[Stevie]

Mark, can you also confirm if it would be OK to control a single ssr with the two controllers, obviously not at the same time. The switch would control the positive to the ssr and the negative from the ssr would go to both controllers. Installing a second ssr wouldn't be hard, but my initial idea follows you KISS method.

[S. cerevisiae]

You are better off switching the negative and positive terminals because the controllers do not share a common DC power supply. In days of yore when linear power supplies ruled the roost, one could tie the grounds from several DC power supplies together.  However, many DC power supplies today are switch-mode power supplies.  Tying the grounds from multiple switch-mode power supplies together can result in ripple interaction between the power supplies.  This problem will more than likely not occur when tying the grounds together in your configuration, but it is worth keeping the outputs isolated from each other in that it eliminates a possible source of gremlins. 

[Stevie]

I would only be switching the control leads to the ssr, not the power to the PIDs themselves. The PIDs will be powered off of the hot and neutral bus that will power all of the 120v items.

Do you think it would be best to switch both the positive and negative control leads?

[S. cerevisiae]

The relay would not be between the element and ssr, it would be before the ssr and would be energized by the same switch that selects which of the two controllers is active, hence the additional pole blocks for the switch. My thought here is power is cut ahead of the ssr.

It does not make a difference if the dry-fire protection relay occurs before or after the SSR.  How are you planning to implement your master power switching circuitry?  I am assuming that you are you planning to have your power switch energize the coil on a master DPDT relay that switches both hot legs of the 240VAC power feed with the other circuits taken off of the outputs of the master relay in a balanced fashion.  I am also assuming that you are planning on a 4-wire feed with two hots, a common, and a ground wire.

[Stevie]

The relay would not be between the element and ssr, it would be before the ssr and would be energized by the same switch that selects which of the two controllers is active, hence the additional pole blocks for the switch. My thought here is power is cut ahead of the ssr.

It does not make a difference if the dry-fire protection relay occurs before or after the SSR.  How are you planning to implement your master power switching circuitry?  I am assuming that you are you planning to have your power switch energize the coil on a master DPDT relay that switches both hot legs of the 240VAC power feed with the other circuits taken off of the outputs of the master relay in a balanced fashion.  I am also assuming that you are planning on a 4-wire feed with two hots, a common, and a ground wire.

Yes, wire with two hots, ground and neutral. The power switch would function just as you are describing, same as Kal's setup. He uses additional relays for the elements as well. I was planning on only using one hot bus off of one of the hot legs, same as Kal's.

[S. cerevisiae]

Do you think it would be best to switch both the positive and negative control leads?

Yes, because it will avoid the possibility of ripple interaction between the DC power supplies on the two controllers.  There's a high probability that ripple interaction between the two power supplies will not occur if you tie the control signal negative (ground, common, 0 volts, or whatever you want to call it) terminals on the controllers to the negative terminal on the SSR, but using a DPDT switch instead of SPDT switch is a small price to pay for complete isolation.

[Stevie]

That is what I was planning to do. Control "whatever" leads would both be connected to the ssr. The two positives would be connected to a three position switch the out from the switch would connect to the ssr positive. Additional blocks on the three position switch isn't a big deal cost wise, just extra depth.

I'm trying to draw up a wiring diagram now. Using Visio, which isn't the best option, but I don't feel like paying for a schematic program.

[Stevie]

Thanks for the help by the way. Just keep it simple.

[S. cerevisiae]

Yes, wire with two hots, ground and neutral. The power switch would function just as you are describing, same as Kal's setup. He uses additional relays for the elements as well. I was planning on only using one hot bus off of one of the hot legs, same as Kal's.

There are actually two hot buses when dealing with 120VAC devices, and they need to balanced across the hot legs.  If one looks at one's electrical distribution panel, one usually sees two rows of breakers.  The 240VAC breakers span both legs while the 120VAC breakers are between one leg and neutral.  When wiring a distribution panel, an electrician spreads the 120VAC circuits across the legs in order to maintain as close to equal current draw on the legs.  I need to check Kal's design, but I do not believe that a qualified electrician or EE would wire a 240VAC control panel with only one 120VAC hot bus.   

[Stevie]

He pulls the bus power off of the shunt best I can tell. I'm going off of his site, but I am considering buying ebook. The amperage draw of all of the 120 items should be quite low. I know my two pumps will only pull 3 amps combined and the PIDs are very low power usage.

[S. cerevisiae]

I managed to locate a clone schematic, and it does appear that running an unbalanced configuration is the norm.  It's not what I would do, but I believe that a March pump only draws 1.4A.

[Stevie]

Oops. Deleted my post.

Wiring diagram below. I think I did ok for draft one. Messy, but I don't feel like cleaning it up after 4 beers. I still need to add the safe start interlock.

Price wise, I'm at around $400 not counting the incoming cable and gfci. That is $100 less compared to high gravity's SV controller, and more feature packed IMO.

[S. cerevisiae]

I would price shop on eBay before committing to purchasing everything from Auber.  I purchased a lot of parts from Auber that I could have purchased for much cheaper on eBay, and we are talking about the same exact part, not a substitution.  Additionally, you can find NOS Crydom SSRs for the same price as made in China specials if you are patient.   You want a Crydom model D2425 or D2440 SSR depending on what wattage (the letter D means that it accepts a control voltage that is between 3 and 32 VDC).  I also found NOS made in Japan electromechanical relays for less than the price of the made in China specials sold by Auber.  I did pay more for my PID, but it is a American made Red Lion T48 that costs $200.00 retail.  It paid $69.00 shipping included, and the PID was truly new-in-box when it arrived at my doorstep. 

[Stevie]

I certainly will shop around. Always do.

[AmandaK]

Steve/Mark, I am following every post in this thread. I may just end up giving this whole "build the control system myself" thing a go. As always, thank you guys. You are both helping me see that maybe this electric thing isn't really that hard.