Converting to an induction stove top

[Marco Flamingo]

Maybe it is time for you to open a boat parts store. Most everything is made overseas.

I bought upgraded cables specifically fabricated in the US using AWG rated tinned-copper cables.

As to boat parts, anybody need a semi-filthy vintage Magic Chef propane stove? I also have 18 inch cheezy unrated cables for an inverter. Neither come with any warranty. Also a little RV sink.

 

[angus99]

The metal sheet is a good conductor of excess heat, but won't protect the marine plywood sides of the cavity from the heat of the cooking appliance on the other side of it. In fact it will be almost exactly the same temperature on the side against the plywood as on the side away from the plywood.
An insulator is required, and some very good insulators are available. My own diesel stove insulation came out of the sailboat built in 1982 from which I borrowed it when swapping its diesel stove for a propane cooker and installing a new diesel stove in my trawler. It is comprised of asbestos compressed into 1/4" sheet pieces, then is covered with stainless steel panels. It insulates that very marine ply, which, on one side, separates the stove from the fridge.
Naturally, most galleys in my size of boat have the heat source positioned as close as possible to the source of cold.

I agree. Even though there was no scorching of the plywood from the old galleymaid Empress through the existing metal liner, I wasn’t comfortable with just the sheet metal. Hence the high capacity blower.

 

[OldDan1943]

I am writing this first thing in the morning without the benefit of a complete cup of coffee.
Double wall and triple wall stove smoke pipe all have two things in common, air space and loosely pack insulation between the walls. IF you install a stove for heating, the backboard has insulators and space between the sheet metal and the flammable wall behind and to the sides of the stove. Two things, there is an air gap between sheet metal and the flammable wall behind the sheet metal and the sheet metal will reflect the heat into the unheated room.
Soooo, by installing fan, directing the air flow between sheet metal and the flammable wall behind it, you are reducing the temp of the sheet metal and affording protection to the flammable wall behind the sheet metal.
Sooooo, IMO installing sheet metal under and around the oven will do little to protect the flammable surface behind the sheet metal without and air gap between the sheet metal. It may in fact increase the heat against flammable surface by spreading the heat to the entire flammable surface.
I could go on and talk about wood stove installations and a 4 inch air gap around the 3way microwave oven, to draw parallels, but I wont.
I think you get my drift.
Briefly, if you put a piece of sheet metal on a grill's surface both sides will have the same temp.
What to do? Rely upon the manufacturers installation instruction putting faith in the boat builder that they will follow the instructions.

Now, I ask you, did this make sense or must I rethink this after I finish my morning coffee?

 

[angus99]

I am writing this first thing in the morning without the benefit of a complete cup of coffee.
Double wall and triple wall stove smoke pipe all have two things in common, air space and loosely pack insulation between the walls. IF you install a stove for heating, the backboard has insulators and space between the sheet metal and the flammable wall behind and to the sides of the stove. Two things, there is an air gap between sheet metal and the flammable wall behind the sheet metal and the sheet metal will reflect the heat into the unheated room.
Soooo, by installing fan, directing the air flow between sheet metal and the flammable wall behind it, you are reducing the temp of the sheet metal and affording protection to the flammable wall behind the sheet metal.
Sooooo, IMO installing sheet metal under and around the oven will do little to protect the flammable surface behind the sheet metal without and air gap between the sheet metal. It may in fact increase the heat against flammable surface by spreading the heat to the entire flammable surface.
I could go on and talk about wood stove installations and a 4 inch air gap around the 3way microwave oven, to draw parallels, but I wont.
I think you get my drift.
Briefly, if you put a piece of sheet metal on a grill's surface both sides will have the same temp.
What to do? Rely upon the manufacturers installation instruction putting faith in the boat builder that they will follow the instructions.

Now, I ask you, did this make sense or must I rethink this after I finish my morning coffee?

Food for thought, Dan. I think you’re right that the air gap is the primary protection. I kept the metal liner because it was already there and there was no evidence of previous overheating to the plywood on the side I had to remove (nor anywhere else). The GE unit I installed is designed to be built into wooden cabinetry and has specific dimensions for the air gaps, which I also observed. Finally, the blower I added provides a source of cooling air flowing through the entire cavity (and also removes any cooking odors). So, bottom line, the sheet metal may or may not help, but I doubt that it hurts in this particular application.

 

[KEMOSABEN40-19]

We recently did the same thing! We removed the propane stove and cooktop. We replaced it with a 2-burner Dickinson propane stovetop (which slide into the existing space, perfectly), built a teak shelf, and, put a Breville convection toaster oven on the bottom of the space (we plugged it into an existing outlet in the galley). We also have a portable induction cooktop, for when we have power or are under engine power. I LOVE it. I'll get you a picture later today. Kristin on KEMO SABE

 

[ranger58sb]

My boat has a genset, but in the two years I've owned it I haven't yet run it. The plan is to not run it. We shall see.

Heh... if you haven't run it, 80% chances are it won't run anyway. Generators on boats are pretty well known for being "use or or lose it" equipment...

-Chris

 

[Marco Flamingo]

The metal sheet is a good conductor of excess heat, but won't protect the marine plywood sides of the cavity from the heat of the cooking appliance on the other side of it. In fact it will be almost exactly the same temperature on the side against the plywood as on the side away from the plywood.

That was the beauty of the heavy copper sheathing. No air space required. The stove was a Washington Stove Work Neptune model from Everett, WA. I haven't seen one of those for awhile. The boat designer was also local. Ed Monk. The copper plate was thick enough and conducted heat so fast that an air space was not required. A tricky design to get a couple more cubic feet of space in a 32' sailboat.

At today's prices, the copper liner would probably cost >$600, not including fabrication. But as a bonus, it looked functional and salty.

 

[Marco Flamingo]

Here is the semi-final installation. Much of my change over had to do with my boat and my ideas of cruising. One of the things that made the switch easy was that the prior owner had moved some of the electrical to the galley area (back side of the aft dinette seat). That is where the 1-2-Both switch is located. That is where the battery monitor is located. Now, that is where the inverter circuit breaker (150A) and inverter remote control is located. Part of what makes people nervous about going electrical is not having a handle on how much electricity is being used. I can simply glance at the gauges and get an exact readout of the batterys' SOC, the amperage being used, etc. Also, the inverter is mounted right under the stove and has additional info such as the DC voltage at the inverter, the AC voltage being produced, etc.

The inverter is mounted in a "fire proof" box, which is really just fire resistant as it needs to be vented because of internal fans. In case of an actual fire, it gives me time to run in circles and scream like a girl. I was able to use it long enough to get the cooling fans to come on, but the inverter was just barely warm and the fans only came on for 15-20 seconds every minute or two.

I went waaaay overboard on inverter size. Several websites said to go 40% over because you will find additional things to plug in and will soon wish that you had gone bigger. I thought I might some day go with a 120V dorm fridge if my ancient AC/DC Norcold ever dies. So I went with a 3,500 watt PSW inverter. Some websites said that a larger than required inverter would waste electricity. Some said it didn't matter. Some said that larger units run at half or less loads were more efficient. There were even websites where inverters were hooked up to fancy electrical diagnostic equipment. Sure enough, each claim could be supported by different inverters. I have no idea which group mine belongs to.

A note on induction stove tops. For my uses, and probably most uses on a boat, induction tops have too much power. Mine automatically comes on at #5, which is medium. That is fine for boiling water and such, but would generally scorch anything to the bottom of the pot if left at #5. I immediately turn it down to #2 or 3. The inverter is wired through a 150A circuit breaker, which trips if both burners are inadvertently turned to maximum. Fine by me.

I only did one real world test of my installation so far. My induction stove top could make a cup of espresso (using cold water) in 3 minutes 24 seconds at the medium-low setting. That used 3 amp hours. That is a lot. That means that with my battery bank I can only make 86.666 cups of coffee and stay above a 50% state of charge. Not really useful information. I also got a chance to try my welding blanket insulation on the Dutch oven. (It's the thing that looks like a Taliban hat in the picture). Worked like a charm. I can easily get the oven to 350F by setting the stove top at #2 (low) and the hob on top at #1 (really low). Because these settings have the induction "elements" turning on and off (on for three seconds, off for three, etc.) the amp reading was constantly bouncing around. I'll have to run the setup for awhile to get an actual usage.

I found a teak door at a boat salvage place that will fit my bonus area left by the propane oven. It came from a boat that spent some time underwater, so it needs to be refinished first. More pictures to come.

 

[Marco Flamingo]

The electrical stuff.

 

[sbman]

One thing I don't understand on your installation. You put in a 3500 watt inverter, but wired it through a 150 amp circuit breaker? If your source is 12V, that's only 1800 watts of energy allowed into a 3500 watt device. Why is the breaker undersized?

 

[catalinajack]

So, Marco, you have a cooktop that allows both burners to operate at max watts? I rather doubt that. Every induction cooktop I have seen has a maximum combined wattage. When one burner is on at max and the other is turned on, the first will automatically be reduced. No way any manufacturer is going to supply a product which can induce a current draw beyond the capacity of the supply circuitry.

 

[sbman]

So, Marco, you have a cooktop that allows both burners to operate at max watts? I rather doubt that. Every induction cooktop I have seen has a maximum combined wattage. When one burner is on at max and the other is turned on, the first will automatically be reduced. No way any manufacturer is going to supply a product which can induce a current draw beyond the capacity of the supply circuitry.

In an earlier post he said that it is limited to 13 amps on the AC input, works with standard outlets.

The breaker, if I understand it correctly is a 150 A breaker on the 12V house side. When the inverter is delivering the full 13 amps, that is the breaker that is popping.

 

[OldDan1943]

But but but before I even consider an induction stove top, let's settle the oven question.
Ya'll are trying to fit this to an inverter and I am trying to fit it on a 30amp boat.

 

[sbman]

But but but before I even consider an induction stove top, let's settle the oven question.
Ya'll are trying to fit this to an inverter and I am trying to fit it on a 30amp boat.

If you have a fancy enough inverter, it can make up the difference in power requirements from your batteries.

Some of the Victron units can mix power from the shore power and the batteries, all seamlessly without you having to do anything. Turn on too many things that your shore power connection can't handle, and it will 'borrow' power from the batteries until you are done, then it charges them back up automatically when you reduce your usage.

 

[Marco Flamingo]

Why is the breaker undersized?

1. Because I had a 150A.
2. Because I don't need the full 3,500W now. Not until I get my table saw on board. Kidding.

The burners power share. They can't be both on max (10) at the same time. Medium (5) seems plenty for all of my needs. So for now the 150A fuse is fine.

I took some pumpernickel bread dough to the boat today and played around much too long with the Dutch oven. The induction stove top worked fine for proofing the bread. Turn it on low for thirty second once every 10 minutes and it keeps the dough at about 80 degrees. No need to preheat the Dutch oven, it heats really fast. I used the welding blanket insulation and immediately got it too hot. After messing with settings, peeking inside, etc. I finally settled on setting the stove top temp to 360F and the upside down hob to #1 (the lowest).

Biggest problem was that the Dutch oven sealed too tight and didn't let steam escape. The bread cooked but too moist and the crust was thin. Without a good crust I might as well buy bread in a plastic bag from the supermarket. It might be possible to cook in the Dutch oven with just the insulation, or with the lid askew, which would allow steam to escape. Needs work.

I found a nice induction popcorn popper. Worked fantastic and a really is the best way to pop. 3 minutes and no old maids. I may be eating popcorn instead of bread.

 

[DDW]

A single burner set at #5 was about 7 amps, just about 1/10 of the draw from the MSW inverter. Both burners at maximum was 11 amps. For a real world test, a burner set to 5 (7 amps) will heat up a can of chili in 6 minutes (1/10th of an hours). Therefore lunch was .7 amp hours. Actually, I'm not figuring in the inefficiency of the inverter yet, so it could be 1 amp hour. I won't have an accurate number until I run the whole thing through the house batteries and the battery monitor.

I will admit I am confused by these numbers. 7 amps of 110V current or 7 amps of 12V current? If 12V that is only 84 watts and unlikely to do a lot of cooking. If 110V then the amp-hour statement is of little relevance, as it would be closer to 10 AH from your 12V system, not .7 AH.

 

[Marco Flamingo]

Those numbers were using AC shore power before I had my inverter installed. I watched the DC numbers today, but forgot them on the boat. Here is part of the problem. I had a burner set at 360F with the Dutch oven on it. The battery monitor would ramp up to about 80A (DC), then fall for a few seconds, back into the 70's, drop again, back up, then down, for a total elapsed "on" time of about 45 seconds over a one minute period. It seemed to be searching and fine tuning to get to 360F. Then "nothing" for 4.5 to 5 minutes (which would still be a 2-3 amp draw because of inverter standby draw and other small electrical things on board). So the instant amp usage to cook a meal or bake bread couldn't be directly read from the meter.

If the bouncing amperage draw for for keeping the Dutch oven at 350F is approximately 80A on a 20% load cycle time, then that would calculate that 16 amps would be used in an hour, about what it takes to bake a loaf of bread. That's about what my battery monitor showed for total usage for the bread even though I was opening the Dutch oven up and changing settings. But, like baking in general, not an exact science.

I'll also admit that I'm confused by some of the numbers. So far, I basically know that it works great for coffee, chili, and popcorn. The three major food groups.

 

[Marco Flamingo]

Here is the finished install. The new teak cupboard door was from a salvage boat. It fits the entire opening so that all of the old oven space is now available for storage. The cupboard basically doubles the storage area in our galley, so it was a trade off that I was willing to make. Getting rid of propane was the main purpose. Coming up with some kind of oven work-around that allows for baking would be a bonus, but not having a dedicated oven isn't the end of the world for me.

The final item was a handhold in the galley area. I found a teak "towel rack" for $14. Good thing it wasn't a teak hand rail for a boat. That would have been twice as much.

 

[Marco Flamingo]

I'll try those pictures again.

 

[Marco Flamingo]

I give up. Even when I rotate them before posting they go the same direction.

 

[ofer]

I give up. Even when I rotate them before posting they go the same direction.

a good exercise for my neck. thank you

 

[Marco Flamingo]

I'm learning more about my induction stove top every day. First, not all bread needs to be baked in an oven. The other day I made some English muffins on the stove top. One for breakfast and a second for a sandwich at lunch. Total amperage was 12 Amp hours, but I'm sure I could get that down once I get a routine. I cooked them on the lid to my Dutch oven.
Picture below.

I'm finding that "amperage insecurity" for the induction stovetop is a bit of a chimera (the runner up name to CHiTON). It turns out that I could bake 25 English muffins and still fire up the engine in the morning, no problem. After a night at anchorage, I could cook 6 English muffins, 6 cups of coffee, a fried egg, 3 poached eggs, listen to the news, get the weather forecast, and still be at 70% SOC. Maybe it's time to stop worrying.

I came up with an induction stove top bread toaster. It is a piece of perf plate steel from the scrap pile. I sit it on the induction burner at the lowest setting and it quickly toasts. I do need to turn over the bread (Whaaaaa, Mom, it's not like the toaster at home!). Next experiment is my cast iron waffle iron.

Here is a picture of me toasting my ham and cheese for lunch today.

 

[ofer]

i thought special cookware is needed for induction stove top.

are we saying any piece of steel will do?

 

[TWedd]

induction requires cookware with steel,(iron). Some cookware has a steel plate imbedded in the bottom of aluminum. I have also seen a steel plate placed on the cooktop and a pan placed on top of the steel plate. Its basically a powerful electro-magnet.

 

[rslifkin]

i thought special cookware is needed for induction stove top.

are we saying any piece of steel will do?

Generally any cookware that's magnetic will work. Stainless pans with the thick bottoms to spread heat often use an insert material that's induction compatible. So as long as you're not using those cheap, thin aluminum pans there's a decent chance of them already being induction compatible.

 

[Marco Flamingo]

Most cookware now says on the bottom whether it is induction compatible and a surprising number now are. Nobody seems to remember the early complaints about microwaves (you need special cookware!!), we have just adapted to not putting metal pots (and lots of other things) in a microwave. Same with induction. Once you are used to how it works, "special cookware" isn't special. It becomes second nature, worth the investment, and better than a microwave for my needs.

It would be possible to put an aluminum pan on a steel plate, heat the steel plate, which would then heat the aluminum pan. It would just be a loss of efficiency (unless you needed really, really low heat, like for a fondue). As you can see from the tempered circle on my steel plate, it is really easy to get it red hot (faster than a normal 120V electric coil element). Hot and fast has never been an issue with induction. Amperage anxiety seems to be the concern.

My lowest setting (#1) is 7 seconds on and seven seconds off at the lower power draw. Even that is faster than I would really like to heat, as some things will stick to the bottom of a pan from heating too fast (e.g., a can of chili). What I do is switch from the #1 setting to the 150 degree setting after a minute. If I just start on the 150 degree temperature setting, it heats too fast and overshoots the 150 degree setting, boiling hard for a minute before the stove top finally registers that it is at 150 degrees, shuts down, and maintains 150. Small issues that keep my induction top from being perfect (no learning curve.)

I really like the timer as a safety feature. If I'm heating a can of soup, I can set the burner at #2 for 4 minutes. It beeps and turns off when done. Nice if I've wandered off and started some project. Surprising how often the beep brings me back from thinking of other things.

My dedicated PSW inverter and stove top combination has a standby usage (under 3 amps) even with the burners automatically off. Not nothing and something that I have to remember to shut down when done cooking at anchor. Again not perfect, but better than forgetting that a convection or propane burner is still on.

 

[HeadedToTexas]

I came up with an induction stove top bread toaster. It is a piece of perf plate steel from the scrap pile. I sit it on the induction burner at the lowest setting and it quickly toasts. I do need to turn over the bread (Whaaaaa, Mom, it's not like the toaster at home!). Next experiment is my cast iron waffle iron.

Smart! Our conventional glass top two burner stove is cracked and I plan to replace it with an induction unit. Saving this idea for when the time comes.

That piece of perforated steel sure packs down a lot smaller than a toaster. How does the toasting time compare between that and a conventional toaster?

 

[bowball]

Are most induction cooktops 220v? Any high end 110v?

 

[HeadedToTexas]

Not sure about 220 VAC, but there are plenty that are 110 VAC.

 

[OldDan1943]

Some of you folks must have a lot of 8D batteries supporting your big inverters.
I have 3X4D supporting a 1800 watt inverter. watching the voltage while supporting the microwave, I get almost 1min before the voltage approaches 10.5 volts.