Chiller loop--Converting H20 to glycol?
I have an institutional building with a primary chiller loop,two 50 hp circ pumps running together in parrallel,on freq drives with a mix of two way and three way cw mixing valves at the airhandlers.
There are four chillers on secondary loops staged by DDC feeding the primary loop.
Due to some recent repiping issues my client would like to convert to using a glycol solution in their loop.
I think i understand the basics of what can be expected,lower chiller operating pressures,reduced pump flow,reduced heat transfer.
Just looking for some feedback on what changes if any might need to be taken to avoid any problems.
Leaving water setpoint changes?,impeller changes?Charge adjustments.
RTAA's and YS's--------------Thanx all.
Adding glycol to a system should not require any machine or setpoint changes unless you are adding a LOT (heavy concentration) of glycol. Just consider that you will lose some heat transfer ability in both the chillers and out in the cooling coils. The chiller manufacturers print charts to calculate the loss for the concentration.
I am guessing you only want enough glycol to prevent freezing in the winter so start by figuring how low your solution temp would have to go. Then check your capacity loss to see if you can tolerate it in your system. Then fiqure how much water you have to replace in the system to get the concentration you need. Will you use the green stuff or the pink stuff?
The equip. will consume more power(chillers and pumps) to do the same work with glycol installed but there is no free lunch.
If this job goes forward let us know as there are other tips we can share with you.
It all depends on the concentration level and which type of glycol you are going to use . The heavier the concentration the more capacity you are going to lose . You will need to change the operational safety setpoints on the RTAA for refrig temperature etc . If you look in IOM 3 there is a chart in it that tells you freeze points based on concentration levels and what the recommended control settings should be . Ethylene glycol is the usual choice of glycol as propylene glycol is far less efficient for heat trensfer but it is environment freindly where ethylene glycol is not .
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When I buy either of glycols, both are clear, they ask me what coloring I want if any. I can make them any color I want. It's just a matter of adding the dyes. I've seen, green, red, purple, and pink, so far. Color is not a reliable indicator of the type of glycol. JMHO
Originally Posted by Chiller Guy
Your poor planning does not constitute an emergency on my part!!!!
Yes,it is to prevent freezing in winter.
Originally Posted by Chiller Guy
This is all for a/c..no process at all.They will not be operating the chillers all winter but they don't want to drain loop.
Thanx for the responses.
Last edited by bc guy; 10-25-2008 at 11:45 AM.
depending upon type and concentration of glycol, you MAY have issues with control valve packings and possibly possibly pump seals leaking. Some manufacturers control valves cannot handle glycol in their newer valves. The older stuff is usually better suited. Also , as stated capacity of heat transfer equipment will be reduced, and pumping requirements may increase. It depends where you fall on the existing pump curve if you can use what you have or possibly impeller change .
As stated above, make sure your system components can work with glycol. Also remember to have the proper inhibitors added to the system Glycol also has to be tested occasionally to prevent it becoming a corrosive. Proper PH levels have to be kept.
As above it will probably be ethylene if its not food process. You may want to consult an engineer to give you some idea on what your losses may be.
We go with a 40% glycol and 60% distilled water solution. You may not need a 40%. This will be based on your OA temps in winter.CG stated this already.
AB's stated about color. I prefer to by it already dyed. My reason for this is because some people like to put their hans on things. A clear solution may not be recognized. Atleast with the dye in it it may make some one think twice. A small amount of ingested glycol can be fatal! It is a pertoleum base product.
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I too have purchased clear glycol which can be dyed any color. The selection of either may be determined by enviromental concerns as much as anything else. The green (ethylene) stuff cannot be used at a lot of sites so be sure to check with your customer. Propylene (pink stuff) has some shortcomings but is safer (can be had in food grade).
Just as a side question, suppose you come up a system that has glycol in it and nobody knows what kind was put in the system. How do you determine if it propylene or ethylene?
Glycol alters (reduces) specific heat
And roughly at a one-to-one rate. That is: add 50% glycol and lose roughly 50% heat exchange rate. If your original sizing was close - you will not be able to tolerate it.
Watch out for low SSH / flooding on DX packages - especially at low loads.
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You can call DOW Chemicals. They will send you some test bottles where you can send them a sample. They give you a chemical break down. There was no charge for this service in the past? I don't know if it's still free.
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I have heard this and I can't confirm it, glycol expands more than water?
May have to biggie size your expansion tank?
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Added a lot of glycol over the years and have not changed a tank yet!