2 AC questions - PeachParts Mercedes-Benz Forum

Zulfiqar · #1 07-06-2012, 04:55 PM

part 1 is the little network room where my office racks are, the AC unit suction port is on the cold side of the racks and far away, right next to its roof tile is a blow vent which is also blowing directly onto the thermostat.

This is causing uneven temperatures, ( I have 3 temperature probes in the room) - I have shrouded the top rack door perforations and remounted the rack helper fans to help blow the hot air up (previously the fan was mounted upside down at the very top) This dropped rack temperatures by 10 degrees easily but the A/C unit cuts out from the T stat which gets too cold from the air blowing on it.

My vague understanding says that the system suction vent should be at the hot side of the racks so it can immediately suck in the hot stack of air rising from the back of the racks - while all blower vents should be blowing to the front of the racks. - Am I wrong here? because the AC contractor that the office uses refuses to swallow my thinking.

Part 2 is residential. - I have lived outside of US and with ducted A/C system, the suction vents were always at the very top and were quite large in area, those ducts then led to the evap unit. My house and nearly all houses I see in US have suction vents on the lower level floors and about one small one on top floors even with a single system. In dubai the house I lived in was 2 floors and had 1 A/C unit which was ducted, the lower floor ducts had fan aids while the top ones did not use such a fan, The house could cool down rather quickly and even out.

spdrun · #2 07-06-2012, 05:07 PM

Move the t-stat or get one with a remote probe. You can also find the thermistor, unsolder it, and run wires to it.

Or move your serverz to ze cloudz. Don'cha know? It's da new hip thing. Ze cloudz, BABY!

Zulfiqar · #3 07-06-2012, 05:27 PM

ze clouds are good I know but the accountants (old folks who use calculators) dont think of it much.

anyways - I know I can move the T stat around but I find the ducting to be wrongly placed. Dont you think that instead of applying a fix a rooted solution would be better.

kerry · #4 07-06-2012, 05:28 PM

Yeah. US central AC system usually just use the existing hot air furnace ductwork which has the returns and the supplies down low. Goofy.

kerry · #5 07-06-2012, 05:30 PM

Actually, after having just turned a fixed skylight in my kitchen to a vented skylight and experienced the substantial difference, I realized if each room in a house had a vent in the ceiling which led up thru the house and outside, the whole house would be much cooler with little expenditure of energy.

Zulfiqar · #6 07-06-2012, 05:41 PM

I think Im gonna beat that AC tech when he comes in next - and make him follow what I want. Why fight nature and end up with high bills.

old buildings in India utilise the hot air stack phenomenon to keep cool inside, they have little slits with backwards facing covers on the super high ceilings to vent out the hot air (no A/C in them buildings) - The walls are also hollow with slits up top and midway too, this causes the inner walls to stay cooler as a column of hot air is always exhausting from the top vents in the summer.

Infact if you look at the Taj Mahal walls, it also has very similar technique but also has some water spray system to cool the marble.

mgburg · #7 07-06-2012, 05:45 PM

Ideally, you'd like the hot air to be sucked up by the I/P to the air-conditioner and the cool air to drop to the floor (or into the bottom of the racks) or an un-occupied (human) area of the room.

Most places, if properly designed, will have venting that allows that type of Heating/Cooling, but in real life, A/C design is usually the last item (if at all) that gets thought-into a real working system.

I have ALWAYS had to deal with A/C systems AFTER the fact and, except at my transmitter site in Colfax, the system-redesign usually has to involve ducting that blocks the lighting in the room (most supervisors hate that immediately) or there's some cobbled pieces of cardbord, duct-tape and bubble-gum to deal with just to SHOW them that if something could be done, you've got the temperatures down maybe a few degrees from what was prevalent before.

The other aspect you could go for is determine the terminal temperature the equipment will fail at, or shut-down. Let management know -via- weekly/monthly reports that if the SDHTF, and the fan quits, "Servers Down!" will be the day's battle cry.

You've CYA and that's the best that some folks may be able to say.

Good luck getting your A/C.

spdrun · #8 07-06-2012, 05:46 PM

Quote:

Originally Posted by Zulfiqar

ze clouds are good I know but the accountants (old folks who use calculators) dont think of it much.

anyways - I know I can move the T stat around but I find the ducting to be wrongly placed. Dont you think that instead of applying a fix a rooted solution would be better.

I was being wholly and entirely sarcastic, btw. I wouldn't put confidential business files in a public storage unit, and I sure as f***ing hell wouldn't want to do the virtual equivalent. The old folks are exactly right.

But server tech has advanced a lot in the past 5 years, and performing basic SMB functions doesn't require a lot of processing power. Have you thought of going with small-form, energy-efficient "micro" servers? SSD for boot. 2.5" drives in soft RAID 1 for data.

Zulfiqar · #9 07-06-2012, 07:38 PM

Quote:

Originally Posted by mgburg

Ideally, you'd like the hot air to be sucked up by the I/P to the air-conditioner and the cool air to drop to the floor (or into the bottom of the racks) or an un-occupied (human) area of the room.

Most places, if properly designed, will have venting that allows that type of Heating/Cooling, but in real life, A/C design is usually the last item (if at all) that gets thought-into a real working system.

I have ALWAYS had to deal with A/C systems AFTER the fact and, except at my transmitter site in Colfax, the system-redesign usually has to involve ducting that blocks the lighting in the room (most supervisors hate that immediately) or there's some cobbled pieces of cardbord, duct-tape and bubble-gum to deal with just to SHOW them that if something could be done, you've got the temperatures down maybe a few degrees from what was prevalent before.

The other aspect you could go for is determine the terminal temperature the equipment will fail at, or shut-down. Let management know -via- weekly/monthly reports that if the SDHTF, and the fan quits, "Servers Down!" will be the day's battle cry.

You've CYA and that's the best that some folks may be able to say.

Good luck getting your A/C.

I have proven the airflow with the paper and packing tape technique to cool down one rack that would heat up stupidly. I also cardboarded some channels together and the temperature monitors were dropping readings really quick. That is how the accountants approved to optimise it.

mgburg · #10 07-07-2012, 05:20 PM

Quote:

Originally Posted by Zulfiqar

I have proven the airflow with the paper and packing tape technique to cool down one rack that would heat up stupidly. I also cardboarded some channels together and the temperature monitors were dropping readings really quick. That is how the accountants approved to optimise it.

Good job...that's about the speed of things when the purse-strings are drawn tight and there's no light bleeding into anyone's wallet. (Except yours!

)