RCD faults

In the last year or so I’ve had some tricky RCD nuisance tripping faults to diagnose and resolve. Normally with these kind of faults, there is an obvious fault on one of the circuits when tested, particularly an insulation resistance fault which causes sufficient current leakage to earth which is potentially dangerous as it can lead to electric shocks when metal appliances, sockets, switches etc are touched. RCDs are specifically designed to guard against this type of fault, better than regular fuses can.

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In 3-4 cases recently however, customers have reported intermittent nuisance tripping of consumer unit RCDs, which then generally can be reset after tripping. Yet I can see no obvious fault when I call round to test the affected circuits. I have noticed that the circuit insulation resistance readings are usually not perfect, but still in the acceptable range (older wiring and connected appliances often show a deterioration in insulation resistance, very few properties ever give an ideal result). The RCDs themselves always test OK for tripping current and speed, so it’s a bit of a mystery in these cases.

In some cases, after a few visits without any luck finding the problem using normal tried and tested diagnostic methods, I have replaced the RCD unit itself as a last measure, despite no obvious problem with it. Rather unexpectedly, this appears to have resolved the nuisance tripping problem in all these cases!

So I think what is happening in these cases is that the RCD function is being compromised by some earth leakage in the electrical installation (normally not enough to trip a healthy RCD) and that in some instances, they are deciding to trip when they shouldn’t.

It may well be that with increasing use of LED lighting, electronic devices & appliances, wireless routers, smart TVs, etc in the home, the combined capacitive effect of all these is raising the background earth leakage on the system, this constant low level may be causing some RCDs to malfunction over time. Interestingly, there is some evidence on the internet now that this may be a growing issue in homes.

So, if you have a stubborn & intermittent RCD fault in your home, give us a call, replacing the RCD may be the answer if all else fails.

Steve Rae

 

Cabling in gardens

Extending lighting & power from the house to the garden is a growing area of activity, with the increasing use of mains electricity for garden offices, sheds, border & tree lighting schemes, water features, etc. LED lighting in particular has dramatically reduced the installation & running cost of extensive garden lighting schemes.

DSC_0208 DSC_0256

But the garden environment can be a harsh one for electric cables & accessories, requiring meticulous attention to waterproofing & electrical safety, and protection against cable damage in particular from abrasion and impact damage from shrub growth, rodents and gardeners (!). It’s easy to make things work when they are new and dry, not so easy after a year or two exposed to the great British weather. Above all, safety must never be compromised when dealing with 230V mains voltage circuits.

Many well-meaning garden electrics schemes fail after a disappointingly short time due to poor choice and installation of cables and accessories. For this reason, steel-wired armoured cable (SWA) in particular is an absolute necessity in this environment, delivering power safely & reliably over quite long distances to endpoints.

SWA cable

SWA being pretty tough cable, is tough to work with, requiring proper metal glands to terminate it safely on waterproofed accessories. Qualified electricians should be used to install this kind of cable, in addition to ensuring all aspects of electrical safety are met during the design and installation of the garden electrics as a whole. For free advice and a quote on all such work, please don’t hesitate to give us a call.

 

 

 

 

Think you can change a light fitting?

One of the common DIY problems with electrics is changing ceiling light fittings. Sounds simple doesn’t it – take the old one off and reconnect all the wires to the new one – right?

Ceiling light 2

Well, it’s fairly simple only when there are 3 wires to worry about. Often though, the old light fitting is also acting as a ‘loop-in, loop-out’ cable joint, in which case there can be many individual wires (live, switched live, neutrals, earth) and it is very easy to mix them up. At best the light won’t work, at worst the fuse on the consumer unit will blow and other lights won’t work either. Add to this working off a ladder, a general lack of suitable test equipment to confirm correct wiring and earthing, particularly to fancy metal fittings, and this ‘simple job’ turns into a drama.

However tempting it is to try and change your own light fittings, it’s generally not a good idea. Even electricians find these to be fiddly and tricky jobs on occasions, but they will always leave it safe and working at the end!

The damage furry rodents can do

The one thing mice, rats and squirrels all have in common is their taste for electric cables which often leads to both their demise and tripped fuses & RCDs in your house and outbuilding/garden circuits.

Often next to their nests in lofts and pipes, the rodents chew off the PVC insulation on the cables, exposing the copper cores and  creating an electrocution hazard to you and them, particularly in lofts. Fire risk and tripped fuses/RCDs from short circuits and earth leakage can also occur.

Mice and squirrels are the main problems found in lofts, particularly the latter which although less in number, can be very destructive in a short space of time. Rats are a particular hazard to non-armoured cables in underground ducts and outbuildings.

The tell-tale signs to look out for are visibly nibbled & chewed cables and nuisance tripping which is often happens when chewed cables get damp or wet.
In all cases, action must be taken quickly to eliminate further cable damage and repair the already damaged cables. This often means removing the rodent activity (particularly in lofts) and/or adding additional protection to cables where it is not feasible to remove the rodents.

So the next time you hear the patter of tiny feet on your ceilings, don’t delay, it could prove an expensive mistake!

 

Changing 12V halogen downlight bulbs for LED

I often get asked if it is OK to just change 12V halogen bulbs like the one below for 12V LED bulbs :

12V bulb

Unfortunately it’s not that simple. The 12V halogen bulbs are powered by a small 12V transformer in the ceiling space, which isn’t really compatible with 12V LED bulbs. It may work if you are lucky but is more likely not to work at all, or cause damage to the LED bulb or itself.

An electrician should always change the transformer for a 12V LED driver like the one below before fitting the LED bulb. The advantage of this option is you get to keep the existing downlight fitting if it is still in good condition.

LED driver

The other option is to remove the need for a transformer or LED driver altogether and replace the downlight fitting with a 230V mains voltage fitting, which allows a 230V LED GU10 bulb to be fitted. The advantage of this option is that there is less to go wrong in the future (only the bulb, which is a DIY replacement).

LED new-gu10-side

The difference in cost between the two options is almost negligible, as the cost of the LED driver offsets the cost of a replacement 230V fitting. Of the two options, I prefer the latter as there is less maintenance cost in the future.

If you’d like to discuss which is best for you, please don’t hesitate to get in touch.

LED lights run a lot cooler than halogen

LED lights are much more efficient, long-lasting and economical to run than the older halogen types they replace.

From an electricians viewpoint however, they also offer a major advantage in the area of operating temperature, as LED runs much cooler than halogen. In recessed downlights in particular, an LED bulb like the one below is only warm to the touch after several hours of operation.

LED new-gu10-side

Whereas a similar halogen bulb like this one would burn your fingers a few seconds after switching on.

12V bulb

Heat management is a critical safety issue with recessed downlights and poorly installed halogen downlights (too close to joists, covered in loft insulation & dust, etc) are a significant fire risk. Having replaced thousands of halogen downlights over the last few years, I reckon around 5-10% have shown evidence of heat damage, some seriously.

So I only ever fit LED bulbs now!

If you are concerned about your old halogen downlights, call for free advice on keeping them safe, including replacing with LED.

 

 

 

 

 

Outhouse supplies

We’ve seen an increasing demand in the last few years for electrical supplies to outhouses such as sheds, summerhouses, garden workshops and offices. No longer is it just a simple light and a socket required, some of these outhouses now require enough power to run electric heaters, washing machines, woodworking machinery and the like. It is not unusual to see up to 7kw load requirements in some cases.

Careful consideration needs to be given to how the electrical supply will originate from the house and how lights and sockets will be supplied in the outhouse. Cable runs from the house need to be thoroughly waterproofed and protected against impact and rodent damage.

In many cases, taking power from the house ring main is not a satisfactory way to deliver sufficient power and resilience to the out-building. New circuits taken directly from the main consumer unit or incoming power supply point are often the best solution wherever possible.

In all cases we would survey the job and advise & quote on the best solution given a full understanding of the customers requirements for the use of the outhouse.

 

 

Replacing light fittings

It’s not uncommon for people to try and change light fittings themselves. After all, it should be an easy job, right?
Wrong! It’s a lot harder than it first appears.
Apart from the obvious electrical risk, common mistakes are:
- underestimating how tricky it can be to securely fix new (often heavier) fittings to plasterboard ceilings and walls
- getting the wires mixed up, leading to lights not working or fuses blowing
- getting all the wires safely terminated into a much smaller space than the original fitting – this is often the case when changing white plastic hanging pendants for more sleek-looking metal fittings
- not testing the circuit afterwards to ensure the fitting is earthed properly and wiring faults have been avoided. Testing is one of the main problems with DIY electrics – without the right test equipment, it is almost impossible to be sure everything has been done safely & correctly. This is why most electrical work should only be done by qualified and competent electricians working to Part P of the Building Regulations.

So next time you are tempted to do DIY on light fittings, remember a lot can go wrong – it will cost more to call out an electrician when all has gone dark, than getting the work quoted for and booked in advance!

 

Wet external electrics

The very wet winter has kept us very busy attending to fault diagnosis & repairs on external electrics, mainly garden lights & sockets.

The problem has rarely been with the actual weatherproof light fittings or sockets themselves, but with cable joints in the supply cables and poorly waterproofed connections to the accessories. Perhaps not surprising given that most external cables are of the armoured type which needs careful termination from both a safety and weatherproofing perspective:

SWA

Such cables need special terminating glands and use of good quality fittings which ensure the cable joints stay dry even when drenched with rain. Any dampness in the joints will inevitably to circuit RCDs tripping, often taking out several house circuits at the same time.

Wiska

If you have any concerns about any external electrics in your garden, don’t delay in getting it looked at, wet joints only ever get wetter!

 

Problem PIRs

Passive Infrared sensors (PIRs), usually known as sensors, are commonly found on external floodlights, but can also be separate from the light they are controlling.

LED PIR                                  PIR sensor

They generally give up to 10 years of service before faults appear:
- erratic operation, including operation during the daytime
- failure to operate the light at all (though this may also be a failed bulb..)
- turning the light permanently on

When such faults appear, unless the light bulb has failed, it is best to replace the sensor light or standalone sensor. This can normally be done in around an hour, a little more if the sensor is at high level on a house when the careful use of long ladders is required.