How to Install a Breather Vent on the PMP 450m Access Point for Enhanced Water Protection

This video demonstrates how to install a breather vent on a Cambium Networks PMP 450M access point. The breather vent is an optional accessory designed for enhanced protection against water ingress, suitable for 3 GHz and 5 GHz band access points.

Please note that the breather vent is not required for any units manufactured after April 2019.

See this post for more information.

Is this due to device failures? Awful late in the product lifecycle to release a new “Optional Accessory”.

I’m going to assume this is more than “Optional” in some climates. Can you or someone specify the climate conditions that would necessitate use for this accessory? Having a good deployment of these, we would like to get as much life out of them as possible.

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That is really late in the cycle since this has been a documented issue from multiple WISPs since 2019: Anybody else have problems with water ingress on 450M?

Not to mention the pricing is a little up there considering this is almost mandatory in any wetter climates; for the radios many are already paying premium pricing on to be able to operate in high noise/high congestion areas due to the features only the M radios can provide.

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Here are some clarifications and a bit of history on this topic.

Due to the size of this radio enclosure, there is a significant volume of space inside the housing (behind the antenna). There is a breather vent (a one-way valve) designed into the seal between radio and antenna. The intent of this vent is to allow the pressure inside the housing to equalize with the outside pressure, and allow moisture to vent out of the interior of the housing. We found that on the initial design, the vent wasn’t big enough to equalize the pressure fast enough when weather conditions cause rapid temperature shifts. (For example, in Texas when it’s very hot and a cold front / rainstorm comes through, dropping the temperature significantly and very quickly). If the pressure differential is not equalized quickly, this can cause a force that pulls moisture up through the cable glands and into the radio housing. If this happens enough, water can build up inside the unit and cause failure.

The vent feature (of the radio itself) was redesigned and released to production in April, 2019. It was made larger (therefore better able to cope with these temperature differentials). These external breather vents were created in order to modify those units that were built prior to this design change, to reduce the possibility of taking in moisture.

This part has been available and is noted on (or near) page 114 of the User Guide for several years. It contains instructions for installation and the part number.

This part is not necessary for any 450m units that were manufactured after April, 2019.

There have been several cases of water ingress reported on 450m (as noted in Nick’s linked thread), and there are critical installation best practices that must be followed to reduce/eliminate the possibility of this occurring:

  1. Use proper outdoor gel-filled cabling.
  2. Ensure the Surge Suppressor is installed with a proper drip loop. (We have found that if the cables are curved too aggressively, they are prone to cracking, which allows water to enter the unit through the cabling).
  3. Ensure all cable glands are tightened with the proper torque.

The purpose of this post was simply a training video on proper installation of these vents.

In summary, these breather vents are not necessary (therefore “optional”) for any 450m radio manufactured after April, 2019. If you have radios manufactured prior to this date, and want to obtain vents for them, please contact support and we will send them to you.

The weather condition that can exacerbate a water ingress issue is rare, but does occur. The breather vent does allow for faster equalization of pressure, so it may be beneficial to add, but is not necessary. Therefore, these parts are available for purchase for anyone that wants them.

As always, Cambium Support is standing by and ready to support our customers with any issues that may occur.

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This part is not necessary for any 450m units that were manufactured after April, 2019.

Is there an easy way to check which of our 450m were made after April 2019; such as by serial, MAC or particular hardware version?

If your radio has a 12-character serial number, then the third character is the year of manufacture and the fourth is the month.

Year code Year
R 2015
S 2016
T 2017
U 2018
V 2019
W 2020
X 2021
Y 2021
Z 2023
A 2024
B 2025
Month code Month
A January
B February
C March
D April
E May
F June
G July
H August
J September
K October
L November
M December

For example, in the serial number XXSFXXXXXXX, S represents the year 2016 and F represents June.

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iremember when ours got RMAd because the ambient humidity condenses inside the housing, We tried ordering that vent and not a single distributor could get one, most didnt even know what the pn was

Thank you for your explanation. Over the years we have had several of these 450M fail for this very reason. While Cambium has never stated the failure reason they have repaired or replaced them. Nonetheless, it still cost us our reputation and subscribers as devices fail, customers go down with some leaving never to return. Not to mention having to cover the replacement expenses (office & tower labor, outgoing shipping, etc) and downtime service credits to customers. So to find that this now being acknowledged is a bit refreshing and vindicating.

However, just as fast as there was hope that Cambium was about to do the right thing and send us the breathing vent as stated by Matt (above), all was dashed upon contacting support as suggested. Support promptly told us to fork out more money and contact our distributor / vendor to purchase the breathing vent units. Below is the full response from support


Sri (Cambium Networks)

Jan 30, 2025, 11:42 AM EST

Hi XXX,

Since your AP shows a January 2019 date, it suggests that it was manufactured before the specified cutoff. Therefore, it might be eligible for a breather vent if you are experiencing issues related to water ingress.

For further assistance regarding the acquisition of a breather vent for your specific unit, it is recommended to directly contact the appropriate channels or distributors from where the equipment was originally purchased. They can provide specific guidance and support based on your unit’s warranty and service conditions.

Regards,

Sri Mani
Fixed Wireless Analyst
Cambium Networks
My working hours are Monday to Friday - GMT 10 AM to 06:00 PM


Way to go Cambium.

Matt, Was there a service bulletin issued for this? I’d sure hope so. I know I had to essentially be a rude troll to get you guys to issue one when the GPS issue was coming around again in Dec2023/Jan2024.

Something like this is essentially a recall for a critical engine component. “Hey, buy this cheap (hopefully) part to protect your $10,000 investment”

Before I react, Was your device April 2019 or before? Or was it after April?

BS either way. “May be beneficial to add” feels like something we’ll refer to in a few years when post April 2019 ones start failing as well.

Just google “Cambium N000000L141A”, 10 packs average $527US pre shipping and taxes. Couldn’t find them at some of the bigger suppliers (DoubleRadius,StreakWave,ISP Supplies), But I was able to find them at CTI connect and a hand full of others with a quick search.

Before April 2019. We had several failures. Usually around June thru July and September thru October. It is worth repeating that Cambium has always repaired them on their dime. Time to repair was usually 30 days or greater. We bought extra units to get our customers up and running or simply to redistribute and pickup the load of the failed units. No compensation for the damage to our company reputation and customer loss as demanding subscribers flee never to return. While we have not had a failure in about 2 years we still have to address the issue now that they are admitting the pre April 2019 design is flawed.

Since our last post we heard back from Cambium. They are promising to send us the relevant breathing vents. We will update if and when it happens.