RCD didnt trip.........

[kayak]

Morning all.

 

I have a bit of a strange query regarding a Victron multi 3000/24. I have had it installed and it has worked faultless for nearly a year in both inverter and charger only mode. It has ran the kettle, radio, battery charger (power tool) water pumps etc, etc with no problems. However, last week i plugged in my new Bosch compound mitre saw (240v). I have used this at home with no problems but when i first pulled the trigger when pluged into a 240v socket on the boat all the power to the other sockets went off. There was nothing else drawing power other that a radio. The saw is only about 1400w. The strage thing was that it didnt trip the main RCD in the consumer unit or the breaker for that particular ringmain. What it did was to shut down the inverter. By the time i had opened the cupboard door i could see the inverter looked as though it had been switched off but the switch was still in Charger only mode. Whilst i looked on, the lights started to flicker back on as they would normally when switching it on at the begining of the weekend (still only there at weekends).

 

Any ideas as to what happened? I was a little concerned at first id blown the inverter up but since then it has worked fine. In the past ive had the kettle boiling and a piller drill or router on at the same time and its been fine. Just puzzleing how if anything was going to trip it wasnt the RDC or the breaker.

 

Any help, advice or ideas appreciated.

Kayak.

[barge sara]

I would guess that despite the saw only being 1400Watt, the starting current was much higher and beyond the 3 KW capacity of the Victron unit.

Hence the shut down and restart.

 

Edit to say:

Fridges and circular saws are notoreous(?) for high starting currents.

Edited May 21, 2010 by barge sara

[Gibbo]

I would guess that despite the saw only being 1400Watt, the starting current was much higher and beyond the 3 KW capacity of the Victron unit.

Hence the shut down and restart.

 

Edit to say:

Fridges and circular saws are notoreous(?) for high starting currents.

 

Seconded. Rule of thumb for power tools is a start up current of 3 to 5 times rated current. I used to have to try to start up big power tools by pulsing the trigger.

[ditchcrawler]

I would guess that despite the saw only being 1400Watt, the starting current was much higher and beyond the 3 KW capacity of the Victron unit.

Hence the shut down and restart.

 

Edit to say:

Fridges and circular saws are notoreous(?) for high starting currents.

Also what was the state of the batteries, did the heavy load make the DC voltage dip to low.

The RCD should only trip if the saw was faulty to earth and the main circuit breaker is slow enough to allow for the start current surge

[kayak]

I would guess that despite the saw only being 1400Watt, the starting current was much higher and beyond the 3 KW capacity of the Victron unit.

Hence the shut down and restart.

 

Edit to say:

Fridges and circular saws are notoreous(?) for high starting currents.

 

Oh, I did wonder if it could be something like that. I hope it will start the fridge and freexer up though when they go in.

 

But just a thought, it was in charger only mode so I would have thought that it would let more than 3kw through it when its not acting as an inverter? (not sure about that though)

 

Kayak.

[WotEver]

Oh, I did wonder if it could be something like that. I hope it will start the fridge and freexer up though when they go in.

 

But just a thought, it was in charger only mode so I would have thought that it would let more than 3kw through it when its not acting as an inverter? (not sure about that though)

 

Kayak.

Ahhh... so you were pulling your power from Shore Power? If that's the case, then it probably went into protective shut down when it saw a huge induced spike on the incoming mains. I think we've had a thread about that recently

 

Tony

[barge sara]

But just a thought, it was in charger only mode so I would have thought that it would let more than 3kw through it when its not acting as an inverter? (not sure about that though)

 

We have a pair of 3000/48s and I've yet to fathom just what they do to the 'pass through' mains supply when in charger only mode.

 

3Kw should be plenty to start your fridge and freezer.

[nb Innisfree]

I think shorepower or a genny is switched through directly via a relay, so it seems to me that shorepower cut out for some reason which would cause Victron to disconnect shorepower then reconnect and ramp up the charge after the prescribed time. I have run a 1.5 kW circular saw off our 24v Multiplus 3 kva, no hesitation and regularly use a 3 kW instant boiler, takes it over the nominal 2.5kva and into the 'red' but no problem, of course it's not the same start up surge as the saw.

[Grace and Favour]

I would guess that despite the saw only being 1400Watt, the starting current was much higher and beyond the 3 KW capacity of the Victron unit.

Hence the shut down and restart.

 

Edit to say:

Fridges and circular saws are notorious for high starting currents.

 

Aye - - ideally you should always use power tools with a 'soft start' facility to avoid the initial spike (though they are dearer of course!)

[Justme]

I think the amp pass through limit was reached.

 

I regularly use my Rage Pro 3 saw (2000w) with my air (1500w) compressor running on my 12v 3000 120 Victron. If both are on then the saw starts slightly slower. I try to not use the saw if the compressor is already on. Saw cut times are only a few seconds at a time.

 

The Victron has a 6kva peak start up load if I remember right. It handles them both in inverter or pass through mode & I have the pass through set to the full 16amps.

 

What is yours set to?

 

Is it set to protect the weak shore power?

[kayak]

I think the amp pass through limit was reached.

 

I regularly use my Rage Pro 3 saw (2000w) with my air (1500w) compressor running on my 12v 3000 120 Victron. If both are on then the saw starts slightly slower. I try to not use the saw if the compressor is already on. Saw cut times are only a few seconds at a time.

 

The Victron has a 6kva peak start up load if I remember right. It handles them both in inverter or pass through mode & I have the pass through set to the full 16amps.

 

What is yours set to?

 

Is it set to protect the weak shore power?

 

To be honest I have no idea what it is set to.......i'll have to ask the guy who installed it. If is has been set to protect a "weak" shore power then it need ajusting because the shore power is more thatn capable of running everything. Before the electrics were installed on the boat everything was ran from an extension lead from the shore supply.

 

K.

[Paul Coleman]

Aye - - ideally you should always use power tools with a 'soft start' facility to avoid the initial spike (though they are dearer of course!)

 

You can make your own soft start extension lead for powertools from a suitably rated NTC thermistor. The idea is that the thermistor has a relatively high resistance when cold, which drops as it warms up. If you put one in series with your power tool, the initial high resitance soft starts the motor and seriously limits the inrush current but passes more current as it warms up allowing the motor to operate at design power.

 

I use one to start a 1500w saw on an 1800w inverter. It works a treat! The only down side is that you need to leave the thermistors to cool down before restarting the saw, else you end up tripping the inverter. The saw is actually nicer to use as it doesn't try and jump out of your hand when you start it. Gives me a fright if I use it on mains power now!

 

I used four SG27 thermistors from RS in a series parallell array to handle the current.

Edited May 24, 2010 by Paul Coleman

[Radio-Ga-Ga]

I had exactly the same problem when I was fitting out (the only time I've had shore power) my 1600 watt saw would shut down the multi-plus even tho higher wattage tools worked ok, after about 30-40 seconds the inverter would re-start. Victon suggested turning off the UPS function. No idea how, but it fixed it!