Induction hobs

Robin

Robin

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In my quest for a live aboard motor yacht several have arisen with all electric cooking only As a fan of gas that would be a concern but we now see two similar boats. one with a 2 burner gas plus 2 electric hob installed, the other 2 burner electric hob only. lateral thinking has me asking if the electric hob could be easily switched out with a new induction model hob, which seem not too expensive and I guess come in standard work top cut out sizes? Has anyone done this and is it a good modification? ideally a new hob would run off standard shorepower power connections although the boats concerned both have generators for when off the grid.


NOT sure if this is a question for here or Blue Peter/ PBO forum, but I will try here first!

TIA,

Robin
 
Robin said:
In my quest for a live aboard motor yacht several have arisen with all electric cooking only As a fan of gas that would be a concern but we now see two similar boats. one with a 2 burner gas plus 2 electric hob installed, the other 2 burner electric hob only. lateral thinking has me asking if the electric hob could be easily switched out with a new induction model hob, which seem not too expensive and I guess come in standard work top cut out sizes? Has anyone done this and is it a good modification? ideally a new hob would run off standard shorepower power connections although the boats concerned both have generators for when off the grid.


NOT sure if this is a question for here or Blue Peter/ PBO forum, but I will try here first!

TIA,

Robin
Click to expand...

I've done this - swapped a two-burner gas for a similar-sized induction hob. I wanted to degas the boat completely, and found a domino induction unit that fitted the oe worktop cut-out very nicely. Absolutely no issues whatsoever using the induction hob when on shorepower, but we've noticed that it can be slightly temperamental when powered from the generator - we need to load the generator up a bit to get the hob to work. I've read that induction hobs are particularly sensitive to mains frequency so my suspicion is that my generator (Onan 4kw) is possibly very slightly over the hob's tolerance, and loading the generator perhaps brings the frequency into limits. This is all a bit guess-worky by me, I haven't done anything scientific like putting a scope on the generator output to prove my theory or anything. I'd certainly spec an induction hob again, I like the ease and immediacy of use.
 
I have induction hob running off genset and to cook on it is obviously a delight. However they create quite significant cyclic/harmonic currents: the thing might appear to draw 10 amps RMS say on a normal ammeter but actually there is an overlaid harmonic making the maximum current (seen transiently) somewhat higher. The genset sees/feels the REAL amps and I find the induction hob can load the genset highly and cause it to drop below 50hz even if the RMS current from the genset is within the machine's limit. So, while a genset on my boat is meant to make 90+ amps I therefore make sure the meter is only showing a max of ~70 amps draw if the induction hob is being used, to get some "headroom" for the harmonic current, and if I need more I start the second genset.

Hence I would warn you, especially if fitting a big induction hob (say, 4 rings and 60cm or wider) to make sure you have plenty of headroom in your generator's nominal rating, and do your sums assuming the hob will want say 1.5x its rated current draw.

The above is rudimentary and I haven't studied this deeply. I have had problems on this topic on my boat from VFDs and have seen boats with quite big filters to take the noise out. It's quite a big topic and others might be able to analyse it better. But I think the bottom line is make sure your genset is big enough and don't take the induction hob's current draw at face value and instead apply a factor (say 1.3-1.5x) to the rated current, to allow for harmonics
 
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jfm said:
I have induction hob running off genset and to cook on it is obviously a delight. However they create quite significant cyclic/harmonic currents: the thing might appear to draw 10 amps RMS say on a normal ammeter but actually there is an overlaid harmonic making the maximum current (seen transiently) somewhat higher. The genset sees/feels the REAL amps and I find the induction hob can load the genset highly and cause it to drop below 50hz even if the RMS current from the genset is within the machine's limit. So, while a genset on my boat is meant to make 90+ amps I therefore make sure the meter is only showing a max of ~70 amps draw if the induction hob is being used, to get some "headroom" for the harmonic current, and if I need more I start the second genset.

Hence I would warn you, especially if fitting a big induction hob (say, 4 rings and 60cm or wider) to make sure you have plenty of headroom in your generator's nominal rating, and do your sums assuming the hob will want say 1.5x its rated current draw.

The above is rudimentary and I haven't studied this deeply. I have had problems on this topic on my boat from VFDs and have seen boats with quite big filters to take the noise out. It's quite a big topic and others might be able to analyse it better. But I think the bottom line is make sure your genset is big enough and don't take the induction hob's current draw at face value and instead apply a factor (say 1.3-1.5x) to the rated current, to allow for harmonics
Click to expand...

One 4 zone hob seen on line is a 13 amp plug in one that self adjusts to stay within the 13A limit overall, I wonder if that might be beneficial in reducing genset loading problems with frequency. Purely a guess on my part, but it seems at least that swapping out a manky 2 hot plate electric one for a decent 2 zone induction one would work. After 50 years on sailboats we are well used to just two burners so 4 are overkill anyway. I just like the controllability of gas and cannot stand the electric cooker we have at home in our condo which is so slow as to be useless and I even resort to using a portable camping stove for wok cookery.
 
We have or should I say the French kitchen fitter put one in our appartment in Antibes , wife not too keen , you need special pans. Not sure you know that ! -your normal pans don,t work ,
When we got the boat ,it had a mixed old style 4burner hob ,3 gas one electic .
Like JTB we degassed ASAP
I had it changed after taking advice from this guy -who is a boat sparky .
He swayed us away from induction into a normal ceramic hob ,which he fitted --they all have seemingly std sizes -well in the EU that is .I recall some gobblegook along the lines of JFM and genys .It was not a cost issue it was a working solution least hassle issue .
Wife's happy means any pan works

I,ll post this pic for the benefit of the Antibes and other SoF mob

Names Enzo --carries spares in the van -on call 24/24 for Sunseeker ---Allways gets a fix -sometimes tempory until correct part next day
null_zpsr0t77ric.jpg
 
jimmy_the_builder said:
You need to try an induction hob - it is just as controllable as gas, but just a lot easier to clean! There's no comparison with the crappy old ceramic electric hobs of yore. This is what I put in my boat:

http://www.appliancecity.co.uk/de-dietrich/hobs/dti1041x/product-9713/
Click to expand...

Our boat ones ok
Can,t recall the brand but it responds immediately iirc it's a special "marine " vs --- uses supposedly less W -but I,am no expert and just followed Enzo,s experianced advice .
 
It's pretty tough finding pans that won't work these days - even good copper sets will have an induction plate - if a magnet will stick to the bottom of your, (flat base), pan, you're good to go.
So much better that ceramic, cleaner and just as quick as gas - and safer than both.

Pfino - don't be such a tight bugger and buy you wife a decent set of pans! ;)
 
jfm said:
I have induction hob running off genset and to cook on it is obviously a delight. However they create quite significant cyclic/harmonic currents: the thing might appear to draw 10 amps RMS say on a normal ammeter but actually there is an overlaid harmonic making the maximum current (seen transiently) somewhat higher. The genset sees/feels the REAL amps and I find the induction hob can load the genset highly and cause it to drop below 50hz even if the RMS current from the genset is within the machine's limit. So, while a genset on my boat is meant to make 90+ amps I therefore make sure the meter is only showing a max of ~70 amps draw if the induction hob is being used, to get some "headroom" for the harmonic current, and if I need more I start the second genset.

Hence I would warn you, especially if fitting a big induction hob (say, 4 rings and 60cm or wider) to make sure you have plenty of headroom in your generator's nominal rating, and do your sums assuming the hob will want say 1.5x its rated current draw.

The above is rudimentary and I haven't studied this deeply. I have had problems on this topic on my boat from VFDs and have seen boats with quite big filters to take the noise out. It's quite a big topic and others might be able to analyse it better. But I think the bottom line is make sure your genset is big enough and don't take the induction hob's current draw at face value and instead apply a factor (say 1.3-1.5x) to the rated current, to allow for harmonics
Click to expand...

We fitted an induction hob to Play d'eau (a De Detrich 740v, 4 burner) which is excellent and there's no way we'd change it. BUT, JFM is spot on when he says it can drag the 50Hz below the hob's lowest operating limit, thereby stopping it from working. To ensure we stay within the hob's 'Hertz' limits, I've adjusted the genny's output to be at hob's max acceptable Hertz when it's drawing its minimum current. Hence, as the hob draws more and more current, yes, the hertz lowers but now stays within its operating limits. Success.
 
It sounds like the overload issues will be due to a high power factor of some, maybe all, induction hobs. I wonded if there are any low power factor units around? It's not something usually advertised in the marketing blurb unfortunately.

I also want to convert to get rid of gas, but prefer to operate off an inverter rather than to fire up the genset three times a day, once for each meal. I have a 5kw inverter with a 7kw peak output, so it might be a struggle. I wonder if an inverter would compensate better for the power problems - has anyone had success doing this?

This one looks interesting, it has a max power connection of 3kw and uses a 13A plug, so no new wires to fit. The downside is it won't let you have all elements on full power all at once.:

http://ao.com/product/ci640cba-candy-plan-induction-hob-black-23157-39.aspx
 
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Zing said:
It sounds like the overload issues will be due to a high power factor of some, maybe all, induction hobs. I wonded if there are any low power factor units around? It's not something usually advertised in the marketing blurb unfortunately.
Click to expand...
Yes it is power factor issue. As you say, manufacturers don't quote it and I guess that is because it is mostly irrelevant for domestic installations, but even if they did you would have more pressing parameters than PF when choosing a hob, like size, brand or even colour (mine is white glass!). In any case, I think the PF will vary with the heat setting you select. In practice it often isn't a problem: except with a very small genset you can just turn something else off (like battery chargers or airco) to release enough headroom in the genset's capacity.

Zing said:
I also want to convert to get rid of gas, but prefer to operate off an inverter rather than to fire up the genset three times a day for each meal. I have a 5kw inverter with a 7kw peak output. I wonder if an inverter would compensate better for the power problems - has anyone had success doing this?
Click to expand...
I have not done this and don't know whether it is better for the power factor problem, but I would think that it is. The inverter cares more about RMS current whereas the diesel engine in a generator cares about the peak current due to the fact it cannot use the "headroom" that it has at the bottom of the waveform to compensate for the extra power it has to develop at the top of the waveform. That said, you would be using up more of the 300 (or so) discharges and recharges that your batteries will give you before they die.

This is a bit each to their own but there is sort of national trend among UK boaters of not wanting to "fire up the genset". In other countries (eg Med) folks just fire them up as and when needed, eg to boil a kettle, or leave them running all day
 
jfm said:
That said, you would be using up more of the 300 (or so) discharges and recharges that your batteries will give you before they die.

This is a bit each to their own but there is sort of national trend among UK boaters of not wanting to "fire up the genset". In other countries (eg Med) folks just fire them up as and when needed, eg to boil a kettle, or leave them running all day
Click to expand...

The loss of battery capacity is small because the amount of energy to cook is small and battery costs are pretty minor anyway. It is a price worth paying. I reckon cooking is less than 10% of my at anchor energy use. Battery capacity loss is broadly proportional to battery use. Also, I would have expected to have had many more 30% cycles out of my old lead batteries than 300. More like double or triple and if you have lithium batteries as I now do, you will get several times greater life, into the thousands of cycles.

My genset is a constant burble in the background. Not noisy, but not silent. I'd rather have silence. It constantly demands my subconscious attention. Is it warm enough to load up? Has the sound changed and should I go in the engine room to check? Is it cool enough to shut down? Is it time to shut down, or should it run a bit longer? Check the temps and pressure? Etc.
- With the inverter. No noise, no distractions, just peace.
 
Few years ago, for the home kitchen, we ditched our gas hob and moved to induction. Would never go back to gas. induction if anything is quicker to heat than gas, instantly controllable and much much quicker to clean. Soon find out if a pan works or not. We binned 10+ pans years ago as they would not work

Got one fitted on the new boat, but not used yet. 95% of the time (in the evening) it is plugged into the mains. Not had a boat with an inverter before (only had one boat before) so will see what that is like. i think i only have 2 hob rings anyway.
 
Zing said:
The loss of battery capacity is small because the amount of energy to cook is small and battery costs are pretty minor anyway. It is a price worth paying. I reckon cooking is less than 10% of my at anchor energy use. Battery capacity loss is broadly proportional to battery use. Also, I would have expected to have had many more 30% cycles out of my old lead batteries than 300. More like double or triple and if you have lithium batteries as I now do, you will get several times greater life, into the thousands of cycles.

My genset is a constant burble in the background. Not noisy, but not silent. I'd rather have silence. It constantly demands my subconscious attention. Is it warm enough to load up? Has the sound changed and should I go in the engine room to check? Is it cool enough to shut down? Is it time to shut down, or should it run a bit longer? Check the temps and pressure? Etc.
- With the inverter. No noise, no distractions, just peace.
Click to expand...

we are a intensive invertor power user (2 x 5Kw Victron Quattro onboard, mostly for the Electric stabilizers)
but wouldn't recommand to run a high power unit like hob from the battery's,
we used to have that experience with our electric oven (we still have gass hobs)

in the past, most of our electric appliences (except airco) were on Invertor power,
on a few occasions, our cook used the oven accidently without switching on the genny,
and because of the huge current, and battery's already partially discharged, soon during or just after the use of the oven,
our battery monitor gave alarm... (battery's below 60% of their capacity)

so conclusion, when using such a huge load, you will have to switch on the genny soon after that anyway,
so therefor we changed the wiring so that our oven only can be used with shore or genny power.

same thing with the dishwasher, wiring has also been changed,
was in doubt, because now we can't run the dishwasher anymore from the engine alternators during navigation...

the oven is roughly 2400W , is 10A@230V, is 100A@24V
we have 630Ah @24V (12 x 12V 105Ah) domestic battery capacity (when new, and fully charged)
our alarm / automatic genny start is at 60% charge, so we have max 248Ah available (when new, and fully charged)

you have litium battery's ? which model and how much capacity ?
they are on my wishlist in the furture,
but Lead batt's are so cheap, and so straight forward to install / service, .. that we postponed that upgrade for a few years
 
BartW said:
we still have gass hobs
Click to expand...
That's the connoisseurs choice! :encouragement:
Who cares if the boat risks to explode, when you can enjoy boiling water for a proper dish of pasta in complete silence, while having a sunset apero...? :cool:
 
MapisM said:
That's the connoisseurs choice! :encouragement:
Who cares if the boat risks to explode, when you can enjoy boiling water for a proper dish of pasta in complete silence, while having a sunset apero...? :cool:
Click to expand...

and not to forget a Bialetti during Sunrise in the morning !
 
BartW said:
we are a intensive invertor power user (2 x 5Kw Victron Quattro onboard, mostly for the Electric stabilizers)
but wouldn't recommand to run a high power unit like hob from the battery's,
we used to have that experience with our electric oven (we still have gass hobs)

in the past, most of our electric appliences (except airco) were on Invertor power,
on a few occasions, our cook used the oven accidently without switching on the genny,
and because of the huge current, and battery's already partially discharged, soon during or just after the use of the oven,
our battery monitor gave alarm... (battery's below 60% of their capacity)

so conclusion, when using such a huge load, you will have to switch on the genny soon after that anyway,
so therefor we changed the wiring so that our oven only can be used with shore or genny power.

same thing with the dishwasher, wiring has also been changed,
was in doubt, because now we can't run the dishwasher anymore from the engine alternators during navigation...

the oven is roughly 2400W , is 10A@230V, is 100A@24V
we have 630Ah @24V (12 x 12V 105Ah) domestic battery capacity (when new, and fully charged)
our alarm / automatic genny start is at 60% charge, so we have max 248Ah available (when new, and fully charged)

you have litium battery's ? which model and how much capacity ?
they are on my wishlist in the furture,
but Lead batt's are so cheap, and so straight forward to install / service, .. that we postponed that upgrade for a few years
Click to expand...

A problem with lead is the peukert factor. Under high loads like you describe your capacity may be halved as well as your voltage dropping hugely, so the alarm should have gone off straight away if it reflected real capacity at 60%, but if a simple amp counter it should have taken a while, but you did say you were part discharged. Still a 2.5kw load is a lot for what may in reality (under load and with aged batteries) be a 6.5kwh battery bank. I have 700Ah of lithium (18Kwh when new). Winston brand. High current draw is one thing they really do exceptionally well. I have a similar load as your oven with my washer/drier at about 2kw. Works well and an insignificant voltage drop too.
 
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