RCBO energy consumption

[John-SJW]

RCBOs consume between 1.5 and 2.5 watts for each pole - according to Wylex. Have a CU with largish bank of DP RCBOs then the annual cost of just having RCBOs is substantial. It is not just a few quid a year in electricity costs to have them. My question is:

Do RCBOs still consume electricity when switched off?

 

[John-SJW]

Did search on Youtube. John Ward stripped down a Hager 20A RCBO. A quick skim thru the vid, not looking at it all - It looks like they do not consume any energy when the switch is off, answering my original question. Needs more looking.

My oven Wylex 16A RCBO was warm with no current draw. I just turned the RCBO off. I will check tomorrow morning again.

 

[brianmoooore]

Silver instead of copper is a bit extreme, but I've posted on here before about using cables for things like cookers, showers, water heaters, etc., a little larger than those required by VD calculations to reduce losses.

 

[brianmoooore]

Is there a significant difference between the consumption of a RCBO and the equivalent MCB, without the RCD part. Both rely on a bimetal strip, which needs heat (= consumption) to work?

 

[John-SJW]

Is there a significant difference between the consumption of a RCBO and the equivalent MCB, without the RCD part. Both rely on a bimetal strip, which needs heat (= consumption) to work?

Aron B posted the data sheets for Hager mcb & RCBOs.

 

[John-SJW]

What's the 'consumption' of a rewireable fuse? They must be resistive to work, and the 'consumption' must be enough to melt copper when the current through it is high enough.

I have never felt a fuse being warm with no current being drawn.

 

[brianmoooore]

I have never felt a fuse being warm with no current being drawn.

Same for a MCB.

 

[John-SJW]

Same for a MCB.

An MCB will not give off heat if current is not drawn thru it. The heat is via the coil inside which all the current runs thru - fault detection coil. Too much current running thru the coil it detects a fault, so the coil becomes a solenoid throwing a pin inside the coil pushing the spring mechanism disconnecting the supply. Over-current is detected via a bi-metal strip. So the bi-metal strip will get hot consuming energy. There is no neutral in an mcb.

RCBO's have a board inside, which is energised permanently having a neutral to the unit, giving off heat even if no current is being drawn thru the unit, as long as the switch is on.

 

[Aaron b]

To lessen the concern of loss, maybe cable makers should look into using silver instead of copper ?

Wonder what a 50mtr drum of 4 mm t&e would be and how long it would take to pay for itself.

Check out the prysmian cable app. It makes recommendations for energy saving. All ocpd have a thermal part so will need to dissipate heat as part of there function.

The original post makes it sound like there's unnecessary electronics. But to answer the question no it doesn't use energy when switched off as the figures are at the rated current of the device.

 

[John-SJW]

The original post makes it sound like there's unnecessary electronics. But to answer the question no it doesn't use energy when switched off as he figures are at the rated current of the device.

Unnecessary? Mmm, no. Some board designs can use more energy than others.
John Wards vid, I posted, shows that an RCBO, well the Hager he looked at, do not consume any energy when off.

 

[pc1966]

To lessen the concern of loss, maybe cable makers should look into using silver instead of copper ?

Wonder what a 50mtr drum of 4 mm t&e would be and how long it would take to pay for itself.

More like how long until stolen?

Recent metal prices are:

• Silver approx $600 / kg
• Copper approx $7.5 / kg
• Aluminium approx $1.8 / kg

If you then look up the resistivity we have:

• Silver 15.87 nOhm.m = 0.945 * Cu
• Copper 16.78
• Aluminium 26.5 = 1.58 * Cu

So you can see silver has about 5.5% percent better conductivity but about 8000% of the cost, while aluminium needs to be 58% thicker to match Cu but is only about 24% of the cost. However, Al is a right pain to use due to galvanic corrosion risks and is prone to fatigue if flexed, so really only worth it for big DNO like cables and carefully planned joints.

However, the lifetime loss cost of cables ought to be considered at the design stage in addition to the usual 5% volt drop limit, etc. For light loads such as LED circuits then they are very unlikely to reach 3% even these days, but for bigger loads maybe worth it.

 

[pc1966]

Just to add, where you do see silver used for better conductivity is in RF parts where they are plated as at high frequencies the current only flows in the very surface of the conductor (typically tens of microns or less due to the skin effect) so Ag plating is as good as solid.

 

[brianmoooore]

Taking the thread totally off topic, l live in the village where the proposed undersea cable from PV in Morocco is due to connect to the grid.
Anyone care to estimate the losses on that cable?

 

[pirate]

When I read up on this project and saw they were building a cable manufacturing facility at Hunterston which is only an hour away from me, I turned up to sign on for a job, clutching my brand new klein automatic cable strippers...
I didn't get the job...

 

[snowhead]

I turned up to sign on for a job, clutching my brand new klein automatic cable strippers...
I didn't get the job...

If you'd gone with Scuba gear they may have been interested.

4 x 3800km, that's a couple of days work to manufacture...

 

[John-SJW]

I switched off overnight the RCBO supplying a radial which only has washing machine on it - washing machine was unplugged. The RCBO was warm before it switched off. This morning is was cold. I switched it back on at 8 a.m. it is now warm.

A CU with say 15 RCBOs can generate a fair bit of heat inside. So, the likes of a Fuse Box CU, which has lots of space inside is the way to go. Metal cases will help dissipate heat of course.