Converting from Dual 120V to 240V

After designing a dual circuit 120V system and building most of the panel, I am thinking of converting to 240V before I finish. I was just getting ready to drill the holes (two in each kettle) for the elements. I have two separate 120V, 20A circuits in close proximity, which is why I thought to go this way.

But now a 240V 30A 4 prong circuit is available where I can brew. I'll probably add a contactor, as my DPST switch, although rated for 20A, would seem a bit marginal for regular use, depending upon how big the elements and fused protection (Opinions?)

I now have two separate PIDs mounted to a heat sink, one driving two 25 Amp SSRs for the boil kettle and the other driving two 25 Amp SSRs for the HLT. The PIDs outputs are wired through a switch so that the boil kettle and the HLT cannot be driven simultaneously.

So other than the switch vs. contactor question above, :
1. In converting to 240V, should I just wire the SSRs in parallel? Or put on on each leg of the 240V?
2. I'm only doing 5.5 gallon batches. What size element would you recommend? 3500 watts?
3. Other than wire sizes, cords and connectors(arrgh), what other things should I be on the lookout for?
4. Anybody need some unused 120V heating elements and connectors? (LOL - I'll post in the classifieds if I do this)

-Rich

RichBenn said:

But now a 240V 30A 4 prong circuit is available where I can brew. I'll probably add a contactor, as my DPST switch, although rated for 20A, would seem a bit marginal for regular use, depending upon how big the elements and fused protection (Opinions?)

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If it's rated for 20A, it's rated for 20A. You should be fine using it all the way up to 20A with no issues. In reality, the switch can probably handle more than 20A, but they engineer in some safety margin and tell you to use it at 20A or less.

With 20A, you can handle a 4500W element.

RichBenn said:

So other than the switch vs. contactor question above, :
1. In converting to 240V, should I just wire the SSRs in parallel? Or put on on each leg of the 240V?

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You can put an SSR on each leg of the 240v if you want, but it isn't necessary. Personally, I would just eliminate 2 of the SSRs in your original design. Run one of the 120V hot legs directly to the element receptacles and put an SSR on the other hot leg going to each receptacle.

RichBenn said:

2. I'm only doing 5.5 gallon batches. What size element would you recommend? 3500 watts?

Click to expand...

3500W will work fine, but you have 30A available and a switch that can handle 4500W, so I'd go with the 4500W if for no reason other than reducing the wait time on heating things up.

Putting an SSR on both legs is including an additional failure point with no benefit. Put an SSR on one hot leg, and run the output of the SSR to some switched means (contactor, relay, or manual switch) with the other hot leg. There are countless reasons why running straight from the SSR to the element is a bad / unsafe plan. A means of physically disconnecting both legs to the element is the smart way to do it.

Throw in the biggest element your setup will allow - you can always throttle a 4500w element down - you can't throttle a 3500w element up.

-Kevin

BadNewsBrewery said:

Put an SSR on one hot leg, and run the output of the SSR to some switched means (contactor, relay, or manual switch) with the other hot leg. There are countless reasons why running straight from the SSR to the element is a bad / unsafe plan. A means of physically disconnecting both legs to the element is the smart way to do it.

Click to expand...

I know what you are saying here, but the exact wording used might mislead some people. It is perfectly fine to have the SSR connected to the outlet or power cord that feeds your element, but you do want a switch in there SOMEWHERE between the main power and the element.

main power --> SSR --> switch --> element is fine
main power --> switch --> SSR --> element is also fine

Fair - there's no appreciable difference if you put your switch before or after the SSR, so long as the switch breaks both legs of the 240v feed and is a true mechanical switch, not an SSR. Thanks for clarifying.

Walker said:

I know what you are saying here, but the exact wording used might mislead some people. It is perfectly fine to have the SSR connected to the outlet or power cord that feeds your element, but you do want a switch in there SOMEWHERE between the main power and the element.

main power --> SSR --> switch --> element is fine
main power --> switch --> SSR --> element is also fine

Click to expand...

In my design, I have a switch on the control side of the SSRs. This is a 3 position switch(HLT/OFF/BOIL). There is also the 20 amp DPST switch that controls the overall power. There are two issues I see with this:

1. Since the circuit breaker is at 30 amps, I'll need to protect the switch (DPST) with 20 amp fuses to protect in the event of a short.
2. If an SSR fails in the "on" state, then it's possible that an element could still be on and I don't know it. (like I switch from HLT to boil PIDs, and the HLT is still on)

It's this second issue that made me wonder if that's why people used contactors in lower wattage applications. But it's not like I'd have my hands in the kettles or HLT without the main power off, and a ground short or both elements on at once would cause the GFCI to fire and/or fuses to blow anyway, so this is probably over obsessing the safety scenarios.

And thanks, Walker, for the recommendation to go to 4500 watts. I'd already gotten to that conclusion by time I'd read your response, but it's nice to have confirmation.

Some suggestions:
* Check all your switches and indicators. You will probably want 240v indicators for power input, power to elements, etc.
* Make sure your panel can only power one element at a time. You could use a 3-way switch rated for 30amps or a low power switch and contactor for each element.
* Use an input power cord rated for 30 amps since your ckt breaker is 30 amps. I would recommend 4-wire 240v so you have a neutral for 120v pumps, etc.
* I rely on the breaker to protect the elements and 240v wiring and a small fuse for PID, pumps, and other low power control wiring. All my 240v wiring is rated for 30 amps.

RichBenn said:

In my design, I have a switch on the control side of the SSRs.

...

2. If an SSR fails in the "on" state, then it's possible that an element could still be on and I don't know it. (like I switch from HLT to boil PIDs, and the HLT is still on)

It's this second issue that made me wonder if that's why people used contactors in lower wattage applications. But it's not like I'd have my hands in the kettles or HLT without the main power off, and a ground short or both elements on at once would cause the GFCI to fire and/or fuses to blow anyway, so this is probably over obsessing the safety scenarios.

Click to expand...

Having the switch that controls the low-voltage input to the SSR is great, but I'd still recommend having the contactor in the main power feed to the SSR or from the SSR to the element. Curret that leaks by a functional SSR, or that pours past a broken SSR, can be dangerous to you as the operator, and may cause your element to burn out (dry fire) in some situations. SSR failures of both types are a known occurance, and the peace of mind that comes from knowing that your element is well and truly off is priceless.

Plus, if you put the contactor in the main feed, you can drop the one on the SSR control line as it won't matter.

Of course - just my opinion. You can build it however suits your needs and desires.

-Kevin

BadNewsBrewery said:

Having the switch that controls the low-voltage input to the SSR is great, but I'd still recommend having the contactor in the main power feed to the SSR or from the SSR to the element. Curret that leaks by a functional SSR, or that pours past a broken SSR, can be dangerous to you as the operator, and may cause your element to burn out (dry fire) in some situations. SSR failures of both types are a known occurance, and the peace of mind that comes from knowing that your element is well and truly off is priceless.

Plus, if you put the contactor in the main feed, you can drop the one on the SSR control line as it won't matter.

Of course - just my opinion. You can build it however suits your needs and desires.

-Kevin

Click to expand...

Just to put into perspective, I cannot eliminate the switch in the SSR control line as it is to control whether the HLT or the Boil pot is active. And I have a low water switch also inline to shut off the SSR.

As to SSR failure, I'm curious about this, as relays (contactors) are far more prone to failure than solid state devices(at least that was the data many years ago). The only advantage the contactor has is the normally open (NO) nature, presumably being unlikely to fail closed. Have there been SSR failures reported here? Did the SSR cause a short, or did a short cause the SSR to open?

RichBenn said:

Just to put into perspective, I cannot eliminate the switch in the SSR control line as it is to control whether the HLT or the Boil pot is active. And I have a low water switch also inline to shut off the SSR.

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Got it - I read that and didn't compute it in your original post. You're using one PID to run 2 different SSRs, one for the HLT and one for the BK. In that case, your setup is good to go (unless, of course, you find a switch capable of handling the full load on the 240v side and just use 1 SSR to control either outlet)

RichBenn said:

As to SSR failure, I'm curious about this, as relays (contactors) are far more prone to failure than solid state devices(at least that was the data many years ago). The only advantage the contactor has is the normally open (NO) nature, presumably being unlikely to fail closed. Have there been SSR failures reported here? Did the SSR cause a short, or did a short cause the SSR to open?

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There are a lot of conversations on the boards about SSR failure. You are correct that contactors tend to fail open and thus are much safer in their failed state. SSRs have been found to fail in any variety of condition, to include a closed state. The other issue is that even a completely functional SSR will still allow some amount of current to leak by, even if it shows that it is 'off'. This may not be enough current to produce much heat from the element, but it could be plenty of current to stop your heart. Conventional wisdom maintains that safety is paramount, and having a means to actually switch power off when you think it's supposed to be off is even better.

In thinking - if you could get a 20-30a (depending on your element wattage), 240v rated 3 way dual pole switch - if they even exist - you could put that downstream of a single SSR. Then use 1 PID and 1 SSR to control either element, and use the 3 way switch to go between the two, or to make sure that both are off. All the birds - one stone.

BadNewsBrewery said:

In thinking - if you could get a 20-30a (depending on your element wattage), 240v rated 3 way dual pole switch - if they even exist - you could put that downstream of a single SSR. Then use 1 PID and 1 SSR to control either element, and use the 3 way switch to go between the two, or to make sure that both are off. All the birds - one stone.

Click to expand...

If I understand correctly, you could also use the single SSR, with the load side wired to the line terminals of two DPST NO mechanical contactors, and the other hot load running to the other line terminal of each contactor, with your 3-position switch wired to the contactor coils. I also consider "off means off" as an important safety feature.

jeffmeh said:

If I understand correctly, you could also use the single SSR, with the load side wired to the line terminals of two DPST NO mechanical contactors, and the other hot load running to the other line terminal of each contactor, with your 3-position switch wired to the contactor coils. I also consider "off means off" as an important safety feature.

Click to expand...

This would totally work - it would allow you to use a much lower voltage rated switch to go between HLT and BK, but would require the use of two contactors.

OP - what you'll get out of both these designs is the "off means off" part...

Well, after adding up all the conversion costs, including the fact that I already have all of it purchased and most of it built (sans installing heating elements into kettles), I'm going to stay with the 120V design.

Still have 2x1650 watt elements for both the HLT and boil kettles, so it'll work fine for 5.5 gallon batches, especially if I insulate.

I also just purchased a bigger (11 gallon) kettle for the boil. Because of the size of the two ULWD elements plus the hop spider, immersion wort chiller, and a typical 1/2 pound of hops or more, a little more headroom will be just the thing needed to prevent boilover inside. Outside? I didn't worry as much about spillage.

Anyway, thanks for everyone's comments.

One last thing that some may have missed - I do have a master OFF switch that removes the voltage from everything. So OFF does mean OFF in that case. The three position switch is for which PID is active.

RichBenn said:

One last thing that some may have missed - I do have a master OFF switch that removes the voltage from everything. So OFF does mean OFF in that case. The three position switch is for which PID is active.

Click to expand...

Totally different than what we're talking about. You could just as easily say "I have a breaker to flip, so off is off" or "I can unplug the panel, so off is off". What we're saying is that, even if you have your 3 way switch set to 'OFF', and the SSRs are getting zero control voltage, there's still a chance that the elements are seeing some amount of power. They're not off until you turn the whole panel off. If you're happy with that, and it sounds like you are, that's totally fine. Just make sure you know that until your panel is 100% power free, your elements may have some voltage on them.

Good luck with the final steps of your build!

BadNewsBrewery said:

Totally different than what we're talking about. You could just as easily say "I have a breaker to flip, so off is off" or "I can unplug the panel, so off is off". What we're saying is that, even if you have your 3 way switch set to 'OFF', and the SSRs are getting zero control voltage, there's still a chance that the elements are seeing some amount of power. They're not off until you turn the whole panel off. If you're happy with that, and it sounds like you are, that's totally fine. Just make sure you know that until your panel is 100% power free, your elements may have some voltage on them.

Good luck with the final steps of your build!

Click to expand...

1. Some people freak out because they see an SSR output voltage with no load, but the semiconducter needs an input signal to enable the output to pass significant current.There is a wee bit of SSR leakage with no input, but we are talking less than 5 ma, not enough to kill you. (It's current that kills you, not voltage, a common misconception)

What happens is that as soon as a load presents itself across the output of the SSR (including the load of a higher resistance like a human body), the voltage drops dramatically. At the resistance a wet hand might present, this voltage would be in the neighborhood of 6 volts or so. Enough EMF (Electro Motive Force) to tingle if you are wet with beer, but not generally life threatening. Still, it's not something that one should be testing, as a little more (>30 ma) could cause fibrillation.

2. Grounding, the GFCI, proper wire size and fusing are key items for safety, and things I worry about people getting wrong, more so than an item like this.

3. Operator training is another key item safety item. I used to work with 10,000 volt devices while live; 120v in a location not accessible is a piece of cake. The point I really want to make here is that anyone working around water and electricity and electric heaters needs to take some basic precautions, whether you have contactors or not.

4. I had an electric turkey fryer for a while. It had UL and CE mark approvals. The heating element was exposed, like in our application. No contactors. Yet, it got approvals. Hmmm, wonder why?

And how many have stirred a pot with the power on? And yet we are worried about a scenario where current is limited, accessibility is limited, pots are grounded, the right size wire is used, fuses are used, GFCI is present, and one hand with a wooden spoon is used for stirring?

Finally, my master switch is not at all like unplugging or a breaker - it's on the control panel, like the 3 position switch. A better analogy would be it's like using a control STOP.

The three position switch is not how I turn off the power to the heating elements; the master switch is. And hands don't go in the pots with heating elements until that switch is off AND the elements are unplugged AND the elements have cooled down. Isn't that what you would do even if you had contactors?

RichBenn said:

1. Some people freak out because they see an SSR output voltage with no load, but the semiconducter needs an input signal to enable the output to pass significant current.There is a wee bit of SSR leakage with no input, but we are talking less than 5 ma, not enough to kill you. (It's current that kills you, not voltage, a common misconception)

What happens is that as soon as a load presents itself across the output of the SSR (including the load of a higher resistance like a human body), the voltage drops dramatically. At the resistance a wet hand might present, this voltage would be in the neighborhood of 6 volts or so. Enough EMF (Electro Motive Force) to tingle if you are wet with beer, but not generally life threatening. Still, it's not something that one should be testing, as a little more (>30 ma) could cause fibrillation.

Click to expand...

Yes, however we are not just solving for "leakage." When an SSR fails closed we can have full load at the element when one thinks it is off. That fails the "off means off" test.

And, for the third time, my power switch is the "OFF means OFf" switch. It breaks the AC to the elements.

There is always water in the pots when this switch is ON, And I am there.

RichBenn said:

And, for the third time, my power switch is the "OFF means OFf" switch. It breaks the AC to the elements.

There is always water in the pots when this switch is ON, And I am there.

Click to expand...

Fair enough. What we have been discussing here is the ability to leave your panel on, say to power pumps and monitor temperature, but to be sure your element is off. If I understand you correctly, this is not a capability you have or care about.