RegiSTR, great question and you are absolutely right. Gauge readings even in a closed system should be corrected based on difference in height of the gauges (P = rho * g * h). But there are exceptions depending on how the gauges are piped. There are often 2 or 3 pipes to a common gauge for a...
Close, but you're overthinking it. Contrary to popular belief on this issue (and possibly others), size does not matter. That's the beauty of a fan or pump curve. Stick them in any system regardless of sizing of inlet or outlet pipes or ducts, they will only produce the flow that the total...
SAK9, likewise, thank you! You and the crew of other usual suspects have been doing so well that I logged out and haven't been back on for a bit. Hope you are well! Odds are I won't have frequent logins but will stop in every now and then to stir the pot...
Snickster articulated well on this - but the whole meaning of these 184 words of mechanical code is "Make sure the contaminated room is not positively pressurized to abutting spaces by appropriately balancing supply and exhaust airflows." I prefer my 19 words, but things that are...
No good for me. And I hope it would be no good for most people.
Take a 1000 cfm fan designed at 4" TSP. The fan shutoff head (or dead head) is say, 6". These are numbers for typical systems. The 4" TSP is only meaningful if it is the outlet static minus the inlet static.
Now let's say the...
The cooling coil: DX or chilled water? That matters. Infiltration: the space should be slightly positive. For a negative space, you can count on the duct sweating, especially if temperature control is cyclical.
The air separator is all about minimizing corrosion and keeping you from having to burp the system. 6 months? Should be fine.
The expansion tank should not be ignored, even if you need a temporary location. If the system stays hot the whole time, all good. If the system cools down, might be...
Do you think your friction loss calcs are so accurate that you would need to correct selected pump head based on a slight change in density due to 25% glycol? No. Heat transfer is de-rated a bit with a glycol solution so go slightly larger on heat exchangers and a smidge larger on pumps, but...
Tough to tell with the givens. What is above? Is this to make the above floor not cold, or protect pipes from freezing? Should be dry sprinkler system in the garage. Also consider making CUH-1 an electric unit (ECUH-1) to eliminate the long HW pipe run.
Total pressure is the sum of static and velocity pressures (usually), but fan curves are no good if they account for velocity pressure. The curve is simply the static pressure at the outlet minus the static pressure at the inlet.
Ummm, DP means differential pressure. You want to control the pump to a constant “flow” at “DP2?” No. Control the pump speed to maintain the differential pressure (like, "DP") at “DP2.” The 3-way valve will maintain minimum flow at what you call “DP1” to keep the chillers happy. I tried, but not...
Dgoodyear, the “best of your abilities” needs to improve. Sorry to be blunt.
“I know that the fan tables with the unit provide a way to measure air flow across the core to facilitate balancing fresh and stale air flows.”
CB: What?
“I have also used the anemometer to do an 50 point average...
Thank you all! Didn't realize there's an extra $150 for the stamp. So just paid that today. Send me all your f'd up designs and I'll stamp them for you, for a small fee... Lol!
Read GT-EGR's answer again. It is perfect. One note to add, water systems typically have the controlling DP sensor near the end of the loop. Air systems, 2/3 down the duct. You can't always achieve this on a water or air system, but these are the "general" rules.
Poorly worded on two counts: 1) Stuff that requires straight runs of duct prior to bends refer to duct diameters, not duct sizes. 2) Volume dampers shouldn't need minimum straight duct runs. Volume FLOW STATIONS controlling VAV boxes, however, may.
Follow-up Mint: ECM = Electronically Commutated Motor. They're taking over HVAC air systems but not yet being applied to pumps. No VFDs. Simpler and supposedly more robust. Many are sold. My best client is putting them throughout a huge-ass renovation. My gut on these are like Victaulics 17...
