mayview Posted July 28, 2012 Share Posted July 28, 2012 I have 2 Stiebel Eltron h/w shower heaters that I wish to substitute for older units. The two independent power sources both have RCB switches in the line supply. Both units are earthedr back to the Supply unit and tested. The two new h/w heaters have these safety devices incorporated. Should I remove the standalone RCB switches from the lines? Is there any risk of having additional RCB's on the same line? Link to comment Share on other sites More sharing options...
BuckarooBanzai Posted July 28, 2012 Share Posted July 28, 2012 Having an additional high quality RCB switch in line with an appropriate leakage setting is a very good idea. Link to comment Share on other sites More sharing options...
lopburi3 Posted July 28, 2012 Share Posted July 28, 2012 As said the second RCB will provide protection for any contact prior to the installed unit (the lines) as well as back-up for installed unit. Link to comment Share on other sites More sharing options...
mayview Posted July 28, 2012 Author Share Posted July 28, 2012 (edited) Having an additional high quality RCB switch in line with an appropriate leakage setting is a very good idea. Thankyou. It stays! The previous line RCB has a 15mA sensitivity I don't know the h/w heater spec for this. Edited July 28, 2012 by mayview Link to comment Share on other sites More sharing options...
mayview Posted July 28, 2012 Author Share Posted July 28, 2012 As said the second RCB will provide protection for any contact prior to the installed unit (the lines) as well as back-up for installed unit. Great to have a confirmation reply on this aspect. Grateful Link to comment Share on other sites More sharing options...
Crossy Posted July 28, 2012 Share Posted July 28, 2012 Yes, leave the existing RCD in place, it can do no harm and (as others have noted) protects you from shock from dodgy joins in the cable. Do verify that your existing breaker and cable are man enough for your new heaters if they are are of higher power than the existing ones. Link to comment Share on other sites More sharing options...
mayview Posted July 28, 2012 Author Share Posted July 28, 2012 Yes, leave the existing RCD in place, it can do no harm and (as others have noted) protects you from shock from dodgy joins in the cable. Do verify that your existing breaker and cable are man enough for your new heaters if they are are of higher power than the existing ones. 5 sq mm cable. 25 amp Type C CB's. 4.2 KW heaters. Hoping this is OK? Link to comment Share on other sites More sharing options...
Crossy Posted July 29, 2012 Share Posted July 29, 2012 5mm2 is an unusual size, are you sure that's what's installed? The common sizes are 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35 mm2 A 4.2kW heater will pull around 20A so it would be OK (just) on 2.5mm2 which is what's often installed. Link to comment Share on other sites More sharing options...
electau Posted July 29, 2012 Share Posted July 29, 2012 Install 6.0sqmm cable with a 25A or 32A RCBO for the final circuit. Earth the heaters using a minimum of 2.5sqmm green or green /yellow insulated conductor. The RCBO should have a sensitivity of 30mA. You retain the existing RCD in the heater. This will only disconnect the heater in the event of an earth fault on the load side of this protective device. 2.5sqmm is permissable as it has a 25A rating under certain installation conditions. Link to comment Share on other sites More sharing options...
lopburi3 Posted July 30, 2012 Share Posted July 30, 2012 Believe 2.5, as you say, in this case should be fine as run should be short and such heaters are normally only used a few minutes a day and seldom at full rated power. Link to comment Share on other sites More sharing options...
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