Hi Fellows,
I'm working a project involving great distances from a main switchboard or power panel to some 250A 480/3 panels. The champion is an 850-foot run. In order to keep voltage drop to less than 3 percent, I calculated the need for 4 sets of 350 MCM per phase at an 80 percent load on the...
Group,
Does one of you perhaps have a VBA routine for linear regression with weighting, without using any built-in Excel functions or plug-ins (boss request).
I've attached a very simple example of data. My program is much more complex, but I've never dealt with weighted regressions before...
Guys and gals,
Original control of a two-speed motor (1/20th HP) was from a transformer with 120V primary and a double-tapped secondary at 85V (for high speed) and 75V (for low speed).
Transformer is no longer available, what would be the downside of using resistors to drop the voltage...
Hi Group,
I have a monster VBA program written, and for the first time ever I want to use a worksheet function (LinEst). I've searched the world, but I can't find the answer to "Run Time Error 424 - Object Required" that I get.
A simple example is attached. Can anyone take the time to point me...
Hi Measurement/Control folks.
I'd appreciate any input you have to this thread in the HVAC/R forum:
http://www.eng-tips.com/viewthread.cfm?qid=408423
Thanks much!
Best to you,
Goober Dave
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Hi Team,
Under near-laboratory conditions and with very accurate instruments, I'm measuring flow through both chilled and condenser water barrels of a chiller. Instead of the expected flow-squared correlation to pressure drop, I'm getting flow to the 1.7 or 1.8 power.
Anyone here ever run into...
Hi Guys,
We run a UL 508a panel shop, and we have a manual checklist for QC. It's quite extensive, but we're looking into automating quality control. Has anyone in a similar shop implemented an automated QC software program? If so, would you share your experience?
If no, please give me an...
Friends,
I've walked up on a chiller with the following settings on its breaker:
Instantaneous pickup 6400A
Short-time pickup 4800A
Short time 0.3s
Earth pickup 640A
Earth time 0.3s
Here's the chiller data. Note it's a Y-Delta starter.
Motor LRA= 2616 A
Primary RLA = 473 A
Min circuit...
I haven't found the magic answer -- if I insert a reference picture (.png), DraftSight draws a box around it that I can't seem to get rid of. Any ideas?
Best to you,
Goober Dave
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Hi Group,
I'm confused on this one for some reason. See attached diagram, I'm boosting 208V to 240V to feed a 31 FLA motor. The size I calculate for the boost transformer is 2 kVA, so its full load input current is 8.3A. But the motor needs a 50A breaker. According to NEC 450.4, though, I...
This happened when updating, and no amount of my Windows kung-fu has been able to get around it. Has anyone here experienced this and fixed it? [pc]
Best to you,
Goober Dave
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For the US folks: Is a PE license required in your state for building energy audit work?
Best to you,
Goober Dave
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Hi group,
Not exactly a thermo problem, but I haven't gotten any responses in the other forum I tried.
The situation is a fire truck with its engine running in its bay in the fire station. The client would like a sensor with alarming on high NO2 level (2 ppm) in case of exhaust leakage.
When...
Hi group,
I need a kick-start, don't know where to look first. We're a US UL508a panel shop, meaning we can assemble various industrial control panels to the UL standard and apply a UL label.
A long-time customer wants us to build some panels for installation in the UK and EU with UK coming...
Hi all, I got myself lost here...
Is there a code or standard that dictates inspect/test for smoke and fire dampers?
How often would that be?
I'm unable to get to the NFPA codes online today or I'd have given it a shot already.
Thanks!
Best to you,
Goober Dave
Haven't see the forum...
Hi all,
I'm scratching my head on this one. I have a column of numbers (30,000+). I can easliy find what number occurs more often than any other with the =MODE(x:y) formula.
What I'd like to know are the numbers that occur second most, third most, etc...
Any quick way to do this without...
I've had this posed to me half a dozen times in the past two months.
"Need a sensor to sense welding smoke to activate / deactivate exhaust fans"
"Need a sensor to sense incense smoke to activate / deactivate exhaust fans"
These things generally happen in large-volume rooms like an auto shop...
OK, Hazardous Engineers:
I'm looking for documentation that says it's OK to pass the capillary tube in a bulb-n-capillary temperature switch when assembling in the field. Of course, the switch itself is in an explosionproof enclosure.
I know it's OK to seal a capillary entering a box, because...
A UL 508a panel shop has been assigned to build a smoke control panel. They can't stick a 508a UL label on it, that is prohibited. UL 864, category code UUKL is what applies to smoke control panels. No panel shop can do UL 864 stuff, that is a standard that must be certified by submitting...
My Google kung-fu and the ABB web site have failed me.
My local utility has a motor starting study done in FeederAll, and they are willing to share the project file with me. The problem is that I don't have FeederAll and cannot for the life of me find how to purchase / download / access the...
