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Thermostat questions

post #1 of 24
Thread Starter 
Hi folks,
I built a fridge smoker using this 5000 watt element: http://http://www.sausagemaker.com/i...ROD&ProdID=267
I am using a thermostat from McMaster Carr and all works well except the temperature range is very wide from turning off to turning back on. I was cold smoking some snack sticks and it would shut off at 110deg. but would not kick back on until it fell to 90deg. or even a little lower. I wanted a much narrower range but was wondering if this was normal?
I was thinking I might replace it with one for an oven but most of those have a range of like 165deg-500deg. Can I calibrate this so I can get a low of around 90 since I will never need anything above 300? Lastly, would the temp. range be narrower than what I am using now?
Thanks for your help!
post #2 of 24
It is normal for thermos to have a range of inacuracy...
10 deg in either direction is normal, but 20 aint right...
Not sure on your type as to being Calibrated but mine you may not...
if you have used it a ton, if the probe is dirty, really dirty, you may have to clean it off... the cleaner it is the more acurate it will be...use a light scrub with a brass or steel brush for heavy fowling, or one of those green kitchen scrubbers for light fowling. hope this helps.
post #3 of 24
What kind of thermometers are you using to check the temps? They might need to be checked for accurice also...Hope that helps............
post #4 of 24
I'm inclined to agree with Fireguy. Sounds like you have about a ten degree range either side of the set point. That is probably reasonable. I will give you advice I've not yet taken myself, that is to call you Tstat dealer. I have a Tstat from Allied-Kenco, and I'm not sure my range is reasonable or that the temp numbers on the face are correlating with the expected range. Alas, I've yet to call them to see if there is in fact a problem or a correction. What is your thermostat make and model anyway?
post #5 of 24
Take a look at a PID controller. I have no experience with one so I can't comment with too much info, but from the research I've done it appears to be the best route to go. I've ordered everything to make one, but I've got my first youngin on the way so I'll start tinkerin with it once he comes and I take my vacation. Check it out............LINK
post #6 of 24
i have cold smoked at 65 degrees
as long as the smoke flows...........i could care less........cold smoking is to me, to add smoke..........nothing else......here in my werld
post #7 of 24
trapper search the net for a Ranco Electronic thermostat they can set the cutin cutout 1to 30deg. I had more for you but my Internet it going down and lost it so sorry till I find a new provider.

Alan. PS. If your 240v keep in mind to check amps needed.
post #8 of 24
That sounds like a typical cheap themostat. Does it have bi-metalic contacts or is it electronic? I guess it doesn't matter, you need something with adjustable hysterisis. This allows you to tighten the turn on turn off around the setpoint.
Don't need a PID controller either, way overkill for smoking food.

What is the model # of it from mcmaster carr?
post #9 of 24
There are thermostats available with a range of about 60* to 200*, the one I have is for an Alto-Sham prime rib cooker and is calibrateable. They are not cheap! I have seen others as well, I beleive Robertshaw makes one in this temp range. Check with a resteraunt supply house or a local company that works on resteraunt equipment. The better the thermostat the better control you will have. You do have to watch the amp load using that 5000 watt element, you will need one that can handle approx. 23 amps, or use a contactor to handle the amp load for the thermostat.

Good luck!
post #10 of 24
The PID controller (Proportional-Integral-Differential) will give you the best control possible but they will be more expensive.
I am not an expert on this but this is my understanding on how these work.
During normal operation the Proportional part of the equation will switch your heating element on and off rapidly, many times per second, in proportion to the heat loss of the system. There are no long periods with the element on or off.
When you open the door of the smoker the temperature sensors sees a sudden drop in temperature. The Integral part of the equation kicks in and tries to head off the temperture drop by applying full power, element on constantly.
As the temperature starts to recover, the Differential part of the equation watches the slope (rate of temp change) and helps to minimize over shoot.
post #11 of 24
I got about 100 bucks in my PID controller, so I ended up spending less than one from allied kinco or the sausage maker. I didn't like the idea of that much of a temp swing in my smoker cause IMO a fews degrees off can render the fat in the sausage and ruin the product. Just my 2 cents. Wully Bully, Thats a fine explanation.
post #12 of 24
Trapper there is a company out there that does supply an inexpensive PID controller http://www.auberins.com/.

What you are experiencing is the time it takes the heater to heat up and then heat the smoker. There is a time factor that results in your temperature swing. With a PID controller you have control over how long the heater is energized and how often. The controller makes the decisions on the timing of it (called autotuning).

These controllers will require a solid state relay in between the controller and the heater. Poke around on the web site they have examples.

If you have more questions please ask
post #13 of 24
Thread Starter 
Thanks for the reply and links. One thing I don't understand is what you mean about the time factor. For example, I watch the thermometer and the heat gets up to 120 deg and it kicks off. It probably took 10 minutes for it to get down to 90 deg and kick back on. Is that consistant with what you are saying?
Anyway, the PID looks real interesting. Am I reading right that I wll need 3 components, this PID: http://auberins.com/index.php?main_p...products_id=14 , this solid state relay: http://auberins.com/index.php?main_p...&products_id=9 and this thermocouple: http://auberins.com/index.php?main_p...&products_id=2 ? If so, is there anything to hooking them up?
Thanks again for the help here! I appreciate it.
post #14 of 24
Here is a break down of the wiring of a PID controller.............LINK
post #15 of 24
Thread Starter 
Thank you sir! Let me digest that a bit, I am challenged when it comes to electricity.
post #16 of 24
Your SSR will have to be mounted on a heat sink! The SSR is listed at 25Amps, but that is with the proper size heat sink.
Attached is my simplified drawing, not step by step instructions, but may give another look.
post #17 of 24
By timing what I mean is that you have to energize the heater and it will take a moment for the heater to come up to full output. The heater will remain on long enough to get the smoker up to temperature. Then the power to the heater will be de-energized. However the heater is still hot and will continue to heat the smoker for a short while. Many cases will cause the smoker temperature to overshoot the temperature set point. The smoker temperature begins to decrease but because it will take a bit to heat it up again it drops below your desired temperature. Hope that helps.
If you want send me your components and I will wire up your controller if you want.
post #18 of 24
That's a mighty fine thing to offer.

One word to describe it as......................Class.
post #19 of 24
hey gritz...........did you notice tho........he didn't say ANYTHING bout sending it back................BWHAHAHAHAHAAHAH

i am SOOOOO bad.................

just kidding dude
post #20 of 24
Hey around the smoker we take care of our own.

Some help with great advise this is just my little way of helping out
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