Cellar Controller wiring and plumbing

[Ogie]

Preparing to wire RTD's and solenoids to cellar controller. I have a few rookie questions.

1) Should RTD and solenoid wiring be run in separate conduits? I don't know if, but wouldn't be surprised if, the current flow in the solenoid wires would affect the RTD signal accuracy.

2) I've seen posts about NOT using solenoids on the glycol. I believe that eminent failure is the reason? What is the recommended alternative?

Thanks!

[gitchegumee]

Greetings! In general, power and signal wires should be in separate conduits, or separate areas of cable trays. But if you have only 24VDC for solenoids, then I would not worry about the tiny (usually 6-8W) power distorting the signal in RTD lines. For all intents & purposes, 24VDC is a signal, not a power line. I run them together without issues. You could also use shielded lines for signals, too. But again in my experience, not necessary. I have voiced support for other than solenoid valves in glycol installations. Especially for anything over 1". But for a small brewery, solenoids are fine. You just have to install a fine mesh strainer on pump discharge. And then keep it clean! Use a high quality pilot-operated valve and observe recommended mounting orientation. Only fools would install cheap solenoids thinking that they are saving money. Best of luck!

[Ogie]

Thank you very much!

[Brewman]

Preparing to wire RTD's and solenoids to cellar controller. I have a few rookie questions.

1) Should RTD and solenoid wiring be run in separate conduits? I don't know if, but wouldn't be surprised if, the current flow in the solenoid wires would affect the RTD signal accuracy.

2) I've seen posts about NOT using solenoids on the glycol. I believe that eminent failure is the reason? What is the recommended alternative?

Thanks!

Hi,

Normally we suggest shielded lines for RTDs(PT100) wire and normal lines for solenoid valve(DC24V).
As sometimes the temp reading might be not accurate if the controller is far from the RTDs.
Contact with us if you need more assistance from us:-)

Cheers,
Brewman Machinery Equipment Co.

[gitchegumee]

Three and four wire RTDs are compensated for length of run, so that should not be an issue. Don't use 2-wire RTDs. If you must use shielded lines, then ground/earth only one end. Not both.

[Ogie]

Yeah, the Colorado cellar controller that I acquired is only configured for 2-wire sensors. And the new unitanks came with 2-wire PT-100 RTD's.

The controller came with standard thermocouple wire (non-shielded). I will look into shielded cable.

I did opt for side-by-side conduits, one for the RTD wires and one for the solenoids... mostly because 1/2" schedule 40 was gonna be tight and I didn't want to upsize, lol.

[gitchegumee]

There are a few red flags here. RTD and thermocouples are totally different instruments. Almost nobody uses 2-wire RTDs. They are not useful in a brewery. Standard is 3-wire. Thermocouples, OTOH are always 2-wire. 3-wire RTD is what I always specify. They are superior to thermocouples for a few reasons; they are more accurate, and do not require special connections to splice. You cannot simply splice thermocouple wire without a special termination block.

Metallic conduit IS your shielding. You do not require more than this. And I would consider separate conduits a bit overkill. And conduit is never sold as schedule 40; that is pipe for liquids. Not electrical.

[Ogie]

Schedule 40 is also standard non-metallic electrical conduit, UV rated for outdoor use. And yes, I know the difference between RTD and thermocouple.
Metallic conduit can be the shielding IF it's grounded at one end (never ground anything at two ends... voltage differentials will always create a current flow) [EDIT: Just noticed you also mentioned only grounding one end, lol.]

The SSBrewTech jacketed unitanks that I purchased came with PT-100 RTDs installed, 4-terminal connectors, but only 2 wire connections according to the data sheet.

The previously owned Colorado Brewing cellar controller had thermocouples on each tank. I have always intended to use PT-100 RTD's instead.

All that said, I just assumed that the Unitronics module (IO-ATC8) in the controller would have a resistance mode, but it only has current, voltage, or thermocouple.
Apparently, I need a different modules for RTD's (IO-PT400)... which I suspect will require changing the programming in the V700 controller. sigh.