I've been using a mini-split unit to cool our server room for over 15 years without any major issues. However, our old unit recently failed after 15+ years. An HVAC company assessed the room—which isn't packed with equipment, just about three-quarters of a full rack—and estimated it generates around 10-15k BTUs of heat. They installed a new mini-split unit rated for 20-24k BTUs to be safe. The unit is set to maintain a temperature of 75°F.
Here's where my concern lies: it cools perfectly fine when the outside temperature is below 60°F, but as soon as it hits 61°F or higher, especially when the sun hits the building, the temperature in the room jumps up by 2-4°F. The unit struggles to bring the temperature back down until later in the evening when it cools off outside. It's a noticeable pattern on our temperature monitors.
I have two main concerns: 1) Is this kind of temperature spike normal for a small network closet? 2) As we move into spring and summer, should I expect these temperature spikes to increase even more? I'm worried since the old unit managed to cool a larger amount of equipment without these issues. What do you think?
5 Answers
Sounds like your new mini-split might be undersized for your cooling needs. It’s essential to accurately calculate how much heat your servers generate—just look at the power they consume and convert that to BTUs. If the cooling system isn't designed to handle that, it’ll struggle as temperatures rise outside. You should definitely double-check the calculations provided by your HVAC company.
If the temperature spikes are causing panic, you might just want to adjust your set temperature lower to offset the hotter outside temps. Remember, 26°C (79°F) isn’t typically alarming unless it starts consistently going above 30°C or so. It sounds like you might be overthinking it!
True! I usually let my servers run a bit warmer too without issues.
Good to know! I’ll keep that in mind.
Just to clarify, 79°F is pretty much within the safe zone for server operation. As for the cooling specs, definitely ask your HVAC guys for insights on both the old and new units to ensure they’re comparable. If this problem continues into the hotter seasons, then you’ll have to devise a backup plan!
Yes, I'm already planning to get those specs!
Three-quarters of a rack isn’t much, but you're right to be concerned. There are factors like windows and insulation that could make a difference too. I’d recommend checking if your unit is an inverter model, as that affects its efficiency. If it’s struggling at 79°F now, it might have trouble with the higher temperatures of summer. Have you thought about installing a second opinion from another HVAC provider?
Good ideas! I’ll definitely look into that. A fresh set of eyes could help spot something I missed.
It's also possible they didn't seal the pathways between the inside and outside well enough. If there's any leak or poor insulation, that could let the heat in. You may want to have them test for leaks again or just check the entire setup. Better safe than sorry!
That’s a great point! I’ll bring that up when I talk to them next.
Do you really think it’s undersized? I mean, it seems to keep the room cool enough at lower outside temps.