MS225-48LP-HW : heat dissipation ?

[FM76]

Hy Meraki community,

We are implementing new MS225-48LP-HW with new cabinets in our company and wondering how to evaluate heat dissipation.

Each cabinet will be installed with 2 x MS225-48LP-HW, connected to 4 wifi AP MR46 by POE.

On 48 ports:

- 36 ports will be in copper cable (so no POE)

- 12 ports will be POE for standard phones

We are looking forward to evaluate and calculate heat dissipation to possible air conditioning for the cabinets.

The datasheet only evaluate :

- power consumption : 53/490 w

- Operating temperature: -5°C to 50°C

Our typical environment is  10 to 35 °C 

Do you have any details or recommendation on this point ?

Thanks for your help and support

[cmr]

@FM76 They will work in 35C ambient temperature, but I would not advise it!  We have had some running in patch rooms with 33C ambient for a few days and 30C for months without issue, but I would cool where you can.

In terms of the load I'd think with only 4x APs your be running less than 80W most of the time.  We have one MS210 with a load of IP cameras connected that budgets 630W PoE (out of 370W available), but only uses about 130W in practice...

[FM76]

Hello cmr,

thanks for this information.

Our rooms are 20C ambiant but can be from 10C to 35C 

[PhilipDAth]

If your cabinets only have switches - you won't need air-conditioning.  All you will need is airflow.  A rack with fans at the top is likely to be sufficient.  A door with a vent fitted into it at the bottom would be a bonus.

Otherwise;

https://documentation.meraki.com/MS/MS_Overview_and_Specifications/MS225_Overview_and_Specifications

The MS225-48 (non-PoE) model lists the max power consumption (under "Power Load (idle/max)") as 42W.  You are adding four APs with a max power consumption for 15W each, for a grand total of 102W.  If you allow for a power factor (PF) of 0.9 (so your power is not perfect, but not bad), you end up with an apprent power consumption of 113W.

Personally, I would doule it and then round it up to 250W.

[FM76]

Hello Philip,

thank for your support.

Concerning the PF, what do you mean by power factor ? How do you evaluate/calculate 0.9 ?

Thanks for your replies

[PhilipDAth]

Power factor is the ratio of the power your device uses compared to what it draws from the grid.  If there is zero lag between voltage and current, and your device does not waste any power, the power factor will be 1.

Otherwise if there is wastage, or the current and voltage are out of phase, you ended up pulling more power from the power socket than you are actually using.

For example, if your PF was 0.9, and you device used 1000W of power, then it would draw 1000/0.9=1111 W.  That means the grid actually needs to supply your device 1111W to operate - even though the device only uses 1000W.

A sparky should be able to measure the PF for your site (it is often done across larger circuits for the the site as a whole).

Some nicer metered PDUs (like APC) can calculate the PF of the load you have plugged in.  An example is the APC 9953 (which is switched and metered - note this one has a 32A 240V input):

https://www.apc.com/my/en/product/APDU9953/apc-rack-pdu-9000-switched-zerou-32a-230v-21-c13-3-c19/