Kay
Acknowledgement: Ban Ban Music Limited
Electric water heater is a commonly used household electrical appliance. The major types of electric water heaters available in the market include instantaneous, shower type (also known as low-pressure storage type or open type) and unvented thermal storage type (also known as high-pressure storage type). A typical shower type electric water heater is equipped with cold and hot water pipes, a mixing faucet, a shower head and thermostat-controlled heating element, as well as a thermal cutout. Although this type of water heater is provided with appropriate safety devices, fire incidents involving these electric water heaters did occasionally occur in the past. Investigation reveals that the main cause of the incidents is improper installation and lack of maintenance.
Shower type electric water heaters in general are designed for taking showers, but some people divert the hot water to wash basins. This modification requires the addition of normal on/off control valves which turn out to be the prime cause of accidents.
The mixing faucet of a shower type electric water heater is not a normal valve. The red knob shown in Figure 1 controls the amount of hot water discharged by the water heater, and is installed at the cold water inlet of the water heater. There is no valve at the hot water outlet of the water heater. When the red knob is turned on, cold water will enter the storage tank from the bottom. The cold water displaces the heated water through the outlet pipe at the top of the water heater, and hot water flows out through the shower head. If the user feels that the temperature of hot water is too high, he may turn on the blue knob shown in the figure, so that cold water enters the mixing faucet outside the water heater and mixes with hot water. This allows the water temperature to be adjusted as desired by the user.
When the water heater is in standby condition (i.e. when the red and blue knobs are turned off), and the water inside the storage tank is being heated, the water undergoes slight thermal expansion. As there is no normal control valve between the mixing faucet and shower head, the pressure inside the storage tank will be released through the shower head. As such, a small amount of water droplets may come out from the shower head during the heating of water inside the storage tank. This is normal and should not be taken as a sign of water leakage. Do not install a normal valve at the outlet just because of this.
If a normal control valve is added at the outlet of the water heater and if there is a fault in the thermostat, the heating element will go on heating the water and the pressure built up inside the storage tank cannot be released. Should the thermal cutout fails to disconnect the power supply, the storage tank may not be able to withstand the increasing pressure and this will result in a burst. To ensure safety, do not add any on/off control valve at the outlet of a shower type electric water heater; and do not connect the outlet pipe of a shower type electric water heater to a wash basin or bath tub, lest the outlet pipe will be blocked, leading to excessive pressure being built up inside the water heater and the occurrence of accident.
The associated water pipes and the fixed electrical installation of the electric water heater (including shower type electric water heater) should be respectively installed by a licensed plumber and a registered electrical worker (REW). When installing the fixed electrical installation of the shower type electric water heater, the REW, apart from effectively earthing the water heater, should also check whether the electric water heater operates properly (including the function of the thermostat) and remind the user not to switch to any non-genuine open type mixing faucet and shower accessories or add any on/off control valve at the outlet of the water heater. When carrying out maintenance work on a shower type electric water heater, the REW should follow the manufacturer’s instructions. He should in particular check whether the fixed electrical installation and pipes are properly installed and whether the thermostat operates normally. If necessary, he should also consult the relevant agent or manufacturer. In case the REW finds that the outlet pipe is not properly installed, he should advise the user to appoint a licensed plumber to fix the problem immediately so as to prevent accidents.
EMSD attaches great importance to the personal safety of registered electrical workers (REWs) conducting electrical work and exercise strict regulation on safety requirements for electrical work. When carrying out electrical work, registered electrical contractors (RECs) and REWs should comply with the requirements set out in the 2009 edition of the Code of Practice for the Electricity (Wiring) Regulations. They should cut off the power supply of the electrical installations and apply suitable safety precautionary measures before carrying out the electrical work.
To ensure the electrical work is carried out in a safe environment, the upstream switch or circuit breaker must be switched off and isolated before the electrical work is carried out. If the switch or circuit breaker is equipped with a locking mechanism, lock off the circuit breaker or switch, and display securely an appropriate warning notice to prevent accidents caused by the switch or circuit breaker being inadvertently turned on during the electrical work.
Furthermore, for the safety of the electrical workers, RECs should cut off the power company’s electricity supply before carrying out periodic inspection and testing for the main switchboard, and ensure that the electrical work is carried out after the electrical installations are isolated. In submitting periodic test certification for endorsement on or after 1 December 2011, the power company’s record for power suspension shall also be submitted for vetting.
For power suspension arrangement for electrical work and other details, please visit the EMSD website.
The Electricity (Registration) Regulations requires that registered electrical workers (REWs) and contractors (RECs) should submit to EMSD applications for renewal of registration at least 1 month in advance, but no more than 4 months before the expiry date of the current registration. All REWs and RECs are reminded again to submit their renewal applications within the above-mentioned period. Applications submitted after the expiry date of the current registration will be treated as new registration applications, and will be assessed in accordance with the statutory requirements of the day. These include requiring REWs to possess recognised academic qualifications in electrical engineering and electrical work experience. If the applicant does not possess the required academic qualifications and is thus considered to be unable to fulfil the relevant registration requirements, the application will be rejected regardless of the previous registration history of the applicant.
In addition, the renewal of registration will be effective from the date of approval. Any electrical worker or contractor who carries out electrical work or undertakes business as an electrical contractor during the period from the expiry date of the certificate of registration to the day before the effective date of the renewal of registration commits an offence and shall be liable upon conviction to imprisonment for 6 months and a fine.
According to section 36 of the Electricity Ordinance, the Director of Electrical and Mechanical Services can take disciplinary action against a registered electrical worker or registered electrical contractor who fails to comply with the requirements of the Ordinance.
The record of disciplinary action taken against registered electrical workers and registered electrical contractors from January to August 2011 is available at EMSD website.
To enhance the standard of Registered Electrical Workers (REWs), the Continuing Professional Development (CPD) Scheme for REWs will be included as a requirement for renewal of registration starting 1 January 2012. According to the CPD Scheme, all REWs are required to have completed two modules of training, including Module 1: Legislative and Safety Requirements and Module 2: Technical Knowledge, before submitting their renewal application.
REWs may meet the training requirement under the CPD Scheme by taking any one of the following options:
Upon receiving a renewal application from an REW, EMSD will check the relevant CPD training record of the applicant before processing the renewal application.
For information on the courses of the CPD Scheme and other details, please visit the EMSD website.
All competent persons engaged in the detection of electricity cables should note the expiry date of their Certification of Approval. If their certificate is due to expire soon, they should apply for renewal of approval as soon as possible. To meet the renewal requirements, they should, within the period of 3 years immediately preceding the application, have had not less than 3 months' practical experience in locating underground electricity cables.
Application for renewal of approval as a competent person should be made at least one month in advance, but no more than 4 months before the expiry of the current approval. A renewed approval shall be valid for a further period of three years after the expiry date of the current approval. Applicants should note that if they fail to submit the renewal application within the designated period, they are required to submit a new application with the relevant supporting documents.
Applicants for renewal of approval should submit (1) application form CPA1, (2) certificates of services or employment and (3) three underground electricity cable detecting reports. Application form CPA1 can be obtained from:
Customer Services Office, G/F, EMSD Headquarters, 3 Kai Shing Street, Kowloon Bay;
District Offices;
Government Forms Website of the Government of the Hong Kong Special Administrative Region.
Submission of the completed application form can be made in person at the Customer Services Office, G/F, EMSD Headquarters during office hours.
Applicants can also submit their application through the following methods:
The General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ) and EMSD held the eighth annual general meeting on the Cooperation Arrangement on Electrical and Mechanical Products Safety and the associated working group meetings in the Headquarters of EMSD from 19 to 20 April 2011.
A 13-member delegation from AQSIQ led by Mr. WANG Xin, Director General of the Department of Supervision on Inspection, attended the meeting in Hong Kong. By our arrangements, members of the delegation attended the general meeting and the working group meetings, as well as paying a visit to Commerce and Economic Development Bureau and going on study tours to the relevant product safety testing laboratories, CLP Energy Efficiency Exhibition Centre, gas installations and amusement rides facilities, etc., to learn more about the work on electrical and mechanical safety and energy efficiency in Hong Kong.
The annual meeting was chaired by Mr. CHAN Hung-cheung, Director of Electrical and Mechanical Services, and Mr. WANG Xin, Director General of the Department of Supervision on Inspection, AQSIQ. At the meeting, members reviewed the work over the past year. Through the efforts of the four working groups on electrical products, gas appliances, lifts and escalators and energy efficiency, close liaison was maintained and work plans were successfully drawn up and implemented. Good progress was made on various cooperation items, including the reporting of non-compliant products, technology exchange and training, certification and examination, etc., and the set targets were met. Heads of both sides were fully satisfied with the results of cooperation over the years and agreed to further extend the Cooperation Arrangement to 2015 at the annual meeting.
The annual meeting was held with great success. The thorough discussions and exchanges on topics of mutual interest conducted and the numerous constructive ideas expressed have produced fruitful results. The contributions made by both sides to the Cooperation Arrangement have further strengthened the foundation of cooperation on electrical and mechanical product safety and energy efficiency, facilitating the development of more new project items and active study on the new direction of cooperation.
Many trade members may well be aware of the term "concealed cables", which generally refers to unarmoured (i.e. not protected by a conduit) electric cables embedded in a concrete structure (e.g. a wall).
When the Electricity (Wiring) Regulations and the Code of Practice for the Electricity (Wiring) Regulations came into effect in 1992, normal PVC cables concealed within a wall are required to be enclosed in conduit, trunking or ducting, or mechanically protected as appropriate, so as to prevent penetration of the cable by nails or drill, etc. (Please refer to 15E of the Code of Practice for details.)
Use a metal detector to locate the position of the cable or pipe concealed in wall
Although the concealed cables are covered by insulating material and also protected by the circuit, it is undeniable that the old concealed cables carry with them a certain amount of risk. Accidental penetration of the cable by nails, screws and the like during works (e.g. renovation works) is the main risk, which may result in electric shock or flashover. To prevent the occurrence of such accidents, we would like to remind trade members to control the risk of damaging the concealed cables through proper work procedures, e.g., cutting off the power supply and using a metal detector to identify the location of the concealed cable before commencement of works.
Please be also reminded that appropriate enforcement action will be taken against unlawful installation of concealed cables or cases of non-compliance involving unsafe work procedures. Registered Electrical Workers and Registered Electrical Contractors contravening the provisions of the above Code of Practice will be liable to disciplinary action.
The Annual Technical Seminar is well-received by the electrical trade
The Eleventh Annual Technical Seminar will be held on 25 November 2011 (Friday) at 7:00 p.m. at the Jockey Club Auditorium of the Hong Kong Polytechnic University. Taking place on the same occasion is the prize presentation ceremony for the Outstanding Safety Performance Awards for Electrical Worker. Persons who are interested in attending the seminar may obtain admission tickets at the branch offices of the Hong Kong and Kowloon Electrical Engineering and Appliances Trade Workers Union (Tel: 2626 1927), or download ticket request forms from our website. Completed forms should be returned to the Electricity Legislation Division by fax or mail (Fax: 2895 4929 Address: 7/F, EMSD Headquarters, 3 Kai Shing Street, Kowloon) before 11 November 2011. Successful applicants will be notified by fax or email before 18 November 2011. Registered electrical workers attending all sessions of the seminar are deemed as having completed Modules (1) and (2) under the Continuing Professional Development Scheme for Registered Electrical Worker.
Ticket request forms may be downloaded at Seminars for Members of the Electrical Trade.
1. |
According to the 2009 edition of the Code of Practice for the Electricity (Wiring) Regulations, a schematic wiring diagram showing the main distribution system should be displayed near the main switch with rating of ________ or above. |
|
2. |
According to the 2009 edition of the Code of Practice for the Electricity (Wiring) Regulations, for Category 1 circuits, what is the minimum cross-sectional area of live conductors for surface wiring using PVC insulated PVC sheath copper cables? |
|
3. |
According to the 2009 edition of the Code of Practice for the Electricity (Wiring) Regulations, the construction and protection of electrical equipment and wiring of electrical installations exposed to potentially explosive atmospheres should adhere to which of the following standards in order to meet the requirements specified for hazardous areas? |
|
4. |
What dreadful consequences may result if an on/off control valve is indiscriminately installed at the water outlet of a shower type electric water heater? |
|
5. |
The digging of trial holes by competent persons engaged in the detection of underground electricity cables is for _______________________.i. facilitating excavation.ii. exposing the target underground electricity cables. iii. soil survey. iv. carrying out active detection to confirm the location and depth of unexposed underground electricity cables. |
|
( Ans: 1A, 2B, 3C, 4C, 5C )
We look forward to receiving your valuable feedback about this newsletter for continuous improvement. Please complete the feedback form below and return it to our Electricity Legislation Division by post, fax or e-mail on or before 30 Nov 2011 (please refer to the contact information at the bottom of this page).
Electricity Legislation Division, EMSD, 3 Kai Shing Street, Kowloon, Hong Kong
1823
2895 4929