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if you just want to control the fan you could interlock the fan contactor to an Remote Bulb Aquastat to close on water temp rise. The bypass is not needed if your chiller is VFD and can handle cold water..I had a trane and had the same set up. I assume you shut down in winter so it pretty easy ..and not expensive at all. As long as you have a call for the tower fans you can break the line with a aquastat and when it closed on temp rise the fan will run. I would put the bulb as close to the inlet to the chiller as possible or if you have a well in the inlet pipe that would work to.
Yup, true enough. Was being a bit exaggerated there. The acceptable range I think went up to 80°F which as an upper limit is pretty low compared to typical chillers. But the best efficiency was at the 65°F mark. This was a nicely done, new building, so I am sure they are taking in to account the great, energy efficient building materials that would hopefully do a much better job of insulating the interior.
Originally Posted by TheControlsFreak Came across one of those newer McQuays that have the magnetic bearing that float the impeller shaft... they like 65°F all day long. Ahhh, the turbocor's... Originally Posted by TheControlsFreak Which is crap... when the chiller is installed in Texas. How the hell you gonna cool condenser water from a centrifugal chiller to 65° on a 101° day?! With a condenser chiller pre-cooling the condenser water. Not crap as they might like it but that doesn't mean that's there only operating range. I can cool condenser water to 60 degrees quite often, but had to put in a low limit of 63 one one building and 57 on the other. One building has only AC units with water side econ coils, the other has some w/o so couldn't go as low, but it really helps in the desert, can see serious evaporation with Out Air Humidity in the single digits... Currently humidity is up around 30%, but at ~92 deg OAT, WB is 68.
Thank you, I will take a look
Originally Posted by Maine Man Believe it or not there are days when the wet bulb drops low enough down here for 60 degree water and below. This is the reason for my inquiry. Yeah same even in the southern states there are actually cool days during that 1 week of Spring and Fall each year. LOL So back to your original question... ofcourse it is possible, but you will need to buy some pieces that may or may not be considered BAS controllers. Essentially you need something that reads the OAT and will spit out a scaled signal... then feed that signal into another device that will scale relays to turn on and off fans etc. or modulate a VFD. This can scale a 4-20ma Temperture sensor to some other signal... ARM Analog Re-Scaling Module Attachment 408021 Feed the above signal into a device like this for Binary on/off control... ATL Analog Input to (4) Adjustable Relay Outputs Attachment 408011 For analog control, well you only need the first item since it will spit out a scaled output on its own. Hope that helps!
Believe it or not there are days when the wet bulb drops low enough down here for 60 degree water and below. This is the reason for my inquiry.
Came across one of those newer McQuays that have the magnetic bearing that float the impeller shaft... they like 65°F all day long. Which is crap... when the chiller is installed in Texas. How the hell you gonna cool condenser water from a centrifugal chiller to 65° on a 101° day?!
I would add some kind of small PLC with a display or with a display you could tie in to adjust as needed as X is saying. The other option is depending on the drive you 'may' be able to utilize the drive's added inputs and logic to do this.
Yes, there is a pneumatically operated bypass. I have no worries about the chiller handling the cold water. This machine was designed for it.
80-85 degrees into the chiller, 90-95 out. Does the tower have some type of bypass?
60 degree condenser water sounds pretty cool. The chiller will shutdown if the water gets too cool. Been there.
I've done something similar with just one control module and a display that connects directly to the control module. I don't think you will find anything "out of the box" that will do what your wanting. The best bet is to call your favorite controls company, they should be able to do what your wanting fairly painlessly.
VFD on tower fan has a pre programmed setpoint of 85 degrees.
What is controlling the towers now?
Have a 2001 centravac, UCP2, that I would like to optimize. It is capable of handling below 60 degree water. There are no BAS controls in bldg. other than a time clock. I would like to reset based on OA wetbulb plus tower approach but do not want to add a complete BAS to get there.
yes, its easy, what are you looking to do
Tower Controls, stand alone Trying to do condenser water reset with stand alone controls. Has anyone attempted this?
Tower Controls, stand alone
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