My Synology DS1621+ is located in a cool room with an ambient temperature of 16–17°C (60–63°F). Despite this, DSM consistently reported a CPU temperature of around 50°C at idle, which immediately raised concerns—especially with summer temperatures in mind.
In this article, I will walk through how I reduced the CPU temperature on my Synology DS1621+, what I changed internally, the risks involved, and whether the results were actually worth the effort.
My Long-Term Experience with the Synology DS1621+
I have owned my Synology DS1621+ since its release, and as of January 2026, it has been running reliably for several years. I use it for:
- General file storage
- Docker containers
- Multiple WordPress containers powering this website
Even though the platform is no longer new, it remains extremely stable and performant for my workload.
Moving the NAS Didn’t Solve the Temperature Issue
Previously, the NAS was installed in my utility room alongside my heating system. During summer, this required increasing fan speed to keep temperatures under control.
After building an annex, I ran network cabling and moved the NAS to a much cooler environment. However, even in these ideal conditions, the idle CPU temperature remained at ~50°C.
That’s when I started worrying about thermal headroom during hotter months.
Searching for a Real Solution
Like most people, I started by searching online. Unfortunately, the vast majority of results focused on:
- Replacing stock fans with quieter alternatives
- Adjusting fan curves in DSM
This wasn’t helpful. I had already replaced the fans when I purchased the unit, and airflow was not the problem.
A Single Forum Post That Made Sense
Eventually, I found a Synology Community forum post where a user with a Synology DS1821+ experienced the same issue and solved it in a surprisingly elegant way:
👉 https://community.synology.com/enu/forum/1/post/186132
That post became the foundation for my own solution.
The Key Insight: Use the Chassis as a Heatsink
The short version of the solution:
- Replacing thermal paste alone had little impact
- Adding thermal pads on top of the CPU heatsink created thermal contact with the metal chassis
- Result: the entire NAS chassis effectively becomes a passive heatsink
This dramatically improves heat dissipation without increasing noise.
The original post contained very little documentation, so I had to figure out the practical implementation myself.
Important Warnings Before You Proceed
Before attempting this modification, you should be fully aware of the risks:
- You will almost certainly void your Synology warranty
- Only use soft thermal pads, such as Arctic TP-3
- If anything breaks, the responsibility is entirely yours
This is an unofficial hardware modification.
Disassembling the Synology DS1621+
To access the CPU heatsink, the DS1621+ must be almost completely disassembled.
The best teardown guide I found is this YouTube video:
👉 https://youtu.be/W9h1cKl6GmY
Follow it carefully—this NAS is tightly packed, and mistakes are easy to make.
Replacing Thermal Material and Installing Thermal Pads
Once the motherboard is removed, you can access the CPU heatsink. Be extremely careful with the two plastic push pins holding it in place. I used needle-nose pliers to gently compress them.
A Surprise: Extremely Degraded Factory Thermal Material
Although the forum post claimed replacing the thermal paste had little effect, I checked anyway—and I’m glad I did.
The factory-installed thermal material was completely dried out.
It took me over 30 minutes to soften and remove it:
- Alcohol-soaked cotton pads placed on the heatsink
- Cotton swabs with alcohol to gently clean the CPU die
Once clean, I:
- Applied new thermal paste
- Installed thermal pads on top of the heatsink, ensuring contact with the metal chassis
Reassembly and Testing
After reassembling the NAS (and yes—accepting the risk of a leftover screw), I powered it back on.
Temperature Results
- Before: ~50°C idle
- After: ~45°C idle
That’s a 5°C reduction, roughly a 10% improvement.
Was It Worth It?
Given the cool ambient temperature, the result isn’t spectacular—but it is meaningful:
- On hot summer days, peak CPU temperatures should drop from ~70°C to ~63–65°C
- The Ryzen V1500B begins throttling at around 70°C
This creates a valuable thermal safety margin.
My Honest Verdict
That said, I expected more:
- The AMD Ryzen V1500B has a TDP of just 16W
- No integrated heat spreader (unlike many Intel CPUs)
- Very delicate exposed die
- Surprisingly poor factory thermal solution
Overall rating: 6–7 out of 10
It works—but Synology should have done better out of the box.
Conclusion
If you’re experiencing high CPU temperatures on a Synology DS1621+, and your warranty has expired, this modification can be worthwhile. It’s not risk-free, but the results are real.
Would I recommend it to everyone? No.
Would I do it again? Yes—but with realistic expectations.
