Solar Pv Fuse Trips Randomly

[slysi16v]

Hoping somebody here may be able to help me.

We have a 2kw solar pv installation that has been up for just over 2 years. When it was first installed it was fine and no problems for several months, then the fuse protecting the solar in the distribution board started tripping at random intervals. We had the installers back in several times to check the system but they could never find a fault, all they seemed to do was increase the rating of the fuse which lessened the frequency of trips. It currently has a clipsal 32A (mcb?) fitted but still trips. 

Part of the 'deal' from the installers was a 'free' VPhase voltage regulator. This was out of stock when the panels were fitted and wasn't fitted until some months after the initial install of the panels. In retrospect it seems possibly more than a coincidence that the problem didn't arise until the VPhase was fitted as the fuse does seem to trip around the same time as when the VPhase cuts in (you can here it switching on which then prompts me to check the solar)

So the real question is, has anyone come across this problem before / does it sound possible for the VPhase to cause this / any other ideas?

Unfortunately the installer went bust some time ago so I am on my own with this. My brother-in-law is a qualified electrician and has had a quick look but can't find anything obvious but has had no experience with solar but did express concern about the size of the fuse.

Any input appreciated thanks.

 

[Doc Hudson]

Welcome to the forum, as you say just increasing the rating of a protective device without establishing a cause does sound rather amateurish as the installation should have been designed correctly to start with. (possibly not surprising the installers went bump?). Can you remove the V-Phase out of the system for a while and see how the solar performs for a few months, (or your brother-in-law assist with disconnection). I don't think it will increase your bill very much as I am not convinced that V-Phase offers vast savings for a domestic installation anyway. Most high power circuits, where big consumption saving could be made, cannot be connected through the typical V-Phase unit. If we can get one of the admins to adjust your settings, can you get a photo of your set up posted as this may be of assistance to other members to contribute.

Doc H.

 

[binky]

the solar should be connected to the house before the V-Phase unit, not after it ie at the consumer unit, which is what it sounds like you have, otherwise its fighting the V-Phase to output to grid. The combination of technologies is relatively new, so problems that arise are little known. Still don't see why its tripping MCB for the solar though, but I've not had much experience of putting the 2 together. I have, however, read many articles on how to install VO units that claim to be solar compliant - I was looking at using VO gear as a form of surge protection for solar systems,  so first port of call check it all been installed correctly.

 

[ProDave]

I'm very sceptical about units like the V Phase, they are very close to falling into the snake oil category if you ask me.

They work by reducing your voltage a bit to reduce your power consumption.

Well that may save you a bit on lighting (at the expense of the lights being a bit dimmer) but any heating appliance or cooking appliance will just run at a lower power, so will take a bit longer to heat up whatever it's heating. So lower power for longer = the same No of KWh. you cannot change the laws of physics.

That asside, I would suggest the v Phase is wired wrong.  the MCB for the solar PV should connect to that, and that alone, and a 16A mcb is correct for a 2KW Pv system.

So I would get an electrican in to disconnect the V Phase unit, and then re connect it properly, without it connecting to the MCB that is fed from the solar.

While there, I would get him to also check that the Solar PV's mcb does NOT feed into a bank of mcb's protected by one RCD, another VERY common mistake seen regularly.

 

[slysi16v]

Thanks for the replies,

As it stands the VPhase is connected to the main lines before the meter and the solar is connected to the consumer unit ie after the meter.

Oddly its only the solar that trips, never any other consumer even though they are all on the same unit.

 The suggestion of disconnecting the Vphase sounds sensible as it will prove one way or another if its the problem, I will have to get the Bro-in-law down to do this so it could be a week or so. I do wonder myself about the benefits of the Vphase as I'm sure something like a freezer will need to run longer to achieve a certain temperature if its working at a lower voltage so it sort of seems self defeating?

Thanks for the interest and I will re-post as soon as anything changes.

I'm very sceptical about units like the V Phase, they are very close to falling into the snake oil category if you ask me.

They work by reducing your voltage a bit to reduce your power consumption.

Well that may save you a bit on lighting (at the expense of the lights being a bit dimmer) but any heating appliance or cooking appliance will just run at a lower power, so will take a bit longer to heat up whatever it's heating. So lower power for longer = the same No of KWh. you cannot change the laws of physics.

That asside, I would suggest the v Phase is wired wrong.  the MCB for the solar PV should connect to that, and that alone, and a 16A mcb is correct for a 2KW Pv system.

So I would get an electrican in to disconnect the V Phase unit, and then re connect it properly, without it connecting to the MCB that is fed from the solar.

While there, I would get him to also check that the Solar PV's mcb does NOT feed into a bank of mcb's protected by one RCD, another VERY common mistake seen regularly.

Thanks for this,

I had just posted about getting the Vphase disconnected to see if this is the cause so it looks worthwhile getting the whole thing checked out to see if its connected properly.

Your comments about the laws of physics have gone through my mind on several occasions so if the Vphase proves to be the  problem it may well just be left disconnected, time will tell.

Thanks once again, I will keep this updated.

 

[SPECIAL LOCATION]

How are your solar & VPhase connected????

http://www.vphase.co.uk/How-It-Works/Solar-PV-and-VPhase

What model Vphase unit do you have?

i.e. from here:-

http://www.vphase.co.uk/getattachment/Trade-Zone/Info---Downloads/HS12059_VPhase-Instruction-Manual_E.pdf

see page 5....

The VX1 must NOT be connected to circuits containing embedded generation, e.g.

solar PV or micro-CHP.

Circuits that must NOT be connected to the VX1:

• Electric shower circuit.

• Immersion heater.

• Dedicated electric cooker circuit.

• Circuits feeding high power tools.

• Circuits where individual loads exceeding

13A rating will be connected.

Guinness

 

[binky]

arrangement should be solar into meter tails, after leccy meter, but before v-phase and house CU, so you will need a mini CU for the solar system tapped into meter tails via meter tail blocks. Does sound like an AC fault on the solar system though, like a damaged cable, or crap piece of wiring in AC isolator or the inverter itself. Get brother in law to wire it properly. Would leave V phase in situ though, whilst Pro D may believe it's snake oil, they do work, especially the industrial units we have fitted, bit like putting your foot on the accelerator in your car, you can accelerate gently to 80mph, or floor it and use more fuel. Either way you get to 80mph but one method is more controlled ie efficient. Actual saving is far more like 8-9% than the 15% they used to claim, but they do also protect everything electrical in the house against voltage spikes, which in turn extends their lives, but its very hard to put a figure on how much by!

 

[SPECIAL LOCATION]

whilst Pro D may believe it's snake oil, they do work, especially the industrial units we have fitted, bit like putting your foot on the accelerator in your car, you can accelerate gently to 80mph, or floor it and use more fuel. Either way you get to 80mph but one method is more controlled ie efficient. Actual saving is far more like 8-9% than the 15% they used to claim, but they do also protect everything electrical in the house against voltage spikes, which in turn extends their lives, but its very hard to put a figure on how much by!

VPhase suggest their device will not protect against spikes..?

"it will not offer protection for the home against transient surges and power spikes."

http://www.vphase.co.uk/Products/FAQs/Does-VPhase-offer-surge-protection

IMHO any real savings have to many variables to predict accurately what any home will get without going through the process of actually installing a unit.. 

A report published in 2011

"Report No: 6508

Energy Saving Trial Report for the

VPhase VX1 Domestic Voltage

Optimisation Device"

https://www.ofgem.gov.uk/ofgem-publications/58457/energy-saving-trial-report-vphase-vx1.pdf

only gave a 3.8% to 6.6% saving over a sample of differing types of property

in some cases NO saving!

Around page 32 of the above report.. 

8.7: Calculated savings varied from -4% to +19%. However, results from individual sites

should not be considered in isolation without reference to confidence limits. For a few

sites, energy saving results were negative.

8.8: The mean saving in electrical energy consumption, attributable to the VXI devices, was

determined from the trial as 5.2%, with a confidence limit on the mean of ± 1.4%.

Industrial is a different ball game to these domestic units, not true like for like comparison..

especially as the domestic ones can actually switch out under high load conditions to prevent overheating... 

The VX1 uses thermal management techniques and innovative design to provide high output

capability in a relatively small unit. The device is able to ride-out short-term high power

demands by allowing the temperatures of key components to rise for short periods. At a

predefined temperature the device cuts itself out-of-circuit (referred to as ‘bypass’) in a

controlled manner, enabling it to cool, returning to its active state when demand has

reduced.

An example of this is the occasional use of several appliances at once –boiling a kettle at the

same time as operating a washing-machine or tumble-dryer.

seems to mean that at the point you hope to get most savings it has switched itself off for a rest!!!!

 

[ProDave]

seems to mean that at the point you hope to get most savings it has switched itself off for a rest!!!!

But they cite as an example, boiling a kettle while the tumble dryer is on.

As both those devices work by heating something, then any "saving" in power will just take longer to dry your clothes, or longer to boil your kettle, so no actual saving is there?

 

[binky]

I get the thermal mass argument and wouldn't disagree with that.

As for surge protection, VO units aren't designed to do that as primary function, so manufacturer would be silly to claim this function, but as they sit in the meter tails, its a bit is hard to avoid