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Need help sizing chillers for UC systems
Is there a formula growers can follow to help them size a chiller to their UC?
Is there a formula growers can follow to help them size a chiller to their UC?
I'm curious especially for growers using multiple systems in a large space using delivery/return manifolds and coils to cool each system from one centralized commercial chiller.
Say, (8X) UCE24XXL's in a 90 x 30 space w/ an ambient temp of 78F? Is there a cooling guru moderating this forum that has any input for us?
Sorry this is a long answer....
There is an accurate way of sizing a chiller for a UC system by calculating the BTU's being absorbed by the water in an hour. What you want to do is first fill the UC system to the highest level that it would ever be at (this level will require the most heat removal because the higher the water volume, the greater the heat absorption). Next turn on the lights over the UC and let the room warm up the the highest temperature that it would be during the on cycle. It's important to turn the lights on because radiant heat from the lights will affect the UC water temp. Ice down the water in the UC to get it around 65, record the water temp....wait one hour and then record the water temp again. This will give you your temp differential over an hour, and from there you can calculate the BTU’s per hour being absorbed by the UC. The formula to find out how many BTU are absorbed in to the water is
Gallons in UC x 8.34 (weight of a gallon of water) x temperature rise in one hour
Example
I've got a 6 site UC with 70 gallons of total water volume, I turned on my lights and got the room to 80 degreees. I started with 65 degree waters....waited one hour and the temp was 70, so a 5 degree rise in temp. While testing if your water temp reaches your room temp before the end of the test then the test must be started over with a cooler starting temp.
70 x 8.34 x 5 = 2,919 BTU per hour.
1 hp (or ton) of cooling = 12,000 BTU, so I would need a 1/4 hp of cooling for my UC system. Most chillers do not perform at their listed rating, instead they usually test at around 80% of their rating, which is the industry standard unfortunately. The only chiller that I've tested that perform at their rating is the ChillKing chillers. Since a typical 1/4 hp chiller only outputs 2,343 BTU (80% of 3000 BTU), I would actually need to step up a size to the ½ HP chiller if going that route. You always want to leave yourself at least a 20% cusion, you never want to size a chiller to exactly what you need b/c it won't cycle properly. You can find the actual chiller BTU output of most chillers online.
Do you know the temperature differential? If you get that measurement then you can use the equation that Chillville posted to let you know how many BTU your system is absorbing and size the chiller accordingly.
Thanks wood I actually brought the cool coil from UC but I only have one unit so I am running the chiller straight so far it's running great I had a 1 hp with my 4xxl 13 it was over kill and very loud so I down graded to 1/4 hp I'm loving it so far thanks once again
I have been running coils in my uc and my DIY UC, they are attached to a 1 hp chiller. I have been running the coils in the epicenter but am going to change it around and run the coils in the res for the chiller and pump the nutrients through the coils. This will put the coils totaly under water and cool the res better, I think. If your looking for coils try brewing stores as they are 1/3 the cost. I got my 50 foot coils for 75$ each, they are SS with hose ends on them.
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