Back to Back batches

[rhizome]

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I am new to the site. I usually brew two to three batches back to back (to back). It appears to me that with this setup you would not be able to simultaneously boil one batch and also heat sparge water in the HLT or mash at the same time. Am I correct? And if so coud this system be modified to be able to run both Heating elements at the same time??

[crush]

I've been thinking about back to back. As you noted, the main limitation is it's not possible to have both elements running simultaneously. Without using lower power elements, or 60A circuits, we can never really use both elements at the same time, but we can fake it, since it's rare we really need both elements at the same time.

The main change is to ensure that even when both elements are "on" (i.e. both SSR signals active) only one of them will fire. One element is the master, the other the slave. We make this happen by using an additional relay that disconnects the signal from the PID to the SSR for the slave element, when the master element is active. Specifically, the coil for the relay is connected to master element power. The signal passing through the relay is the SSR signal from the slave element's PID. Output is taken from the NC (normally connected) output of the relay.

The relay implements the logic: when the master element is on, this slave is off. When the master element is off, the slave is controlled by the PID. Importantly, the switching is done by the SSRs, not the power relays, so there is no mechanical wear.

You can choose which is the master or slave element. I'm thinking that the HLT element should be the master, since that is never needed to full capacity for long periods, while the BK element could in principle be run (unnecessarily) at full capacity boiling the wort extremely vigorously. To ensure the slave element gets some time, the duty cycle on the master should be less than 100% or that the target temperature is less than boiling, so the target temperature can be reached and the master element switched off.

With the master/slave relay in place, it's safe to attempt to switch on both elements since only one will actually fire. The final change is then how we allow both elements to be active in the control panel.

1. separate ON/OFF switch for each element.
2. a 3 way switch to select the active element (BK/BOTH/HLT) and a common ON/OFF switch - HEAT ON/OFF that is the master control to power to both elements.


I know this is not so clear with words, I'll try to draw a diagram soon!

[crush]

I think I now have the design sorted for this. Using a mechanical relay has been bothering me, since it could potentially wear out in a few years, so I've been looking for an alternative. Reed relays are fantastically reliable, rated to hundreds of millions if not billions of operations. They usually come in a IC form factor, dual inline 14-pin. Another alternative is to use logic gates, but most logic gates function at TTL levels, 5v, and not the 12v that is used to control the SSRs.

So, going with a from B (normally closed) reed-relay, one like this.
(bigger the better!)

I was struggling with how to simply mount this, so that it's easily replaceable. I was thinking of DIL mounts used to mount ICs, but that requires building a small PCB, and that seems like too much of a pain. There's a much simpler alternative - use a self-adhesive nylon tie - since these are already used in the build. The relay can be fixed to the backplane by a nylon tie.

The two 12v control signals from the PIDs to the SSRs are connected via the coil and load of the relay. The master is wired through the coil, and the slave through the load. The wires are connected to the pins of the relay using jumpers, either home made (http://www.basicxandrobotics.com/tutorials/jumpers/index.html), or ready made


So, the circuit modifications are fairly straightforward, costing maybe $10. The harder part is reworking the control panel. Allowing both elements to be on at the same time, either means having separate switches for each element, or making the 3 way controller function as BK-BOTH-HLT, and then have a master ON/OFF element switch.

I like the Kal's current panel design, and any change I try to make to accommodate allowing both elements at once seems to be like a step backwards. Suggestions on how to layout the lights/switches so both elements can be active are very welcome!

[kal]

The control panel as built does not allow for both elements to run at the same time as it only has a 30A input. You'd require a 60A input.

This was a conscious design choice on my part since I never brew back to back. Limiting to 30A is also much less expensive and makes the setup somewhat portable.

Go to 60A and my guess is that the price would go up 50% or more. As soon as you go above 30A the parts and wiring are considerably more expensive as they're not as standard.

You can certainly modify the setup to allow for it however. It would have a domino effect and some parts, wiring, switches, outlets, etc. would have to be upgraded.

Kal

[kal]

The control panel as built does not allow for both elements to run at the same time as it only has a 30A input. You'd require a 60A input.

This was a conscious design choice on my part since I never brew back to back. Limiting to 30A is also much less expensive and makes the setup somewhat portable.

Go to 60A and my guess is that the price would go up 50% or more. As soon as you go above 30A the parts and wiring are considerably more expensive as they're not as standard.

You can certainly modify the setup to allow for it however. It would have a domino effect and some parts, wiring, switches, outlets, etc. would have to be upgraded.

Kal

[crush]

Kal, I'm aiming for alternating control to both elements, so that they can be used from the same 30A source. Both elements are never on at the same time, but by alternating quickly, you get the power distributed to both. In the worst case, it's like having two 2.75kW elements - that's when both elements are on full, with a 50% duty cycle. In practice, I imagine the HLT to be very low usage since it's just compensating for heat loss, so it will rarely need 50%, but maybe 10%, leaving a good capacity for the BK.

The circuit I sketch above makes one element the master and the other the slave - either element can be active alone, but the slave can't be on while the master is active. To allow for both on at the same time, we use alternation - the alternation between master/slave comes from the PIDs themselves, since they can be programmed with a duty cycle. Set the PID for the master (the HLT) to have a duty cycle (say 50%), so that the slave has chance to also fire in when needed. This is a basically a priority scheme - either element can be active on it's own, but when there is contention, one (the master) wins. As I said before, 50/50 divide is the worst case. Usually the HLT requires little power and is off for most of the time, so the BK gets the power it needs. When the HLT does need power, the 50% duty cycle (or whatever you choose) ensures the BK doesn't completely shut off.

In essence, this emulates a 60A feed but only uses 30A. I'm pretty sure the circuit will work, but I don't know how best to lay out the panel. If you could have both elements active at once (either via 60A or this circuit) how would you design the panel?

There's something really tidy about the 2 yellow lights and a single switch. The alternate designs I've tried seem to remove some of that elegance or usability. Any help greatly valued!

PS: 60A would be great, but besides being prohibitive as to cost, and finding components, I only have 50A coming into my house! It's hard enough getting 30A power here, let alone 60A. The average circuit is 10A here in Norway (16A in newer houses), and 30A (often just 25A) is a special circuit just for the oven in the kitchen. It's also illegal to make any permanent changes to the house unless you are a qualified sparky. But... I can plug in anything I like... .. as long as I stand responsible should it cause any damage or fire. But since it's your panel, Kal, I've put a big fireproof tag on the cable that says "Big up, Kal was here!" so they know where to come and look, should it malfunction and burn down my premises!

[kal]

[kal]

[kal]

The other thing I'll point out is that I'm sure that 50% duty cycle on the boil kettle would be enough when boiling 10-15 gallons. I often start with around 15 gallons and I usually have the boil duty cycle at 80-90%, sometimes even 100% if I'm doing a good vigorous boil for a lager/pils.

Kal

[kal]

The other thing I'll point out is that I'm sure that 50% duty cycle on the boil kettle would be enough when boiling 10-15 gallons. I often start with around 15 gallons and I usually have the boil duty cycle at 80-90%, sometimes even 100% if I'm doing a good vigorous boil for a lager/pils.

Kal

[crush]

Thanks for the feedback, Kal. I was wondering about how much juice is needed for the boil - although using 80% duty sounds like it would be ok. Do you think 20% or ca 1100W would be more than enough to maintain the temperature of the HLT/mash? Of course, it will make temperature rises slower. I will also be insulating the kettles with some removable reflectix, which apparently can make a significant difference to the efficiency.

If there's a batch that needs 100% duty to boil, then of course this rules out using both elements. But I'm hoping this is relatively uncommon, or can be planned for in advance. Brew days are becoming a scarce commodity for me, so being able to get 20 gallons and 2 different styles from one day will be a real benefit.

Ok Teacher, I'll do my assignment and have a go at laying out the panel!

I'm not 100% sure I will actually implement this, but I think it's interesting to plan it out to see where it goes.

[kal]

[kal]

[hennesse]

Back-to-back batches? Think co-generation! The wastewater from the wort chiller is already warm - recycling this into the HLT would reduce the heat required to reheat the HLT.

My original brewery plans called for using a copper coil in the HLT (full of cold water) for cooling the wort. At the end of the wort cooling, I'd have a HLT full of hot water - almost ready for the next batch. However, my rough calculations showed that it wouldn't achieve my goal of cooling the wort to 70degreesF in less than 30 minutes. I'd have to dump my HLT and refill with cold water to achieve that goal. Ugh - all the nice hot water going down the drain!

I used the 60-80 Btu/ft2 hr degreeF figure from the water-copper-water row at (1) to arrive at this conclusion. Since I couldn't remember any of that calculus stuff, I just constructed an Excel spreadsheet calculating the time to lower 1 gallon of wort 1 degree F - at a starting differential of (212 - 52 degrees) - this would also raise the 1 gal of HLT 1 degree. As the HLT heated, the temperature differential would decrease, increasing the time required for the next degree.

The outcome of all this (and someone should check my math - it's pretty rusty) was that half-way through the wort cooling, I'd have to dump and refill the HLT with nice cold 52 degree water to produce 70 degree wort in less than 30 minutes.

OK, that didn't work out, but if you recycle your wort cooling wastewater back into your HLT, you can recover a significant fraction of the heat. It's cheaper to heat 100 degree water to strike temperature than heat 52 degree water to strike temperature.

Even if you're not doing back-to-back batches, you can re-utilize that hot (warm) water for cleaning purposes instead of dumping it straight down the drain.

This may not be important in the city, but out here in rural well-and-septic land, water consumption is an issue. On the other hand, there ain't no chlorine nor chloramine in the feedwater - or in the beer!






(1) http://www.engineeringtoolbox.com/overall-heat-transfer-coefficients-d_284.html

[crush]

This is a good idea. And if it is necessary to dump the HLT water to replace with cold, it could be transferred to the cleaned MLT and saved for the next batch. And like you say, if we have more water than we need for the next batch, then keeping it handy for cleaning duties avoids waste.

[JAZONG]

Back to back batches was one of my design criteria as well. Once I decided to go this route instead on the old two burner RIMS route I had to rethink the importance of many of those criteria. Lucky for me I was able to preserve this one. My solution only works for those of us with good enough ventilation to use a Blichmann (or other) floor standing burner (I'll be in a workshop). Because I will be splitting boils from time to time in order to get two beers out of a single 10 gallon batch I will have to have an extra boil kettle and a propane burner. These two pieces of equipment can also be used to heat up water for a second batch of beer while the boil is still running. Once the boil is finished and chilling has begun the water pump can be used to transfer the water into the HLT.

Downside is that I'll either have to get a drastically over sized kettle for my split boils, or I'll only be able to heat up 10-15 gallons of the 20 gallons needed for the mash and heat exchange processes. Another option is to do only do a 5 or 6 gallon batch for that second run.

-J

[Sparky]

Come to the Dark Side! Just go 60amps and you will sleep well at night.
It is not hard, as I found out. Just a couple tweeks, some bigger wire, and finding good sources for some of those components.
But, I do like Crush's enthusiasm and creativity for eeeking out the most power for his system.

Hey, Crush, I will be in Belgium, France, Germany and Netherlands next month. Maybe I should carry over a nice Krouse Hinds 60 amp pin/sleeve for you!

[crush]

Nice! But my whole house has only 50A, I think. AFAIK, newer houses here have 66A, but still woefully inadequate!

[Grandequeso]

hey crush do you have two, or thee phases in your house? If you do you could go with 400volt elements and do two 5500 watt elements and only be at 27 amps. If you can't find them listed for european 400volts, you can use the 480volt US ones. They will be a wee bit more expensive as they are not commonly used in US houses, but still its not a incredibly unusual part to find.

[pola0502ds]

Regarding the waste water, a buddy of mine has a old 50 gallon hot water tank in his garage that he just turned into a water storage tank. All and any waste water gets returned to this vessel and used for brewing or watering his hop garden. He also uses it to collect rain water. I like the idea of having a water storage tank in my garage.

[crush]

Grandesquo, It's an old-ish house - from mid 70s. unfortunately only 1 phase in my house. 3 phase would have been nice. I'll have to make to with running just one element at a time, but I'm hoping that automated switching between the elements will work. If not, then it's no back to back batches for me. We'll just have to see how much energy it takes to maintain the HLT temp.

[crush]

I've implemented the small additional circuit to enable back to back batches. Not yet field tested - but it seems to be ok in principle.

Instead of a three-way switch to control the HLT and BK elements, I use two 2-way switches, one to each HLT and BK relay coil. Although both switches can be switched to the on position, only one element will fire at a time. If both try to fire, only the BK element will fire. This should work in practice, since the BK is usually set to a duty cycle rather than being always on until a set temp is reached. This means the BK fires for the duration you set (e.g. 60 or 80%) and the HLT fires the remainder of the time, if it needs to.

The circuit works by only allowing the HLT PID control signal to reach the HLT SSR only when the BK SSR signal is off - either because the element is switched off, or the PID has turned off the element. I use a reed relay, since they are silent (I can imagine the repeated clicking being quite distracting!) and also because they last for billions of operations.

I'm almost done with wiring, so hopefully will be testing next weekend!

[kal]

Crush,

What do you have in place to ensure that the first SSR opens before the second closes? You need what's called some sort of "break before make" logic so that there's a lag between the two where nothing is on.

Otherwise if both are on (even for just a split second) you'll draw twice as much current and overload something.

On my original design, this "break before make" is done by the 3-way ELEMENT SELECT switch in that the user must go through the center "OFF" position before the new element fires.

Electromagnetic switches or even solid state relays (SSRs) aren't instantaneous at turning on or off so you have to be careful with the design.

Kal

[kal]

Crush,

What do you have in place to ensure that the first SSR opens before the second closes? You need what's called some sort of "break before make" logic so that there's a lag between the two where nothing is on.

Otherwise if both are on (even for just a split second) you'll draw twice as much current and overload something.

On my original design, this "break before make" is done by the 3-way ELEMENT SELECT switch in that the user must go through the center "OFF" position before the new element fires.

Electromagnetic switches or even solid state relays (SSRs) aren't instantaneous at turning on or off so you have to be careful with the design.

Kal

[crush]

Thanks for that tip Kal, I'd not considered that. I have a 30A overcurrent device installed, so I will see if it reacts. I'll have to think through the design to create the make before break.