Propane smoker temperature controller and safety shutoff

[novasquid]

I first posted this elsewhere but thought some of you guys would appreciate it too.

I installed a needle valve, safety shutoff valve, and a solenoid valve with PID controller to maintain propane flow and smoker temperature to my masterbuilt 40 inch propane smoker.

I got the idea and inspiration for the safety shutoff and solenoid valve from glenwillits on this thread. So big thanks to glenwillits.

After initial install, I let it run to double check for leaks and to make sure the solenoid valve and PID were playing nice. It's been a couple weeks now and I did another test run today and my target temperature was 225. It was able to maintain +/-1 degree, 224-226F. I couldn't be happier with this setup. I can now truly set it and forget it, and if the burner flame happens to go out, the safety valve will prevent the smoker turning into a bomb.

Here are all the parts laid out before install. The Auber PID controller was the only thing i already had on hand.

The solenoid valve and needle valve assembled. The Auber has a built-in solid state relay, and it's 12v 1a output is able to control the solenoid valve directly. The needle valve portion controls the ”pilot light" aspect of the setup and is always on and dialed in to a lower temperature, eg 220F. The solenoid portion is normally closed, and the PID controller can open it for full propane flow in order to maintain the target temperature, eg 225F.

The smoker's burner assembly already had a hole that i used to mount the safety shutoff thermocouple.

Everything installed under the smoker.

Front view after installation. Safety shutoff is to the left of center, and to the right is the solenoid and needle valve.

 

[jpbsarris]

I have worked with several people that have tried a similar setup at this. One thing that sometimes is an issue is that the burner on lowest stable setting will still result in higher than 225 degrees. To get down that low may result in a flame that is too easily blown out and unsafe in windy conditions. A flame safety device like you are using is an ABSOLUTE MUST as far as I am concerned. Most of the time I have used a strong standing pilot with a safety thermocouple instead of trying to get the idle flame low enough. This can result in little more of a temp variation between off and on of the main burner but from my experience this has minimal effect on the cooking time if your target temp is somewhere in the middle of the range. Even a mechanical thermostat with a 15 degree range seemed to work with little overall effect. Jet burners however work well with a low and high setup as you have made as they are still very hard to blow out at a lower setting. I have made several deep fryers that use jet burners and they work perfect with a lower flow for idle and a max flow when frying. One other suggestion is that I would not use a rubber hose and clamps with a gas setup anywhere near a burner area. If you had a grease fire that could be unsafe. A better setup would be 1/4 copper tubing and compression fittings.

 

[novasquid]

I have worked with several people that have tried a similar setup at this. One thing that sometimes is an issue is that the burner on lowest stable setting will still result in higher than 225 degrees. To get down that low may result in a flame that is too easily blown out and unsafe in windy conditions. A flame safety device like you are using is an ABSOLUTE MUST as far as I am concerned. Most of the time I have used a strong standing pilot with a safety thermocouple instead of trying to get the idle flame low enough. This can result in little more of a temp variation between off and on of the main burner but from my experience this has minimal effect on the cooking time if your target temp is somewhere in the middle of the range. Even a mechanical thermostat with a 15 degree range seemed to work with little overall effect. Jet burners however work well with a low and high setup as you have made as they are still very hard to blow out at a lower setting. I have made several deep fryers that use jet burners and they work perfect with a lower flow for idle and a max flow when frying. One other suggestion is that I would not use a rubber hose and clamps with a gas setup anywhere near a burner area. If you had a grease fire that could be unsafe. A better setup would be 1/4 copper tubing and compression fittings.

I keep my pilot light setting to be close to but just under the target temperature, in this case 220F when my taget is 225F. With this set up I was able to maintain +/-1F so it works for me. The initial thread where i got the inspiration for this mod has his set to lowest stable flame but i didn't want to risk a flame blow out, which is why i use a much higher, stable flame.

The masterbuilt burner already has a hole which i assume is meant for a safety shutoff thermocouple, but they must've left it out to save costs. At a minimum, I feel every propane smoker owner should add a safety shutoff to their smoker if it doesn't already have one.

It's not just a plain rubber hose. It's a low pressure propane hose that I cut to size. I'm not too concerned about grease fires outside of the smoker box but i suppose it's a possibility. I could put foil above the hoses to create a heatshield/firewall. And the propane regulator is low pressure at <1psi so i have no concerns about leaks at the hose fittings. During my leak test, it was actually the brass fittings that leaked, even with Teflon tape I really had to tighten them down to stop all the leaks.

 

[jpbsarris]

I have had issues with leaks with some brass threads on safety valves and gas valves as well. I found out that some are manufactured with British standard threads. Although some sizes will thread onto American standard threads there is a slight difference on the thread pitch and they will not have enough contact surface to seal properly. Shouldn't be a concern with a low pressure use as long as they are tightened very tight.

 

[Joshw]

Nice post. I recently purchased a propane smoker, and plan on doing something like this. My goal is to maintain very low temps 120 or so. Do you know what temp the safety valve shuts off? Also do you have links to it, the solenoid valve, and pid?

 

[novasquid]

Nice post. I recently purchased a propane smoker, and plan on doing something like this. My goal is to maintain very low temps 120 or so. Do you know what temp the safety valve shuts off? Also do you have links to it, the solenoid valve, and pid?

The safety shutoff thermocouple doesn't work on a set temperature. It's a probe that sits within the burner's flame, heat activates it and keeps the valve open. If the flame were to blow out, then the probe cools and shuts off the valve.

Safety shutoff and themocouple:
https://www.amazon.com/gp/aw/d/B000H7QWFI
https://www.amazon.com/gp/aw/d/B000BP7LJ2

Auber PID (i have the older 1614 version):
https://www.auberins.com/index.php?main_page=index&cPath=14_27

Solenoid valve:
https://www.amazon.com/gp/aw/d/B00APDNPXG

With that said, you'll probably have a very difficult if not impossible time maintaining 120F with the stock propane burner. It'll keep blowing out. You may be better off using an electric hot plate inside the smoker box to get such low temperatures.

 

[Joshw]

Thanks!

 

[jpbsarris]

For a few bucks more this company sells a great stainless steel valve. This is the one I use with my high pressure jet burners and low pressure burners. They have these in 12v or 120v. Never had a problem with this company.
https://www.ebay.com/itm/300521903427

 

[novasquid]

wow 19k sales with 100% positive reviews is a good sign. if my US Solid unit ever breaks down, i'll take a look at the ebay unit. thanks for the link.