July 28, 201213 yr 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?
July 28, 201213 yr Having an additional high quality RCB switch in line with an appropriate leakage setting is a very good idea.
July 28, 201213 yr 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.
July 28, 201213 yr Author 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.
July 28, 201213 yr Author 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
July 28, 201213 yr 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. "I don't want to know why you can't. I want to know how you can!"
July 28, 201213 yr Author 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?
July 29, 201213 yr 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. "I don't want to know why you can't. I want to know how you can!"
July 29, 201213 yr 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.
July 30, 201213 yr 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.
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