Author Topic: Limit 400V three phase current  (Read 4772 times)

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Online themadhippy

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Re: Limit 400V three phase current
« Reply #25 on: December 15, 2024, 01:39:19 pm »
Quote
The generator is a HBM model 9063 7900W Diesel generator.
looks like your genny  is 100w short of a full load
 

Offline Siwastaja

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Re: Limit 400V three phase current
« Reply #26 on: December 15, 2024, 01:47:28 pm »
Oh, so information about "fuses blowing" was bogus; that changes everything. So it seems there is no fuse and probably not even an MCB, but some other kind of switch. It is well possible that this generator switch triggers at much less overcurrent than a fuse does.

Water heater resistor kits are not expensive, instead of trying to limit the power of existing set it might be simpler to replace with a lower-wattage set, if you find one dimensionally suitable for the tank.
 
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Offline DefinitivVair0Topic starter

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Re: Limit 400V three phase current
« Reply #27 on: December 15, 2024, 01:52:06 pm »
Oh, so information about "fuses blowing" was bogus; that changes everything. So it seems there is no fuse and probably not even an MCB, but some other kind of switch. It is well possible that this generator switch triggers at much less overcurrent than a fuse does.

Water heater resistor kits are not expensive, instead of trying to limit the power of existing set it might be simpler to replace with a lower-wattage set, if you find one dimensionally suitable for the tank.

Ok. Thanks for the answer.

But would there be a theoretically suitable way to limit the current flow to something under 16 or would that just not be possible? Just to finally put an end to this thread 😅
 

Offline Siwastaja

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Re: Limit 400V three phase current
« Reply #28 on: December 15, 2024, 02:29:31 pm »
It depends what exactly is the problem - if it's "overload" of some sort, then how that overload switch works. For example, triac dimming could work, but no one can guarantee you that, maybe the switch would still trigger. You could also wire the resistors in series, but if you wire them in series then you are down to single-phase solution and lose probably too much of the power.

A beefy enough 3-phase triac dimmer is probably the simplest option you can try, but it is probably more expensive than a lower power resistor kit, and there is no guarantee of success.
 

Online langwadt

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Re: Limit 400V three phase current
« Reply #29 on: December 15, 2024, 02:46:22 pm »
It depends what exactly is the problem - if it's "overload" of some sort, then how that overload switch works. For example, triac dimming could work, but no one can guarantee you that, maybe the switch would still trigger. You could also wire the resistors in series, but if you wire them in series then you are down to single-phase solution and lose probably too much of the power.

A beefy enough 3-phase triac dimmer is probably the simplest option you can try, but it is probably more expensive than a lower power resistor kit, and there is no guarantee of success.

if the heaters are wired in delta it might be possible to wire them in wye instead
 

Offline DefinitivVair0Topic starter

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Re: Limit 400V three phase current
« Reply #30 on: December 15, 2024, 02:48:09 pm »
I attatched some images on an earlier reply. Maby you can tell what it is because I sure can't.
 

Online themadhippy

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Re: Limit 400V three phase current
« Reply #31 on: December 15, 2024, 02:50:12 pm »
Is this the badger?

https://toolsidee.co.uk/product/hbm-7900-watt-standby-silent-diesel-power-generator-aggregate-P4461.html

If its is seems i was a bit out on being 100w short,from the specs
Quote
Rated power: 6.3 kVA (400) / 5.0 kVA (230).
Maximum power: 7.0 kVA (400) / 5.5 kVA (230).

so at least  1kva short,no wonder its getting upset.
 

Offline DefinitivVair0Topic starter

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Re: Limit 400V three phase current
« Reply #32 on: December 15, 2024, 05:35:15 pm »
Yea thats the one.
 

Offline Gregg

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Re: Limit 400V three phase current
« Reply #33 on: December 15, 2024, 06:37:10 pm »
Your cheapest solution would be to buy another generator rated for at least 10% over the actual load as measured at the heater running on mains power.
The rating of the generator you have are probably quite optimistic at best.
 

Offline Siwastaja

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Re: Limit 400V three phase current
« Reply #34 on: December 15, 2024, 07:39:30 pm »
Your cheapest solution would be to buy another generator

Lower power water heater is less than half of the price of the generator, even if you buy the whole thing new. Of course, question is how much heating power is truly needed. If it's totally tankless heater and OP wants to take hot showers with high flow rate, then they could be disappointed if they go much below 8kW.
 

Offline DefinitivVair0Topic starter

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Re: Limit 400V three phase current
« Reply #35 on: December 15, 2024, 07:48:37 pm »
The 8kW heater was picked because it was the rated power of the heat pump (idk if its the right word in english). But it is basically only used to prevent the underfloor heating from freezing in case of a power outage or heat pump failure. So less wattage would also work.

So basically I will buy another heater or maby disconnect one of the three heating filaments. But thanks for the very helpful replies from everyone :D
 

Offline Gregg

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Re: Limit 400V three phase current
« Reply #36 on: December 15, 2024, 08:26:52 pm »
The 8kW heater was picked because it was the rated power of the heat pump (idk if its the right word in english). But it is basically only used to prevent the underfloor heating from freezing in case of a power outage or heat pump failure. So less wattage would also work.

So basically I will buy another heater or maby disconnect one of the three heating filaments. But thanks for the very helpful replies from everyone :D
Does the same generator also run a circulation pump? If so what are its power requirements?  The reason I ask is that it would be fairly simple to use the generator's 230V 3 phase settings for the heating elements for much reduced power requirements, but it may not work well with the pump.
(edit:) Disconnecting one of the heating elements will lead to major phase imbalance in the generator. 
« Last Edit: December 15, 2024, 08:30:03 pm by Gregg »
 

Offline DefinitivVair0Topic starter

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Re: Limit 400V three phase current
« Reply #37 on: December 15, 2024, 08:45:31 pm »
The generator itself does not run a circulation pump. Also, I believe the 230V is single phase. But wouldn't it theoretically be possible to use a 3-phase transformer to step down the 400V to something like 200V but now with higher amperage? (Should result in about 31A)

But on the other hand, a lower power heater is probably cheaper and easier to work with than a giant 3-phase transformer
« Last Edit: December 15, 2024, 09:11:43 pm by DefinitivVair0 »
 

Online themadhippy

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Re: Limit 400V three phase current
« Reply #38 on: December 15, 2024, 09:09:23 pm »
Quote
Also, I believe the 230V is single phase. But wouldn't it theoretically be possible to use a 3-phase transformer to step down the 400V to something like 20pV but now with higher amperage? (Should result in about 31A)
wont do any good as youve still only got 7kva  available from the generator ,
 

Offline Gregg

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Re: Limit 400V three phase current
« Reply #39 on: December 15, 2024, 09:14:17 pm »
I just assumed from the limited specs of the link provided that the generator might be 400/230V 3ph switchable.  It depends on how the thing is wound; you would know better than me as you can look at it. 
If the heating elements have separate connections, you could connect two of the elements in parallel and power them with the 230V single phase.  A real nightmare to change over from mains 3ph when needed.
Isn't the water you are heating treated and have anti-freeze for use in an area where freezing is expected?
 

Offline DefinitivVair0Topic starter

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Re: Limit 400V three phase current
« Reply #40 on: December 15, 2024, 09:25:21 pm »
The generator can be switched between 400V and 230V. I cant look at the manual right now but since there are three seperate "fuses" for 400V but only one for 230V, my guess is that 230V runs on a single phase. Also since its more or less for personal and not commercial use, most 230V devices that you plug in won't handle 3-phase. (For 230V its just a standart wall outlet socket)


Also, to be totally honest here, I am not the one who built the whole heating construction. I am just the one writing the post. Weather its for the underfloor heating or for normal water supply or whatever. Its a heater for keeping some kind of water from freezing. And this will be accomplished with a lower power heater.

Btw., will a lower voltage like 230V even work or will the resistance of the heater filaments just be to high?
 

Offline Siwastaja

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Re: Limit 400V three phase current
« Reply #41 on: December 16, 2024, 07:54:25 am »
The generator can be switched between 400V and 230V.

When looking at the generator specs, I was already wondering what that even means. 3-phase it outputs is both 400V and 230V at the same time. 400V between phases, 230V between phase and neutral. So maybe it's just marketing speak and there is no switching of anything?

If there really is something to switch "between 400 and 230",  it can only mean two things:
Going from 400/230 to 690/400, or to 230/132V. Latter would be extremely useful for your need. But see the manual if it explains what this voltage switching means. But I would put my money on their "voltage switching" claims being bogus.

One viable option, if you don't want to buy a new smaller heater, is to rewire two of the resistors in series and run it using a single phase:
8000W / 3 / 230V = 11.59A
230V/11.59A = 19.84 ohm (expected resistance of a single element, you can verify this with multimeter)
Two in series, current = 230V / (2*19.84ohm) = 5.80A, power = 5.80A*230V = 1334W

I'm quite sure keeping the circulation pump running and heating at 1300W is sufficient to prevent freezing. Unless you have some record-low -25degC sustained over a week or something.

And then again, if you do this, a smaller single phase generator would be well sufficient. Something rated to 2000W continuous.
 

Offline DefinitivVair0Topic starter

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Re: Limit 400V three phase current
« Reply #42 on: December 16, 2024, 08:07:05 am »
Thanks for the answer,
I will definetly take a look at the manual.

Also, J have a feeling that my memory is wrong and it was in fact 230V 3-phase judging from the outlet. But I can't check on it until thursday so I'll keep this post updated once I checked it.
 

Offline Siwastaja

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Re: Limit 400V three phase current
« Reply #43 on: December 16, 2024, 08:29:05 am »
230V 3-phase judging from the outlet

Terminology with 3-phase is confusing. 3-phase, with neutral available, always has two voltages 1.73x apart from each other. When someone says 400V 3-phase and someone else says 230V 3-phase, they probably mean the exact same thing!

There are exceptions, e.g. IIRC in Norway neutral-less (3-wire, phases only) 3-phase 230V is available. So this is lower voltage, but absence of neutral prevents getting 132V out of it. Maybe the switching options refers to this kind of relatively rare "delta-only" system. If the generator can be switched to do that, and still provide neutral, that would make it a special/rare 230V/132V system, which would be perfect for your needs.

But Germany is 400V between phases and 230V between phase and neutral.
« Last Edit: December 16, 2024, 08:30:43 am by Siwastaja »
 

Offline Wolfram

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Re: Limit 400V three phase current
« Reply #44 on: December 18, 2024, 01:17:35 pm »
If the generator is 400 V star with a neutral, and the heater is star-wired using 230 V elements, then you have another option as well. Just wiring up one of the elements between L and N will reduce the overall power to 1/3, but still draw the same current from the phase in use, potentially leading to problems. Disconnecting one of the phases between the generator and heater will reduce the power to 1/2, and draw current between two phases. Those two phases will then be loaded to sqrt(3)/2 times the current in the 3 phase case, which might be enough to save you here.
 


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