One for the sparkeys out there (1 Viewer)

[tick59]

When my motorhome is plugged into mains everything is ok ecept when you switch the water heater on then the house electrics blow. Have checked fuses in van all ok only the house electrics affected. ????

 

[dunnah01]

So how does that work?
A kitchen ring main uses the same size cabling, the same capacity circuit breakers and the same outlet sockets as any other power circuit in the house.
So how can it have a higher load capacity?

I think he meant the cooker socket

 

[autorouter]

I'd think he's referring to the cooker supply circuit, which probably has a 40A MCB on it, rather than 32A like a standard ring. OK, it's a radial rather than a ring, but people tend to refer to any mains circuit as a ring, even if technically it's not.

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[silverbolt]

It would surprise me if they run 240v for high power appliances.

We run some high power stuff on site and it’s all 110v

15A at 120v is only 1800 watts and so most houses in the US are supplied with 240v. Each half of the consumer unit is 120v to run lights and sockets. large AC units, electric cookers, and clothes dryers etc use dedicated 240v supply taken across both 120v legs to get the 240v for the high power appliance.

 

[bigalw35]

In the UK we have 240 for domestic appliances, the exception is industrial/commercial where they generally use 415 volts

 

[autorouter]

When my motorhome is plugged into mains everything is ok ecept when you switch the water heater on then the house electrics blow. Have checked fuses in van all ok only the house electrics affected. ????

I think you want the answer to the question why do the house electrics trip, and nothing in the motorhome trips, when the fault is clearly in the motorhome?

There are basically two kinds of electrical fault: excessive current or earth leakage.

Miniature circuit breakers (MCBs) protect against excessive current, to avoid heating up the wires and causing a fire. In older installations, fuse wire did this job. If the current is excessive, the fuse wire melts and disconnects the cable. An MCB does the same thing - excessive current makes it trip. In this case, I think there is no excessive current, so none of the MCBs will trip.

Residual Current Devices (RCDs) protect against earth leakage. The RCD compares the outgoing current along the live wire with the returning current along the neutral wire. Normally, outgoing and incoming current are exactly equal. If there is leakage, and the difference is more than 30mA, then the RCD will trip.

RCDs are comparatively modern, compared with fuses and MCBs, so many people are not very clear what they do. When you get an electric shock, electricity travels through you to earth. The RCD detects this earth leakage, and trips before it causes harm. RCDs protect against electric shock

So, back to the heater element fault. It looks like the fault is failed insulation, causing earth leakage. Not a short circuit causing excessive current. So the MCBs won't trip, but the RCD will trip.

Next question, why does the house RCD trip, but the MH RCD doesn't trip? That's what I said in post #52:

RCDs are set to trip at 30 milliamps. Two RCDs on the same circuit will trip at slightly different currents. Each RCD will be slightly different, so maybe one trips at 29.8mA and another trips at 30.2mA. It's just the luck of the draw that the house RCD trips before the motorhome RCD. If you hooked up to a different house you might find the motorhome RCD trips first.

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[RandallC]

I think he meant the cooker socket

However that will be fed from the same main circuit ELCB even if from a split load board via the 13amp socket outlet on the front face.

QED no difference to any 3 pin wall socket outlet.

Will admit in days gone by some cooker supplies were via a 100Ma ELCB due to poor heater element construction and caused nuisance tripping on 30Ma ELCBs

 

[dunnah01]

However that will be fed from the same main circuit ELCB even if from a split load board via the 13amp socket outlet on the front face.

QED no difference to any 3 pin wall socket outlet.

Will admit in days gone by some cooker supplies were via a 100Ma ELCB due to poor heater element construction and caused nuisance tripping on 30Ma ELCBs

cooker sockets are typically 45amps with 6.0mm cable to a dedicated 40 amp MCB and the ELCB will be 64+amps so plenty of welly available. The ELCB will still probably be 30mA so plenty safe enough to mess around a bit to find non earth faults

 

[RandallC]

cooker sockets are typically 45amps with 6.0mm cable to a dedicated 40 amp MCB and the ELCB will be 64+amps so plenty of welly available. The ELCB will still probably be 30mA so plenty safe enough to mess around a bit to find non earth faults

Agreed but if op has an earth leakage problem make no difference if cable supply to the earth fault is 0.5mm or 16mm.

If ELCB is 30Ma it trips a circa 30Ma current leakage to earth.

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[bigalw35]

I’m too old now to even be bothered but there is a subtle difference between a E.L.C.B and a R.C.D, they both more or less perform the same function

 

[RandallC]

I’m too old now to even be bothered but there is a subtle difference between a E.L.C.B and a R.C.D, they both more or less perform the same function

Yes, sorry my fault.
Technically.
ELCB monitors the earth potential and should trip at =< 40v max

RCD monitors the current balance between live and neutral and assumes the difference is leakage to earth and trips circa rcd Ma setting.

Tend to use the terms unreservedly to mean in today's terms the same thing.

However installations need only comply with regs current at the time of install. THAT may not be best practice these days

 

[dunnah01]

Agreed but if op has an earth leakage problem make no difference if cable supply to the earth fault is 0.5mm or 16mm.

If ELCB is 30Ma it trips a circa 30Ma current leakage to earth.

I think we're near to violently agreeing

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[TheBig1]

I do think a basic explanation of what the heating element is, and why it fails short to earth on fault usually.

The actual heating part is a wire designed to take advantage of getting hot with a known current passing through it. This bare wire element is suspended inside a metal casing that is connected to earth for safety. If the wire burns out, the end can drop and short to the casing

Replacing the element is simple enough with the truma heater on the bench, but can be all but impossible in some vans due to furniture built round it. An auto electrician would not be interested in taking on that challenge

 

[emjaiuk]

It would surprise me if they run 240v for high power appliances.

We run some high power stuff on site and it’s all 110v

I’m sure they do, and I think 240v is available at some US campsite hookups

 

[gpat]

I think we're near to violently agreeing

An old boss of mine used to call arguments - A constructive conflict

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[Clive and Sally]

I think you want the answer to the question why do the house electrics trip, and nothing in the motorhome trips, when the fault is clearly in the motorhome?

There are basically two kinds of electrical fault: excessive current or earth leakage.

Miniature circuit breakers (MCBs) protect against excessive current, to avoid heating up the wires and causing a fire. In older installations, fuse wire did this job. If the current is excessive, the fuse wire melts and disconnects the cable. An MCB does the same thing - excessive current makes it trip. In this case, I think there is no excessive current, so none of the MCBs will trip.

Residual Current Devices (RCDs) protect against earth leakage. The RCD compares the outgoing current along the live wire with the returning current along the neutral wire. Normally, outgoing and incoming current are exactly equal. If there is leakage, and the difference is more than 30mA, then the RCD will trip.

RCDs are comparatively modern, compared with fuses and MCBs, so many people are not very clear what they do. When you get an electric shock, electricity travels through you to earth. The RCD detects this earth leakage, and trips before it causes harm. RCDs protect against electric shock

So, back to the heater element fault. It looks like the fault is failed insulation, causing earth leakage. Not a short circuit causing excessive current. So the MCBs won't trip, but the RCD will trip.

Next question, why does the house RCD trip, but the MH RCD doesn't trip? That's what I said in post #52:

Excellent explanation & I couldn't have explained it any better in layman's terms for people who know nothing about electrics.
I would also like to know why any new houses or older ones that have a consumer unit replaced aren't fitted with a wholly RCBO one with just a main switch rather than either one fitted with a single RCD as in the original posters case or a split board with two RCD's, as this would only trip the once circuit whether it be over current or an earth leakage fault.
I changed by consumer unit for an RCBO one about 5 years ago & last year also fitted one, complete with a surge protector, in an outbuilding that we've converted into holiday accommodation

Cheers Clive

 

[RandallC]

Excellent explanation & I couldn't have explained it any better in layman's terms for people who know nothing about electrics.
I would also like to know why any new houses or older ones that have a consumer unit replaced aren't fitted with a wholly RCBO one with just a main switch rather than either one fitted with a single RCD as in the original posters case or a split board with two RCD's, as this would only trip the once circuit whether it be over current or an earth leakage fault.
I changed by consumer unit for an RCBO one about 5 years ago & last year also fitted one, complete with a surge protector, in an outbuilding that we've converted into holiday accommodation

Cheers Clive

Think main reason for not fitting RCBOs is cost.

Minimum should be split load board and and at least one RCBO fitted per circuit for smoke detectors and/or other safety circuits.

 

[Clive and Sally]

Think main reason for not fitting RCBOs is cost.

Minimum should be split load board and and at least one RCBO fitted per circuit for smoke detectors and/or other safety circuits.

Hi Randall, In years gone by RCBO's were indeed very expensive & I can remember paying around £40.00 for them but the last ones I bought last year to fit into the consumer unit with the surge protector were only £10.70 incl. VAT so yes they are still more expensive but In my opinion well worth fitting. Obviously because they are longer than a MCB you need a consumer unit designed for them.
I'll post the details if anyone is interested.

Cheers

Clive

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[RandallC]

Hi Randall, In years gone by RCBO's were indeed very expensive & I can remember paying around £40.00 for them but the last ones I bought last year to fit into the consumer unit with the surge protector were only £10.70 incl. VAT so yes they are still more expensive but In my opinion well worth fitting. Obviously because they are longer than a MCB you need a consumer unit designed for them.
I'll post the details if anyone is interested.

Cheers

Clive

Hi Clive.

I'm well out of touch and yes when I rewired our place in 2016 RCBO were a significant cost compared to a split load board (12way & populated) from screwfix at circa £70-120.

Hence comment on split load board, but can I ask where your buying RCBOs at that price (don't have access to trade buys these days) so the likes of screwfix are on average £30 which makes a 12 way board a bit eye watering in comparison.

the domestic end of the supply chain isn't my forte, very much more at home with power station control and electrical systems up to 400Kv.

Hands up anyone who has been in an enclosed 400Kv substation with a fluorescent tube in their hand? Especially post Star wars.

 

[Clive and Sally]

Hi Clive.

I'm well out of touch and yes when I rewired our place in 2016 RCBO were a significant cost compared to a split load board (12way & populated) from screwfix at circa £70-120.

Hence comment on split load board, but can I ask where your buying RCBOs at that price (don't have access to trade buys these days) so the likes of screwfix are on average £30 which makes a 12 way board a bit eye watering in comparison.

the domestic end of the supply chain isn't my forte, very much more at home with power station control and electrical systems up to 400Kv.

Hands up anyone who has been in an enclosed 400Kv substation with a fluorescent tube in their hand? Especially post Star wars.

Hi Randall,
The consumer units & various breakers are made by a relatively new company CP Electric & are sold under the Fusebox name. The owner of the company along with other family members used to have a company called Control Gear Direct that made the Denman Curve all RCBO consumer units that I fitted in my house over 5 years ago. At the time there were virtually no other companies making consumer units specifically to take RCBO'S which are much taller so although they could be fitted into existing units they where a painto wire as there wasn't enough space!
CGD was sold to Lewden & so he started CP Electric in 2017 & started selling his Fusebox range.
Last year I needed an 18th edition consumer unit for an outbuilding we'd converted. I decided to fit one with a surge protection device as that was the latest regulations & having looked around discovered that an SPD module on its own was around £100.00. Looking into it further I discovered that a Fusebox RCBO consumer unit was available which included a main switch & a SPD so ended up buying one along with 13 off of their RCBO'S & this came to £202.00 including VAT i.e cheaper than a split board from the likes of Screwfix fitted with a SPD!
Fusebox products only seem to be available from a few wholesalers & I bought mine online from expertelectrical.co.uk
I hope this is of some use to you & other funsters that might need a new consumer unit to the latest specifications.

Cheers

Clive

 

[RandallC]

Hi Randall,
The consumer units & various breakers are made by a relatively new company CP Electric & are sold under the Fusebox name. The owner of the company along with other family members used to have a company called Control Gear Direct that made the Denman Curve all RCBO consumer units that I fitted in my house over 5 years ago. At the time there were virtually no other companies making consumer units specifically to take RCBO'S which are much taller so although they could be fitted into existing units they where a painto wire as there wasn't enough space!
CGD was sold to Lewden & so he started CP Electric in 2017 & started selling his Fusebox range.
Last year I needed an 18th edition consumer unit for an outbuilding we'd converted. I decided to fit one with a surge protection device as that was the latest regulations & having looked around discovered that an SPD module on its own was around £100.00. Looking into it further I discovered that a Fusebox RCBO consumer unit was available which included a main switch & a SPD so ended up buying one along with 13 off of their RCBO'S & this came to £202.00 including VAT i.e cheaper than a split board from the likes of Screwfix fitted with a SPD!
Fusebox products only seem to be available from a few wholesalers & I bought mine online from expertelectrical.co.uk
I hope this is of some use to you & other funsters that might need a new consumer unit to the latest specifications.

Cheers

Clive

Cheers Clive,

good info.

Stay safe.

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[Raul]

Hi Randall,
The consumer units & various breakers are made by a relatively new company CP Electric & are sold under the Fusebox name. The owner of the company along with other family members used to have a company called Control Gear Direct that made the Denman Curve all RCBO consumer units that I fitted in my house over 5 years ago. At the time there were virtually no other companies making consumer units specifically to take RCBO'S which are much taller so although they could be fitted into existing units they where a painto wire as there wasn't enough space!
CGD was sold to Lewden & so he started CP Electric in 2017 & started selling his Fusebox range.
Last year I needed an 18th edition consumer unit for an outbuilding we'd converted. I decided to fit one with a surge protection device as that was the latest regulations & having looked around discovered that an SPD module on its own was around £100.00. Looking into it further I discovered that a Fusebox RCBO consumer unit was available which included a main switch & a SPD so ended up buying one along with 13 off of their RCBO'S & this came to £202.00 including VAT i.e cheaper than a split board from the likes of Screwfix fitted with a SPD!
Fusebox products only seem to be available from a few wholesalers & I bought mine online from expertelectrical.co.uk
I hope this is of some use to you & other funsters that might need a new consumer unit to the latest specifications.

Cheers

Clive

Could I ask a favour?
can you tell me the spec of the SPD and if is re setable? I’m in need of 2 in cascade to protect a fixed solar installation.
Dehn are the best but, eye watering pricey. Thank you.

 

[Clive and Sally]

Could I ask a favour?
can you tell me the spec of the SPD and if is re setable? I’m in need of 2 in cascade to protect a fixed solar installation.
Dehn are the best but, eye watering pricey. Thank you.

Hi Raul,
Unfortunately these modules aren't resettable. I've no idea how much the Dehn units cost but the Fusebox ones are available for £33.00 incl. VAT
I guess it really comes down to how likely the solar installation is likely to be hit by a surge & whether you can easily swap out the module if it needs replacing.
Attached is a spec sheet on the Fusebox one.

Cheers

Clive

PS As you seem to an expert on solar kit I'll PM you in a while to discuss fitting a system to my motorhome if you don't mind.

 

[Raul]

Thank you for the info, happy to help if I can.

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[Baden87]

Is there water in the boiler, I had this happen to me boiler was switched on withought water and it tripped, turned electric supply to boiler didn’t trip

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