ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Shout Box
Recent Posts
VDE 0100 to introduce AFCIs
by sparky. 01/20/18 05:09 PM
MRI LED lights dimmer control replacement - wow!
by Potseal. 01/19/18 08:52 PM
Video: Inventor of the GFCI self-testing shocks
by Bill Addiss. 01/17/18 11:11 PM
FPE in Germany
by HotLine1. 01/17/18 07:07 PM
Fujifilm Recalls Power Adapter Wall Plugs
by Admin. 01/16/18 07:04 PM
New in the Gallery:
Housebilding DIY wiring
SE cable question
Who's Online Now
1 registered members (sparky), 7 guests, and 12 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Something Simpler? #181359
10/05/08 12:30 PM
10/05/08 12:30 PM
M
MTWire  Offline OP
Junior Member
Joined: Apr 2006
Posts: 6
Kalispell, MT, USA
Ok, I know there has to be a simpler way of accomplishing what I want to accomplish, but I can't really see it right now. I have 4 5HP 3PH 208V exhaust fans, each controlled by a VFD, I want all exhaust fans to turn on when the temperature exceeds 90 degrees Fahrenheit, and turn off when the temperature drops below 90 degrees Fahrenheit. Between 90 and 125 degrees I want all 4 motors to ramp up to 25% or around 525 rpm, between 120 - 130 degrees to 50% or 1050 RPM, from 130 - 140 degrees to 75% or 1575 RPM, from 140 - 150 degrees to 100% or 2100 RPM, and 160+ degrees, I want the motor to ramp up to 125% or 2625 RPM. I also have a CO Monitor with 24V control relays that I want to turn the fans on to 25% when 22 ppm is reached, and then to 100% if 28+ ppm is reached.

My only thoughts would be to use small PLC controller to control all 4 VFDs, and then have a digital temperature probe as an input and the CO monitor as two on/off inputs for warning and danger conditions. I realize that a setup like this would be quite expensive, so I am trying to think if there is anything less that would do the same thing, or if this would be my best bet.

Work Gear for Electricians and the Trades
Re: Something Simpler? [Re: MTWire] #181360
10/05/08 03:11 PM
10/05/08 03:11 PM
S
SolarPowered  Offline
Member
Joined: Jul 2004
Posts: 625
Palo Alto, CA, USA
Please define "quite expensive." Four 5 HP VFDs are going to cost a pretty fair chunk of change; I don't imagine that a small PLC is all that much in comparison to the rest of project.

Re: Something Simpler? [Re: SolarPowered] #181362
10/05/08 03:36 PM
10/05/08 03:36 PM
T
Tesla  Offline
Member
Joined: Jun 2004
Posts: 1,273
Sacramento, CA
I'm at a loss as to what heat load could give you the heat profile you're targeting.

Are these VFD's already installed and running?

As to the stair step increases in power... why not a linear run-up?

Carbon Monoxide monitor...? Are you exhausting air from some confined diesel-electric set?

I'd throw the whole problem over to an engineer.

For such a costly system, any PLC expense will be dwarfed by the design effort.



Tesla
Re: Something Simpler? [Re: Tesla] #181374
10/06/08 12:16 AM
10/06/08 12:16 AM
M
MTWire  Offline OP
Junior Member
Joined: Apr 2006
Posts: 6
Kalispell, MT, USA
The design is actually more of a theoretical at this point in time, and is part of a project I am working on designing for one of my old professors classes. Kind of an overkill I know, but something that "might" be seen in the real world, trying to give them a somewhat real world example of how motor controls and such would be used in everyday applications. In the plans I am using, which are for a 12000 sq. ft night club with a 3000 person occupancy, the plans call for 4 5HP exhaust fans which are to be controlled by a simple start stop station connected with a CO monitor (not quite sure the exact purpose of the CO monitor as of yet)... so my thoughts were to go a little further and allow the fans to do more than simply turn on or off at full speed according to a single set temperature, thus I am thinking that a PLC controller running 4 5HP VFD's would be best suited for running the system. Cost.. is and isn't really a consideration.... I want a system that someone would be proud of designing in its simplicity and effectiveness, and not a Rube Goldberg of a motor control.

I appreciate all your input.

Re: Something Simpler? [Re: MTWire] #181376
10/06/08 01:39 AM
10/06/08 01:39 AM
Trumpy  Offline

Member
Joined: Jul 2002
Posts: 8,231
SI,New Zealand
Wow,
A night-club with REAL ventilation!
This is ground-breaking.

Just make sure that the ventilation system doesn't cause a fire started in another part of the building to spread.

You need to prove to a Fire Marshall or the like to make sure that what you install is not going to "link" fire compartments, especially with an occupancy rating of 3000 people, some of whom may have taken illict drugs and may not be able to evacuate like the other drunken ones.

This is NOT a wind-up, I have been there before as a Fire Officer.

Re: Something Simpler? [Re: Trumpy] #181377
10/06/08 05:51 AM
10/06/08 05:51 AM
S
SteveFehr  Offline
Member
Joined: Mar 2005
Posts: 1,213
Chesapeake, VA
If you're looking for an example, a real-world application you might also consider is emergency ventilation in a data center. If the AC fails, the equipment will quickly overheat, and is frequently fitted with emergency ventilation fans so the data center can maintain operation.

I've never seen these fitting with VFD, it's either required because the AC failed, or it's not, there's very little in-between.

As in everything else, it must be tied into the fire protection system to not spread smoke and fan the flames. Also, FM200 requires the space be absolutely sealed.

Re: Something Simpler? [Re: SteveFehr] #181389
10/06/08 02:49 PM
10/06/08 02:49 PM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,166
Estero,Fl,usa
Back in the olden days when there really were data centers they had redundant HVAC systems so you lose a whole system and still have enough HVAC to keep the DP system going. Some even had huge storage tanks on the water chillers so you could lose all the A/C and still have time for an orderly shutdown/transfer to the backup site.
I am not sure we even have that kind of data center anymore. When I was leaving they were turning those "glass house" operations into a small room with few racks that replaced a half acre of raised floor. (most of the reason I left). Some could live in the "office" ambient air.
When the bad card has a red blinking light on it and you can hot swap in a new one without taking down the system you don't need me.


Greg Fretwell
Re: Something Simpler? [Re: MTWire] #181393
10/06/08 03:54 PM
10/06/08 03:54 PM
L
LarryC  Offline
Member
Joined: Jul 2004
Posts: 783
Winchester, NH, US
If the VFD's can accept an analog input, use a 4-20 mA output or 1-5 V transducer for the temperature based speed control.

If the units can accept a Master / Slave relationship or a follower input, set one unit as the master and slave the other three off of it.

Larry C

Re: Something Simpler? [Re: gfretwell] #181415
10/07/08 05:48 AM
10/07/08 05:48 AM
S
SteveFehr  Offline
Member
Joined: Mar 2005
Posts: 1,213
Chesapeake, VA
Originally Posted by gfretwell
Back in the olden days when there really were data centers they had redundant HVAC systems so you lose a whole system and still have enough HVAC to keep the DP system going. Some even had huge storage tanks on the water chillers so you could lose all the A/C and still have time for an orderly shutdown/transfer to the backup site.
I am not sure we even have that kind of data center anymore. When I was leaving they were turning those "glass house" operations into a small room with few racks that replaced a half acre of raised floor. (most of the reason I left). Some could live in the "office" ambient air.
When the bad card has a red blinking light on it and you can hot swap in a new one without taking down the system you don't need me.
Yes, data centers still do have this, and in fact it's gotten even more obscene for some of those commercial data centers where every outage means millions of dollars lost. 2(N+1) redundant AC, with wells and/or water tanks for the chillers, and emergency ventilation as backup. The emergency ventilation uses little power and is sometimes connected to the UPS, as well- if there is a multiple generator failure, a datacenter running for 2+ hours on UPS power without cooling can get miiighty hot. (sure, the UPS is only designed for 15 minutes, but with 2(N+1) units for redundancy upon redundancy (you wouldn't feed those redundant power supplies from the same N+1 UPS bus, would you?), each with a 15+ minute battery powering a system that probably isn't anywhere close to UPS capacity...

And yes, this is what it takes to go from 99.999% to 99.9999%. It's really really hard to get that extra 9!

Re: Something Simpler? [Re: SteveFehr] #181419
10/07/08 11:05 AM
10/07/08 11:05 AM
G
gfretwell  Offline

Member
Joined: Jul 2004
Posts: 9,166
Estero,Fl,usa
I have been out of this for over a decade but the plan IBM was selling was redundant sites. You would have a mirror site 1000 miles away that could handle all of your critical applications with a moment's notice. That way you could switch over in the few minutes a basic UPS gives you and avoid all that redundancy on site. Money wise it really may end up cheaper, or at least that was what the selling point was. With national broad band capability, it is not really important where you are. I know IBM maintained mirrors in several places for our internal operations as far back as the 70s so they had experience.
The redundant site might actually be backing up dozens of sites but as long as they are not all down at once a minimal amount of hardware will do. Even if there is a bottleneck, slow is better than nothing at all.


Greg Fretwell
Page 1 of 2 1 2

Featured:

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
BEAMEUP
BEAMEUP
WA
Posts: 27
Joined: December 2004
Show All Member Profiles 
Top Posters(30 Days)
Admin 20
Potseal 15
sparky 15
Popular Topics(Views)
243,571 Are you busy
180,368 Re: Forum
170,845 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.6.1
(Release build 20180101)
Page Time: 0.065s Queries: 16 (0.022s) Memory: 1.0282 MB (Peak: 1.2077 MB) Zlib enabled. Server Time: 2018-01-20 23:00:09 UTC