Powering a Bosch induction hob with two unsynchronised 240V feeds

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davelondon

Joined Mar 30, 2021
21
Note: I figure this is probably not exactly the right forum for this question - If anyone knows a better place to ask, let me know.

I'm building an expedition vehicle with a large 60kWh, 48V DC electrical system. I will use Victron equipment to convert the 48V DC to 240V AC. I'd like to use this Bosch PVQ731F15E 4-burner induction hob in the kitchen. Here's some background:

  • An induction hob requires huge 240V electrical input.
  • The Bosch PVQ731F15E can draw up to 7.4kW.
  • I’d like to use two independent inverters so I have redundancy in the event of a hardware failure.
  • The zero load draw of an inverter is significant, so I’d like to just use one inverter for most loads (washing machine, dishwasher, single burner hob), and only turn the second inverter on when we need to use the full 4-burner hob.
  • Using two Victron Multiplus inverters in parallel mode is possible, but fiddly to set up, both go offline if one fails, and far too fiddly to switch between parallel / single mode (e.g. reconfiguring firmware etc.)
  • Additionally, the new lightweight 6kVA RS range (Multi RS Solar, Inverter RS Smart Solar, Inverter RS Smart) do not support parallel operation.
  • The hob supports two modes of operation (see here page 4):
    • Panel 19 shows 3 phase operation, where phases L2 and L3 are connected to two separate induction elements.
    • Panel 21 shows single phase operation where both elements are connected to the live.

Screenshot 2022-11-04 at 10.23.58.png

I guess from this that ports 2 and 3 connect to induction elements on separate sides of the hob - if they were connected to two elements under each burner, then I think destructive interference between the phases would reduce the overall power? I'd love your opinions on this. If I’m right, then connecting ports 2 and 3 to separate (unsynchronised) mains circuits (from separate inverters) should work.

My plan is to have two Victron inverters from the RS Solar (6 kVA) range. I will have two modes of operation:

Normal mode.
Only one inverter is powered on. It is connected to the hob in single phase mode (e.g. panel 21). It will only be able to supply ~5kW. This will be fine for normal usage of the hob when only using one or two burners.

Boost mode.
When cooking a large meal, we will start the second inverter, and change the hob connection so ports 2 and 3 are connected to separate inverters (e.g. panel 19). The two inverters will be able to supply all the power the hob needs.

A few worries:

  1. The whole thing will explode?
  2. The hob will just show an error and not work?
  3. Somehow the unsynchronised AC feeds will interfere with each other and boost mode won't work at full power?
  4. In normal mode, perhaps the hob will overload the inverter? There's a Power management function (see here page 21) to prevent this, but changing the settings every time I switch between normal and boost mode isn't something I'd want to do. I hope that with just a 1 or 2 burners on, this won't be a problem...

I'd appreciate some advice!
 
Last edited:

strantor

Joined Oct 3, 2010
6,335
If this were my project and I wanted to go about it the way that you want to go about it, then I could read the manuals for inverter and cook tops several times and perform several experiments to answer the questions you've asked. If I had all the hardware to play with, and all my tools/test equipment, it would only take a couple of days.

Trying to do it vicariously through you however, it would take much longer. That's no criticism of you, just a fact. And when you consider that this happens in a public forum with many people offering conflicting advice simultaneously, it becomes impossible.

My advice is to find a simpler solution. It sounds like you will only rarely need the functionality you described (for large meals). So why not install only a 2-burner inductive cook top? You can have another two portable/tabletop inductive hotplates that you store in a cabinet and bring out only for large meals. You can plug these into your second inverter. This will free up counter space for you too; no doubt counter space will be prime real estate in a mobile domicile. The separate hotplates would give you flexibility. They could be placed on a picnic table outside for example. This would also greatly expand your layers of redundancy. Many things would need to fail before you're left entirely unable to cook with electricity.
 

bassbindevil

Joined Jan 23, 2014
639
Induction hot plates may not be very reliable, if I can believe the Amazon reviews, so that's another argument in favor of using two 2-burners.
 
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