unvented type models, the preheating time was 18 to 24 minutes with those of 23-25L capacity, and for the models with bigger capacity of 38L, the preheating time spanned from 29 to 36 minutes.  

The test also found varying performance in the average temperature of hot water delivery when the thermostat was set at 65°C, only 2 of the samples could achieve average water temperature above 60°C.  In the case of the shower type water heaters, the average temperature of hot water delivery was 46-60°C, a difference of 14°C between the best and least performers.  In the case of the unvented type water heaters, the average temperature was between 42 and 64°C, with a difference of over 20°C.

In additional to reference to respective international testing standards, the Council simulated the general use of consumers to measure the hot water delivery time. On the maximum time of hot water delivery the samples were tested under the conditions of water flow rate of 5L per minute, the hot water delivered at around 45°C and dropped to 40°C. The result showed 3 shower type samples with bigger capacity could maintain the time of hot water delivery for 7.2 to 9.8 minutes; and for the 3 samples of capacity 18L, none could last more than 4.5 minutes.  In the case of the 38L unvented type water heaters, all could achieve hot water delivery for over 9 minutes, but 3 others with smaller capacity, they lasted only 5.5 to 6.5 minutes.  Consumer should pay heed that regardless of the capacity of both unvented type and shower type water heaters, their maximum time of hot water delivery was not more than 10 minutes.

Based on their standby power consumption, the samples were computed for their annual standby electricity costs.   Assuming the annual standby time to be 1,800 hours, i.e. around 5 hours per day, and at electricity tariffs of $1.2 per unit, the unvented type of smaller capacity would cost $59-$109 and of the bigger capacity samples $78-$94. Among the shower type models, those with smaller capacity, the annual cost was estimated at $64-$70, and models of bigger capacity $53-$74.  Consumers are reminded that if the electric storage water heaters are habitually kept on for preheating, the actual electricity costs may even be higher, consumers are advised to switch off the appliance after use to ensure safety and cost savings.

Consumers choosing electric storage water heaters should pay heed to the following:

- The installation or modification of electric storage water heaters should be carried out by registered electrical contractors and licensed plumbers;
- The water outlet pipe of shower-type electric water heater must be kept un-obstructed, and should only be connected to shower head without an on/off control valve. Never connect the water outlet pipe with any on/off control valves or to other wash basins or bathtubs, to avoid building up pressure in the water tank and resulting in explosion;
- If circuit breaker tripping happened in the course of usage or unusual emission of steam from the shower head or pressure relief valve drain pipe, consumers should stop using the water heater immediately and arrange for repair;
- Electricity supply of the electric water heaters should be turned off after use to save energy.

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