Will this cheap 3500 watt induction burner work?

[sumbrewindude]

Added reflectix to my pot and did a boil test, the diffrences between no insulation and with reflectix was marginal. Been trying to buy a Keg Koozie or Keg Skin like AnOldUR but they seem to be having issues with their suppliers. I priced sheet neoprene and making my own, which I might have to do.

This place can get you neoprene in any size/thickness you'd ever want - just keep an eye on the price!

http://www.rockywoods.com/Fabrics-Kits/Neoprene_Fabrics

They carry the fabric backed neoprene that works with velcro too - that'd make fitting much easier.


I sure wish my Avantco would show up. I'm trying to decide between a Concord 6.5gal pot or a Bayou 1032 (8gal with spigot). I can't believe it, but the 1032 is cheaper than the pot only version (1308) and it's a tri-layer bottom.

Trying to stay in the 12" diameter range for the pot, and that's difficult for some reason.

 

[NathPowe]

I have a question for the electricians following this thread (in reading through, it seems like there are some folks that fit this bill). Before I ask, I'd like to clarify that I have no intention of actually trying to install receptacles/change wiring/do any actual electrical work related to my question - regardless of the answers I get. I know that if "I have to ask, I need to have a professional do it", and that's what I would do. I am simply posing a question as to whether or not something is even possible, to determine whether I take the next step in contacting a local electrician. Okay, that's my disclaimer -

I have two separate 120V 20Amp circuits running out to my workshop. They are on a tandem 20A breaker and only provide power to the workshop (nothing else in the house, etc.). Both circuits were run to the workshop using 12 gauge wire. Is there any possible way that the receptacle required for the induction burner discussed in this thread could safely be installed/operated in my workshop WITHOUT having to replace the 12 gauge wire feeding the workshop?

Thank you for your time. Cheers.

 

[AnOldUR]

I have two separate 120V 20Amp circuits running out to my workshop . . . Is there any possible way that the receptacle required for the induction burner discussed in this thread could safely be installed/operated in my workshop WITHOUT having to replace the 12 gauge wire feeding the workshop?

Yes. You could change one of the circuits to 240V.

If you have room in your panel for a seperate 240V breaker and you changed every outlet on the one circuit to 20amp / 240V.

 

[MerlinWerks]

I have a question for the electricians following this thread (in reading through, it seems like there are some folks that fit this bill). Before I ask, I'd like to clarify that I have no intention of actually trying to install receptacles/change wiring/do any actual electrical work related to my question - regardless of the answers I get. I know that if "I have to ask, I need to have a professional do it", and that's what I would do. I am simply posing a question as to whether or not something is even possible, to determine whether I take the next step in contacting a local electrician. Okay, that's my disclaimer -

I have two separate 120V 20Amp circuits running out to my workshop. They are on a tandem 20A breaker and only provide power to the workshop (nothing else in the house, etc.). Both circuits were run to the workshop using 12 gauge wire. Is there any possible way that the receptacle required for the induction burner discussed in this thread could safely be installed/operated in my workshop WITHOUT having to replace the 12 gauge wire feeding the workshop?

Thank you for your time. Cheers.

The 12ga wiring should be fine for a 20A circuit, but you will need to change the breaker out for a two pole breaker so you will need an additional space in your panel. Plus what AnOldUR said about replacing existing receptacles, although I'm not sure if code allows more than one outlet on a 240V circuit.

 

[IslandLizard]

Yes. You could change one of the circuits to 240V.

If you have room in your panel for a seperate 240V breaker and you changed every outlet on the one circuit to 20amp / 240V.

Shouldn't that become a "dedicated circuit" for one single 240V/20A outlet?
Or could it be branched, to have access in 2 or more locations, like front and back of shop, but not used simultaneously?

 

[IslandLizard]

The 12ga wiring should be fine for a 20A circuit, but you will need to change the breaker out for a two pole breaker so you will need an additional space in your panel. Plus what AnOldUR said about replacing existing receptacles, although I'm not sure if code allows more than one outlet on a 240V circuit.

Funny you say that. In Europe everything is 220/240V and branched similarly to our 120V circuits in the US, alas carrying half the currents for the same load (wattage). Now 380V/420V there has different rules...

 

[NathPowe]

Thank you for the replies. After reading them I realized I left out an important piece of the puzzle, which I think affects the feasibility of this. When I was checking out the wiring for the shop, I noticed that the two lines out to the shop aren't connected directly to the breaker. They run from a junction box, which is fed by a 12-3 wire from the breaker. So they must be sharing the neutral and ground between the junction box and the breaker. I believe this complicates things?

Any of you care to weigh in on this new information? There isn't any other information I've left out, so that should do it. Hopefully I'm not getting the thread too far off-topic.

Thanks for your time.

 

[IslandLizard]

If your 12-3 wire is actually carrying 2 circuits from the tandem breaker to your shop something isn't right. Unless only one pole of the tandem breaker is used, and one wire of the 12-3 is capped, so effectively it would be one single 120V circuit, with a surplus wire.

That setup is easily convertible to a 240V, except where is your shop going to get its 120V feed from, for the lights and outlets?

 

[dyqik]

Funny you say that. In Europe everything is 220/240V and branched similarly to our 120V circuits in the US, alas carrying half the currents for the same load (wattage). Now 380V/420V there has different rules...

Except in the older UK system, which carries 240V single phase on a ring main, fed with a fuse/breaker at each end, with many sockets between the ends. Each socket can pull up to 13A, and you can have two 13A appliances at any location on a single ring main, fed by 13A fuses at each end. </boring electrical nerdery>

 

[IslandLizard]

Except in the older UK system, which carries 240V single phase on a ring main, fed with a fuse/breaker at each end, with many sockets between the ends. Each socket can pull up to 13A, and you can have two 13A appliances at any location on a single ring main, fed by 13A fuses at each end. </boring electrical nerdery>

Since when is the UK part of Europe?

Yes, their circuits were baffling for continentals. A fuse for each outlet, and a fuse in each plug. The plug was sometimes larger or heavier than the appliances it connected, such as a curling iron or radio. Why does the Titanic come to mind...?

 

[Hello]

This place can get you neoprene in any size/thickness you'd ever want - just keep an eye on the price!

http://www.rockywoods.com/Fabrics-Kits/Neoprene_Fabrics

They carry the fabric backed neoprene that works with velcro too - that'd make fitting much easier.


I sure wish my Avantco would show up. I'm trying to decide between a Concord 6.5gal pot or a Bayou 1032 (8gal with spigot). I can't believe it, but the 1032 is cheaper than the pot only version (1308) and it's a tri-layer bottom.

Trying to stay in the 12" diameter range for the pot, and that's difficult for some reason.

Do you think the 3.0mm thickness is enough? I like orange and it only comes in 3.00 mm max.

 

[sumbrewindude]

Hello -

Honestly I haven't the foggiest. Doing a look online, it looks like Keg-Skin's neoprene wrap is at 10mm:
http://www.amazon.com/dp/B00BW9EWWA/?tag=skimlinks_replacement-20

So, using that as a model, you may need to wrap the pot a few times to build up the thickness as necessary.

YMMV, of course.

 

[AnOldUR]

Do you think the 3.0mm thickness is enough? I like orange and it only comes in 3.00 mm max.

Just for reference. It's too squishy to get a good measurement, but I'd say the Koozy is at least twice that thick.

 

[IslandLizard]

Do you think the 3.0mm thickness is enough? I like orange and it only comes in 3.00 mm max.

3mm (~1/8") is too thin to make much difference. I was looking at 6mm (~1/4") and that was getting pricey already. And very limited colors for the thicker stuff.

Neoprene pipe insulation used for AC and Heatpumps is typically 1/2" thick. That's around a rather skinny copper tube.

Hello -

Honestly I haven't the foggiest. Doing a look online, it looks like Keg-Skin's neoprene wrap is at 10mm:
http://www.amazon.com/dp/B00BW9EWWA/?tag=skimlinks_replacement-20

So, using that as a model, you may need to wrap the pot a few times to build up the thickness as necessary.

YMMV, of course.

Pricewise that sounds like a decent alternative. Or pilfer some old scuba suits off Craigslist

Cold water scuba suits are typically 7-9mm. But they compress to 2-3mm under pressure at diving depths.

 

[dyqik]

Since when is the UK part of Europe?

Yes, their circuits were baffling for continentals. A fuse for each outlet, and a fuse in each plug. The plug was sometimes larger or heavier than the appliances it connected, such as a curling iron or radio. Why does the Titanic come to mind...?

Since the mid-Atlantic tectonic plate boundary opened up. Or 1973, depending which way you look at it.

And if the 240V 20A plugs here in the US had fuses in them, we wouldn't be having the discussion about the problems of putting a 20A device on a 50A circuit...

 

[sumbrewindude]

Another possible option for neoprene, is neoprene foam. It's closed cell so leaks/splashes won't soak it, and you can get quite a bit for much less than neoprene backed fabric.

Here's an example, the high quality foam is rated over 212F -
https://www.foambymail.com/NE/neoprene-foam-sheets.html

You could get a 3/8" thick roll and do two pots (diameter dependant, of course), which would be 9.5mm equivalent. They've got thicker foam also, but I'd start questioning it's ability to wrap neatly and tightly around the pot once you start getting larger...

 

[Jpartschjr]

These are photos of the box built to utilize my 220/50a service.


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[NTBeer]

I have been lurking here and considering various electrical brewing options for a couple years now, and had been accumulating the pieces to build a 5500W 50L ebiab setup when I came upon the Avantco. I had previously considered induction, but was discouraged by the lack of higher power options to make varying batch sizes feasible. I purchased an Avantco about three weeks ago, and did one seven gallon boil test before doing an extract brew last weekend. The brew went mostly to plan, though for the first 10 minutes or so it wasn't heating. I turned the unit off and 'rebooted', and water heated as it did in my test after that. After completing the brew, I found this....



(not sure I understand uploading images, should be a picture of the bottom of my pot)

I am using a 10 gallon Northern Brewer megapot (original), with a tri ply bottom about, I believe, 5 mm thick, much thicker than I believe the Bayou Classic most of you are using is. I now have a "burned" area about 1 1/2 inches in diameter where the pot would have been on the back left part of the burner, and the bottom of the pot is no longer flat.

What do you guys think? Was the problem with the burner, or is it because of the construction of the pot?

 

[Hello]

Maybe instead of neoprene for now, I'll just buy the other reflective stuff.

 

[fbold1]

I have been lurking here and considering various electrical brewing options for a couple years now, and had been accumulating the pieces to build a 5500W 50L ebiab setup when I came upon the Avantco. I had previously considered induction, but was discouraged by the lack of higher power options to make varying batch sizes feasible. I purchased an Avantco about three weeks ago, and did one seven gallon boil test before doing an extract brew last weekend. The brew went mostly to plan, though for the first 10 minutes or so it wasn't heating. I turned the unit off and 'rebooted', and water heated as it did in my test after that. After completing the brew, I found this....



(not sure I understand uploading images, should be a picture of the bottom of my pot)

I am using a 10 gallon Northern Brewer megapot (original), with a tri ply bottom about, I believe, 5 mm thick, much thicker than I believe the Bayou Classic most of you are using is. I now have a "burned" area about 1 1/2 inches in diameter where the pot would have been on the back left part of the burner, and the bottom of the pot is no longer flat.

What do you guys think? Was the problem with the burner, or is it because of the construction of the pot?

I would get a piece of sheet metal and see how it heats. If it has the same heat pattern it is the burner, if it heats evenly, it's your pot. If the bottom of your pot is not flat, induction won't work properly.

 

[IslandLizard]

These are photos of the box built to utilize my 220/50a service.

That looks like a very good and simple solution. Isn't that the spot where an electric stove goes, usually? Don't you have one?

 

[IslandLizard]

[...] I am using a 10 gallon Northern Brewer megapot (original), with a tri ply bottom about, I believe, 5 mm thick, much thicker than I believe the Bayou Classic most of you are using is. I now have a "burned" area about 1 1/2 inches in diameter where the pot would have been on the back left part of the burner, and the bottom of the pot is no longer flat.

What do you guys think? Was the problem with the burner, or is it because of the construction of the pot?

Although I marked the post as "liked" I really don't like the look of that at all!

I'm really sorry to hear this happened to your pot. Are you saying the bottom of your pot is bulging now? Like it got warped/melted by extreme localized heat? That's not good news! I don't think I've heard or seen anything like this before.

I have a similarly constructed pot, an 8 gallon Heavy Duty MoreBeer one, also with a 5mm tri-clad sandwich bottom. I think there is an aluminum "disk" between the actual pot bottom and the outer SS bottom dish. Maybe the SS dish bottom warps and/or the aluminum melts from the induction heat.

Yowsers!

 

[Jpartschjr]

That looks like a very good and simple solution. Isn't that the spot where an electric stove goes, usually? Don't you have one?

I own a two family home and just remodeled. I don't plan to rent out either unit until i move so i am using the spare stove socket. Was going to do an electric build but don't have the room so this worked. This was a safe approved solution and it works very well.


Sent from my iPhone using Home Brew

 

[IslandLizard]

I would get a piece of sheet metal and see how it heats. If it has the same heat pattern it is the burner, if it heats evenly, it's your pot. If the bottom of your pot is not flat, induction won't work properly.

That would be a good test. The tri-ply bottoms of those type of pots are very flat, at least before he used it on the IC3500. I don't think lack of flatness was an issue here.

Has anyone else used these tri-clad bottom pots with induction? Are they incompatible perhaps? See my previous message about possible warping and melting.

I got my IC3500 delivered yesterday, which is in record time. The pot looks great sitting on that hotplate, but I haven't been able to pull a wire and install the receptacle yet, so I can't try it. I'm a bit hesitant now...

 

[IslandLizard]

I own a two family home and just remodeled. I don't plan to rent out either unit until i move so i am using the spare stove socket. Was going to do an electric build but don't have the room so this worked. This was a safe approved solution and it works very well.

Ah, excellent testing area, lots of space!

It doesn't look your sub panel has built-in GFCI, just a double pole (30A?) breaker, right?

[Added] Conceivably, could you have mounted the receptacle in the short side or lower right side of the breaker box instead of the conduit to the work box?

 

[Jpartschjr]

I did not build the unit myself but i do agree. A larger box with the female socket in the box. I had my electrician build this for me. I did not use GFCI, with the double pole 20a plug in sub panel i was told it is within code (from building inspector) and that this will protect the line.

What benefit would i gain from GFCI? I was quickly approaching my budget with the unit i have, ($150, parts were about 65% of that).


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[AnOldUR]

What benefit would i gain from GFCI?

Could be wrong, but heard that these induction cooktops do not need to be on a GFCI. If you have an electric range in your kitchen, is that GFCI protected? We switched to gas, but the electric range I took out wasn't. New code?

 

[sumbrewindude]

I have been lurking here and considering various electrical brewing options for a couple years now, and had been accumulating the pieces to build a 5500W 50L ebiab setup when I came upon the Avantco. I had previously considered induction, but was discouraged by the lack of higher power options to make varying batch sizes feasible. I purchased an Avantco about three weeks ago, and did one seven gallon boil test before doing an extract brew last weekend. The brew went mostly to plan, though for the first 10 minutes or so it wasn't heating. I turned the unit off and 'rebooted', and water heated as it did in my test after that. After completing the brew, I found this....



(not sure I understand uploading images, should be a picture of the bottom of my pot)

I am using a 10 gallon Northern Brewer megapot (original), with a tri ply bottom about, I believe, 5 mm thick, much thicker than I believe the Bayou Classic most of you are using is. I now have a "burned" area about 1 1/2 inches in diameter where the pot would have been on the back left part of the burner, and the bottom of the pot is no longer flat.

What do you guys think? Was the problem with the burner, or is it because of the construction of the pot?

Looks like a hot spot, and judging from the diameter of the pot (I think the old mega's were the same as the SPS 40qt's) which was 16"+/-. From where it is, it's like the IC3500 thought it was a smaller pot and tried to use the small burner to heat it. All that heat in a small area could warp the pot for sure.

Maybe there was an excessive amount of iron in that area of the pot's construction?

 

[geoffm33]

Thanks sumbrewindude!

Question for All:

When I turn on my IC3500 with my Bayou Classic 1044 the bottom immediately buckles as the magnetic field kicks in. If you look at where the cooktop surface meets the pot, just the middle 7 or so inches is touching the unit. It was sitting completely flat prior to turning it on.

I imagine this is due to the thin makeup of the BC pots, and may not happen on thinker or tri-ply pot bottom pots.

Anyone else notice this?

Any efficiency downsides?

Looking at AnOldUR's 85% efficiency compared to my 74% I am looking at all options

Last night I was doing a boil to test the ball valve I installed in the BC 1044 and this buckling happened as expected. So I gently applied downward pressure to the rim of the kettle and it flattened out. I wasn't testing temp/times so no clue if it improved efficiency. I can test that later.

 

[chocotaco]

What benefit would i gain from GFCI? I was quickly approaching my budget with the unit i have, ($150, parts were about 65% of that).


Sent from my iPhone using Home Brew

GFCI is not intended to protect the line or the burner. It is intended to protect your life. If you start being electrocuted, GFCI can detect this and turn off the power. It is very important to use GFCI in any conditions which may become wet - this is why you always see GFCI receptacles in bathrooms and kitchens.

A 20A double-pole GFCI breaker will probably cost you 2-3 times what a non-GFCI breaker would, but I would not skimp on it if I were you - especially when your panel is already a bit of a "contraption".

Skipping GFCI may be perfectly "to code", but that's because the code doesn't account for the fact that you're going to be cooking large volumes of liquid using this particular receptacle.

 

[Dotay]

I used this induction burner this past weekend with the megapot 1.2 and it worked wonderfully. I'll have to check to see if I've got a hot spot like that on mine but I'm pretty sure I don't.

 

[IslandLizard]

I used this induction burner this past weekend with the megapot 1.2 and it worked wonderfully. I'll have to check to see if I've got a hot spot like that on mine but I'm pretty sure I don't.

Yes, please check also for the bottom being warped or bulged.

I just looked up induction compatibilty on the MoreBeer website:

Our heavy duty kettles work on induction stove tops!
Our heavy duty stain[l]ess steel kettles will work on an induction stove top! Please note however, depending on how powerful the stove top is, boiling times may vary.​

MoreBeer's heavy duty pots, like NB's MegaPots, also have 1.2mm walls. The aspect ratio of MoreBeer's pots is low and wide. Like my 8 gallon one is 14" wide and 12" high. They have a 10 year warranty, so I guess it's worth a try.

I'm still puzzled how NTBeer ended up with a blistered pot.

 

[Jpartschjr]

GFCI is not intended to protect the line or the burner. It is intended to protect your life. If you start being electrocuted, GFCI can detect this and turn off the power. It is very important to use GFCI in any conditions which may become wet - this is why you always see GFCI receptacles in bathrooms and kitchens.



A 20A double-pole GFCI breaker will probably cost you 2-3 times what a non-GFCI breaker would, but I would not skimp on it if I were you - especially when your panel is already a bit of a "contraption".



Skipping GFCI may be perfectly "to code", but that's because the code doesn't account for the fact that you're going to be cooking large volumes of liquid using this particular receptacle.

Why are electric stoves not GFCI or washing machines? I am just trying to understand better. I agree it is a contraption and i keep my water far from the open receptacles. Maybe a GFCI is in the future for this "contraption". Until then, YOLO (yes i did). In all seriousness, i appreciate the knowledge sharing.


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[mredge73]

Motors are not friendly with GFCI receptacles. This is why you won't see them being used for Refrigerators, Washers, and Dryers.

 

[chocotaco]

Why are electric stoves not GFCI or washing machines? I am just trying to understand better. I agree it is a contraption and i keep my water far from the open receptacles. Maybe a GFCI is in the future for this "contraption". Until then, YOLO (yes i did). In all seriousness, i appreciate the knowledge sharing.


Sent from my iPhone using Home Brew

My apologies if I came off as condescending; I wasn't trying to be. If your "spider box" (colloquial name for a temporary power distribution center) was given a sign-off by the inspector, I'm certainly not qualified to say otherwise.

My understanding is that the NEC doesn't require GFCI for 220V receptacles mainly because it would be a financial burden to do so. Since any electric stove is likely to be 220V, that explains why they aren't typically placed on GFCI breakers.

That being said, I think it's likely that an electric range does include some kind of built-in ground fault protection - either on the individual burners or collectively. I am not an electrician, but it would be a massive liability not to include that on a high-voltage, high current commercial device where someone is eventually going to spill large quantities of liquid and immediately attempt to clean it up without thinking to unplug it first.

 

[Jpartschjr]

You were not condescending at all, i truly appreciate the knowledge and advice. I would rather be safe so i am definitely going to look for a GFCI for the future update to this.

Inspector said it was electrically sound, doesn't mean it is "safe" so i agree with your original thought to cya. A regular socket is up to code (typically) but without specific sockets can still zap you if it is disrespected and used wrong.

Thank you again, it is truly appreciated.




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[NTBeer]

Yes, please check also for the bottom being warped or bulged.

I just looked up induction compatibilty on the MoreBeer website:

Our heavy duty kettles work on induction stove tops!
Our heavy duty stain[l]ess steel kettles will work on an induction stove top! Please note however, depending on how powerful the stove top is, boiling times may vary.​

MoreBeer's heavy duty pots, like NB's MegaPots, also have 1.2mm walls. The aspect ratio of MoreBeer's pots is low and wide. Like my 8 gallon one is 14" wide and 12" high. They have a 10 year warranty, so I guess it's worth a try.

I'm still puzzled how NTBeer ended up with a blistered pot.

I'm puzzled as well. The pot bottom WAS perfectly flat when I started, and I have been using this pot on the stovetop for about 2 years without so much as a stain. I have no proof, but I believe this happened when I first started the Avantco up and it ran for about ten minutes without significantly heating the water. My theory is that there may have been a void in the tri ply that shaped and concentrated the magnetic fields. Though I can't explain why this excessive heat wouldn't have transferred to the water.

It worked well in my initial water only test, though even in that test I thought the area being heated was smaller than I expected.

As I bought the pot intending to install an immersible element, it is wider than the normal pot. I can't deny that that may be a factor, as it is almost double the recommended size for the burner.

Unfortunately, I was brewing a porter and thus couldn't really monitor the size of the area being heated while boiling as it was effectively hidden.

I intend to contact Webstaurant, and will update this when I hear from them.

Tom

 

[IslandLizard]

Took me a few hours Friday to locate the Nema 6-20 receptacle. But it beats waiting for an Amazon order to arrive. Besides, mail ordering mundane things like electrical and plumbing supplies is ridiculous, at least in my book of ethics.

HD or other "hardware" stores don't stock them, special order and up to a week's wait only. Then I found an electrical supply place that did (through internet and yellow pages), an outfit where the contractors go. I wonder if it's just me, but finding those kind of suppliers outside the HD/Lowes/(Ace) realm seems to become increasingly more difficult.

Then most of Sunday I spent running the wire from the panel to the kitchen and installing the new outlet. I'm familiar with that kind of work, it just takes time and you got to cut holes in ceilings, walls etc. Perpetual remodeling.

OK, we were finally ready for the test last night at 7 pm. Put a gallon of water into my 8 gallon, 14" wide MoreBeer Heavy Duty kettle with the tri-ply bottom.
In that pot, a gallon of water is only 1.5" high. I turned on the induction plate, first at low wattages, later at "full 3500W blast," periodically checking the outside bottom for any discoloring, blistering, buckling, or other unusual things.

Everything behaved as it should, without any buckling or distortions of the very flat and thick bottom. What I did notice was a slight darkening ring on the inside of the pot, in the center, about a good inch wide on a 5" diameter. It seems only the small, 5" coil is being activated, although the kettle is 14" wide and even hangs a bit over the sides of the plate. All heating and boiling seems to take place from this small center area. It's that 5" region that boils violently, the rest doesn't, it's only around 209.6°F, until I put the lid on.

Is this something you guys experience too? Why is the outer ring not on? wouldn't that be better for heat transfer and possibly more heat generation. I doubt I really pumped 3500 watt out of that small circle. That does not look efficient or right at all. Any ideas?

 

[brewman !]

Everything behaved as it should, without any buckling or distortions of the very flat and thick bottom. What I did notice was a slight darkening ring on the inside of the pot, in the center, about a good inch wide on a 5" diameter. It seems only the small, 5" coil is being activated, although the kettle is 14" wide and even hangs a bit over the sides of the plate. All heating and boiling seems to take place from this small center area. It's that 5" region that boils violently, the rest doesn't, it's only around 209.6°F, until I put the lid on.

For those not aware, boils need to be done with the lid off so as to drive DMS from the wort. If you heat system doesn't have enough power to bring the wort to a full roiling boil without the lid, you need more power. Keeping the lid on will result in beer with high levels of DMS and the resulting taste from it.

http://byo.com/stories/item/1650-wort-boiling-homebrew-science

 

[IslandLizard]

For those not aware, boils need to be done with the lid off so as to drive DMS from the wort. If you heat system doesn't have enough power to bring the wort to a full roiling boil without the lid, you need more power. Keeping the lid on will result in beer with high levels of DMS and the resulting taste from it.

http://byo.com/stories/item/1650-wort-boiling-homebrew-science

+1
Although that's true (at least to a certain extend), please note I was testing the unit with plain tap water, and only a gallon, 1.5 inch high in the pot. The lid-on was part of the test.

I'm sure the action of the boiling (heating and agitation) will extend normally through the whole kettle if it were fuller. Whether it can keep the whole 7 gallons in the kettle at a rolling boil with the lid off still needs to be determined.

I noticed only the 5" center being the sole source of the boil.