Node placement may be less than ideal but it works

[Sharpbarb]

I needed 5ghz wifi coverage in a couple bedrooms at the far end of our house and I thought about placing a mesh node in the ceiling. I didn't want it to be visible so I wanted to place it in an enclosure behind the drywall.

I was concerned about the 5ghz signal getting attenuated and the router overheating.

I wanted the router in a small enclosure that would be protected from the temperature extremes in the attic. I used my old RT-AC68U which can lay down flat against the drywall. I cut an access hole in the wood planks in our attic and cut out a section of insulation. Using some nails on the inside of the framing and a thin board I made a cover over the router. The insulation then went back on the cover.

I relied on the exposed drywall in the enclosure to act as a heat sink, the ceiling drywall temperature is usually 68-74F. With the attic at 95F, the router temperature (found via ssh) was about 185F (85C). Inside the house I measured the ceiling temperature with an IR gun and there was about a 1 foot square spot at about 100F with the surrounding temperature about 70F, which is exactly what I would expect.

At first I didn't use a fan, but the attic can get to 120F in the summer and I wanted to get that temperature down. I used cardboard, glue, and staples to make a frame to hold an 80mm fan that could blow on the drywall and router. The temperature of the node stays relatively constant at around 70-75C even when the attic temperature swings from 60F-110F during the day.

The 5Ghz signal is great in the area I wanted to cover, so I'm happy with the outcome.

 

[Sharpbarb]

 

[OzarkEdge]

I relied on the exposed drywall in the enclosure to act as a heat sink, the ceiling drywall temperature is usually 68-74F. With the attic at 95F, the router temperature (found via ssh) was about 185F (85C). Inside the house I measured the ceiling temperature with an IR gun and there was about a 1 foot square spot at about 100F with the surrounding temperature about 70F, which is exactly what I would expect.

At first I didn't use a fan, but the attic can get to 120F in the summer and I wanted to get that temperature down. I used cardboard, glue, and staples to make a frame to hold an 80mm fan that could blow on the drywall and router. The temperature of the node stays relatively constant at around 70-75C even when the attic temperature swings from 60F-110F during the day.

The goal shouldn't be that it works. The goal should be that it doesn't fail and/or burn your house down.

I would not enclose that router.

https://dlcdnets.asus.com/pub/ASUS/...6.1993468583.1588122758-2046540302.1584849218

OE

 

[Keith Gorham]

Nice idea, but I would have vented the fan from the attic air instead of recirculating the air inside the small enclosed area.

 

[Sharpbarb]

The goal shouldn't be that it works. The goal should be that it doesn't fail and/or burn your house down.

The operating temperature is referring to the surrounding environmental temperature. In my case, the fan/drywall system keeps the enclosure temperature just a few degrees higher than the temperature inside my house (~75F or 24C).

I did a bit of research before going down this road and 85C is a normal CPU temperature for this router. Mine is running between 70-75F.

https://www.snbforums.com/threads/rt-ac68u-temperatures.17418/
https://www.snbforums.com/threads/rt-ac68u-temperatures.22121/

Nice idea, but I would have vented the fan from the attic air instead of recirculating the air inside the small enclosed area.

Although it's small (15" x 15" x 4"), the fan/drywall keeps the temperature about the same as inside my house. My attic will easily get to 120F-130F in the summer. I wouldn't want to blow that hot air into the enclosure.

 

[OzarkEdge]

My attic will easily get to 120F-130F in the summer.

You should hope to maintain an ambient steady-state operating temp of less than 40C or 104F next to the router. With a 95F attic temp, your IR gun measured an inside ceiling temp of 100F. Let's just assume the attic side of the ceiling temp is 104F to give you that temp delta and prerequisite heat transfer. Now let's raise the attic temp ***35*** degrees to 130F... and raise the inside air temp because your HVAC is going to slump a bit on hotter days. Now, do you still think your enclosed router space is going to hold the same 104F?

Bring the Ethernet down out of the attic and place the router inside... anywhere will be better than the attic. You'll thank me every time you have to access the router for some reason.

OE

 

[Trip]

@Sharpbarb - Simply put, wrong hardware and/or location for the job.

If you want to keep that consumer box, you'll need to get it out of the attic and down into a much more well-cooled area. Period.

If you absolutely must hide an AP in that spot, I'm not a big fan of the idea, but at minimum you need proper hardware in there; something designed to operate well beyond the temps you may see up there, on its own -- no jury-rigged cooling fans required (yikes!). An example would be an enterprise-class outdoor, IP-rated access point, such as a Ruckus T300 or T310, which is designed to operate at up to 149F.... but it's intended to be used just like that... outdoors, where you have proper venting/radiating.

And on that last note, not being able to vent/radiate temperatures that hot means you should probably go with the first approach and get the AP out of the attic altogether, regardless of the class of hardware being used.

 

[Sharpbarb]

With a 95F attic temp, your IR gun measured an inside ceiling temp of 100F.
OE

That was without a fan. As I type the inside of my house is 75F (Which is bit warmer than usual, trying to save a little on A/C). Outdoor temperature is 84F. Attic temperature is 108F.

The inside surface temperature of my ceiling is currently 77F (general area). The temperature in a small spot right underneath the router is 92F, but the general temperature in the 15" x 15" enclosure is about 85F.

The reported CPU temperature is 76C (169F).

 

[OzarkEdge]

That was without a fan. As I type the inside of my house is 75F (Which is bit warmer than usual, trying to save a little on A/C). Outdoor temperature is 84F. Attic temperature is 108F.

The inside surface temperature of my ceiling is currently 77F (general area). The temperature in a small spot right underneath the router is 92F, but the general temperature in the 15" x 15" enclosure is about 85F.

The reported CPU temperature is 76C (169F).

So, your temp measurements:
outdoor air = 84F
attic air = 108F (max may be ~130F)
insulation
enclosed router air = 85F (max should be less than 104F)
inside ceiling at router= 92F
inside air = 75F

The theory of heat transfer is a simple equilibrium between two different temps. Heat energy flows from the high temp to the low temp until the temps are equal. You need a temp differential to affect heat transfer.

Can you better measure the air temp at the router... place a thermometer next to the router under the insulation and stream some traffic through the node for 1o minutes. Then check the temp. If you want... not really required, of course!

OE

 

[Sharpbarb]

Can you better measure the air temp at the router... place a thermometer next to the router under the insulation and stream some traffic through the node for 1o minutes.
OE

Yes actually. I happen to have a thermometer prototype I can use. It has two probes that average the temperature. I didn't previously show an additional scrap of insulation I had thrown on what I showed above.

The temperature on top of the insulation is 102.6F. The remote sensor measuring temperature in the attic is right in the middle, whereas this node located near a roof and gable vent, so it makes sense the temperature here is a little lower. I then placed the probes next the the router and measured 91.1F.

I've been trying to get iperf to work for the last hour with no luck. If you have a suggestion for how to stress test the router I'm all ears.

 

[OzarkEdge]

Yes actually. I happen to have a thermometer prototype I can use. It has two probes that average the temperature. I didn't previously show an additional scrap of insulation I had thrown on what I showed above.

The temperature on top of the insulation is 102.6F. The remote sensor measuring temperature in the attic is right in the middle, whereas this node located near a roof and gable vent, so it makes sense the temperature here is a little lower. I then placed the probes next the the router and measured 91.1F.

I've been trying to get iperf to work for the last hour with no luck. If you have a suggestion for how to stress test the router I'm all ears.

Interesting tool!

So, enclosed router air = 91F (not 85F) at rest... that does fit into the temp sandwich a bit better, imo.

I have not used iPerf. My thought was to just stream some Internet media like TuneIn through the node... probably not much stress in that.

I still think you will overheat that router. If it only runs hot, you may shorten its life. Time will tell.

OE

 

[Sharpbarb]

I threw a remote temperature sensor in the small enclosed space where the node router is located and took some measurements when we had a warm day. The router CPU temperature hovers between 70C and 82C which is well within normal. The other thing to consider is that the temperature rating of the router (40C) is under natural convection conditions. With a fan blowing over the router heat can leave the router much more efficiently.

 

[Trip]

With all due respect, this looks like a shortened lifespan at best, hazard at worst, if/when that fan turns off or fails.

I would either get beefier hardware in there, rated for 65+C natively, optionally with the cover/casing removed, or get that Asus out of there and into the house, concealed well enough, perhaps on top of a book shelf.

 

[Sharpbarb]

With all due respect, this looks like a shortened lifespan at best, hazard at worst, if/when that fan turns off or fails.

I would either get beefier hardware in there, rated for 65+C natively, optionally with the cover/casing removed, or get that Asus out of there and into the house, concealed well enough, perhaps on top of a book shelf.

In my experience fans tend to whine and squeal before they fail completely. At the moment, when it's very quiet, you can just hear the fan inside the house when standing directly underneath so I would hear if the fan started degrading. Also, I suspect equipment rated for 65C operation would have integral fans that could theoretically fail.

Anything involving electricity is a potential hazard but in my application I don't see a hazard beyond what is typical. The fan/router is low voltage DC. The only thing that worries me (in general) is the wall adapters. They tend to be robust but they can fail and start a fire. Most are UL listed for that reason. Do you have any wall adapters behind a couch or bed?

I did get curious and went and turned the fan off. I'll see how the temperatures behave and report.

 

[Trip]

Plenty of APs that are outdoor-rated are design with a max of 65C, passively cooled (although being outdoors, easy heat radiation is assumed). For example, the Ruckus T series (T300, 310, 610, 710, etc.) Regarding power source, AC adapters need not be a concern because they're powered via PoE, which is the optimal way to do it, especially in inclement conditions. And yes, I understand outdoor-rated, pro-level APs are often spendy (although you can find them on eBay for hundreds less), but I would roll with something like that long before a consumer all-in-one, but to each their own.

 

[Razor512]

One other risk from an enclosed space is that there are many components on a PCB which do not like high temperatures, e.g., capacitors and many other passives. They will likely not last very long.

What needs to be measures is the ambient air temperature within the enclosure.
Other risks involve if there are ever any insects making their way to the router. While it is rare for them to set up nest in an attic since even with a ridge vent, an attic can easily hit 150f on a sunny day in the summer, during the winter, it can remain cool enough for some insects to try and crawl around, especially if you use a soffit vent or gable vents with larger mesh openings.

 

[K-2SO]

With a fan blowing over the router heat can leave the router much more efficiently.

Get the PCB out of the router housing. Nobody sees it there anyway. Big improvement in heat dissipation.

 

[--Manu--]

I am german, so i hope i will find the correct words in english.

I can't see where the fan gets cold air from.In this construction, the fan will only circulate the heated air.

In my opinion....now comes the difficult part for a non english speaker^^......i would insert the fan in the interior panneling (maybe covered with a fan cover) which blows the air to a "plastic tube" into the "router chamber"...I hope everyone understands what I mean.

I would also put the router in a "plastic tub" to keep dirt, dust and maybe insects (more or less) away.
Since this is not 100% airtight, the warm air would escape ... and with a little luck you can create a minimal overpressure in the chamber (against dust)

 

[Sharpbarb]

I turned the enclosure fan off yesterday at 9AM and continued recording temperatures. The thing I found interesting is that the temperature of the small router enclosure did not change very much and didn't exceed 91F (33C). I suppose this makes sense because the total heat input to the space didn't change. The CPU temperatures on the other hand went from a peak of 180F (82C) to 196F (91C). While this is toasty, a quick search of the forum will find that these temperatures are not extraordinary.

What needs to be measures is the ambient air temperature within the enclosure.
Other risks involve if there are ever any insects making their way to the router. While it is rare for them to set up nest in an attic since even with a ridge vent, an attic can easily hit 150f on a sunny day in the summer, during the winter, it can remain cool enough for some insects to try and crawl around, especially if you use a soffit vent or gable vents with larger mesh openings.

The "Router Space" temperature is from a remote sensor inside the small enclosure. I'm not too worried about insects. I've always been surprised by the lack of insects inside my attic; I'm not really sure what keeps them out.

Get the PCB out of the router housing. Nobody sees it there anyway. Big improvement in heat dissipation.

This doesn't sound like a bad idea. No real reason to keep the plastic shell on the router...

I can't see where the fan gets cold air from.In this construction, the fan will only circulate the heated air.

I would also put the router in a "plastic tub" to keep dirt, dust and maybe insects (more or less) away.
Since this is not 100% airtight, the warm air would escape ... and with a little luck you can create a minimal overpressure in the chamber (against dust)

There is no cold air intake; you're correct that the fan will only circulate heated air. I'm relying on the un-insulated drywall to reject heat from the enclosure. The purpose of the fan is to help get heat out of the router and into the enclosure.

Since the system only circulates air I'm not sure if dust will be an issue.