Network cabinet - fire mitigation

[Tim Watts]

I'm looking to site a small 19" network cabinet in my attic space, near the main ELV cable tray.

It will contain some running equipment - PoE network switch, IP Cam recorder, UniFi Wifi controller.

Probably not my 2 small servers - they;d be better on a shelf in the hall. So probably 200-300 watts of net consumption at worst - ie needs some ventilation but not loads.

Mindful of a piece of faulty equipment not starting a fire in a space filled with wood and stored "stuff", I am thinking of a full metal cabinet, the sort with lots of small vent holes/slots all over.

My feeling is:

*If* (and it's rare, but I have seen it happen, couple of items from 1000s of bits of kit I've been involved with over the decades) a bit of equipment incinerates, that doing so inside a metal box is likely to significantly reduce the likelihood of any fire spreading outside before fuses blow and the source of the fire quenches. There after all is not actually that much burnable material in say a metal boxed network switch.

Given a bundle of Cat-x cables are coming in, let's also assume I'll use low-smoke LSZH type cables as far as practical.

Any comments?

[Bob Minchin]

[John Rumm]

That pretty much describes most comms cabinets these days... (although they normally have a glass front door). e.g:

You could clad it in insulation for added fire protection and protection from ambient temperatures in the loft, but then you would need to have some active airflow through the cabinet. You could fit a network connected temperature sensor. (I note that some of the draytek wireless APs have that built in now).

If you are fitting mains interlinked smoke detectors, then fitting one in the loft would seem like a good idea.

The first cabinet I used domestically was a plastic cabinet (only because they were available in smaller sizes and significantly cheaper at the time). I more recently rehoused everything in a metal one as I needed more space (and these days the metal ones are pretty cheap). Mine is in an under stair cupboard, so perhaps more noticeable if things were to get too toastie!

[Tim Watts]

Good question and it's a retro warm roof (from the POV of being inside).

That is to say, there is 75mm celotex between the rafters, 15mm under and then 9.5mm PB over the more accessible parts to protect the celotext from dents and fire.

The attic is thermally part of the upstairs room (thin pannelling will separate them)

[Tim Watts]

Forgot to say, but Bob asked, the attic is thermally part of the upstairs - so warm (but not baked in summer) and dry and otherwise fairly airtight from the outside.

but then you would need to have

Yes - I do and adding one in the void may not be a bad idea.

[Tim Watts]

^^^ 25mm under

[tabbypurr]

Ye oldie bimetal room thermostat set to 30 in the cabinet could cut power in case of fire, you'd just need to ensure just enough airflow to avoid it hitting 30C in normal use.

I wouldn't insulate the cab, it won't help in case of fire, it'll make it worse, and it won't help with anything else.

NT

[Tim Watts]

A bit of old-skool protection wouldn't be a bad idea. Could even stick a low temperature thermal fuse in a small box with some vent holes inside the cabinet.

I agree (I think there was an assumption the attic was cold, it's not).

I'm thinking to maybe line a space with PB (the roof is already lined) a few inches bigger all round than the cabinet then site the cabinet in there. Stick a couple of intumescent air vents top and bottom for some basic convection.

[Brian Gaff]

Yes some insulation needed and perhaps forced ventilation too. There used to be a fire detecting extinguisher available for such racks back in the 80s, but cannot remember where from now. Brian

[tabbypurr]

You could but I don't think it's needed. A fire inside the cab quickly goes out if there's little external airflow.

NT

[Huge]

[26 lines snipped]

Any way of fitting some sort of extinguishing system? One of those vehicle types where a fire melts a plastic tube which squirts extinguishant, perhaps?

[spuorgelgoog]

Fire extinguishers are available eg

or you can get small halon-replacement cylinders eg

You can get relay interface bases for most common smoke detectors, so if it detects smoke it could cut the power to the rack. This might be more reliable than a high-temp thermostat especially for a smouldering plasticy fire.

Owain

[Tim Watts]

That's really interesting - relatively inexpensive - thanks!

Yes - I think I've seen those for the Ei-Aico units I have.

Great ideas...

[Dave Liquorice]

Interesting idea but is there a UPS? I guess you could put the break after the UPS but it needs to be fail safe, ie no power = UPS disconnected otherwise there are possibilties that power (from the UPS) is supplied when you don't want it to be. But you have to account for power cuts when you do want power from the UPS.

And if interlinked, which is also a good idea, you don't want the rack power dumped when you burn the toast.

I'm sure it's possible but needs a bit of thought and careful examination of the logic truth table of anything designed.