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CrabbeMan
10-08-2015, 06:01 AM
Hello,

I am trying to figure out what my cooling issue may be.



I have 2 issues.

1. The unit constantly cycles on and off with no load(Every 5 minutes). I have it set with 2 degree deadband and itt seems the temp raises couple degrees pretty quickly causing it to turn back on. The temp sensor that controls the compressors is at the bottom of evap barrel and had it down to 25, by the time it hits the supply header which goes though maybe 2 bends and 2 feet of pipe, my analog sensor is showing 30. I have a bypass valve at the end so I know it is circulating, but wondering if its restricted somewhere? I know if pumps dead head, the paddles will immediately heat up the glycol causing the unit to cycle.

2. False temp readings- My thermo wells in my tanks maybe stick in maybe less than 1/4". My rancos "struggle" to make "36 degrees f". I put those in quotes as we did our first canning run Tuesday and the more beer we drained, the colder my ranco showed. The canning machine showed 34 degrees at start, and 29.5 at the end. This issue maybe due to thermos not being long enough?

My glycol system has an submerged evaporator in a insulated drum. I am the 3rd owner so i assume it was custom built back in the day. psi on supply showing around 10 psi, return psi shows about 5psi. Running 1" insulated lines using first in, last out method. My solenoid valves are on supply side feeding bottom ports of tanks, with returning coming out the top.

So why constant cycle and why is the top of my tanks at the return side colder than what my ranco shows at supply side?

27008

rdcpro
10-08-2015, 09:50 AM
Hello,

I am trying to figure out what my cooling issue may be.



A couple thoughts for you:

1. Your glycol reservoir looks pretty small. That's probably why it short cycles, as the glycol absorbs heat when the loop is circulating. How many gallons does it hold?

2. The temperature gauges on your supply and return headers are mounted in an odd way. Usually you want them mounted so the probe points toward the incoming or outgoing flow. So, if you have a tee, then the process flow comes in one side of the "run" of the tee, and goes out the branch (or vice versa). The gauge mounts at the other end of the run of the tee. They way they are mounted in the photo, I suspect you're not getting a good measurement of the glycol temp. Also, unless you've calibrated them, I wouldn't assume they will all read the same thing at the same temp. My Dad always said "if you want to know what time it is, only look at one clock".

I'm not sure about your FVs, but 1/4" sounds too short for sure.

Mike

jebzter
10-08-2015, 09:57 AM
The general rule of thumb for temperature probes is that they extend in about 1/3 the radius of the tank. The other issue you may be experiencing is the submerged coil method of chilling your glycol, the cold glycol will sink to the bottom of the tank pretty quickly, so it may not be cooling the tank evenly, also if the probe is anywhere in proximity to the coil it will read the temperature close to the coil which will be lower than the surroundings. It may be better to have a larger reservoir with a probe that controls the glycol unit, and a separate pump that cycles glycol from the reservoir to the heat exchanger.

CrabbeMan
10-08-2015, 09:58 AM
A couple thoughts for you:

1. Your glycol reservoir looks pretty small. That's probably why it short cycles, as the glycol absorbs heat when the loop is circulating. How many gallons does it hold?

2. The temperature gauges on your supply and return headers are mounted in an odd way. Usually you want them mounted so the probe points toward the incoming or outgoing flow. So, if you have a tee, then the process flow comes in one side of the "run" of the tee, and goes out the branch (or vice versa). The gauge mounts at the other end of the run of the tee. They way they are mounted in the photo, I suspect you're not getting a good measurement of the glycol temp. Also, unless you've calibrated them, I wouldn't assume they will all read the same thing at the same temp. My Dad always said "if you want to know what time it is, only look at one clock".

I'm not sure about your FVs, but 1/4" sounds too short for sure.

Mike

Thanks for the reply.

We are not sure how much it holds. Would think at least 25 gallon? Could be more or less....Its very well insulated. Do you suggest we put in an additional holding tank with more glycol?

The digital temp gauge reads right out of the barrel so i dont even look at analog gaues. I suppose temperature isnt the real issue of glycol, its more of flow and short cycle. With no load and full recirc, it still cycles and runs.

I guess its down to flow issue? Still dont understand why top of tank is colder at the return side, but at therm well its warmer where supply is. As the beer drained, the ranco went colder. Stumped me on this one.

CrabbeMan
10-08-2015, 10:08 AM
The general rule of thumb for temperature probes is that they extend in about 1/3 the radius of the tank. The other issue you may be experiencing is the submerged coil method of chilling your glycol, the cold glycol will sink to the bottom of the tank pretty quickly, so it may not be cooling the tank evenly, also if the probe is anywhere in proximity to the coil it will read the temperature close to the coil which will be lower than the surroundings. It may be better to have a larger reservoir with a probe that controls the glycol unit, and a separate pump that cycles glycol from the reservoir to the heat exchanger.

Great suggestion. I will look into this idea for bigger reservoir.




Thanks

TGTimm
10-08-2015, 10:19 AM
Electronic temperature probes are no more accurate than your dial thermos--especially the ones that your Ranco thermostat uses (3 or 4 wire RTDs are extremely accurate, but still need calibration). I have 3 compressors with three sensors in the same place in our glycol back, and all read differently--by as much as five degrees! I used my MIG calibration thermo to find out what the temp actually was, then set my thermostats to compensate for the different readings from the sensors.

And, yes, 25 gallons is very small for a glycol back and is probably causing your short-cycling--which will soon be causing a short lifespan of your chiller compressor.