The hob should be installed in accordance with the electrical connection requirements, described in the instruction book. All work should be done by a competent person. If you have just installed the product and find that only one of the cooking rings is heating up, the possible cause may be due to an electrical connection issue. Please contact your installer to check the wiring to the electrical supply.
If you have been using the hob for some time and this fault has suddenly developed then please contact us for further advice.