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-   -   eHerms build questions (http://www.homebrewtalk.com/f170/eherms-build-questions-281994/)

Dohboy 11-18-2011 09:07 PM

eHerms build questions
 
Hi guys
I am about to start my HERMS build, i have all 3 vessels and all the hardware i need for them (thanks Wayne-bargainfittings.com for helping me with the hot water elements:mug:).
I live in New Zealand so will be using 240v and have 2 5500w elements for the BK and HLT on there way.
I have a couple of questions regarding the controls.
I only want a simple control box, the plain at this stage is to have a main on/off switch, 2 PID's ( to maintain temp in the BK and wort temp) with on/off switch's and switch's to turn the 2 pumps on/off.

Questions
Will my plain work?
Where is the best place to control the wort temp, in the HLT or the outlet for the HERMS coil.
Will these PIDs and temt probs be ok they seem to be a good price.
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Thanks Dean

zeus53219 11-18-2011 09:39 PM

Yes these PIDs will work. I have a friend that is using 3 in his set-up. The only downfall is you can not use a RTD wired to 3,4, and 5, you can only use a thermocouple wired at 3 and 4. But you cant beat the price. You will also need a few contactors for your elements and main power, similar to these http://www.homebrewtalk.com/f16/contactors-e-brew-heating-elements-273489/ Also you will need a 3 position selector switch to either run your BK or HLT element, one at a time assuming you are running 30 max amps from your panel.

Dohboy 11-19-2011 01:03 AM

Quote:

Originally Posted by zeus53219 (Post 3498154)
The only downfall is you can not use a RTD wired to 3,4, and 5, you can only use a thermocouple wired at 3 and 4.

Sorry dont want to sound dumb but what is a RTD?

You will also need a few contactors for your elements and main power,

How many do you think i will need
.

.

zeus53219 11-19-2011 11:47 AM

Thermocouples- inexpensive and can operate over a wide temperature range. A thermocouple is created whenever two dissimilar metals touch and the contact point produces a small open-circuit voltage as a function of temperature. This thermoelectric voltage is known as the Seebeck voltage, and this is what is sent back to your PID.

RTDs- Resistance temperature detectors are simalar to thermocouples but use 3-wires instead of 2. They operate on the principle of changes in the electrical resistance of pure metals and are characterized by a linear positive change in resistance with temperature, hence the 3rd wire. RTDs are slightly more accurate but if you calibrate your PIDs you will be fine with thermocouples.

I use thermocouples in my HLT, and BK, and use a RTD in my MLT.

If you are running your control panel at 30 max amps and using only two elements, then I would suggest 3 contactors. 1 to turn your main power on using a 120v switch, and 2 for your elements(1 for the HLT, and 1 for the BK). But remember you are going to want to run ONLY 1 element at a time. A 3 position selector switch will allow you to do this. 5500w=23amps@240v, this will leave you enough power to run your pumps safely.


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