PID vs on/off temp controllers

I am in the market for a temp controller to be used in a RIMS/HERMS system. I'm going to use a water heater element to heat water surrounding a HERMS coil.

I'm wondering what type of controller would best fit my use. I don't know if I need the thing to do math I won't even attempt when I just need it to tell a relay when to energize.

My temp probe will be at the exit of the HERMS coil (as opposed to the MLT) which I believe would eliminate a lot of the math a PID would need to do...I may be wrong. Having a dual display for set point, and actual temperature would be nice. I'm not looking to spend a lot of money, but don't want to short change myself either.

Any help or advice would be appreciated.

-Dixon

I used one of THESE on my setup to control a hot water heater element and, so far, it has worked fine. They're pretty reasonably priced on eBay. This particular model does have a relay built in, but it is not rated to handle the load of a hot water heater element, so I did have to use a seperate relay.

I placed my temp sensor on the exit-end of my heat transfer coil, so it is measured right before going back into the mash tun. You just set these like a thermostat, and (assuming you've wired it up right!) that's about all you have to do in order to maintain a temp. One display is for the actual temp, the other is for the target temp.

I have some pics of when I was test-wiring mine here: http://www.photosbyjasonsmith.com/electrical

nice thing about using a PID is the variable set point and digital readout. You have described my HERMS to a tee, probe on the out put means the wort going into the mash is always at the setpoint temp.
the real cheap PIDs you can find on Ebay work great

Thanks a lot for the quick replies guys. I just finished building my heat exchanger, can't wait to get that PID!! (and SSR, and silicone tubing, and QD's, and...sheesh)

Cheers,
-Dixon

Don't forget a thermocouple!! That was another item I grabbed on eBay. Believe mine was a type K.

I have a tip on QD's.... I searched lonnnng and hard for them. Found one little place tucked away at the back of the Internet that was selling them for about half of the best pricing I could find everywhere else.

http://www.quickcouplings.net

John Alicandro ([email protected]) was the rep there that took my order and was incredibly friendly and helpful in keeping me up to date on it. One of the parts I needed was backordered, so he kept me current on the status plus helped me find the parts I was after.

I wound up going with HFC17835, HFC24835, and then coming back and ordering a couple with 1-way valves (HFCD17835) to help with pump back-flow.

Have fun and have a few beers ready for when the credit card bill comes...

-jason

Wow, those QDs are a lot cheaper than what I've been able to find, thanks. I have been told to get a type "T" thermocouple. Does it matter what type I use or is it just based on how I want it mounted?

Anyone know any places to buy march pumps cheap by chance?


My wife's gonna hate me by the time this thing is built, not to mention all the revisons...

-Dixon

I use a PID controller on my RIMS to control the in-line heater. I also have one on my meat smoker to control the temperature of it.

I have purchased few of these on ebay over the years and had good success with them when building projects. A couple things to look for when purchasing a PID controller is to get one that will operate a solid state relay. Not all of them are readily set up to control a solid state relay module.

The second thing to consider is the type of temperature sensor you are going to be using. The better PID units are compatible with either RTD or Thermocouple types of sensors and can be configured to use either.

The less expensive PID units may only be compatible with one type, usually a thermocouple.

Many PID units have a self tuning feature that makes setting them up easy. Make sure that you down load the instruction/spec sheet for what ever model you are considering.

The manual will give you a lot of good information that may or may not be there in the ebay listing.