Lid Open Cycling during Startup


 
B

Bob C

TVWBB Member
I am testing my 4.3 HeaterMeter in a sous vide setup with a crock pot. I have my temp set to 165 F. As the water was heating up and got to about 115 the meter started continuously cycling the lid open.

I initially had the lid open at 20% I have tried 99% and 6% and it keeps cycling. Why is this happening? Is there a way to turn off the lid open feature?

Also have updated to the latest RPI 3 software as well as changed the line noise from off to 60hz



Lid%20Open%20Pic_zps3wjvo0b4.png
 
Any chance your pit probe is coming loose?

Since you're in sous vide mode, do you have fan min and max set to 100%
 
I went ahead and set the setpoint temp to below my current temperature and the lid open feature keeps coming on.
 
Steve_M said:
Any chance your pit probe is coming loose?

Since you're in sous vide mode, do you have fan min and max set to 100%
Click to expand...

It is a brand new thermoworks water proof probe and I am not moving the heater meter so it shouldn't be coming loose.


I have the following settings

PID = 10, 0.007, 16
Fan Pulse
on above 5%
Min 100%
max 100%
Start up Max 100%
 
I'd check the left button on the board to see if maybe it's shorting out on its own, telling the HM to activate lid mode.
 
The lid mode shouldn't start to trigger until after you have achieved your setpoint for the first time. From your graph it looks like you never hit the setpoint, therefore lid mode shouldn't be kicking in, unless you click the left button... so perhaps you have something flaky with the left button?
 
Steve_M said:
I'd check the left button on the board to see if maybe it's shorting out on its own, telling the HM to activate lid mode.
Click to expand...

Thanks for the suggestion. I removed the LCD/button board and am doing another test. Hopefully this fixes it.
 
Bob C said:
Thanks for the suggestion. I removed the LCD/button board and am doing another test. Hopefully this fixes it.
Click to expand...


That was the problem. The test with the LCD/button board removed worked as expected. I'm going to have to play with my PID settings. At the set temp the SSR device would cycle about every 8 seconds. I would rather have a little temp variation with less cycling.

Thanks everyone for the suggestions and help.
 
Bob C said:
That was the problem. The test with the LCD/button board removed worked as expected. I'm going to have to play with my PID settings. At the set temp the SSR device would cycle about every 8 seconds. I would rather have a little temp variation with less cycling.

Thanks everyone for the suggestions and help.
Click to expand...

Why would you want less cycling? With your current settings, your SSR is on for 2 seconds, and off for 8 seconds, or on 20%. If it's maintaining a constant temp, then this is what is required.
 
WBegg said:
Why would you want less cycling? With your current settings, your SSR is on for 2 seconds, and off for 8 seconds, or on 20%. If it's maintaining a constant temp, then this is what is required.
Click to expand...

I'm not worried about +- 2 degrees so i would prefer the crock pot come on till it goes up a degree then go off till it is a degree below my set point. This is pretty much how my furnace works. I wouldn't want my furnace cycling every 8 seconds. It just seems like that would be bad for the furnace.

I know the SSR is rated at 5 Million operations. I would assume the crock pot is a lot less than that.

Also how quickly does the heating element of the crockpot heat up? is 2 seconds enough? How much does the element cool off in the 8 seconds? I may be wrong but it just seems like this would be inefficient and adversely effect the life of the equipment.
 
There's no way to get HeaterMeter to run like a normal climate control or water heater thermostat with a deadband, or bang-bang operation.

Crock pots and other heater elements are pure resistive loads though so it isn't like turning on a compressor or anything where there's a large load at turn on that lowers equipment life. Heater elements are literally just a wire. You're right though, it does take time for them to heat up after power is applied, and it takes a while for them to cool back down after power is off. This is accounted for because if it is on for 2 seconds and off for 8 seconds, then after a few cycles it is now modulating centered around the temperature you want it to be.

Because it is not getting fully 100% hot and 0% cold between cycles (like you'd get with a deadband controller), the element isn't expanding and contracting fully due to heat which has a higher chance of degrading the element than keeping the element warm continuously.
 
What about using the alarm setpoint on the pit probe. If you want to fluctuate between 144 and 146 with an average of 145, you could start off with a set point of 145 and then set the high alarm setpoint to 144 and the low alarm setpoint to 146. This should keep changing the setpoint to 144 > 146 > 144 > 146
 
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