Results 14 to 26 of 37
02-15-2013, 10:11 AM #14"The bitterness of poor quality remains long after the sweetness of low price is forgotten". --Benjamin Franklin
"Don't argue with an idiot, they will drag you down to their level and beat you with experience". --Mark Twain
"Beer is living proof that God loves us and wants us to be happy" --Benjamin Franklin
02-15-2013, 10:45 AM #15
I would be wary of the status relays on the drive, without profiling the current, you won't be able to tell if a belt broke, etc. (or you might not care). In general, we don't care.
I agree, network communications (integration) is probably the best way to monitor energy usage (kW/kWh).
02-15-2013, 03:36 PM #16
02-15-2013, 04:04 PM #17
02-15-2013, 07:15 PM #18
We use them on the vast majority of our projects. They seem to work well and save costs on new projects. This is reflected on bid day and customers seem to respond….
VFD rated units I have tested, never impressed. Installed upstream of a VFD and adjusted properly, they work fine. All and all, my experience with switches has been good. We adjust them close, and more often than not return to the site to decrease the setpoint.
Proper install / adjustment is key with both.
02-15-2013, 07:19 PM #19
02-15-2013, 07:37 PM #20Professional Member
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02-15-2013, 07:43 PM #21
Most of the time....move less air, use less power regardless of the cause.
I have not use analog sensors enough yet, but I would think these with custom tailored logic per fan type could provide superior performance to both dp and current switches. Remotely adjustable to boot.
Last edited by orion242; 02-15-2013 at 08:02 PM.
02-15-2013, 08:08 PM #22
We use Hawkeye 608's mostly. Half our work is data centers so they will have the e-clipse bypasses and when it's in bypass, the drive goes down.
The problem I see with them is when they are less than 30 Hz. We see the life with 608's is around 5-7 years. Even at that, they have gotten their money's worth out of it!"If you can't explain it simply, you don't understand it well enough”
"Don't you just love when the flames burn off the wiring schematic?" hvacvegas-HTALK member
02-15-2013, 08:35 PM #23
We typically use the same sensor installed on the line side of the VFD. Adjust the switch with the motor at or near the minimum expected running speed.
1hp motor draws a lot more power at min speed than any of the electronics in the VFD. Bypass is also not an issue.
02-18-2013, 07:46 AM #24
02-18-2013, 07:55 AM #25
I guess I'll order a couple of DP sensors for my ECMs. Thanks!
02-18-2013, 11:48 AM #26
Here's the first question to ask when installing ANY control. WHY are you monitoring this point? In this case, what do the operators really care about. Is the air handler doing it's job. The only real thing that shows this is Air flow. There are a few ways to go about this, but first would be, obviously, an air flow sensor. Second best, would be duct static. Odds are, if these units have VFD's, they already have at least one of those things.
Our new units do not have fan DP switches, but do have both duct static AND duct flow. However, we still need actual fan status, because they are fan wall designed units (a couple of them have 9 supply fans). In this case, we also need to know if a single fan fails (they each have their own overload/isolation breaker). For that, we use current switches. however, they are direct drive, so the 'has to be calibrated correctly to detect belt loss' problem is not there. So, the graphic for these units shows status a number of ways. Duct flow and static are shows. The fan animation themselves is from the drive status. Then there are a row of green-red indicators for each individual fan switch. No bypass units on these drives, but they are redundant drives, so there is still logic in there to only check the status of the selected drive.