MJNewton

Whilst I'm no expert on the common causes of fire it wouldn't surprise me if the biggest risk in a (our) family room might be from faulty electrical equipment (AV kit, chargers etc) and perhaps candles rather than situations that heat alarms are aimed towards (eg chip pan fires?).

I am getting to the end of an extension to create a 'family room' - an open-plan kitchen/diner/lounge and am wondering what best to do about smoke/heat alarms.... Given the risk of false alarms I understand that a heat alarm is most appropriate for a kitchen however do they still perform adequately in a large room (9m x 5m)? There will be a defined kitchen area and so I was going to locate it there - perhaps above / to the side of the hob+oven? Or should I be looking at something else? (Maybe some sort of best-of-both-worlds combined affair that I might not be aware of?) The rest of the house used interlinked Aico alarms and so they would be my starting point, and perhaps finishing point too if alarms from different manufacturers cannot be mixed.

Following up on some of the mentions about hole limitations in I-joists, Simpson make an 'I-Joist Hole Support' that enables you to put holes upto 250mm wide (and full height of the webbing) anywhere you like beyond 50mm from the bearing points if need be.

I had a cut on my forearm that I didn't think much of but as it developed a scar I started to feel almost like there was something inside it. Casually mentioning it to the doctor one day whilst there for something else he sent me to hospital for an x-ray where they discovered there was indeed something inside... Two weeks later I am lay on a bed with my arm stretched out to one side with a plastic surgeon cutting my arm open. Local aesthetic so I was awake, and petrified (really quite squirmish) so when his assistant tripped over the wheel of the trolley table my arm was on I didn't see the funny side (I can now). Anyway, he pulled the object out and identified it as a piece of porcelain tile! Cue sudden flashback to six months earlier when I was chipping tiles off the wall and noticed a small cut on my forearm and wondering what had happened!

...not wishing to muddy the waters just as we were reaching some clarity but even a time-delayed RCD couldn't necessarilly guarantee the expected outcome as with a 60mA earth fault a 30mA RCD has a maximum trip time of 150ms and yet a time-delayed 100mA RCD has a minimum trip time of 130ms. That still leaves a 20ms window within which the time-delayed 100mA could end up beating the non-delayed 30mA potentially leaving the latter untripped. ? In practice I would expect it to work as intended though as non-delayed trip times are usually significantly shorter than what the standards require.

It is absolutely possible, yes, even if both devices are operating within spec.

It is more nuanced than that. The performance characteristics for RCDs are laid down by BS61008 which includes maximum trip times that vary depending on comparison to the rated trip current (In). This is necessary given the increased risk arising from increased exposure time and not just increased current. The base times specified are: Hence, an earth fault of 100mA would require a 30mA RCD (detecting 3.33 x 30mA) to trip within 150ms and a 100mA RCD (detecting 1 x In) to trip within 300ms but there are no *minimum* trip times specified (this is only done for time-delay RCDs) and so it is not possible to determine which would/should trip first. Moreover, for earth faults >150mA a 30mA and 100mA RCD would both be required to trip within the same maximum time (that's not to say they would do so if daisy-chained in the same circuit of course because an early trip from one may limit the exposure time of the other to the current imbalance).

I've just re-read and spotted there was a 5mm gap, albeit filled with foam?

If the studs weren't in direct contact with the wall (ie even just a small air gap) might that help?

Generally just TT earth systems where the supplier doesn't provide an earth, which can also include outbuildings where the earth isn't exported from the main building. Absolutely agree; I was just pointing out that even daisy chaining a 30mA downstream of an 100mA is still not good as it doesn't provide the discrimination that is often assumed to be the case.

This is not the case. Trip time depends on exactly that - trip time - you cannot with any certainty determine whether the 30mA or 100mA RCD/RCBO will trip first, regardless of where they are located. The only exception to this is if the fault current is between 30mA and 100mA in which case the 100mA RCD/RCBO will of course not trip at all. The only way of being deterministic is with time-delay RCDs/RCBOs which in most situations will undermine the protection that are usually employed to provide.

I've always regarded their price list as a catalogue of sorts, if that might suffice?

Yes, I was thinking about similar. Did you have a particular plan in mind? I assumed that a non-contact current transformer wrapped around the live feed would be the best sensor but wasn't sure on the best/safest place to do this given that the cores are only separated at each end where there's not much room to fit anything else like this? That said, I was assuming it'd be done at the hob/oven end but maybe inside the consumer unit would actually be the easiest place to do it?

For ours the RH sensor works extremely well for showers, baths, some cooking (boiling) and drying clothes... However, it's obviously no good for cooking smells so for that we've got a boost button next to the hob. Similarly, we have boost buttona outside the bathrooms but tend to rarely use them. The boost buttons are actually wired as inputs to a smart relay which, in turn, triggers the boost function as eventually once I get more time (yeah right!) I'd like to experiment more with home automation, voice control etc for various things which may or may not include the ventilation system.

That should be straightforward to recreate. Most (all?) MVHR units have boost inputs and as a boost switch in the kitchen makes sense anyway a non-contact current sensing relay wired in parallel (example) should work well.

Can you elaborate on the 'cooker hood mode' bit? Presumably, given the choice of words, it doesn't come with a cooker hood but is some sort of changed behaviour when the cooker hood is running? If so, I would imagine most units could be manipulated to do similar without too much effort (and a £10 smart relay) - unless the feature is more advanced than I am imagining.

Yes, they're got their own carriers.

The 221s arrived without much fanfare, and it doesn't help that the 222s are still around yet I would've expected them to have replaced them. They're such an improvement; easier levers and they have squared edges so can be 'stacked' a lot easier to reduce space.

There are smaller lever Wagos available too - the 221 series: Same rating as the 222's, and I prefer the transparent case for reassurance of correct insertion. Incidentally, re the push connectors they are releasable/reusable - you just twist the wire whilst pulling.

Oh I do panic panic Peter... Don't know why. I used to be so easy going - and indeed still consider myself to be - but when it comes to detail like this (particularly when it comes to the house for some reason) I'll keep myself awake at night over this sort of thing!

In my new family room extension I've included four runs of Cat 5e network cable for TV (and related items) and another for an outdoor IP camera. With the runs coming back to the central wiring cupboard (where the remainder of the house is already connected to) there's about 40m added in total... I bought my cable from a local electrical distributor TLC Direct as I buy a lot of my electrical kit, wiring etc, from there and have always been very pleased. They sell Cat 5e cable either by the metre or on 50m/100m coils as seen here. There's quite a saving to be had buying it by the coil and so I went for a 50m coil for this job... Little did I realise at the time but the by-the-metre cable isn't the same as the by-the-coil; the former is solid copper whereas the latter is copper over 0.5mm aluminium. Grrr. From what I can gather (from a cursory Internet search) CCA network cable is seemingly not compliant with the specs (which calls for 'copper') and is what you get when you buy cheap off eBay. I feel a bit duped to be honest as I didn't spot this detail when I ordered. Just how bad is CCA cable? Each of my runs is <10m and is currently running at 100Mbps but of course I might one day want/need to increase that. It is perhaps more the outdoor IP camera that I am concerned about as I am powering that over PoE, or at least the 'poor mans' method that uses the same pairs is 'proper' PoE but is done using a crude injector/splitter and with a dumb 12v PSU. That said, the camera has worked faultlessly for six months so I know it works but I am concerned about longevity and other potential issues that CCA is seemingly criticised with (e.g. higher resistance). I am tempted to rip it all out but that'd be a bit of a pain for the camera cable give it is run through the external wall, all nicely sealed up etc. I think what I'd rather do is be convinced that I am worrying over nothing (like I do), that there's a million other buildings out there with CCA network cable in working just fine, and I need to get on with 1001 other jobs that still need completing! Don't hold back though - feed my anxieties if that's more appropriate! P.S. The cable sheaf seems to have all the right markings on and doesn't mention CCA.. but then I guess it wouldn't?

Yes, I'm keen on experimenting with some sort of miniature programmable board as I would like a smart dimmer that also has local control through a rotary knob (not push buttons). I've been trying to convince Allterco to add rotary encoder inputs to their new Shelly dimmer module and might be making some progress which would be great so I don't have to roll my own!

That does of course depend on which 'standard' is being followed (convention would be more accurate). All our lighting circuits are looped in at the switches and so have a neutral available. I wouldn't be surprised if this isn't becoming more commonplace as it gives a greater choice of light fixtures (as there's no need for them to accommodate multiple cables) and does of course help with 'smartifying' the switches.

Why not just screw them on from the inside? Or have I misunderstood the situation?

I suppose the flip side to that is that the 'attack surface', to coin a security phrase, is reduced with only having that single intake.