Mounting Consumer Unit outside within enclosure

[aptsys]

It's certainly not an issue provided you can allow adequate protection from the elements. You'll find normal MCBs, RCBOs etc in external cabinets for streetlighting feeder pillars for example.

 

[JohnW2]

It's certainly not an issue provided you can allow adequate protection from the elements. You'll find normal MCBs, RCBOs etc in external cabinets for streetlighting feeder pillars for example.

I suppose that depends upon what you mean by "adequate protection from the elements". Protection from water ought to be achievable, but what about temperature?

Per my comments in post #8 above, do you think it would be acceptable to 'ignore' manufacturer's ratings in relation to ambient temp - since (if those MK figures are typical), I'm sure that, in the UK, one couldn't guarantee that the temp in an outside cabinet would never fall below -5°C, and I'm doubtful that, even in the UK, one could guarantee that it would never exceed 40°C ?

Kind Regards, John

 

[mfarrow]

You're best getting a little heater (say a Pentagon 20W) plus thermostat set to 5°C. Anything lower carries a risk of condensation and corrosion.

 

[ban-all-sheds]

Until I got down to that post I was going to say that in practice, with our weather, condensation is probably the biggest risk.

And corrosion may not be the main concern re condensation on MCBs etc.

 

[JohnW2]

You're best getting a little heater (say a Pentagon 20W) plus thermostat set to 5°C. Anything lower carries a risk of condensation and corrosion.

What about the 'top end' of the temp ratings? Even in the UK, air temperature can get up to 30°C, or a bit higher, so I find it hard to believe that the inside of a cabinet exposed to direct sunlight could never get above 40°C.

Kind Regards, John

 

[mfarrow]

The "outside" industries such as the railways and communications don't worry too much about the upper limit as it's not usually that hot, and certainly not for long. It may approach the limits but the likes of cabinet manufacturers and assemblers don't seem overly concerned by the threat of an odd scorcher.

It's the corrosion which is the most problematic. Steel CUs and labels etc just get ruined in a few years.

 

[ban-all-sheds]

There are external IP rated CUs/DBs available which are not made of metal.

One could always take the view that mounted outside on a garage wall is not "within" the premises.

 

[JohnW2]

The "outside" industries such as the railways and communications don't worry too much about the upper limit as it's not usually that hot, and certainly not for long.

Fair enough - so, as I asked aptsys, does that mean that you feel it would be acceptable to 'ignore' the manufacturer's stated maximum operating ambient temperature (on the grounds that you didn't think it would be exceeded by much and/or for very long)? (all MK devices that one is likely to find in a CU appear to have max ambient temp ratings of 40°C).

Kind Regards, John

 

[skenk]

Probably more likely to exceed 40deg indoors, it's not likely at all. Presumably it can be 40deg ambient temperature outside the cabinet and a fully loaded board with all breakers carrying their full load (with the heat that generates), and that is never going to happen in a normal domestic setting. See also railway and lighting comments above.

 

[aptsys]

You're best getting a little heater (say a Pentagon 20W) plus thermostat set to 5°C. Anything lower carries a risk of condensation and corrosion.

Yep, this is the normal way

 

[JohnW2]

Probably more likely to exceed 40deg indoors, it's not likely at all. Presumably it can be 40deg ambient temperature outside the cabinet and a fully loaded board with all breakers carrying their full load (with the heat that generates), and that is never going to happen in a normal domestic setting.

Fair enough. However, I can't really see how the ambient temperature inside a UK house could ever be anything like 40° - the operating temp within a CU (and components therein) of the is obviously a different matter. As for outdoors, objects left in 'full midday sun' (like my metal garden furniture!) can get far too hot to touch, so a lot above 40°, but I don't know what the temp inside a cabinet might reach.

Don't get me wrong. I would personally not worry at all about this (albeit I wouldn't want to put any of my CUs 'outdoors'!), and would, in any event, probably take the ambient temp 'ratings' with a large pinch of salt. However, given the world we live in, I was wondering (so that the OP could be advised accordingly) about the regulatory implications of (possible/probable) non-adherence to the manufacturer's specified 'ratings' of devices within the CU. People here have been known to get excited about such non-adherences!

Kind Regards, John

 

[John D v2.0]

The "outside" industries such as the railways and communications don't worry too much about the upper limit as it's not usually that hot, and certainly not for long. It may approach the limits but the likes of cabinet manufacturers and assemblers don't seem overly concerned by the threat of an odd scorcher.

agree re comms industry, virgin media weren't too worried about the odd scorcher, in one place our internet used to go off for a few hours on any hot and sunny day. Eventually when an engineer came they said it's if the cabinet is in a warm position with direct sun, it just overheats and shuts down for a while. But it's too expensive to relocate.
For rail I would have thought they'd be extra careful due to the high cost of downtime?

The MCB limits might be more about tripping too early in hot temperatures. If they don't comply with the curve then that temperature won't be allowed in the spec.

 

[JohnW2]

The MCB limits might be more about tripping too early in hot temperatures. If they don't comply with the curve then that temperature won't be allowed in the spec.

That's very possible, but we just don't know the reason. As I've said, it really wouldn't concern me very much, but in comparable situations, people have thrown at me "specs are specs" (and/or "regs are regs", in the days when BS7671 required compliance with MIs)!

Interestingly, I now see that Wylex don't appear to specify a maximum ambient temp (like MK's 40°C max) but they do indicate a 'de-rating factor' (0.9) to be applied at an ambient temp of 60°C - so maybe those are the ones to go for in an outdoor, sun-exposed, cabinet!

Kind Regards, John

 

[Bucks_Refurb]

Thanks guys - will fit the small heater.

 

[ban-all-sheds]

OOI, Bucks - have you ever encountered, or heard of, anybody with their CU outside?