Glycol chilling from cold room compressor

[almalkin]

Our glycol chiller is having a hard time keeping up with the demand now that the weather is getting a bit warmer and we are needing to crash more than one tank at a time. It's a small unit, and definitely undersized for what we are asking from it, chilling (3) 7 bbl unitanks. I'm looking at getting a larger unit in the future but hoping to be able to temporarily task our cold room compressor to help out with the load.

We purchased a modular walk-in unit with all the necessary hardware, but ended up using about half of the available panels to create a smaller cold room. The compressor that is currently cooling the room does a great job and is oversized for the space that we have right now. What I would like to do is tee off of the refrigerant line coming into the cold room, install another solenoid valve and temp controller and run this into some coils in a glycol reservoir. The reservoir would sit in the cold room and I could pump out of that into my current glycol plumbing and use the smaller chiller for something else.

I'm going to run this by the HVAC/Refrigeration guys, but I wanted to see if this was even possible or recommended. I'm not super familiar with the mechanics of this system so I may be barking up the wrong tree. Any thought?

-Steve

[Scott M]

You would need an expansion device for the gycol loop, solenoid valves to isolate the cold room refrigerant loop from the glycol loop, and a seperate control system that would lock out chiller demand when the glycol loop required the compressor and a similar lockout at some temperature above 50 degrees that would lock out the glycol loop in benefit of the cold room. The glycol resivour would have to be sized to the capacity of the cold room compressor to prevent liquid refrigerant from flooding the comp and destroying the valves.

In other words, it would have to be engineered. Not anything I would recommend.

You might save some cash by just insulating the Fv's.

[yap]

I can't answer your actual question but I will pose a different one to you instead.....

Is it worthwhile to make such a modification vs. getting a bigger chiller? Even if your HVAC guys say it is possible, I doubt anyone can tell you definitively what it will gain you. Say you get it all put together and it only helps a little bit but doesn't solve your problem?

Alternately, maybe it solves your problem for the next six months and then this winter you buy another tank due to expansion. Then next summer you are potentially right back in the same boat....

I am going through a similar situation right now. My chiller is undersized to run the 3 tanks it is hooked to. I knew this going in, but as a start-up I "did what I had to do" to get open. I now regret it. Volume has grown and now I have a huge bottleneck in my process because I can't crash my tanks properly. If I had it to do over again (hindsight=20/20) I would have paid a little more up front for a bigger chiller when I still had capital to spend. I'm now a year in, scraping by day to day and can't get the capital I need to remove this bottleneck.

I guess what I am saying is in my opinion (and yes I know opinions are like assholes) you should put your efforts towards a longer term solution if at all possible instead of a quick band-aid...

[jimvgjr]

I have to agree with the other responses.

A big concern I have is making the investment to purchase the added components and have them installed and find out the resulting capacity increase is less than anticipated or needed. Another concern is by installing these components you create a new problem that results in a system/compressor failure and you then lose cooling to your cold room too.

It is more tricky than it sounds to feed multiple evaporators from a common condensing unit, especially if the evaporators are servicing two different applications. There's many things you need to be cautious of when doing this- I definitely agree and support taking the time to review with your refrigeration contractor- they should be able to give you a price and help you determine if its worth it or not.

We will often purchase old chillers from customers who upgrade to a new system, perhaps this would make it more feasible to help get a chiller system adequate for your cooling demand? Today there is a definite demand for small used chiller systems, you may want to sell your existing chiller yourself on this forum.

Good luck,

Jim VanderGiessen
jimvgjr@prorefrigeration.com

https://www.prochiller.com

[almalkin]

Thanks for the reality check guys. I hadn't really considered the hurdles involved in feeding two separate circuits with different demands. I guess the other downside would be that if this unit goes down, all my chilling capacity is offline. The quick feedback I have received from the refrigeration guys is that this is not a great idea, for most of the reasons that have been posted. As with most quick and dirty fixes, this looks like it probably will not be worthwhile.

Scott L, it sounds like we are in a similar boat right now. We are trying to cut out any bottlenecks to meet demand, and are looking to add more capacity soon. Time to shop for a new chiller.

Thanks again for the help guys!

-Steve

[Scott M]

One thing I just thought of was to place a new, clean evaporator; less the expansion valve, over the evap in your cold room (about 2" from the evap) and pass your glycol through it prior to its going into the glycol chiller. Set your cold room fans to run continuously to pre-chill the glycol. Cheap and may not provide any benefit, just a thought, and depends on the temperature of your cold room and the return glycol temperature.