Originally Posted by acefaser
Squeeky and PJ -
Thanks for the great electrical schematic. I am looking at building this design and was wondering what the best way to incorporate the temp probes into the switch. The 4 pole DT has been mentioned, but doesn't seem to be the best choice. Is there a way to put in relays after the DPDT switch to have the correct thermocouple information displayed on the PID with the DPDT switch position? I could just add another switch for the temp probes, but I can see the day that I forget to switch it and it reads the wrong probe.
I have some concerns with this as it could complicate your build a little bit. It certainly can be done and there are a few ways to accomplish the task. So with that said, lets look at the options:
With the setup as shown (Post #6 in this thread), there is no real need to have a temp probe in the boil kettle. With that said, the probe remains in the HLT to manage the strike water temp. If you are using a cooler for the MASH tun it's a done deal. On the other hand, if you are using a kettle for the mash, recirculating HLT temp controlled water is a must. A HERMS coil would be used for that. Both of these methods require the temp probe to be in the HLT.
Now we move to the next step. Wort is transferred to the BOIL kettle and brought to the boil. The PID requires a temp probe to be connected for it to function. No problem - it's still in the HLT and once the boil comes to a boil you use the PID in manual mode to set the percent of power to control the boil. Temperature? Keep in mind that a raging boil has a temperature of 212°F and a simmer boil also has a temperature of 212°F. Thus the use of manual mode as a temp probe does not enter into the process.
Ok... Maybe a reason for wanting a probe in the boil kettle. To monitor chilling the wort when using an immersion chiller. Ok. I can do that, But, I do not like the idea of using a 4 pole switch to accomplish this task along with switching the power to the elements. There is another way.
Buy this Cube Relays QM4N1-A120
and the Socket SQM14D
It is a 4 pole double throw - low current relay. It should be energized whenever the element switch is set to the BOIL kettle. Another detail - because you are switching temp probes, I strongly
recommend that you use RTD probes for this task - thus (3 wire probe) the 4 pole double throw relay. (Plus the probes are a lot easier to mount in the kettles)
When switch #1 is set to HLT or CENTER OFF the PID uses the temp probe in the HLT. When switch #1 is set to BOIL, the relay energizes and transfers to the RTD probe in the boil kettle. HOWEVER this is not going to work for you for chilling
as the BOIL element is energized. One more switch is required to open one of the PID to SSR lines so that you can drop the power to the boil element.
So in summary: This becomes a complex issue. It can be done - no sweat - but I'd like you to think about it a little bit. Then if you really want to go this route, please let me know and I'll come up with a modified diagram for you.
What do you think? Or maybe you have another reason for requiring a second temp probe. I'd like to know. Help me help you.