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Hello, I have a glycol system connected to 8 conical fermenters with stainless steel coils with motorized valves. Is it better to have a constant flow via a bypass or constant pressure with a booster pump? What would the optimum flow or pressure be?
There are two main issues that matter to every glycol system.
1) Maximum expected BTU load.
2) Reservoir temperature variation and recovery time.
Item one is the temperature differential between the process (fermentation, crashing, chill-proofing, wort chilling, etc.) and the glycol supply. The supply has to maintain enough temperature difference to remove heat effectively and smoothly (no inversion layers). Your coils and larger glycol jackets are already designed to present enough surface area to be effective under specific circumstances.
Item two is the load on the chiller to take he heat out of the glycol and keep enough BTUs to allow enough temperature difference (delta) to stay handle your heaviest need.
With those two issues figured out, you then size your chiller. Or, you can use the chiller power as a max limit for what you are able to do at any given point in the brewing cycle. From the chiller power standpoint, you can estimate the load of idle glycol as a BTU load that the chiller has to recover. The longer and larger your lines, the bigger the idle load.
Compare the idle load to the BTU cost of a single feed line with a small return line at the farthest point. This setup will keep cold glycol in the lines to the fermenter, speeding up the reaction time once the valves open.
In 2018, I built a small glycol system for a total of five 1bbl conicals. Each had its own individually pumped run, ranging 5 to 20 feet, and the chiller had no problem keeping up. In the heat of summer, crashing took a few hours longer and needed a bit of insulation to maintain chill proofing temperature. The glycol reservoir was 40 gallons and stayed 30oF all year.