On Wed, 17 Jan 2024 at 03:18, <bzs@theworld.com> wrote:
Others have pointed to references, I found some others, it's all pretty boring but perhaps one should embrace the general point that some equipment may not like abrupt temperature changes.
Can you share them? Only one I've found is: https://www.ashrae.org/file%20library/technical%20resources/bookstore/supple... Which quotes 20c/h, which is a much higher rate than almost anyone has ability to perform in their DC ambient. But it makes no explanation where this comes from. I believe in reality there is immense complexity here - Gradient depends on processes and materials used in manufacturing (like pre/post ROHS will certainly have different gradient) - Gradient has directionality, unlike ASHRAE quotes, because devices are engineered to go from 20C to 90C in very short moment, when turned on, but there was less engineering pressure for similar cooling rates - Gradient has positionality going 20C between any two pairs does not mean equal risk And likely no one knows well, because no one has had to know well, because it's not expensive enough to derisk. But what we do know well - ASHRAE quotes rate which you are unlikely to be able to hit - Devices that travel with you, regularly see 50c instant ambient gradients, both directions, multiple times a day - Devices see large fast gradients when turned on, but slower when turned off - Compute people quote ASHRAE, Networking people appear not to, perhaps like you say spindles is the ultimately reason for the limits to exist I think generally we have bias in that we like to identify risks and then add them as organisational knowledge, but ultimately all these new rules and exceptions you introduce, increase cost, complexity, reduce efficiency and productivity. So we should be very critical about them. It is fine to realise risks, and use realised risks as data to analyse if avoiding those risks makes sense. It's very easy to build poorly defined rules over poorly defined rules and arrive in high cost, low efficiency operations. Like this 'few centigrades per hour' is an exceedingly palatable rule-of-thumb, it sounds good, unless you stop to think about it. I would not recommend spending any time or money derisking gradients, I would hope that rules that redisk condensation are enough to cover derisking gradients and I would re-evaluate after sufficient realised risks. -- ++ytti