Induction vs Gas Cooking

[Dsanduril]

Originally Posted by Adelie

That's a tautology.

The point I was making is that if you are drawing 1000W at the windlass, the draw on the battery, 30' away, will be larger than if you are drawing 1000W at the inverter right next to the battery.

Remember, the inverter is not 100% efficient. More like 91-93%. Which balances pretty well with the voltage drop in the windlass cables, which are generally sized to a 10% voltage drop. From the perspective of the power available at the load it's about wash.

[Dockhead]

Originally Posted by Dsanduril

Rings are great at reducing voltage drop and wire sizes (advantages). But most rings (certainly not all, but those installed to British code) are installed with wire ampacity that is greater than half the ring capacity but less than 100% of the ring capacity (the code calls for 2/3). If the ring becomes single-ended then the loaded wire can become overloaded. Single-ending a ring can happen without any fault being detected. Upsizing the wire to meet the full ring capacity increases costs and thus negates some of the benefits.

Sort of a corollary to that, fault currents in a ring circuit are much more complicated to calculate, measure, and clear because there are two potential flow paths.

Definitely not saying rings are a bad thing, in certain ways, to me, they make more sense than radial systems. As with everything though, there are pluses and minuses to both approaches.

That makes sense, thanks. Wow, you are knowledgeable



My ring main uses 10mm2 tinned wiring, so sized for 32 amps, although it's a 16 amp circuit. I don't think it was designed that way to save copper, but to increase reliability and to save the number of cable runs, which would have been a massive tangle with a radial system and 10 sockets spread out around the boat.


I am pleased with it. I've had basically zero electrical problems with this boat in going on 11 years of ownership. Some of the wiring is my own -- the boat did not have an inverter when I bought her, and I had to change a number of things to install the Victron charger/inverter. I am thinking about re-doing that wiring as I now know that in those days I was (even) less of an electrician than I am now. Although, it hasn't given any trouble.

[Adelie]

Originally Posted by Dockhead

….

A big gas burner I'm sure will heat up a pan as fast as induction. A big gas burner can be a lot more than 2000 watts. I was comparing to the burners on boat stoves, which are far weaker. The difference is huge.

…..

Alas no, even the big burners waste a lot of the heat they generate and even a moderate sized countertop hob is likely to be faster.

http://m.youtube.com/watch?v=h45dzeugIZw

[Dsanduril]

On a boat, one very minor consideration of rings is magnetism. It is entirely possible for the current in the hot leg to flow through one side of the ring, and the neutral to return through the other side. All depends on the resistance on each side, and clearly is more likely to occur when using a receptacle near the ring's center. In this case magnetic fields don't cancel each other as they would in a radial system.

On the radial side, it only takes one corroded connection to create high resistance and the possibility of fire. The ring provides redundant connections (I know you like redundancy); if one connection has high resistance the current simply goes the other way around.

[s/v Jedi]

Also, professional grade induction cookers give all the control and speed that gas provides and chefs do not mind induction at all. For them the difference is that they used to adjust flame height and now need to get used to a percentage display. Some manufacturers have even used LED lighting to simulate the flame

On speed: I have a 3,000 Watt Cooktek and that is because I did not feel like ordering the 3,500W model. Like gas, you can get induction any size, even wok burners.

You should see my kettle bringing water to a boil on the 3,000W Cooktek... it’s brutal

[Dockhead]

Originally Posted by Adelie

DC & AC electrical start 52% of fires per the link provided. I'm not sure I would be willing to describe that as "overwhelming".

Looking more closely at the breakdown, of the 35% for DC 13% is for the engine so there would be no risk change to that regardless of whether you had electrical cooking or not. 6% are related to batteries and the article makes the comment that the batteries being in the engine compartment is a big part of that.

For the remainder of DC ignitions the article indicates "Outside of the engine room, there is no single area where most of the remaining DC electrical fires originate. Locations are pretty much equally spread across electrical panels, instrument panel gauges, bilge pumps, lights, and equipment of various types, including air conditioners, windlasses, and winches. Most of these fires could have been prevented if adequately sized, marine-grade wiring had been used and loose or corroded connections had been located and addressed." So using the right cabling and doing some maintenance would alleviate most of the risk.

For the AC side the article points to shorepower connections (cord and boatside connector), heaters used in stead of winterizing and battery chargers (specifically citing use of automotive rather than marine chargers) as major, possibly the majority of ignition sources for this type. It does not breakdown the actual numbers.

Electrical fires that would be related to electrical cooking would be a small fraction of the electrically started fires.

How many fires are caused by electricity is irrelevant.


The question is how much extra risk do you get, by adding electric cooking to your electrical system. What is the delta risk, not the total risk.



The percentage of fires is altogether irrelvant. A percentage of how many fires? And of what consequence? If no one is ever killed by a boat fire, or if it only happens once every 10 years, then that is altogether a smaller risk than gas explosions, in terms of life and limb, even if there are thousands of boat fires.



The only relevant question is the change of risk by adding electrical cooking, and no facts have been presented which say anything at all about this one way or the other.

[Adelie]

Originally Posted by Dockhead

How many fires are caused by electricity is irrelevant.


The question is how much extra risk do you get, by adding electric cooking to your electrical system. What is the delta risk, not the total risk.



The percentage of fires is altogether irrelvant. A percentage of how many fires? And of what consequence? If no one is ever killed by a boat fire, or if it only happens once every 10 years, then that is altogether a smaller risk than gas explosions, in terms of life and limb, even if there are thousands of boat fires.



The only relevant question is the change of risk by adding electrical cooking, and no facts have been presented which say anything at all about this one way or the other.

What I was trying to get at with Auspicious, is that he was tossing numbers out and misrepresenting the case.

You articulated what I was trying to get at much better than I did.

[Adelie]

Originally Posted by Dockhead

Great, real life experience


Do you have numbers on daily AH used for cooking?

Originally Posted by CatNewBee

Its hard to measure, because it is always a mix of things we use at the same time, when you cook, you also wash some stuff with hot water, so the boiler gets also some power, up to 100A are comming in from solar, so not clear how many Ah actually comming from the battery and going to the induction hob.

We have some raw values about our consumption, 30% are direct solar use, 70% go into the battery and are used from the battery daily. We produce and use between 8 and 10kWh per day, but this includes hot water, refrigeration, cooking and all other things.

I ran numbers based on A64Pilot's propane usage about a year ago.

Originally Posted by Adelie

So 10lb is 2.4 gal. Which is equivalent to 67.73kWh. Which works out to 2.14kWh/d.

If there was a 1:1 equivalence with electricity that would be 171 a-hr/d.

Really there's not, a lot of the energy from propane is waste heat. From this site (https://www.pcrichard.com/library/bl...00371.pcra#gas) it looks like the food gets 90% of the heat from induction compared to 40-55% from gas. Let's assume 2:1.

That's 86.5 a-hr/d including simmering for long periods on some days.

If you used the Wonderbag or any kind of pot cozy you could cut even that down. Fact is a Wonderbag or cozy could be put around and over the pot while it's on the induction burner, that would cut heat lose and energy usage considerably. Don't know if it could be put under the pot while cooking.

Looking at SWL's usage of 10kg/21d that would be about 6.45kWh/d with a 1:1 equivalency. With a 2:1 equivalency it would 3.23kWh/d.
At 12v that would be 269 Ah/d.

[Dockhead]

Originally Posted by Adelie

Alas no, even the big burners waste a lot of the heat they generate and even a moderate sized countertop hob is likely to be faster.

I'm surprised by that test -- showed a $69 portable induction hob boiling a kettle of water almost twice as fast as a big gas burner.



But maybe not so surprising. The concentration of all that heat into the pan changes everything.


The following video touts the safety advantage of induction which follows from having no flame, and actually nothing at all which is hot other than the pan itself. For all the talk about electrical fires, we didn't talk about fires started by open flames, but that's got to be a pretty huge advantage. I wonder how many fires are started on gas stoves.



I actually had a small fire on my boat while cooking when something got tossed into the way of the flames, in a rough sea. Fortunately I was standing next and took swift action, but it could have turned out differently. Couldn't happen with induction; nothing at all, including the pan, is hot enough to set anything on fire.

[Dsanduril]

While it has nothing to do with induction, standard electric ranges are about 2x as likely as gas ranges to cause kitchen fires and deaths related to kitchen fires (~40/60 split between gas/electric as kitchen fuel in the US, about 20/80 split on fires/deaths). Electric range fires result in even proportionally more fire-related injuries and costs (3-4x that of gas).

https://www.nfpa.org//-/media/Files/...kingTables.pdf

Will be interesting to see how that changes once induction is a large enough percentage of the installed base to be separated out.

[Auspicious]

Originally Posted by BlackHeron

After you passed through the Lady's Island Bridge in Beaufort SC there is little Creek to starboard.

Ah. We started North of you and just kept getting further away.

Holler if I can help with local knowledge on the Chesapeake.

[Auspicious]

Jeepers I’m getting tired.

Originally Posted by Dockhead

3. absence of combustion products in the cabin, 4. higher quality of the cooking experience; 5. reduction of the number of systems to maintain; 6. reduction of the number of different fuels to supply. Compared to gas, efficiency is not an advantage of induction.

3. Products of ideal combustion are carbon dioxide (CO2) and water (H2O). If you’re getting CO or other carbon compounds in more than trivial amounts you have another problem. 4. Quality of cooking experience is subjective; a good chef can cook anything anywhere with anything but the pros still prefer gas. 5. Down this path lies electric propulsion; there is more to systems choices than maintenance (digression below). 6. Absolutely agree. The day I can find a 10 hp diesel fueled outboard engine that weighs a reasonable amount (whatever that is) I’m in. I’ve looked hard at diesel and its cousin kerosene cookers for this reason. Too many drawbacks.

Digression: In my narrow professional niche and in the United States there are three big players. Webb, University of Michigan, and MIT. One of the reasons Webb stands out in employment statistics Is that we have required work terms. Not co-ops, we still have eight semesters with a lot of credit hours for a dual degree. Freshman winter you work in a shipyard for two months. Sophomore year you go to sea for two months. Junior and senior years you work in an office. Add three summers and we graduate with nearly a year of professional experience plus practical dirt-under-the-fingernails experience. This is relevant because it embeds the implications of design decisions on manufacture, installation, repair, and maintenance. In my professional opinion the very light maintenance required of LPG cooking is worthwhile. I feel the same about outdoor cooking aka “grilling” which may include roasting and baking. I’m less inclined toward on-demand water heating but that’s another matter.

Originally Posted by Dockhead

That fact /Insurance industry statistics point to electrical sources as the overwhelming cause of fire/ is not relevant to the relative safety of gas vs electric cooking. By itself, that fact shows nothing. The average gas explosion is probably 100x more destructive and more likely to cause injury or death, than the average electrical fire. The 100x is a guess, but we have to know this coefficient in order for the relative frequency of fires or explosions, to have any meaning.

The fact is entirely relevant. Note that I and someone else (sorry someone – I’m on a roll so I’ll buy you a beer in Annapolis for forgetting your name) have cited insurance statistics and in someone’s case NFPA statistics. That means our numbers do NOT include trivial events, only those of significance that lead to official reporting. Please note the causality percentages in the NFPA table. I’ll need footnotes for the 100x number. Maybe debris distribution but not financial loss and not casualties. Have you ever seen a fiberglass boat burn? I have. It’s fast.

We’re talking about reportable events, not a cigarette lighter plug overheating, a curtain catching fire, or smoke billowing from a convenience outlet that is dealt with by flipping off a breaker. NONE of those things show up in the statistics. They never get reported.

I agree with your statement “It's comparing the total fire/explosion risk of a boat which uses induction vs. the total fire/explosion risk of a boat which uses gas.” This is exactly the point I’ve been making. I’ve not forgotten and spent a few minutes tracking down the math. I’ve on track to the right search terms. *grin* I found this so far https://link.springer.com/article/10.1007/BF01079631 and the last sentence of the abstract is where I’m headed. Paywall so I’m still looking. The target (financial portfolio risk) doesn’t matter as the math is the same. The term “independent risk” is what I was looking for. Still in work. The math will be a minor slog – lots of statistics and some integral calculus. No differential equations.

Originally Posted by Dockhead

You have not yet shown why eliminating the risk of gas explosions without increasing the risk of electrical fires does not reduce the risk overall.

That’s what I’m working on. It takes real math to demonstrate and I have not done this stuff for thirty-five years. I reviewed it, I made decisions based on it, and I approved the course of large acquisitions based on it but the math is rusty. I don’t want to go off memory.

I also point out that for MOST boats there IS a significant increase in the risk of electrical fire. On your boat with huge continuous electrical loads there is still an increase in risk but not of the magnitude of most boats. We’ll get back to that.

Originally Posted by Dockhead

I can see how if adding induction cooking to a boat without other high current AC loads might materially increase risk of electrical fires. This would not be the case on boats where adding inductive cooking does not materially increase the total amount of the load.

There are other factors than maximum load. Duration and cycle times count also. We’ll talk about that more in a bit when we get to connectors. Promise.

Originally Posted by Dockhead

I gave a list of gas explosions in the UK over 6 years on cruising-sized boats, possibly not a complete list.

And that isn’t relevant either. What would be interesting is to chat up an actuary from Pantaenius and get their risk profile and history. That’s what led to Beth’s BoatUS article and the NFPA table. THAT is a statistically significant data set. Six, or sixty, gas events without the context of electrically initiated fires. In addition the big boom gets the attention but where are the forensic reports to show that an electrical fault did not start a fire and the propane exploded when the fire reached the propane locker? Most people have seen video of train derailments and lorry accidents where fire comes first before fuel or gas tanks explode.

This is why actuaries make such fascinating dinner companions. For any actuaries out there, I’m quite serious. I’ll eat with you anytime. Now about accounting for aggregating independent risks if you could help me out I’ll be grateful.

Originally Posted by Dockhead

The list of cruising-sized boats destroyed, with human injuries, by electrical fires is not an order of magnitude more than this, in fact, I think the list is shorter. In fact, I don't recall a single electrical fire on a cruising boat in the UK with human injury, much less death. Maybe (probably) the wiring is better quality here, and of course 230v is much safer from point of view of fire, and POSSIBLY this makes the whole equation different here than in the U.S.

I don’t think the wiring is better quality. The connectors certainly are. Certainly the higher voltage halves current and there heat to a quarter. No panacea. Start chatting up those Pantaenius actuaries. The ignition temperature of most wood is around 500F (260C). Fiberglass is 600-700F (350-400C) depending on the resin. Balsa cored glass is a nightmare.

Originally Posted by Dockhead

Risk vs. utility of gas systems, which serve only one function, has got to be vastly less, orders of magnitude less, than the risk vs. utility of electrical systems which serve dozens of functions.

First we’ll have to talk about what an order of magnitude is and second I suggest that not all functions have equal utility. There is some subjectivity here. I think cooking has more utility than drying your clothes. You, with a vegetarian raw-dominated diet, may feel differently. In that respect you probably do not represent the general case.

Originally Posted by Dockhead

OK, so if adding inductive cooking does not materially increase magnitude or time domain or magnitude x time domain, or whatever, of the electrical loads, then risk doesn't increase, right? That accords with common sense.

Common sense is rarely common and often not sensible. We’ll break a candidate system down (yours because you’re handy and have lots of stuff). I need to get the risk math numbers in order first and I’m working on that. I don’t want to ask you to take my word for it.

Originally Posted by Dockhead

I think the different types of connectors vary a lot in quality. The cheap U.S. NEMA 1-15 ones are shocking. Especially considering that for a given wattage this connector has to carry double the current. The continental Shuko ones are better -- probably what SWL has, right? But I really like the expensive and bulky UK BS1363 individually fused ones.

I agree with your assessment. Mostly on the basis of wiper contact area, also on the basis of construction specifications, and particularly some of the CE requirements compared to US NMEC. One thing I really like about CE is that hot and neutral are both ALWAYS to be treated as hot. This mandate ripples through the system (lots of double-pole breakers and switches). It brings many safety benefits. I am also fond of the BS1363 related standard of switches at the outlet and fuses in the plug. They are big and clunky and not very attractive. I can live with that. If they thermal breakers in the socket instead of fuses in the plug I’d be even more impressed. Oh – the author of the Fast Company article is not an engineer. He’s got all the right pieces but he doesn’t appreciate all of them—or describe them—properly.

Originally Posted by Dockhead

I do get that from a U.S. perspective dealing with a 110v system and these crappy connectors, using high load AC gear seems much scarier, than it does to us.

Most of the high loads we’re talking about here in the US run off 240VAC 60 Hz. Machts nichts. Differences are consumer grade induction hobs and consumer fan heaters.

Originally Posted by Dockhead

the combustion products in the cabin are unpleasant, and I believe, unhealthy. Condensation is noticeable. This is a significant downside of LPG cooking.

CO and NOx are definitely not good for you. If your gas alarm is not going off (most I know respond to CO as well as propane) there isn’t health there. I suspect the smell is some combination of unburned propane and NOx. Toothbrush. Really. Disassemble the burners and give them a good scrub. Don’t forget the central orifice. By the way, I can tell you how to make a wok burner using the central orifice. There is a YouTube video. You wouldn’t want to do it at sea but it would be fun at anchor.

Originally Posted by Dockhead

I've had boats with two burners, three, and four. I don't cook such elaborate meals, especially not in a seaway, so I am not particularly bothered by the number of burners. But I would like to have space for larger pans for sure. As you say it gets to be a real issue with a large crew so cooking larger quantities of food.

Right. Two decent burners that fit big pots and pans are better (opinion) than four small ones, but four burners help sell boats at boat shows so four burners it is. We pay the price.

Originally Posted by s/v Jedi

It is important to have an induction plate that reduces power by actually lowering amps instead of cycling a full 1,800W on and off. The better units have more settings that don’t cycle and cycle much smaller loads.

Fully agree. These are not the WalMart cheapos.

Originally Posted by s/v Jedi

Our setup is based on decades of experience, not just an opinion floated here.

I’m trying to separate fact from opinion. I wasn’t recommending combo microwaves. I was noting their existence in case they had escaped your notice. Rule on my boats is that it is better to tell someone something they know than to assume they know what they don’t. No argument about multi-purpose devices as a general matter. The Instant Pot comes to mind. That thing makes me rabid. It’s a Jim Jones cult. On the other hand, not everyone has the counter space you have. Remember that “air-fry” is just convection cooking. Same thing with marketing wrapped around it.

Originally Posted by Pelagic

But the fact that an individual "Feels" safer cooking with induction rather than an open flame and explosive gasses, should not be dismissed as being entirely wrong, or without merit.

Correct. Fear is irrational but nonetheless real. If someone were to say “I’m afraid of LPG so I use induction” that is an entirely different matter than “Induction is safer.” The first is self-aware. The second is wrong.

Originally Posted by Pelagic

I don't cook much and admire someone like Auspicious who obviously excels at it and is passionate about keeping that standard up at Sea.

Well thank you. I have mentors and models that keep me inspired. Some are friends like Chef Shawn Harlan and Chef Bernie Meehan. Some are idols like Jacques Pépin or Julia Child. Any time I start feeling cocky I watch

https://www.youtube.com/watch?v=JMA2SqaDgG8

. I do some cooking ahead but at sea I still mostly cook from scratch. That lets me tailor to how the crew is feeling. It’s morale for crew. Some of that is a good meal in stomachs. Some of it, I believe, is crew feeling a little banged around and stressed seeing Dave wedged into the galley making dinner.

Originally Posted by Adelie

DC & AC electrical start 52% of fires per the link provided. I'm not sure I would be willing to describe that as "overwhelming".

As opposed to cooking fuels including alcohol that are buried in other.

Originally Posted by Adelie

For the remainder of DC ignitions the article indicates "Outside of the engine room, there is no single area where most of the remaining DC electrical fires originate. Locations are pretty much equally spread across electrical panels, instrument panel gauges, bilge pumps, lights, and equipment of various types, including air conditioners, windlasses, and winches. Most of these fires could have been prevented if adequately sized, marine-grade wiring had been used and loose or corroded connections had been located and addressed." So using the right cabling and doing some maintenance would alleviate most of the risk.

Which is exactly what I’ve said over and over. The issue is at connections and connectors and high loads through those are have the most risk.

Originally Posted by Dsanduril

While it has nothing to do with induction, standard electric ranges are about 2x as likely as gas ranges to cause kitchen fires and deaths related to kitchen fires (~40/60 split between gas/electric as kitchen fuel in the US, about 20/80 split on fires/deaths). Electric range fires result in even proportionally more fire-related injuries and costs (3-4x that of gas).

https://www.nfpa.org//-/media/Files/...kingTables.pdf

Will be interesting to see how that changes once induction is a large enough percentage of the installed base to be separated out.

Thank you.

[Auspicious]

For the sorts of failures and effects we’re discussing there are two common approaches to risk analysis. Insurance companies have a lot of data and use that information to perform stochastic analysis. Note that they don’t really care about our safety or risk. They care about their financial exposure. If their risk goes up so do premiums until their anticipated exposure is covered. We can still learn from those large data sets as we have from the BoatUS/GEICO numbers and the NFPA table.

Alternatively there is systems risk assessment. We look at the components of a system (or system of systems) and build up to an overall assessment. There remain some qualitative elements even in numerical risk analysis.

Let’s start with AC. We know from experience that connections and connectors are the areas of greatest concern. Assuming wire is properly sized and material selection is appropriate we have chafe, work hardening, and damage to think about; we can set those aside as second order factors. One of the reasons connectors/connections fail is because of disparate materials with different coefficients of thermal expansion. There might be tinned copper wire coming into an aluminum fitting with brass and aluminum screws or mild steel or even silver compression connections. There may be ring terminals. Every use cycle the connection heats and cools and loosens as a result.

We can divide AC loads into categories. Tiny loads like charging phones we can ignore. Moderate loads such as charging a laptop, table lamps, TV, etc. we can probably lump into one “load.” Large loads are the ones that deserve greatest attention. On Dockhead’s boat which we will use as an example there are to my knowledge the following major loads: inductive hobs (two?), clothes dryer, water heater, battery charger, two fan heaters, a kettle, and perhaps a coffee maker. We’ll lump the kettle and coffee maker into one item and call it kettle. The big loads matter most because the heat swing over a thermal cycle increases as the square of the load (I²R). If you don’t accept that connectors/connections are the greatest source of resistance that leads to heat that leads to fire than I’ll just have to give up.

The inductive hobs may be used three to eight times per day. If a hob gets turned up and down three times during preparation of a meal that’s three cycles, thus the higher numbers. For the sort of hob that itself cycles on and off at full power to produce lower power cycles (common in the regularly cited inexpensive hobs) if we assume a ten second cycle and meal prep is generally twenty minutes but a few days per week there is simmering and therefore more cycles over an hour. Dockhead says he eats a lot of raw food so let’s say four cooking cycles per day, mostly short, three big pots of beans per week. Reducing the regular cooking by the beans that’s a bit over 4000 thermal cycles per week.

Clothes dryer has been reported to run 4 to 5 hours per week. My experience with Splendide washer/dryers and their ilk is that cycle times are very long, so let’s call that two cycles per week.

Water heater runs full bore until the water is hot then shuts off. Two generator runs per day have been reported. Water stays hot on most boats for quite a while; usually we run out before it gets cold. So water may be heated only once per day vice twice. Regardless we’re looking at either 7 or 14 cycles per week.

Battery charger will draw quite a bit at first in bulk, less in absorption, and probably doesn’t reach float during generator runs. We can call off to bulk to absorption to off one cycle. We could break that into two but like the water heater the numbers are low: 14 to 28 cycles per week.

Fan heaters really depend on the particular model. Most modern ones have thermostats and so cycle on and off. Dockhead is in cold climes and he has mentioned big dorades and other ventilation so we can really presume that poor things never catch up and say 7 cycles per week each.

Dockhead mentioned drinking rather a lot of tea if I recall correctly. Let’s say three pots a day and use of the ‘keep warm’ function. Then we’ll increase that by 50% to account for an average that includes guests which have also been reported.

We also have three sources: the inverter which is on just about all the time, the generator twice per day, and sometimes shore power. Even with pretty consistent totals we’ll see thermal cycling at the source end due to load management (switching something off in order to switch something else on). A conservative approach would be to simply duplicate the load cycles. There is a time domain for connections/connectors and most of the cycle times are either quite short or quite long so we’ll just bear in mind that there are source connections/connectors as well as load connections/connectors.

All of the large loads are 1000W to perhaps 2000W. While that is a factor of 4 variation compared to the tiny and moderate loads that range isn’t very relevant. We aren’t going to be doing thermal analysis anyway so it’s fair to just call them all large loads.

We haven’t accounted for any other large appliances like blenders or vacuum cleaners. I also didn’t account for the clothes washing cycle as that probably falls into the moderate load category.

We end up with nearly 4300 thermal cycles per week of which just over 4200 take place in the galley and nearly all of which are due to induction hobs.

Note that this does show that there is significant incremental risk associated with adding induction cooking to a boat. Can anything be done to mitigate the risk? We’ve talked previously about regular inspections (IR thermometer) and maintenance (tightening). We could cut off the connections and hardwire large loads, reducing the number of connections by two-thirds. This is common in the US where electrical appliances like cooktops, ovens, and water heaters are often hardwired. Note that we have not quantified the risk of loosening connections and I don’t plan to. The methodology leads to results consistent with the NFPA data which shows electrical fires overwhelmingly start in the kitchen (93% if I recall correctly).

This does say that adding induction cooking or any other additional large load to an existing AC system, even one that is used intensely, does increase risk.

Propane is different. Cycles don’t really matter and to the extent they do may actually improve performance. People have been cooking with gas *grin* for a long time and we know how to do that really well. There are standards based on experience and analysis to promote safety: remotely operated solenoids, installation guidelines, gas alarms, thermal interlocks at burners, transition from pilot lights to spark ignitors. Failure modes for a tank are so improbable as to not be worth considering. Solenoids fail closed (that’s why they draw an amp when in use – so they’ll fail closed – instead of latching). Similarly the thermal interlocks at the burner fail ‘off’ not only at the interlock but at the sensor and in the wiring loom. Gas alarms are designed to fail with a false positive. The significant failure modes are a hose failure and a connection failure. There should be no more than two connections inside the boat and usually there is one. We have to beware of chafe and hose deterioration due to age. Remember propane includes an additive specifically to make it smell pretty bad.

The piece of hose at greatest risk is the exposed hose leading the gimbal. This should be inspected regularly and the opportunity taken to inspect and tighten the connection to the cooker.

I am no more in a position to quantify the risk of propane than of large AC loads. We can again point to insurance data (and the NFPA table) to show that in the real world reportable electrical fire is a more significant casualty than propane fire/explosion.

What units would we even use? Failures per million sea miles? Failures per 100,000 days? Does storage time count? The units would have to be applicable to both induction and gas cooking.

I’ve been through scholar.google.com on risk management, independent risk analysis, numerical risk analysis, and whatever else I can think of until my brain bleeds out my ear looking for what I remember from college P&RP about combining independent probabilities. I vaguely remember it looked like calculating the total resistance of different parallel resistors but I tried that form and it doesn’t work out (the low probability of occurrence dominates). Most of the literature is tools and support methods for strategic risk management and that’s very qualitative, even in financial management (think about that when you look at your retirement portfolio). The risk management in my professional life was mostly stoplight charts. Even with quantitative guidelines based on CPI and SPI there was a subjective quality. This is going on my “science project” list. I do plan to write to the current P&RP professor at my alma mater which may be the most productive.

[slug]

Originally Posted by Dockhead

That makes sense, thanks. Wow, you are knowledgeable



My ring main uses 10mm2 tinned wiring, so sized for 32 amps, although it's a 16 amp circuit. I don't think it was designed that way to save copper, but to increase reliability and to save the number of cable runs, which would have been a massive tangle with a radial system and 10 sockets spread out around the boat.


I am pleased with it. I've had basically zero electrical problems with this boat in going on 11 years of ownership. Some of the wiring is my own -- the boat did not have an inverter when I bought her, and I had to change a number of things to install the Victron charger/inverter. I am thinking about re-doing that wiring as I now know that in those days I was (even) less of an electrician than I am now. Although, it hasn't given any trouble.

Be alert As your boat ages

An absolutely predictable fire scenario is caused by high amperage dc relays

As the relay ages its contacts become pitted ...causing arcing , overheat

These aged contacts can weld themselves into the closed position causing the consumer to run wild and burn up

Starter motors, refer compressors , anchor winches Hydraulic power packs ...

Replace ,inspect all old relays

The enclosed type relays must be thrown out

Open style relays can be inspected . Cleaned and contacts can be replaced

The common , high quality , open relay is made by Albright

https://www.albrightinternational.com/

On the AC side keep an eye on the main shore power relay, breaker and yacht side shore power plug

[DanCan]

Originally Posted by Auspicious

For the sorts of failures and effects we’re discussing there are two common approaches to risk analysis. Insurance companies have a lot of data and use that information to perform stochastic analysis. Note that they don’t really care about our safety or risk. They care about their financial exposure. If their risk goes up so do premiums until their anticipated exposure is covered. We can still learn from those large data sets as we have from the BoatUS/GEICO numbers and the NFPA table.



Alternatively there is systems risk assessment. We look at the components of a system (or system of systems) and build up to an overall assessment. There remain some qualitative elements even in numerical risk analysis.



Let’s start with AC. We know from experience that connections and connectors are the areas of greatest concern. Assuming wire is properly sized and material selection is appropriate we have chafe, work hardening, and damage to think about; we can set those aside as second order factors. One of the reasons connectors/connections fail is because of disparate materials with different coefficients of thermal expansion. There might be tinned copper wire coming into an aluminum fitting with brass and aluminum screws or mild steel or even silver compression connections. There may be ring terminals. Every use cycle the connection heats and cools and loosens as a result.



We can divide AC loads into categories. Tiny loads like charging phones we can ignore. Moderate loads such as charging a laptop, table lamps, TV, etc. we can probably lump into one “load.” Large loads are the ones that deserve greatest attention. On Dockhead’s boat which we will use as an example there are to my knowledge the following major loads: inductive hobs (two?), clothes dryer, water heater, battery charger, two fan heaters, a kettle, and perhaps a coffee maker. We’ll lump the kettle and coffee maker into one item and call it kettle. The big loads matter most because the heat swing over a thermal cycle increases as the square of the load (I²R). If you don’t accept that connectors/connections are the greatest source of resistance that leads to heat that leads to fire than I’ll just have to give up.



The inductive hobs may be used three to eight times per day. If a hob gets turned up and down three times during preparation of a meal that’s three cycles, thus the higher numbers. For the sort of hob that itself cycles on and off at full power to produce lower power cycles (common in the regularly cited inexpensive hobs) if we assume a ten second cycle and meal prep is generally twenty minutes but a few days per week there is simmering and therefore more cycles over an hour. Dockhead says he eats a lot of raw food so let’s say four cooking cycles per day, mostly short, three big pots of beans per week. Reducing the regular cooking by the beans that’s a bit over 4000 thermal cycles per week.



Clothes dryer has been reported to run 4 to 5 hours per week. My experience with Splendide washer/dryers and their ilk is that cycle times are very long, so let’s call that two cycles per week.



Water heater runs full bore until the water is hot then shuts off. Two generator runs per day have been reported. Water stays hot on most boats for quite a while; usually we run out before it gets cold. So water may be heated only once per day vice twice. Regardless we’re looking at either 7 or 14 cycles per week.



Battery charger will draw quite a bit at first in bulk, less in absorption, and probably doesn’t reach float during generator runs. We can call off to bulk to absorption to off one cycle. We could break that into two but like the water heater the numbers are low: 14 to 28 cycles per week.



Fan heaters really depend on the particular model. Most modern ones have thermostats and so cycle on and off. Dockhead is in cold climes and he has mentioned big dorades and other ventilation so we can really presume that poor things never catch up and say 7 cycles per week each.



Dockhead mentioned drinking rather a lot of tea if I recall correctly. Let’s say three pots a day and use of the ‘keep warm’ function. Then we’ll increase that by 50% to account for an average that includes guests which have also been reported.



We also have three sources: the inverter which is on just about all the time, the generator twice per day, and sometimes shore power. Even with pretty consistent totals we’ll see thermal cycling at the source end due to load management (switching something off in order to switch something else on). A conservative approach would be to simply duplicate the load cycles. There is a time domain for connections/connectors and most of the cycle times are either quite short or quite long so we’ll just bear in mind that there are source connections/connectors as well as load connections/connectors.



All of the large loads are 1000W to perhaps 2000W. While that is a factor of 4 variation compared to the tiny and moderate loads that range isn’t very relevant. We aren’t going to be doing thermal analysis anyway so it’s fair to just call them all large loads.



We haven’t accounted for any other large appliances like blenders or vacuum cleaners. I also didn’t account for the clothes washing cycle as that probably falls into the moderate load category.



We end up with nearly 4300 thermal cycles per week of which just over 4200 take place in the galley and nearly all of which are due to induction hobs.



Note that this does show that there is significant incremental risk associated with adding induction cooking to a boat. Can anything be done to mitigate the risk? We’ve talked previously about regular inspections (IR thermometer) and maintenance (tightening). We could cut off the connections and hardwire large loads, reducing the number of connections by two-thirds. This is common in the US where electrical appliances like cooktops, ovens, and water heaters are often hardwired. Note that we have not quantified the risk of loosening connections and I don’t plan to. The methodology leads to results consistent with the NFPA data which shows electrical fires overwhelmingly start in the kitchen (93% if I recall correctly).



This does say that adding induction cooking or any other additional large load to an existing AC system, even one that is used intensely, does increase risk.



Propane is different. Cycles don’t really matter and to the extent they do may actually improve performance. People have been cooking with gas *grin* for a long time and we know how to do that really well. There are standards based on experience and analysis to promote safety: remotely operated solenoids, installation guidelines, gas alarms, thermal interlocks at burners, transition from pilot lights to spark ignitors. Failure modes for a tank are so improbable as to not be worth considering. Solenoids fail closed (that’s why they draw an amp when in use – so they’ll fail closed – instead of latching). Similarly the thermal interlocks at the burner fail ‘off’ not only at the interlock but at the sensor and in the wiring loom. Gas alarms are designed to fail with a false positive. The significant failure modes are a hose failure and a connection failure. There should be no more than two connections inside the boat and usually there is one. We have to beware of chafe and hose deterioration due to age. Remember propane includes an additive specifically to make it smell pretty bad.



The piece of hose at greatest risk is the exposed hose leading the gimbal. This should be inspected regularly and the opportunity taken to inspect and tighten the connection to the cooker.



I am no more in a position to quantify the risk of propane than of large AC loads. We can again point to insurance data (and the NFPA table) to show that in the real world reportable electrical fire is a more significant casualty than propane fire/explosion.



What units would we even use? Failures per million sea miles? Failures per 100,000 days? Does storage time count? The units would have to be applicable to both induction and gas cooking.



I’ve been through scholar.google.com on risk management, independent risk analysis, numerical risk analysis, and whatever else I can think of until my brain bleeds out my ear looking for what I remember from college P&RP about combining independent probabilities. I vaguely remember it looked like calculating the total resistance of different parallel resistors but I tried that form and it doesn’t work out (the low probability of occurrence dominates). Most of the literature is tools and support methods for strategic risk management and that’s very qualitative, even in financial management (think about that when you look at your retirement portfolio). The risk management in my professional life was mostly stoplight charts. Even with quantitative guidelines based on CPI and SPI there was a subjective quality. This is going on my “science project” list. I do plan to write to the current P&RP professor at my alma mater which may be the most productive.

Wow dude, pretty interesting analysis! A lot of food for thought here.