Original message
| uta
 |  "Evapco cooling tower"
, posted Wed 21 Dec 00:21  
when we run our fans to keep up with demand during winter freecooling, we are constantly having problems with the panels freezing up. we have 2) 400 ton cells with variable freq. drives and were able to reverse the rotation as well. When everything is running we need about 380 tons of cooling.
Is the towers capacity much less when freecooling or you guys have any ideas to keep it from icing up?
thanks in advance
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Replies:
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| chiller guy
| "Re(1):Evapco cooling tower" , posted Wed 21 Dec 16:43
A couple of things hit me here! It looks like you require 47% of the tower capacity in freecooling. What does the design indicate you will get and at what conditions (TEMPS & FLOWS). Are you going through a plate & frame heat X, mixing the chilled water. or through a chiller?
You will probably see some icing in the tower (what part of the country?) The issue is wether or not it is affecting capacity. Is this a new problem with an older system or a new system? I am guessing this is a production facility so at full load you may need to go back to mechanical cooling to keep up.
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| | uta
| "Re(2):Evapco cooling tower" , posted Thu 22 Dec 00:03
ok...We are in the Milwaukee Wi. area and I believe this has been a problem since the systems been online 9 yrs.ago. We try to hold a temperature below 55 since it goes into alarm at 60 degrees and will shut down production. We do utilize a plate and frame heat x ( which was existing, and you may have answered my question already :) Will need to get back to you on the design and capacities if need be? I'm kinda glad to see you think its normal to have some ice build-up because 55-58 return water dripping over it, We thought it would keep it cleared.
thank you
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| | melaman
| "Re(3):Evapco cooling tower" , posted Tue 27 Dec 00:43
I have twin Evapco towers that I run 24-7 all year long in Ontario Canada.
The facility is an office building with computer labs relying on the chilled water. Because all my AC units are duel coil units, I have the flexibility to allow my chilled water to rise up to 63 deg F. But most of the time when it is really cold I run about 59 deg F . You are correct, it is a task to keep the panels from freezing up. Since I can allow my chilled water to run warmer, this helps me keep the tower relatively ice free. I use a plate heat X, Condenser water to chilled. My towers run two speeds forward, high and low, and one speed in reverse, low. When the OAT gets below (-21F) I raise my leaving condenser water set point from 35.6 F to 46.5F. and run my fans in reverse to help keep that warmer moist air flowing across the grills. Yes I end up with warmer chilled but as I said, I have some flexibility with chilled temps. If it is really really cold I have programming that reduces flow to the tower for short periods to help warm up the water. You are walking a fine line though as you do not want to freeze up the tower. I made the programming changes two years ago and it has worked well. Even though extended periods of 5 F and lower temps. You mentioned that you have VS drives and they can go in reverse. I am sure they are already going very slow to maintain condenser water set point. I would make sure they are going as slow as possible or try reverse operation with a very low speed. It will be a bit of a balancing act so you will have to do some trial and error testing. I do realize that you need a colder chilled water temp then I can get away with.
Good luck
Pareto's Law
If a group of tasks are arranged in order of their priority 80% of the value come from the top 20% of the list.
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| | chiller guy
| "Re(3):Evapco cooling tower" , posted Thu 22 Dec 09:46
Been down this road here on the East coast.Sometimes just talking to someone else about the problem makes you start thinking from a different angle.
Good Luck
All refrigerants are safe - All refrigerant are dangerous. The difference is YOU !!!
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| | harpo
| "Re(4):Evapco cooling tower" , posted Fri 20 Jan 06:18:
what i have seen on the discharge section of say a BAC tower was a sheet metal plate the size of that opening.they mount it about 12" away from the opening with brackets when the fan does cycle it discharges the heat against it but with the plate some bounces back to keep the tower ice free.reason for the BAC EX... don't know the style of Evapco you have,then remove for the summer season.
9
It ain't going to get any lighter looking at it!
[this message was edited by harpo on Fri 20 Jan 06:22] |
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