CHS_LHS

30366461EN-08 13 LU-VE Group reserves the right to change specifications without prior notification. Î Heavy frost build up on the fan guards can hinder the cold air flow over the motors and lead to overheating and burning of the motors. EC fan and motor assemblies are not designed for replacement or servicing of individual parts. Replace only as a complete assembly. Where fan guards or portions of the casing have had to be removed for inspection, ensure that these items have been refitted and secured correctly before restarting the heat exchanger. We recommend that a "Permit to Work" system be used to carry out all maintenance work, to ensure that only properly qualified staff carry out the work and that other staff on the site are made aware of the safety aspects related to the heat exchanger. 4.6 Shut down periods During prolonged shut down periods, maintenance should be carried out as detailed above. If the shut down period is extended, all electric motors should be run once every four weeks for a minimum of 4 hours. EC fans must be kept powered during shut down periods to ensure that the motor heating prevents the rotor from freezing. 4.7 Electric defrost Should heavy frost or ice remain on the finned coil after a regular defrost cycle, the following procedure should be carried out: Î Commence manual electric defrost and check each heater element using 'clip on' ammeter instrument. A phase amperage reading at the control panel is not sufficiently accurate. Any heater element found to be not working should be checked for electrical connection faults and if found to be defective it should be replaced (see additional notes on replacement of electrical heater elements). • The ice should be removed from the finned block and from the drain tray. This process can be speeded up by covering fan apertures/guards and discharge outlet with polythene sheeting, etc. It may even be necessary to use warm water or hot air in the defrost process. • The timing and frequency of the defrost should be set to allow time for the cooler to accumulate a generous frost load. This gives a better defrost result during the next defrost cycle and enhances the washing effect in the drain tray. Î A lightly frosted coil will defrost very quickly. As a result of the short defrost period, the drain tray may not heat sufficiently, which can cause a build up of solid ice in the drain tray. 4.8 Replacement of electric heater elements It is crucial that before any work on the electric heating elements is performed, the electrical mains supply is turned off and the cooler is completely isolated. The following checks should be made prior to attempting withdrawal of heating elements: • Check the phase fuse. • The heater elements are wired so that they are evenly spread across the three phases. If there is a phase problem and the coil is icing, there will be a band of frost across the one third of the finned block that corresponds with the phase that has gone down. • Check the resistance of the element before removing. No measurable resistance means that the element is defective. Then check the ground leak resistance of the heating element before removing it. This should be done by checking the resistance between the live and ground terminals. If the resistance is below 0,1 Meg Ohm, there is reasonable cause to change the element. • Check the drain tray heater elements: these are also connected across the three phases. If one of these elements fails or shorts out it can knock out a whole phase. To remove a heater element from the coil, first disconnect the electrical connection boxes and remove the fixing screw. Pull the heater element out using as little force as possible. If the element should feel stuck, give it a little twist and continue pulling. The replacement is merely the reverse of removal, but it is most important to check the spade connectors to see whether they are straight before insertion into the coil block. If necessary, draw the cables through the defrost tubes using a string or cord. When inserting the elements keep them as straight as possible in order to facilitate assembly and avoid their becoming jammed.