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Two high-power appliances on a single 40A RCD
Former Community Member
I have an electric shower installed on a 40A RCD, in a room adjacent to my kitchen. The shower is only used in an emergency - i.e. when our gas boiler is unable to provide hot water to our main bathroom. I would like to take a spur from this 40A connection to use for a new double oven, which is rated at 32A. Can anyone advise on a safe and legal way to do this, ensuring that only one of the two appliances can be connected at any one time?
I really am quite disappointed Gentlemen. No one has really understood the situation properly have you?
OK you could install a new circuit, but the point is "is it necessary?". All of the above posts have failed to understand what "overload protection" really means, and seem to assume that overload should be eliminated by design, that is more final circuits! Overload already has a device provided to prevent damage to the installation and that is the CPD. Andy has tried to turn this into "catastrophic damasge to the electrical installation". This is more than foolish, it is outright dishonest. An MCB trip is catastrophic eh, that sounds like a threat to me to extract money? It is certainly very unprofessional.
There is a way to do this which is perfectly permitted. The downside is that a trip might occur if the customer uses all the appliances at once. This is his choice, it is not up to you, you should explain carefully what might happen and why. From the OP he has no intention of using the full load at once so any tripping would simply a warning that he has forgotten the choice. All the nosense that it is in some way not safe is fantastic and untrue. Some of you need to get a grip, because many people are very suspiciousof trades already and you are making this worse.
For my motor example the cables may be chosen on rating at FLC, although some extra cross section may be required by starting volt drop which make start cycles much slower and may cause motor stall. Overload protection would be by phase loss relay and suitable time delay setting and current on the MCCB. The final circuit can be overloaded but has suitable protection. Why is the phase loss relay so important? There is a time diversity on the start cycles and this will limit temperature rise to a manageable level. If starts were at a rate of one per minute with the 30 seconds start time we would need to take the average current into account in the cable rating, not the peak value because the average describes the overall heating effect. Apply that to the OP and you will get exactly my answer.
I really am quite disappointed Gentlemen. No one has really understood the situation properly have you?
OK you could install a new circuit, but the point is "is it necessary?". All of the above posts have failed to understand what "overload protection" really means, and seem to assume that overload should be eliminated by design, that is more final circuits! Overload already has a device provided to prevent damage to the installation and that is the CPD. Andy has tried to turn this into "catastrophic damasge to the electrical installation". This is more than foolish, it is outright dishonest. An MCB trip is catastrophic eh, that sounds like a threat to me to extract money? It is certainly very unprofessional.
There is a way to do this which is perfectly permitted. The downside is that a trip might occur if the customer uses all the appliances at once. This is his choice, it is not up to you, you should explain carefully what might happen and why. From the OP he has no intention of using the full load at once so any tripping would simply a warning that he has forgotten the choice. All the nosense that it is in some way not safe is fantastic and untrue. Some of you need to get a grip, because many people are very suspiciousof trades already and you are making this worse.
For my motor example the cables may be chosen on rating at FLC, although some extra cross section may be required by starting volt drop which make start cycles much slower and may cause motor stall. Overload protection would be by phase loss relay and suitable time delay setting and current on the MCCB. The final circuit can be overloaded but has suitable protection. Why is the phase loss relay so important? There is a time diversity on the start cycles and this will limit temperature rise to a manageable level. If starts were at a rate of one per minute with the 30 seconds start time we would need to take the average current into account in the cable rating, not the peak value because the average describes the overall heating effect. Apply that to the OP and you will get exactly my answer.
