Suitable fuse box

[lumepo]

My house was constructed around 1986. It is a three-bedroom one, with a kitchen in the ground floor, three bedrooms and a bathroom I the first floor. The house is central heated with a 5-year boiler in the ground kitchen, an immersion heater and a shower pump in the first floor, and a water tank in the loft. The cooker is electrical.
I would like to extend the house into the loft, and add 2 bedrooms and a bathroom. If possible I would like to remove unnecessary appliances/the water tanks to create space. I am enquiring about plumbing requirements and constraints. From you I need suggestions on a suitable fuse box that can service al requirements.
The attached photographs show the current fuse box.

 

[ericmark]

A consumer unit (CU) no longer called fuse box as it no longer has fuses, today come in many flavours, the main point is how many RCD's are fitted, a RCBO is a RCD (which detects leakage to earth) so you could have just two or you could have 20.

The RCD is a problem in that 30 mA is not much, and having just two means with a large installation they may trip for no apparent reason on a regular basis, the RCBO is in general less likely to trip for no reason. But using RCBO's lifts the price. So you need to balance cost and inconvenience.

As to plumbing the instant water heating offered by the combi-boiler seems good, but many are returning to using tanks again. The combi will only supply one shower at a time and it will not allow solar power to be used to heat water, often the boiler has a small reservoir so water starts cold goes hot then cold again then hot and stays hot as reservoir empties before heater has warmed replacement water.

Also any power showers become illegal and have to be removed.

 

[Taylortwocities]

It would be nice to see behind the cover to see what sort of protective devices you have.
But my guess it is the old style re-wireable fuses and your installation does not have any RCD protection.
RCD protection is mandatory for new circuits so you will be needing to change that old furseboard for one that meets today's regulations.

A suitable fusebox will be one that is designed and supplied by a registered electrician as the work you have in mind will need to be notified by a member of a CPS scheme, otherwise you will not get a completion notice from BC for your house extension.

 

[Spark123]

You can ask for a fully loaded RCBO type consumer unit (an RCBO combines an RCD and MCB). This will be expensive but an issue on a socket circuit circuit (i.e. dodgy kettle etc) won't trip anything else i.e. your lights.

You can ask for a "17th edition" consumer unit which usually has two RCDs and then splits the circuits between them with MCBs. The downside of this is having lights and sockets on the same RCD, if a fault occurs it can trip the lights. The advice is to have up lights and down sockets on one RCD, vice versa on the other. This is usually the cheapest compliant option.

You can ask for a "17th edition" consumer unit with a few RCBOs on the high integrity ways and MCBs on the other two RCDs. If you only have one socket circuit this is probably the lesser of the evils, where your lights are on their own RCBOs so a fault on a socket circuit doesn't trip the lights.
It is up to you what you want to pay for, your electrician will be able to give more advice.

 

[ban-all-sheds]

I would like to extend the house into the loft, and add 2 bedrooms and a bathroom.

You cannot possibly, unless you are virtually certifiably insane, even think about doing that without Building Regulations approval.

Therefore....

From you I need suggestions on a suitable fuse box that can service al requirements.

No - from us you need it pointing out that you are going to have to use an electrician, a registered one (probably - unless you want to needlessly pay more money to Building Control), and that therefore you should leave it up to him what to do about replacing the CU.

 

[ericmark]

I would like to extend the house into the loft, and add 2 bedrooms and a bathroom.

You cannot possibly, unless you are virtually certifiably insane, even think about doing that without Building Regulations approval.

Therefore....

From you I need suggestions on a suitable fuse box that can service al requirements.

No - from us you need it pointing out that you are going to have to use an electrician, a registered one (probably - unless you want to needlessly pay more money to Building Control), and that therefore you should leave it up to him what to do about replacing the CU.

To extend into loft it will need the involvement of Building Control, to add electrics to the submittal price wise depends on if it will move the cost into the next band, it could cost nothing, and it will cost less than just doing electrical work. My area first step is £2000 worth of work so new sockets in a kitchen can cost same as full require on council charges, but that is not a problem when added to other work.

What is more of a problem is getting the council to accept you have the skill required. They may simply say no, or they may require the installation to be over seen by some one they have selected to ensure it meets the required standards, or they may decide that your qualifications are good enough for you to sign the installation certificate, and if they were you would not be asking questions on here.

So in real terms it is likely cheaper even when you are already involving building control to use a scheme member electrician. However even using an electrician he will need instruction on what you want and how important it is to you that from time to time power will be lost due to earth leakage or spikes on the supply which can trip a device sitting near to the limit.

Standard cables all have earth wires, and capacitive and inductive links mean some power is wasted, it is very little and nothing to worry about, but it means the more cable you have the more power naturally leaks to earth, the more the installation is split up into circuits with independent RCD protection the less the problem is with circuits tripping.

The problem then becomes knowing a circuit has tripped. Although both my fridge/freezer and freezer have little blue symbols to show they have power, lack of those lights is not something which tends to alert one of a power failure. However seeing the landing light come on as the emergency batteries take over in a power cut is rarely missed. And during the night loss of lights is a good indication of power loss. A simple emergency torch on same circuit as freezer is enough to alert one. Having said that mothers house has a kitchen CU with 5 RCBO's which have never tripped, the RCD covering wet room has, but not the RCBO's likely simply because less cable on the circuits.

The X-Pole RCD claims to trip at 90 ~ 100% of rating rather than 50~100% and also has a warning lamp to show when nearing the limit, it is claimed to not trip with spikes on the supply line, so all 30 mA and 40 ms RCD's are not equal. But the problem is still price, you have to balance price and inconvenience. The electrician can't do that for you, he can only guide you.

I am not a scheme member but I am fully qualified to do a complete rewire including inspection and testing, and I have access to all the test equipment. However I will still pay a scheme member electrician to rewire my mothers house. By time I have paid the LABC it's just not worth DIY.

 

[winston1]

Standard cables all have earth wires, and capacitive and inductive links mean some power is wasted,

Power is NOT wasted as it capacitive and inductive current is at zero power factor.

 

[ericmark]

Standard cables all have earth wires, and capacitive and inductive links mean some power is wasted,

Power is NOT wasted as it capacitive and inductive current is at zero power factor.

In an ideal world where you are using balanced feeders and the cable is correctly terminated yes, but with 50 Hz supplies no one bothers to use balanced feeders so power is wasted, although it is so small as to be hard to measure. But in resent years we have seen how feeds to LED lamps have gained enough power from capacitive and inductive coupling to cause them not to switch off. In theroy we should use capacitors or inductors to correct any unbalanced feeder. In practice only high frequency feeders like those used between radios and their aerials are corrected to ensure the voltage standing wave ratio is as close to unity as one can get.

At the moment my son has my university books or I would quote chapter and verse.

 

[winston1]

All well and good but power is not wasted in the indance or capacitance. Power can be wasted if that current also flows through a "resistive" component in series such as an LED.

 

[ericmark]

Try it, next time your in an empty house with power, put your clamp-on meter around the supply and set to mA range. It will not be much, and not enough to worry about, but it will have some current being used even with an empty house.

You have seen the demo with fluorescent lamp under power lines, do you really think that leakage stops when you take the lamp away? Only with DC can you get no leakage, with AC it is a fact of life.

If you ever study to become an electrical engineer, not sure if taught to electricians but it should be, you will find the lectures on transmission lines become rather complex, the section in my bible used when I studied to become an electrical engineer was quite thick. As a radio ham I had seen some of it before, and it seems the names used by electrical engineers are not quite the same as those used by radio hams, but the principle is the same.

The distance between two cables is rather important. If we look at 300Ω feeder cable it is not that much different to twin and earth. So using the theroy we should not use the UK method of sending just the line wires to the switch, specially with a two way system. However we have done it for many years without problem, only when the LED light came on the seen did we encounter a problem. As a result today LED's often include a small resistor to stop leaking power lighting them.

As you say the LED as a lamp is well know for wasting power, the raw LED will produce around 100 lumen per watt, but in the lamp package it is often down to 70 lumen per watt or lower. While in university we did try getting more light out of LED's. However the problem is how to measure. The LUX meter will show how much light, but flashing the LED with more than it's rated current may be perceived but the human to be brighter but the LUX meter will not show that perception and however much we try and develop a method of measuring light used by humans to see with, we have really only got an approximation with the lumen. Walk into two rooms one with LED lamps and other with CFL both with same lumen output and the LED room seems brighter. However try to read a book in the room and one realises the CFL is just as bright. Our eyes and brain can't be emulated and each person is different.

 

[winston1]

Try it, next time your in an empty house with power, put your clamp-on meter around the supply and set to mA range. It will not be much, and not enough to worry about, but it will have some current being used even with an empty house.

But is that reactive current at 90˚ out of phase with the voltage? If so there will be no power drawn. Power =VI cos phase angle. Cos 90˚ = zero so the power will be zero.

 

[bernardgreen]

Winston

It is NOT purely reactive as there are impedances distributed along the cabling, These are resistive along the entire length and inductive at each bend in the cable. The value of these impedances are very small but so is the stray capacity in the cable.

 

[lumepo]

Thank you all for your invaluable advice.