Control Panel - Contactor and Switch Wiring

[Slapstik007]

I would like to thank this forum for all the great info; I have been pouring over it for weeks now and have found so much great info.

I am looking at building a KAL clone and using one of P-J's wiring schematics. I finally found one that is exactly what I want. The diagram is this one.
http://www.pjmuth.org/beerstuff/images/Auberin-wiring1-a11e-RIMS-SYL-2352-4500w.jpg

I have a few questions about using the contactor and wiring in switchs/power keys.

I don't understand how you can wire the Power Key (Auber SW8) into the main power line coming in that is 50 amps coming in from the breaker. The SW8 has a current rated at 10 amps. My logic would tell me that the 50 amps coming in would be to high of a load for this and would fry this in a moment.

I see the same issue with the SW2 that is used for switches 1-4. It is rated at 10 amps and the breaker controlling it is 15 amps. Am I missing something here?

Is there a reason that the contactor on the main line is only rated at 40 amps? Isn't this an issue with the load placed on the contactor if both 4500 elements are on at the same time? Would a 50-60 amp contactor be much better rated if I was to switch two of the kettles on at the same time?

I calculate this system as running 11,000 watts if the three elements on. As I understand this would be 100% of the system running on 50 amps. My guess is that this design was developed around the idea of never firing all three elements at once rather only working with two at a time. Would this asumption be correct; or does it actually running at 240 volts over calibrate this within an acceptable range? (I am in CO, USA)

Additionall how important is a timer? I am looking at the Auberins Timer for Beer Brewing, Multi-Events; not sure if the wiring is worth all the extra effort.

As always this forum makes this all happen! Thanks so muck in advance. I cant wait to begin the build.

 

[itsnotrequired]

I would like to thank this forum for all the great info; I have been pouring over it for weeks now and have found so much great info.

I am looking at building a KAL clone and using one of P-J's wiring schematics. I finally found one that is exactly what I want. The diagram is this one.
http://www.pjmuth.org/beerstuff/images/Auberin-wiring1-a11e-RIMS-SYL-2352-4500w.jpg

I have a few questions about using the contactor and wiring in switchs/power keys.

I don't understand how you can wire the Power Key (Auber SW8) into the main power line coming in that is 50 amps coming in from the breaker. The SW8 has a current rated at 10 amps. My logic would tell me that the 50 amps coming in would be to high of a load for this and would fry this in a moment.

I see the same issue with the SW2 that is used for switches 1-4. It is rated at 10 amps and the breaker controlling it is 15 amps. Am I missing something here?

Is there a reason that the contactor on the main line is only rated at 40 amps? Isn't this an issue with the load placed on the contactor if both 4500 elements are on at the same time? Would a 50-60 amp contactor be much better rated if I was to switch two of the kettles on at the same time?

I calculate this system as running 11,000 watts if the three elements on. As I understand this would be 100% of the system running on 50 amps. My guess is that this design was developed around the idea of never firing all three elements at once rather only working with two at a time. Would this asumption be correct; or does it actually running at 240 volts over calibrate this within an acceptable range? (I am in CO, USA)

Additionall how important is a timer? I am looking at the Auberins Timer for Beer Brewing, Multi-Events; not sure if the wiring is worth all the extra effort.

As always this forum makes this all happen! Thanks so muck in advance. I cant wait to begin the build.

key switch: the line side of the switch is connected to the incoming circuit but the load side runs through the coil of the contactor, not the contactor itself. the coil will limit the current to a miniscule amount, less than an amp.

other switches: the load the switch controls are rated less than 10 amps. the 15 amp breaker is there to protect the conductors from overload and to interrupt a short circuit. no worries.

max load: the arrangement has the capability to fire all the elements at the same time, including the pumps. no worries.

timer: your call. it is nice to have it built into the panel but you can use your watch, kitchen timer, whatever and accomplish the same thing.

 

[stlbeer]

I used this schematic for my build minus the key switch and main power contactor. I supply 50 amps to the panel.

Google "electricheat.xls'. Use this to size your components.

4500w elements at 240v draw 18.75 amps. Two will draw 37.5 amps
2000w elements at 240v draw 8.33 amps.
If all of this is on at the same time your total draw is 45.83 amps.

So this is if your 240 is really 240. Mine is 244 so it's a little less amps.
If your high voltage is really 220, you're much closer to 50 amps.

 

[Bobby_M]

I used this schematic for my build minus the key switch and main power contactor. I supply 50 amps to the panel.

Google "electricheat.xls'. Use this to size your components.

4500w elements at 240v draw 18.75 amps. Two will draw 37.5 amps
2000w elements at 240v draw 8.33 amps.
If all of this is on at the same time your total draw is 45.83 amps.

So this is if your 240 is really 240. Mine is 244 so it's a little less amps.
If your high voltage is really 220, you're much closer to 50 amps.

It doesn't work that way. The elements are rated at those wattages at 240v because their resistance is fixed. As the voltage goes down, the current also goes down per Ohm's Law.

4500w / 240v = 18.75 amps 240v / 18.75 = 12.8 ohms.

If you really have 244 volts, it's 244 / 12.8 ohm = 19 amps.
If you really have 230v it's 230 / 12.8 = 18 amps and 4140 effective watts.

 

[BrunDog]

In other words, the resistive elements don't automatically use the power they are rated for. As Bobby said, fixed resistance and ohms law. Voltage and current are proportional.

 

[Slapstik007]

Thanks for all the great information. This helped me out quite a bit.

I am now cindering scaling up all of the contractors, SSR's and breakers to 30 or ever 40 amps to allow for some scalability of the system for the future? Would there be any adversity in doing so? Considering it will all be behind a 50a-60a GFCI spa panel I figure that would be the weakest point in the system and would trip if there was any feedback.

 

[BrunDog]

I don't think there is any harm in incrementally upsizing components if you think your pathway will require it.

 

[itsnotrequired]

I don't think there is any harm in incrementally upsizing components if you think your pathway will require it.

to the op, be sure your conductors are upsized as well. this includes inside the panel.

 

[Slapstik007]

I was looking at going to 60a service to the spa panel. The with a 30a breaker on all 3 elements, 40a SSR and 32a conductors. This would give me to option of using 5500 watt elements if I decide I want to scale up. As I calculate it this should be within 80% load for 240v. I still have to test exactly how many volts I am actually pulling into my basement.