kostal pico 3.6 inverter - wool pulled over eyes?

[kirk]

Hello and good evening - my first post and a question for those in the know.
I'm a 40 year old maintenance tech ( mech' biased) for a large motor manufacturing comapany in the north east.
I've recently had a 4kw pv system installed (16 REC panels and a Kostal pico 3.6 inverter - wired into my DB)
system working great - generated 270kw so far in three weeks.
Soon after installation I clamped my British Gas home energy meter around the incoming live conductor from my inverter to see what sort of power was being produced to help use household appliances according to output.
I found to my alarm that overnight the inverter was pulling around 70w. I checked the inverter to confirm it was in stanby which it was.
I contacted the installer who said it was impossible. after a few days the installer electrician came out to investigate. he tested system and concluded the inverter was in fact pulling 70w - 270miliamps.
the installation company have apparently been in touch with Kostal tech department who have been unable to replicate this fault.
the install company have swapped the inverter and the same fault was evident - 70w.
The electrician told me whilst refitting the old inverter that sometimes inverters will "bounce power back and forth without actually using it"
this sounds like a load of tosh to me and would like some expert advice before i part with my money.
I thought it might be noise fooling my energy meter and have since fitted ferrite cores in the hope of suppressing it - but to no avail.
Any help advice greatly appreciated - my installer and his electrician are visiting tomorrow to collect final payment and convince me that all is well with my inverter.

sorry for the long winded first post - but realy need some advice before paying in full for system

 

[Glen Powell]

This is not always the case, this one always confuses people and I have a job getting my head around it however it is down to active energy and inactive energy (they do have different names but keeping things simple).

The meters from BG and others work on pulses and cannot decide which way, if any, the power / energy is going. There is capacitance in the inverter which has inactive energy, energy that is not being used, however the monitor will pick this up. anywhere between 30w and 100w of inactive energy has been picked up dependent on inverter and wire length.

I at this point would not be too worried about this, if the inverter shuts down completely at night time it will not be using energy, unless you have a monitoring device inbuilt to the inverter then you will see true usage of power added on to the inactive energy or deducted from (dependent on monitoring device).

 

[SibertSolar]

Could it be reactive power rather than active, and the meter is unable to differentiate? I don't think that this is an uncommon occurrence and I'm sure some knowledgeable installers will be along in a mo to give a definitive answer...

 

[Glen Powell]

Could it be reactive power rather than active, and the meter is unable to differentiate? I don't think that this is an uncommon occurrence and I'm sure some knowledgeable installers will be along in a mo to give a definitive answer...

Thanks for that, I wasn't aware I didn't have the knowledge, my statement did say I was keeping it simple

 

[SibertSolar]

lol, I posted my reply before yours (I thought) but yours came out first.....

 

[BruceB]

This is in fact very common. When the inverter is effectively off at night it is a very reactive load (not sure whether inductive or capacitive off the top of my head), so the voltage and current going through it are not in phase and therefore it is not using much power. The cheap power monitors only measure current rather than the voltage as well and therefore assume the voltage in order to calculate the power displayed. There are many threads here and elsewhere about devices like the Wattson Solar reading high at night when in reality not much power is being used. It should be low single figures watts from most inverter specs.

Regards
Bruce

 

[VMan]

its quite common kirk, i think the sparky that came out to you needs to brush up on some AC theory, Inductors and Capacitors.

Check the label of your inverter, i bet the Power factor isn't 1, and its probably a transformer-less inverter.

Its a 'Phantom' current that the meter is detecting, its not actually using anything.

Maybe a look at the following article may give you an idea :
Power factor - Wikipedia, the free encyclopedia
.
If you are still in doubt, turn off all your power circuits except the PV at night, see if your electricity meter is flashing / sp

 

[Glen Powell]

If you are still in doubt, turn off all your power circuits except the PV at night, see if your electricity meter is flashing / sp

God how long you want the poor guy to sit in the dark for ??

 

[VMan]

God how long you want the poor guy to sit in the dark for ??

until he's satisfied...with the meter not spinning that is.

Or perhaps, if competent to, shut down the inverter and leave the DC isolator off during the day, then turn all other circuits off (except PV) so he can the see if the meter is spinning?!?!

 

[kirk]

Thankyou one and all for your input - quite overwhelming for a newbie to get such response!
I have just tried a wee test.
basically sitting in the dark with torch.
meter no showing any usage.
to confirm test I turned on lighting circuit CB and switched on a 60w lamp and timed led flash on meter at around 40secs.
them timed flashes with inverter CB isolated - again 40secs
crude test but seems to show no consumption by inverter.
I feel less reluctant to pay for system now!
many thanks again for your help.
I'll be back asking / offering all kinds shortly - like immersion heater circuits etc etc.
cheers

 

[Earthstore]

Noooo, not the immersion thing again..

 

[kirk]

Noooo, not the immersion thing again..

Yes the immersion thing again. Got a system up and running diverting most of my excess energy to a series of three immersion heaters 500w 1kw and 2kw in 500w steps depending on surplus power. Controlled by an old omron PLC. Just trying to fine tune it now before installing remainder of hardware and building an "airing cupboard" to house hot water cyclinder.