How quickly can you heat 20 gal with RIMS?

[Brewsit]

I’m curious what other people are seeing out of their RIMS, specifically 5500w 240v RIMS to heat 20ish gallons of cold HLT water, for example.

I have an HLT I’m using as a holding vessel with the RIMS to heat strike and sparge water. 25 gallon vessel, tap water is 45 degrees.

I ran a test run on my system and while I wasn’t measuring flow rate precisely, I had the valve throttled down low enough that any more would be closed... and I was only seeing a 30 degree jump in the temp in the tube.

It took 2 hours to heat about 20 gallons from 45 to 165 this way.

I’m suspicious that it’s my crappy Fotek SSRs that may be limiting me. At one point I got a 45 degree change, and at another point only saw 5.

So again my question would be... what should I expect to be seeing for time to heat that volume and temp change in relation to flow?

 

[schematix]

Ramp Rate in °F/minute = 0.0068 X Watts / gallons

So for you that should be 5500 * 0.0068 / 20 = 1.9F/min

You were measuring a 120F rise. Should have been closer to an hour than 2.

So you're definitely low. Is your kettle insulated? Was your RIMS set to 100% power, or were they controlling to temp or constant power?

Its possible if they were controlling to temp that they weren't requesting full power from the PIDs.

 

[Brewsit]

Thanks for that formula. Kettle is not insulated but it’s indoors and I’ve never had much of an issue at these volumes with heat loss. I watched it when it sat with some water and maintained temp pretty well, losing about a degree every 15 minutes or so.

RIMS was set to a hysteresis control with temp of 180, and it ran pretty much constant. Temp probe is at the top of the tube, element is a few inches from it. It’s the Brewers Hardware 1.5” setup with one of Kal’s elements.

 

[schematix]

If you are suspicious of the SSR you could try the experiment again but direct wire the SSR to the element. Just make sure to keep your recirc flow as high as possible.

 

[Brewsit]

I should add that I’m using BruControl for controlling the elements. I didn’t have a light hooked up so I could see any nuanced changes in the power, just that it showed “on” whenever the system sampled.

I have some better SSRs I’m going to swap out and see if that changes anything. I’m curious if a PID would be better? I didn’t want to mess with that because of such a quick sample temp change potential.

 

[schematix]

I doubt its the SSRs. Those things are commodity. Usually they work or they don't, and when they don't, they smoke!

Does the SSR have an LED on it to indicate when control power is applied? Is it blinking or seem dim?

 

[Brewsit]

Hard to say, it’s inside a giant box that I keep closed when connected to power because two runs of 30A 220v feed in to it (GFCI but still...). So if it’s not the SSR maybe the hysteresis is too conservative?

 

[schematix]

whats the hysteresis window set to?

 

[Brewsit]

I played with it a couple times, but had it set to 180 for the majority.

 

[schematix]

not the set point, the hysteresis.

 

[Brewsit]

Sorry, realized what you were asking a second ago. I had it at -2 with a 1 second delay

 

[schematix]

ok so that shouldn't be the issue.

any idea on your recirc rate? you should be running as fast as possible during heating phase.

does your controller have an actual temp display?

where is your temp sensor located?

did it heat faster at lower temps then slow down drastically?

 

[Brewsit]

Control does have a temp display, there’s a probe near the bottom of the HLT and one in the RIMS. I was probably recirculating around a gallon a minute or slower at times, and others full throttle. I saw a degree a minute just about consistently through the entire time no matter what speed I used. When full throttle it had less than a 5 degree temp difference from the incoming to outgoing water. The temp of the water did not affect this either.

 

[schematix]

which sensor is being used for control?

 

[Brewsit]

The one in the RIMS. I also switched to my boil kettle which also has a 5500w element and saw it heat up much faster, about in line with the formula. I plugged it in to the same SSR. Just thought of that. So yea, the only variable is the hysteresis or the element itself being bad.

 

[schematix]

if you have a multi meter you can check the elements by checking their resistance.

should see R=V^2/P = 10.5 ohms

can you put the controller in a manual power mode? its possible you are getting close to set point in the recirc loop and the controller is backing off.

 

[Brewsit]

I’ll give those a shot. It’s easy enough to put it on 100% duty cycle.

 

[BrunDog]

Sorry I overlooked this. I would suggest the test with a digital output on that port - this way it is on 100%. That will prove if it is a hardware issue or software.

If you are running hysteresis to only 180 with very slow flow, the liquid in the tube can heat up then be read by the temp probe and shut off the heat again. Without an LED or paying close attention to the report on screen, you may be having periods where the element is in fact off in software.

 

[Brewsit]

No worries Pete, I was gonna ping you next about this. You can’t be everywhere at once. Or can you? I’m going to run that test on Saturday, I’ll let you know what I find. The inaugural 15 gallon brew is happening on Sunday and I’m confident it will work out.

 

[Brewsit]

It was definitely the hysteresis holding the temp back. Running with duty cycle I’m getting the temp to ramp up in line with what it should be.

 

[BrunDog]

In my rig, I heat my strike water directly in my MLT at full duty 5500W and fairly good flow rate (~16+ QPM). I use a script in BC that looks at the temp of the water exiting the MLT. When it reaches 3 degrees less than strike temp, the heating mode switches from 100% duty to a PID st the Strike Temp + 2 degrees. After a few minutes, it’s settled at the right strike temp.

 

[Brewsit]

Would you mind sending me that code? I love that idea. I was running it at 100% duty cycle but ended up switching to hysteresis to keep it from boiling in the tube, which was more of a manual process.

 

[BrunDog]

Here are the relevant sections of my code, (with the extra stuff removed):

[prep_strike]
"Pump 1" State = on
sleep 10000
wait "Flowmeter 1" Rate > 5
"RIMS Heat Duty" DutyCycle = 100
"RIMS Heat Duty" Enabled = true

[strike]
new value PreStrikeTemp
PreStrikeTemp = StrikeTemp - 3
wait "Mash Temp" Value > PreStrikeTemp
"RIMS Heat PID" Target = StrikeTemp + 2
"RIMS Heat PID" Enabled = true
delete PreStrikeTemp

[strike_loop]
if "Mash Temp" Value >= StrikeTemp
	"Brew Alarm" Active = true
	"RIMS Heat PID" Target = StrikeTemp + 1
	goto dough_in
endif
sleep 3000
goto strike_loop

[dough_in]
// continue doing stuff here

Let me know if this requires any explanation.

 

[Brewsit]

It looks pretty simple. What are your PID settings for the RIMS?

 

[BrunDog]

I’ll have to get back to you as I’m away from it right now.

 

[Brewsit]

No worries.

 

[BrunDog]

My RIMs properties: Kp: 30, Ki: 1, Kd: 5. Max output: 100%, Max Integral: 50%. Calc time: 1, Out Time: 3.

I don’t make any changes in the script for these - they stay constant whether the RIMs is running at 120V or 240V.

 

[Brewsit]

Just saw this, thanks!