45 AMP DP ISOLATOR SWITCH TO IMMERSION HEATER QUERIED BY ELECTRICIAN

[chris murphy]

Hello All,

Sorry if this is a ridiculous question - as I am not an Electrician I wanted to check whether my initial thoughts were correct before answering a question from a neighbour

I have been asked by a neighbour whether a 45 Amp DP switch with Neon indicator is a correct isolator switch for an ordinary / vented copper Hot Water Cylinder Immersion Heater with a Digital Timeswitch.

Apparently a friend {calling themselves an Electrician / possibly with Electrical knowledge ?] who was doing her a favour by replacing her Immersion Heater stated that the switch should not be any higher rated than 20 Amp.

My neighbour is a pensioner and cannot afford to engage another Electrician to ask about this.

My initial thoughts were that as it is O.K. BECAUSE it is rated higher than a 20 Amp DP switch and as the switch is just to isolate the Electricity to the Digital Timer and Immersion Heater ?

Chris

 

[Bob Geldoff1234]

Hello All,

Sorry if this is a ridiculous question - as I am not an Electrician I wanted to check whether my initial thoughts were correct before answering a question from a neighbour

I have been asked by a neighbour whether a 45 Amp DP switch with Neon indicator is a correct isolator switch for an ordinary / vented copper Hot Water Cylinder Immersion Heater with a Digital Timeswitch.

Apparently a friend who was replacing her Immersion Heater stated that the switch should not be any higher rated than 20 Amp.

My neighbour is a pensioner and cannot afford to engage an Electrician to ask about this.

My initial thoughts were that as it is O.K. BECAUSE it is rated higher than a 20 Amp DP switch and as the switch is just to isolate the Electricity to the Digital Timer and Immersion Heater ?

Chris

Usually a 20 amp double pole switch is used for an immersion heater but a 45amp double pole switch is just as good if not better.The reason why we don't usually use 45amp switches is down to cost.Your friends immersion is fine to stay as it is.

 

[DPG]

If he thinks that having an isolator which has a higher current rating than the device it feeds is a problem then he is not an electrician!

 

[UNG]

If he thinks that having an isolator which has a higher current rating than the device it feeds is a problem then he is not an electrician!

I've got agree

Where do people find these "electricians"

 

[littlespark]

It’s not the isolator switch that needs looked at.

The problem may be that the circuit the immersion is on is maybe an old shower circuit, with a 45A circuit breaker and 6mm cable. Then drops to 1.5 flex to the immersion without being fused down.

We need the full story, before assuming it’s just an oversized isolator

 

[DPG]

It’s not the isolator switch that needs looked at.

The problem may be that the circuit the immersion is on is maybe an old shower circuit, with a 45A circuit breaker and 6mm cable. Then drops to 1.5 flex to the immersion without being fused down.

We need the full story, before assuming it’s just an oversized isolator

We can only go on the info given, where the spark says the switch is too big.

If he'd have said the overcurrent protection is too high a value then yes fair enough.

 

[littlespark]

Well if the so called electrician just looked at a switch and said “it’s too big a switch” and he should know better…. Maybe he didn’t check the OCPD.

just saying, further investigation required.

 

[Petej999]

If he thinks that having an isolator which has a higher current rating than the device it feeds is a problem then he is not an electrician!

Agree

 

[johntheo]

A neighbour of mine recently changed his 8.5kw electric shower which was protected with a 40A/30MA RCBO for a pumped (hot&cold) one which only now draws a few amps at the most, he got a electrician to wire it up and he used the same 6 mm2 cable and left the 40A RCBO as is, my neighbour is a bit uneasy about this so I advised him to get it changed to a 10A RCBO, is this advisable/unnecessary or not?.

 

[DPG]

A neighbour of mine recently changed his 8.5kw electric shower which was protected with a 40A/30MA RCBO for a pumped (hot&cold) one which only now draws a few amps at the most, he got a electrician to wire it up and he used the same 6 mm2 cable and left the 40A RCBO as is, my neighbour is a bit uneasy about this so I advised him to get it changed to a 10A RCBO, is this advisable/unnecessary or not?.

Does the 6mm cable feed an FCU, then the pump?

 

[chris murphy]

Hello again Gentlemen,

Thanks for all of your replies.

I do know for a fact that there is a 10mm cable directly from the Consumer Unit to the Hot Water Cylinder / 45 Amp DP isolator switch because it was run when I was installing a Heating system [including a new Hot Water Cylinder] at the property a few years ago when my neighbours Son lived there.

He was a friend of mine and he helped with taking up floorboards and cutting holes for me and the Electrician who was wiring my Heating system controls and wiring a new supply for the new Cylinder Immersion Heater / Isolator and Timeswitch.

My friend no longer lives at his Mothers home - he has moved quite a long way away and we have lost touch but my neighbour probably phoned him and was told - ask Chris about the 45 Amp switch.

I had hoped that the 45 Amp switch would be O.K. as I had engaged the Electrician to carry out the Heating Controls wiring and the dedicated 10mm supply to the Immersion Heater - I don`t know why he would have used a 45 Amp switch but he was a very professional Electrician / Tradesman - perhaps he just had it and as the switch is permissible he fitted it ?

Thanks to Members who replied describing situations where the fitting of a 45 Amp switch might be an indicator of incorrect over-current protection or another serious defect.

Chris

 

[johntheo]

Does the 6mm cable feed an FCU, then the pump?

Yes.

 

[DPG]

Yes.

The 40A RCBO protects the 6mm feed, the FCU protects the cable to the pump.

 

[littlespark]

weve got 2 problems now on the same thread causing confusion