Induction vs Gas Cooking

[noelex 77]

Personally, if well done, I don’t think gas or electric cooking provides much risk. Most of the dangerous failures (fire, explosion etc) seem to be due to poor installation or maintenance.

If you look at cruising boats, there are some terrible electrical systems in particular. One of the big factors here is that many cruising boats were constructed when high powered electrical systems running from the batteries, were not common. These systems have been added, often poorly by their owners or tradesmen in countries where electrical standards are poor.

Gas systems have at least usually been installed at the time of construction, but here many boats are suffering from ageing of these components.

Reliability rather than safety concerns me much more, as providing you have a sound initial installation and reasonable maintenance, the risk of a serious safety issue is tiny. Even following this advice, it is much harder to ensure a reliable system and I think this is where the attention should be focused.

Having both gas and electric cooking options carries a slight extra safety risk over installing just one system, but the redundancy of two completely independent systems both of which work well, increases reliably enormously.

[Auspicious]

Originally Posted by noelex 77

If you look at cruising boats, there are some terrible electrical systems in particular. One of the big factors here is that many cruising boats were constructed when high powered electrical systems running from the batteries, were not common. These systems have been added, often poorly by their owners or tradesmen in countries where electrical standards are poor.

Some poor installations are also added by owners or tradesmen in countries where electrical standards are quite good. *sigh* Aging applies across the board.

Reliability and safety really go hand in hand. This is the downside of approaches like the previously discussed ring topology; there can be a failure that isn’t apparent.

To throw another acronym into the mix there is RMA – reliability, maintainability, and availability. We’re not plowing new ground here either. How often does something fail (mean time before failure MTBF is a common measure), how hard is it to maintain so it doesn’t fail, and how much of the time is it available for use (which addresses mean time to repair MTTR, MTBF, and being offline for maintenance). There is fitness for purpose also which captures things like water tightness and potential for breakage as well as functionality. Opportunities for field repair also get addressed in engineering although in recent years that seems of less interest in consumer products due to buyer priorities.

Opportunities for field repair is a shining point for gas cooking. We went over field repair for both gas cooking and induction cooking earlier in the thread for those so inclined who were late to the party. I came across this today

https://www.youtube.com/watch?v=9WT2PUJ8h74

.

[DanCan]

Why would you spend so much electricity on a washer/dryer when you can do it on solar (also manual ones)? Really a most green, less power hungry lifestyle.

https://m.youtube.com/watch?v=PxweVFPTSpA

[noelex 77]

Originally Posted by Auspicious

Some poor installations are also added by owners or tradesmen in countries where electrical standards are quite good.

.

Originally Posted by Auspicious

Reliability and safety really go hand in hand. This is the downside of approaches like the previously discussed ring topology; there can be a failure that isn’t apparent.

This may be true in some cases, but surely not all.

If a boat owner adds a second inverter to guard against the possibility of the first one failing and leaving him stranded, reliability is improved but not safety.

Certainly a boat owner who installs both an electric cooking system (generator, high powered inverter, cooktop and the associated wiring) and also a gas system (bottles, regulator piping and cooktop) is improving the reliability. He is very unlikely to experience a failure in both systems that will prevent him cooking a meal, but the safety has been decreased by the possible failure of the extra hardware.

[slug]

Originally Posted by DanCan

Why would you spend so much electricity on a washer/dryer when you can do it on solar (also manual ones)? Really a most green, less power hungry lifestyle.

Not bad

Throw out the old rusty propane tanks , rip out the old plumbing , then mount that handy washer in the old propane locker

I like it

A washer is a most valuable piece of equipment

[Auspicious]

Originally Posted by DanCan

Why would you spend so much electricity on a washer/dryer when you can do it on solar (also manual ones)? Really a most green, less power hungry lifestyle.

The elephant in the room is washing sheets and towels.

I'll stick with ammonia-water, a bucket, and a plunger.

In Dockhead's case, and other high latitude cruisers, the little doodad you linked won't fly.

For the record solar is NOT green. That's marketing hype. If you look up where panels come from and where they go you'll see they are not green. Hint: not renewable either.

[Auspicious]

Originally Posted by noelex 77

If a boat owner adds a second inverter to guard against the possibility of the first one failing and leaving him stranded, reliability is improved but not safety.

Certainly a boat owner who installs both an electric cooking system (generator, inverter, cooktop and the associated wiring) and also a gas system (bottles, regulator piping and cooktop) is improving the reliability. He is very unlikely to experience a failure in both systems that will prevent him cooking a meal, but the safety has been decreased by the possible failure of the extra hardware.

Mostly. If adding a second inverter that is ganged to the first (frequency synchronization) as Dockhead describes partial, degraded availability is improved but not reliability per se (a failed inverter is a failed inverter, in the parallel installation the impact is reduced). You might use one hob instead of two, or have to turn more things off in order to cook. Granted this is vocabulary, but words are all we have to communicate with.

You do however raise the issue of system independence in providing redundancy. Although my outside grill is plumbed to the boat propane I carry a couple of 1# propane cans in case a possible though unlikely failure occurs. I can always cook. I have an electric slow cooker (60W on low) that can run off my inverter. My failure plan includes shakshouka. *grin* Oh – and chili. Beans.

[noelex 77]

Originally Posted by Auspicious

Mostly. If adding a second inverter that is ganged to the first (frequency synchronization) as Dockhead describes partial, degraded availability is improved but not reliability per se (a failed inverter is a failed inverter, in the parallel installation the impact is reduced).

Sure, so you would not install a second inverter in this way if the primary goal was to improve reliability. For maximum reliability a second inverter would be independent, capable of running the electric cooking on its own and wired separately. This would improve reliability (especially with a solar based system) by removing one failure point, but it does not help safety. All the extra wiring, switches and electrical connections would decrease, not improve safety.

In the above case there is still only one cooking system (electric), but it is just one example of a functional change that improves reliability but does not help, or even on a practical level decreases safety.

[Dockhead]

Originally Posted by Auspicious

. . . Opportunities for field repair is a shining point for gas cooking. We went over field repair for both gas cooking and induction cooking earlier in the thread for those so inclined who were late to the party. I came across this today .. .

Sure, but why would you ever try to repair an induction hob? It's not meaningful. With a choice between a field-repairable gas system and several disposable induction hobs on board, I would take the latter. Even easy field repairs take time, parts, tools.

I don't think the reliability of the appliances is an issue at all. I broke a resistive hot plate once on board, but after years, broke the glass top. I've never heard of an induction hob just stopping working; I guess MTBF is pretty good. And if you have a couple of backups on board, it's just irrelevant.


It's like thinking about what's inside your mobile phone or IPad. You don't care about field repairing those things; their field-repairability is irrelevant -- you just keep backups -- they are simple and cheap to replace and easy to store.

[slug]

[QUOTE=Dockhead;3147692]Sure, but why would you ever try to repair an induction hob? It's not meaningful. With a choice between a field-repairable gas system and several disposable induction hobs on board, I would take the latter. Even easy field repairs take time, parts, tools.

I don't think the reliability of the appliances is an issue at all. I broke a resistive hot plate once on board, but after years, broke the glass top. I've never heard of an induction hob just stopping working; I guess MTBF is pretty good. And if you have a couple of backups on board, it's just irrelevant.

They do fail

In the picture you can see the cooling fan

The induction electronics don’t like to get hot

Remember this when you install a induction cook top

Ventilation is important

Be alert

[Dockhead]

Originally Posted by noelex 77

Sure, so you would not install a second inverter in this way if the primary goal was to improve reliability. For maximum reliability a second inverter would be independent, capable of running the electric cooking on its own and wired separately. This would improve reliability (especially with a solar based system) by removing one failure point, but it does not help safety. All the extra wiring, switches and electrical connections would decrease, not improve safety.

In the above case there is still only one cooking system (electric), but it is just one example of a functional change that improves reliability but does not help, or even on a practical level decreases safety.

I would gang them. It's true that if one goes down, the whole system goes down, but it's a 5 minute job, or 3 minutes job, to reconfigure the surviving one to run as stand alone. You just flip 3 dip switches.



The efficiency gained here is you get to a higher capacity but you have fallback "limp home" capacity built in. I would do 2x of the 3000VA Victron ones (about 2500 realistic watts, about 5kW surge). That would comfortably run any combination of gear you would normally run off shore power (typicallyl 3.6kW). If you had to use just one, then you have to be a bit more careful, but I have been running my boat on a single 3000VA Victron for 10 years by now, including induction cooking, and it's fine.



Downside of dual ones is the idle power overhead is greater by 10 or 15 watts. If you wanted to live within 3000VA and get rid of this overhead, you might then want to wire them up like Nick's on Jedi.


But none of this is a big deal. These things are reliable enough that even having a backup in a box would be no big deal. If MTBF is 5 years, it's not a big deal to spend an hour or whatever, uninstalling the bad one, and installing the spare. Upside of this configuration is simpler wiring, and less space required. In this case, you might want a 5000VA one as the primary, with a 3000VA one as a spare.


With lithium batteries you will want the extra charging capacity of 2x 3000VA ones -- 140 amps x 24v, so would use all of the capacity of a 3.6kW shore power connection, and would use generator capacity efficiently.

[Dockhead]

Originally Posted by noelex 77

Personally, if well done, I don’t think gas or electric cooking provides much risk. Most of the dangerous failures (fire, explosion etc) seem to be due to poor installation or maintenance.

If you look at cruising boats, there are some terrible electrical systems in particular. One of the big factors here is that many cruising boats were constructed when high powered electrical systems running from the batteries, were not common. These systems have been added, often poorly by their owners or tradesmen in countries where electrical standards are poor.

Gas systems have at least usually been installed at the time of construction, but here many boats are suffering from ageing of these components.

Reliability rather than safety concerns me much more, as providing you have a sound initial installation and reasonable maintenance, the risk of a serious safety issue is tiny. Even following this advice, it is much harder to ensure a reliable system and I think this is where the attention should be focused.

Having both gas and electric cooking options carries a slight extra safety risk over installing just one system, but the redundancy of two completely independent systems both of which work well, increases reliably enormously.

My own feeling is we underestimate the risks with gas. It's a fairly small risk of something very, very bad happening, which is the type of risks that human nature typically underestimates.


We go 20 years without getting blown up and think we're supermen of maintenance.


But I don't care how good we are, or how thorough we think we are, we just can't and don't notice everything. And the more systems there are, the more your maintenance attention is diffused and attenuated.


With gas, the potential screwups are legion. Lord Trenchard I think is an extremely illustrative case, as that was a British military training vessel which was FANATICALLY maintained, maintained by the book. Yet they missed a tiny leak between the gas locker and the hull, and missed a tiny leak in hose. I can assure you that those guys went to their bunks every night thinking -- we're the most thorough people in the business, nothign gets by us, gas is perfectly safe in our hands. Only slobs blow themselves up. They even pumped out the dry bilges every night to get any possible leaked gas out! That's how thorough their procedures were.


Yet, Lord Trenchard was blown to smithereens and a cadet lost a leg, maimed for life. Miracle no one was killed. The explosion blew windows out on Poole Quay. Propane has more explosive power per gram than TNT; propane in you bilge is basically a fuel-air bomb.



I think we should be humble about these things. I try to be really good with my gas system, go over the hoses with manifying glass (literally), replace the hoses every 2 or 3 years, do leak testing (do you have a bubble tester? huh?), carefully check the gas locker for leaks, test my alarms, but at the end of the day, luck plays a big role in it, you just can't catch everything 100%. It took me years to discover that my gas locker drain was basically useless -- had a slight high spot in the line which trapped a little bit of water, enough to block any gas from flowing out. Not visible without a mirror, so I never noticed it The idiot I was -- I tested it by pouring water in it!! Finally realized that is completely useless. Are you absolutely sure that you are that much smarter than the British military, and me? I was just lucky that I never had a gas spill all those years I was sailing around with non-functional gas locker drain.


Yeah, if you're careful, if you're thorough, it's PRETTY safe. But if you think you're smarter and more thorough than everyone who got blown up -- you're kidding yourself.

[mako]

[QUOTE=slug;3147696]

Originally Posted by Dockhead

With a choice between a field-repairable gas system and several disposable induction hobs on board, I would take the latter.

Makes sense as single burner units are so cheap these days, but a lightning EMP will take out the electronics easily enough. So store the spare in a metal box with your other spare electronics.

However for true redundancy we still need gas cooking, so an LP tank up on deck feeding the BBQ works great with pretty extremely low risk.

[Dockhead]

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.

This is really interesting; thanks for taking the time to think about this and write this up.


One way or the other, I'm going to understand a whole lot more about this stuff by the time we've finished this discussion.


I've now enlisted my little brother and niece into this question. My brother is a former math and physics prof who taught graduate-level courses in probability. His daughter is an engineering grad student at Cal Tech and just happens to be in the middle of an advanced course on civil engineering risk management, with a guy who apparently wrote one of the primary texts on the subject, one Prof. Moss. She's going to take our question to Moss this week and I'll let you know what conclusions are reached.



Thanks to everyone for this great discussion!


I will study Auspicious' interesting post in more depth when I have time, but it looks like at first glance we don't actually disagree about the approach any longer. One thing for sure about this which my brother already told me, is that risks associated with independent systems are additive, no magic there, and it looks like Auspicious is now treating them like that, so that would eliminate what looked to me like a fundamental disagreement. If that's really so, then we're really just down to feeding representative data into the correct math.

[kmgiunta]

[QUOTE= I had just totally forgotten how gas sucks, compared to induction! There will be no gas on my next boat![/QUOTE]

If one looks at the issue from a purely practical perspective, Induction could be a viable alternative. For Chefs, as I am, gas wins. Always has, always will. The level of control that exists for gas is incomparable. For us, it's about the food and the art of preparing it, not what is convenient. But, each to his own.