BIAB, PID, Propane, Recirculation, Hope, Dreams, and Questions

[petemoss]

Hey gang,

I am currently BIABing by heating my water to strike temp with a Blichman propane burner. I then mash in and cover the kettle with a sleeping bag for insulation. I'll check temp and stir a couple of times during the mash. I do have a screen in the bottom of the kettle to keep from burning the bag in case I need to heat the water a little during the mash.

I am looking into the possibility of using a PID controller and gas valve setup to just keep the temp at the proper temperature without worrying about the sleeping bag and all that.

Question 1: If I am heating the water little by little during the mash to maintain temperature, do I need to recirculate the wort to keep even distribution of heat throughout the kettle? When I add heat manually I stir like the dickens. It seems like that might not be practical if the system is turning heat on and off all the time.

Question 2: I am thinking about going with a simple on/off gas valve. I was thinking that I should manually run the burner wide open to get near strike temp and then turn on the PID to let it control the last little bit and take over temp stability after that. If this makes sense to this point, once I engage the PID, should I close down the propane valve to limit the heat so that I'm not doing blowtorch on/off, but rather more of a gentle heating?

 

[PsychoBiter]

1. You will need to recirculate to keep an even temp or stir a lot like you do now when heating. I assume you are doing this to make it more hands off, you will need a pump to be more hands off.

I don't have any experInce with valves, but I would figure it would control the flow depending what the controller tells it.

 

[The_Bishop]

Usually gas valves are on/off affairs. Regulating the flow of gas (heat applied) is via a valve downstream of the gas solenoid valve. The issue with automating a gas rig (and what makes it a bit expensive) is the safety factor; you really need a pilot flame/igniter and a sensor to ensure the burner is lit, otherwise you'll be dumping gas with no flame creating an explosion hazard.

 

[cease]

Is electric an option? Gas would make the build a bit more complicated. A Blichman boilcoil on a controller has worked great for me.

 

[petemoss]

Hey thanks everyone. I had originally thought that since I already had the nice burner that I should just try to automate things using it. However, since I would have to get recirculation capability anyway plus a controller plus a gas valve. Then I would have to modify the burner for safety reasons to add a pilot light or whatever. Maybe going electric would be the way to go.

If I went electric many of the components would be the same anyway. Plus without the propane I could probably start brewing in my garage which would be pretty awesome.

That leads to a couple of other questions. It seems to me that I could go one of two ways. I could add an element to the kettle itself. This would require me to add a new port to the kettle. If I have the element in the bottom of the kettle, it seems like it would burn the bag. Would I have to change to a mesh metal basket?

Secondly, I could use one of those RIMS gadgets to heat the wort. Since I would be pulling the wort from of the kettle through the valve, would there be any issue with the bag clogging the hole? Would I have to add a filter device / false bottom like they use for three vessel brewing?

Thanks

 

[jrcrilly]

It is neither difficult nor expensive to attain PID control of a propane burner. Using standard furnace hardware ensures that the same safety features in your home furnace are present in your brewing rig.

Once rigged, the PID controls the rate of heating in the same way as in an electric system - it sets the duty cycle. If it determines that only 10% of max heat should be applied to prevent overshoot, it operates the heat 10% of the time. In electric systems, the time frame is milliseconds while in gas systems the period is tens of seconds. Response time is the same in the end, as the liquid being heated can't respond instantaneously anyway.

 

[petemoss]

That leads me to another thought. When you have an electric setup, and let's say it is running at 30% output, does it have On and Off cycles that use pulse width modulation during the On cycle, or does it basically stay on continuously and pulse width modulate the entire time.

For example:
ON pwm OFF / time time / ON pwm OFF / time time / ON pwm OFF
- or -
ON pwm pwm pwm pwm pwm pwm pwm pwm OFF

I am just curious how a PID and SSR output a non 100% output. It is my understanding that a PID and/or SSR are On / Off devices rather than supporting actual analog output.

Thanks

 

[The_Bishop]

SSR devices are on/off switches, but they can switch very, very quickly. Depending on what controller you have, the on/off speeds are either a 2-second window (Most/all PID) or at the power frequency (Auber's DSPR 120 which I highly recommend as an electric controller) which means they can cycle at 60/50 hz depending on the mains power frequency where you live.

 

[sikkingj]

I'd like to hear more about this (PID control of a propane burner) - has anyone built one. Bill of Materials, costs?

 

[jrcrilly]

I'd like to hear more about this (PID control of a propane burner) - has anyone built one. Bill of Materials, costs?

https://www.homebrewtalk.com/budget-h...-part-one.html

https://www.homebrewtalk.com/budget-h...-part-two.html

 

[The_Bishop]

Neither of those links are working, unless you're referring to the lower two links in your signature?

 

[jrcrilly]

Neither of those links are working, unless you're referring to the lower two links in your signature?

Sorry; I must have goofed the links up. They were intended to go the same places as the last two sigline links. If I had remembered those were there, I would have just pointed to them!