3 Position Switch for 2 Elements?

[handbrewing]

I current have a 2 position switch in a 50amp controller that switches two elements on or off. I would like to change it to 3 position so I can switch from OFF position to 1 element ON position or to both elements ON position.

Can I do this?

My current system is run on a single 80A SSR to one 63A contactor then split to two 32A breakers.

Do I need to change to 2 SSRs to have this ability?

Any wiring diagram would be awesome as I was having trouble finding one for this setup.

 

[day_trippr]

A two gang four position rotary switch could do that properly wired - if you used a pair of SSRs and switched their control inputs. I don't think you'd want to try to switch the load side as it would take some pretty hunky rotary switch modules and probably be subject to arcing the contacts...

Cheers!

 

[doug293cz]

Are both elements in the same vessel? If so, what's the thinking behind wanting to use only one of the elements? A good PID or EZBoil can reduce the power without having to shut off one element. The benefit of both elements at low power is lower watts/in^2, which lessens the chance of scorching or deposit build-up on the elements.

You can do what you want, but you need either two contactors or two SSRs. It will also require an extra switch block on the three position switch.

Brew on

 

[AlexKay]

Not a pro, but I’m not sure I see why a four-pole, three position rotary switch wouldn’t do it all by itself … except you’ll never find one that can handle that kind of current. Or if you did find one it would weigh a ton and cost a fortune. So you’re back to relays.

 

[handbrewing]

Are both elements in the same vessel? If so, what's the thinking behind wanting to use only one of the elements? A good PID or EZBoil can reduce the power without having to shut off one element. The benefit of both elements at low power is lower watts/in^2, which lessens the chance of scorching or deposit build-up on the elements.

You can do what you want, but you need either two contactors or two SSRs. It will also require an extra switch block on the three position switch.

Brew on

Really just extra flexibility with my system. Yes I have two element in same boil kettle but I’m also implementing a rims on my mash. Either way I’d have to unplug and plug in elements during my process since I only have to element plugs. I’m just playing around with how I can reconfigure my controller in away that reduces errors or extra steps in my process.

 

[doug293cz]

What size batches are you brewing? You really don't want to be plugging and unplugging elements, and also plugging and unplugging temp sensors (or switching them. If you are using the same outlet for multiple elements, that implies you are using the same controller for more than one element, so it will need more than one temp sensor to that controller.) during a brew session, as that's a recipe for mistakes.

I have a design that allows for an "any two of three" elements to be selected on a 50A circuit. Sounds like something like this is what you might need.

Brew on

 

[handbrewing]

What size batches are you brewing? You really don't want to be plugging and unplugging elements, and also plugging and unplugging temp sensors (or switching them. If you are using the same outlet for multiple elements, that implies you are using the same controller for more than one element, so it will need more than one temp sensor to that controller.) during a brew session, as that's a recipe for mistakes.

I have a design that allows for an "any two of three" elements to be selected on a 50A circuit. Sounds like something like this is what you might need.

Brew on

I have 30 gal kettles. If I add a third element connection on my panel for the rims element is it possible to run 1 PID and use a switch to select which elements the PID runs? I currently have one ezboil PID in the panel. The two elements in the boil kettle would be ran together while the rims would be run independently while the kettle elements are off.

 

[jerrylotto]

Why not just put in an on'/off switch for 1 element?

 

[doug293cz]

I have 30 gal kettles. If I add a third element connection on my panel for the rims element is it possible to run 1 PID and use a switch to select which elements the PID runs? I currently have one ezboil PID in the panel. The two elements in the boil kettle would be ran together while the rims would be run independently while the kettle elements are off.

Are you going to have separate power outlets for each element, or are you going to be plugging/unplugging power cables from the panel outlets?

For separate outlets, you can use a single SSR, and multiple contactors between the SSR and the element outlets to route power safely. Switching needs to make sure that you cannot enable more elements (total wattage) than your 50A power feed can handle (two 5500W elements and 2 pumps would max you out.)

You also need to switch between temps sensors, depending on which element(s) you are trying to control, and you cannot simultaneously control power to two different vessels with a single PID/EZBoil.

Ideally you would use a single selector switch to control both element selection, and temp sensor selection, so that you cannot switch one and forget to switch the other (cause you will if it requires two separate switches.)

If you are plugging and unplugging element power cords, then you only need the selector switch for the temp senors, and you will have to live with the risk of not properly selecting cables and temp sensors.

Brew on

 

[Bobby_M]

Add one 30amp contactor. Feed the line side from the line side of the 63A contactor. Change the selector switch to an On/Off/On with N.O. blocks. One position fires up the coil on the 63A contactor and the other position powers the new 30amp contactor and output to the RIMS. You can stack additional switch blocks to switch temp probes. Keep in mind that the EZboil will complain a bit when it doesn't sense any probes connected.

 

[doug293cz]

Add one 30amp contactor. Feed the line side from the line side of the 63A contactor. Change the selector switch to an On/Off/On with N.O. blocks. One position fires up the coil on the 63A contactor and the other position powers the new 30amp contactor and output to the RIMS. You can stack additional switch blocks to switch temp probes. Keep in mind that the EZboil will complain a bit when it doesn't sense any probes connected.

The problem with stacking switch blocks for temp probes is that RTDs require three contact pairs each, so on a typical ON-OFF-ON selector switch, you end up with four switch blocks stacked on each side (one for the contactor, and three for the temp probe. - I don't know if that exceeds limits or not.)

Brew on

 

[Bobby_M]

I got it to work by connecting both probes to the 3 and 4 terminals and just switching the 5. I'm not speculating, I just built a controller that does it.

 

[doug293cz]

I got it to work by connecting both probes to the 3 and 4 terminals and just switching the 5. I'm not speculating, I just built a controller that does it.

View attachment 814058

Have you checked the accuracy of the temp probes in this arrangement. My understanding of how we get a three wire precision resistance measurement (how an RTD "measures" temperature) is that all three wires + connections need to have equal resistance (as contrasted with a true 4-wire measurement where lead resistance is canceled out.) If you switch only one of the wires, then this basic requirement is not met. Perhaps I don't understand how a three wire measurement compensates for lead and contact resistance. I do know that Auber offers a 3PDT switch to switch all three RTD wires, and keep the paths consistent.

Edit: Here is an explanation of 2, 3, and 4 wire resistance measurements that confirms what I thought I knew about 3 wire measurements.

Brew on

 

[Bobby_M]

Have you checked the accuracy of the temp probes in this arrangement. My understanding of how we get a three wire precision resistance measurement (how an RTD "measures" temperature) is that all three wires + connections need to have equal resistance (as contrasted with a true 4-wire measurement where lead resistance is canceled out.) If you switch only one of the wires, then this basic requirement is not met. Perhaps I don't understand how a three wire measurement compensates for lead and contact resistance. I do know that Auber offers a 3PDT switch to switch all three RTD wires, and keep the paths consistent.

Edit: Here is an explanation of 2, 3, and 4 wire resistance measurements that confirms what I thought I knew about 3 wire measurements.

Brew on

Yes, and no. Both probes read 70F in a 70F room so I declared success, but I didn't check accuracy at higher temps which admittedly might be where the plan would fail.