suspended cable to Detached garage

[JohnW2]

Yes of course I can explain, it's blisteringly obvious the inspector is either:
1) Desperate for work, or
2) A con artist, or
3) Totally incompetent.

Great minds As I wrote ...

Sure - as, I imagine, also can you .... either the person (maybe an 'electrician'!) who undertook the EICR hasn't got a clue and/or he was hoping to make money by attending to "... not only has the cable to be disconnected but it has all to come down so it can't be re-connected when he's left." (and then re-doing it in some fashion)!

Kind Regards, John

 

[JohnW2]

What would be an appropriate de-rating factor for the cable when inside a black conduit that was being heated by solar radiation ?

Good question. About the nearest the regs get to that are the de-rating factors for ambient temp (see below). However, they obviously assume that ambient temp will not be higher than the maximum conductor operating temp (hence the tabulated values 'stop' above that temp), although I don't think there can be any guarantee that the ambient temp experience by the cable won't rise to above that 'maximum'.

White (rather than black) would obviously help to some extent but, in the case of protracted periods of intense sunlight, I'm not sure that would necessarily do more than slow down the heating (rather than restricting the max temp achieved).

Kind Regards, John

 

[securespark]

Enclosed in insulation?

 

[JohnW2]

Enclosed in insulation?

I don't think that would be 'enough'. With "enclosed in insulation", the only temperature rise of the cable (to above ambient temp) would be that due to current flowing in it - i.e. if there were no current, the cable would be AT ambient temp.

However, today being a prize example, it would not surprise me if the something inside of black conduit in my garden could easily be be 40-50 degrees with no current in the cable (the air temp is currently 33 degrees), and any additional heat due to current flowing in the cable would raise the temp even further.

Indeed, on a day like today, it's not impossible that cable within black conduit exposed to the sun could actually rise to (or above) the "maximum conductor temp" of the cable - in which case the de-rating factor would theoretically become 'zero' (i.e. the cable could not safely carry any current at all).

Kind Regards, John

 

[bernardgreen]

Just conducted as experiment, 2 feet of 25mm black conduit horizontal in free air and in direct sunlight with a mercury in glass thermometer inside the conduit,

After 10 minutes the temperature inside the conduit was 110°F = 43.333°C.

Can't take it further as the conduit came loose and the thermometer fell to the ground and broke,

 

[JohnW2]

Just conducted as experiment, 2 feet of 25mm black conduit horizontal in free air and in direct sunlight with a mercury in glass thermometer inside the conduit, fter 10 minutes the temperature inside the conduit was 110°F = 43.333°C.

That doesn't surprise me. As I said, I would think that the temp inside black conduit in sunlight today could, in my garden, probably easily exceed 50°C+, particularly given that even the air temp is around 32-33°C.

However, in terms of this discussion, de-rating factors for high ambient temp are going to be essentially the same for any type of cable - and SWA (almost always black) would probably get at least as hot as some other cable within black conduit.

I'll see if I can also do some experiments - but may have to wait until tomorrow, since the sunlight today has now become very 'hazy'

Kind Regards, John

 

[securespark]

Consider a very hot day in a loft, with the cable under 400mm of insulation, or even between layers of insulation.

 

[JohnW2]

Consider a very hot day in a loft, with the cable under 400mm of insulation, or even between layers of insulation.

Sure, the ambient temp in a loft can also get very high - which, as I said, would add to the problem (need for de-rating) associated with the cable being buried under thermal insulation.

If there is any 'silver lining' in that situation, if the period of very high ambient temp in the loft is not too prolonged, the insulation might prevent the ambient temp of the cable getting as high as it would without the insulation.

Having said all that, I suspect that not too many people think all that much about the potential implications of having cables in lofts etc.

Kind Regards, John

 

[billm]

I've changed my mind;
Yes of course I can explain, it's blisteringly obvious the inspector is either:
1) Desperate for work, or
2) A con artist, or
3) Totally incompetent.

I think I am inclined to agree. But its cost me £180 so far to get the full list of faults which I am steadily working through and correcting irrespective of the Code. Then I will get a different Certified examiner in to check the house again and hopefully get a Landlord Certificate without any C3 "advisories". I will disconnect the aerial cable to garage for the test and later on consider wrapping it in flexible conduit after I have the Certificate and perhaps put a garage CU on the end rather than feed it into a socket as it is now.

 

[JohnW2]

Just conducted as experiment, 2 feet of 25mm black conduit horizontal in free air and in direct sunlight with a mercury in glass thermometer inside the conduit, .... After 10 minutes the temperature inside the conduit was 110°F = 43.333°C.

I'll see if I can also do some experiments - but may have to wait until tomorrow, since the sunlight today has now become very 'hazy'

I've just had a go with some flexible black conduit, and, even with the haze (virtually no shadows), got figures very similar to yours. Assuming tomorrow is less hazy (and even hotter), I'll try again tomorrow and report back!

Kind Regards, John

 

[JohnW2]

I think I am inclined to agree. But its cost me £180 so far to get the full list of faults which I am steadily working through and correcting irrespective of the Code. Then I will get a different Certified examiner in to check the house again and hopefully get a Landlord Certificate without any C3 "advisories". I will disconnect the aerial cable to garage for the test and later on consider wrapping it in flexible conduit after I have the Certificate and perhaps put a garage CU on the end rather than feed it into a socket as it is now.

That all sounds very sensible, and I would be comfortable with that course if it were me.

However, the trouble with the legislation, as written, is that, strictly speaking, it seems that one is meant to provide the first EICR to the tenant (if there is one), and to to LA 'if requested', with no apparent provision for a 'second' (or subsequent) one - and that that 'first' EICR triggers a requirement for all C2s (and any C1s) to be remedied within 28 days of that EICR.

I presume that, as with much legislation and regulations, it isn't necessarily meant to 'make sense'

Kind Regards, John

 

[sparkwright]

I've changed my mind;
Yes of course I can explain, it's blisteringly obvious the inspector is either:
1) Desperate for work, or
2) A con artist, or
3) Totally incompetent.

or
4) More anal than Katie Price.

 

[SimonH2]

and perhaps put a garage CU on the end rather than feed it into a socket as it is now.

Probably no benefit. What size cable, and what is protecting it at the source end ? Unless it's some unusual combination, putting it directly into a (BS1363) socket is perfectly fine as the fuse in the plug will provide protection for the plug, socket, and appliance cable - and if the circuit is correctly designed and installed then the upstream protection will protect the cable run.
Many, many installations are nothing more that a spur, with one or more "13A" sockets on the end, and a fused connection unit (FCU) for the lights - usually a switched FCU so it provides both the down-fusing and switching in one accessory.

However, the trouble with the legislation, as written, is that, strictly speaking, it seems that one is meant to provide the first EICR to the tenant (if there is one)

If there is a tenant in-situ then one is supposed to supply each EICR to them. If there isn't, then it's perfectly OK to only offer the latest.

, and to to LA 'if requested'

I do have to wonder how often they ever ask for one unless there's something else going on to attract their attention ?

, with no apparent provision for a 'second' (or subsequent) one - and that that 'first' EICR triggers a requirement for all C2s (and any C1s) to be remedied within 28 days of that EICR.

A second (or subsequent) EICR is sufficient to prove having dealt with any C1 or C2 defects on the earlier one. And if you read the regs taking each EICR in isolation, it makes more sense.
I.e., each EICR you have done, you have to provide to any existing tenant (and the LA if they ask for it) - if there isn't one, then you don't have to give it to anyone (I think, not even the LA if they ask for it as at the time the property doesn't have a tenancy.) If you are taking on a tenant, they only need the last one, and once the tenancy has started and the regs kick in, then you would only be bound to supply the latest one to the LA.

 

[billm]

There haven't been any tenants in the property so far, I'm just putting the finishing touches to the house since inheriting it and getting the Gas tested etc before putting it in the hands of an estate Agent. So should it pass a 2nd test with a different examiner hopefully that will be all ok.

As I said I'd doing all the Code 3's on his list as well - except the "No surge protection installed" which a) I haven't got a clue what that is/entails and b) he looked in the external meter box and said one wouldn't fit in there anyway, but he still put it down as a Code 3.

Regarding the garage connection, I was thinking of wiring the 2.5mm T&E aerial cable into the ring main in the attic and run it to the garage. Would it be better to take a spur off the ring main in the attic to a socket with a surface box and then a 13 amp 3 pin plug from there to the garage. That would be similar to a FCU and provide protection for the cable to the garage and anything connected in there which is only a double socket and 2 lights ?

 

[SimonH2]

There haven't been any tenants in the property so far, I'm just putting the finishing touches to the house since inheriting it and getting the Gas tested etc before putting it in the hands of an estate Agent. So should it pass a 2nd test with a different examiner hopefully that will be all ok.

Yes. Until it is actually let, there is no legal requirement for an EICR.

As I said I'd doing all the Code 3's on his list as well - except the "No surge protection installed" which a) I haven't got a clue what that is/entails and b) he looked in the external meter box and said one wouldn't fit in there anyway, but he still put it down as a Code 3.

Surge protection doesn't normally (for a small installation like a house) go in the meter box, it goes in the CU. You can split the tails and put one at the service entry, but for a domestic, it would normally be "just another device" in the CU.
As to what they are, consider lightning is around. That can induce massive voltage surges into the power lines, which can "blow" your sensitive electrical equipment - mostly because most of it is cheap s**t designed by clueless f**kwits with no idea how to design robust power supplies - coupled with penny pinching beancounter that will do anything to shave 0.1p off the cost of production if they can. A surge protector is basically a small box with some voltage sensitive devices in - if the voltage across it reaches a certain level, it will start to conduct, and shunt the surge off to earth.

Regarding the garage connection, I was thinking of wiring the 2.5mm T&E aerial cable into the ring main in the attic and run it to the garage. Would it be better to take a spur off the ring main in the attic to a socket with a surface box and then a 13 amp 3 pin plug from there to the garage. That would be similar to a FCU and provide protection for the cable to the garage and anything connected in there which is only a double socket and 2 lights ?

Plug and socket gives little if any advantage over an FCU (fused connection unit). But if tee-ing off the ring with 2.5mm² T&E, there are restrictions on what you can put on the end of it unless it's fused down. Certainly if that's what you have, then there is zero benefit of fitting a garage CU - just take the cable into the socket(s) and a switched FCU for the light.
Just be aware that you'll be "a bit irritated" if you start to use the garage for serious DIY (such as doing some welding) and keep blowing the fuse - needing a trip to the attic every time. And be prepared for a tenant to replace the fuse with a 1/4" bolt if they have that problem (check it as part of your routine inspections if there's any hint of it !)