DC Isolator between Solar panels and Hybrid Inverter

Hi,

I have 14 panels on 2 strings that are connected directly to my 5kw Hybrid inverter without a DC isolator between them (I can't see one anyway), is this correct or should there be an isolator?

Many Thanks

Mine hasn't got isolators on the strings, just a common one to the inverter.
Not really sure why you would want to have one if I'm honest. (Open circuit voltages and all that!)

Mine is the same. I asked the installer about this and he said there is a DC isolator in the inverter. There is a black knob/switch underneath, left of middle that you can rotate to an on or off position, this is the DC isolator. That’s what I was told anyway.

Yes you are right - I'd forgotten about that one!

c_squared Thanks, that is what I had figured as I'd seen that on the underside of the inverter, but having seen/heard other things I was starting to question it!

dm0806 The Givenergy schematics all show a separate DC isolator for each string before the inverter. I have two strings on each inverter and they pass through an external DC four pole isolator before the inverter isolator. I guess the thing is that if you needed to change the inverter at some point, it would be safer to have isolators external to the inverter connections so it would be isolated from all energy sources while you were working.

That is how mine is wired to the loft inverter - a separate isolator for each string prior to the inverter. Then there is an isolator between the batteries and the AC3.0 in the garage.

I have 2 strings into a 5kw hybrid and both have a DC isolation switch prior to the inverter.

As already mentioned the GE circuit diagrams have DC isolation on the PV strings so it could void any warranty as the installation isn't as per the manufacturers specification.

It would seem that strings require a ' readily accessible disconnection device shall be provided to isolate individual strings'. Source PV in buildings, guide to installation of PV systems, 2nd edition.

If it helps, I don't have separate DC isolators for the incoming PV strings and just use the common DC isolator on the Hybrid inverter. I too was concerned at first after seeing the GE schematics but it turns out its not an issue. 2 weeks ago I had two assessors from MCS to evaluate my system for my installers MCS renewal, and they said the DC isolator on the hybrid by itself was completely fine...... in fact they said that separate DC isolators can be a little unreliable sometimes?

BoeingBoy Seems to be a wider concern if an On/Off switch can be considered unreliable!

One of the two DC isolators failed on mine recently. The kit was installed at the beginning of the year, sonit was effectively brand new. Isolators aren't really built for DC so they tend to arc, which might explain why they can fail so quickly.

Zakalwe Isolators aren't switches (although they do) and are intended to be operated without any load passing through them. DC will arc more than AC across a switch but should operate correctly for however many cycles they're designed for. If you follow the startup/shutdown procedure for the Givenergy systems, they say to open the external DC isolator before the inverter isolator. I'm guessing that they say this so that their internal isolator is less likely to fail.

Thinking about it, it would be useful if the remote control panel for the inverters had a command/switch to shut it down electronically so that all inputs (AC and DC) were carrying no load before you went to the plant to isolate it physically.

Tim it kind of does, remote control > Inverter Max Output Active Power Percent > 0%
Essentially pauses the entire inverter.

Tim
"Isolators aren't switches (although they do) and are intended to be operated without any load passing through them. DC will arc more than AC across a switch but should operate correctly for however many cycles they're designed for."
And yet, it still failed.

If a separate isolator is fitted, it will/should be a DC isolator. They are readily available from electrical factors for about £30+VAT including the box.

[https://www.cef.co.uk/catalogue/products/1933711-16a-4-pole-450v-dc-surface-mounting-isolator-ip65]

hoggy (or anyone else for that matter) do you know if the hybrid inverter would be able to detect whether the battery was electrically connected? The reason for asking is that the isolator between one of my inverters and it's battery has tripped three times in the last 48 hours. I've emailed support@givenergy.com to ask them to look at why the battery would only charge to 90% yesterday and then to 88% today (battery calibration will probably fix). The isolator tripped quite some time after the battery stopped charging. I've also emailed my installer asking him to check out the system and replace the isolator if that's the cause of the problem. However, if I wasn't still "checking" the portal several times a day, I wouldn't necessarily have noticed the battery capacity appeared to suddenly drop to zero. There's nothing recorded in the event log to indicate this loss of battery connection and I'm wondering if it would be difficult for Givenergy to enable this monitoring. If so, then I've already asked if they could enable email notification in the event of certain events being logged. Having the battery isolator trip is definitely something that is of interest and I'd like to know about it asap. It'd also be useful to know if the AC connection to the consumer unit was lost for any reason as well.

Tim Funnily enough I turned my hybrid off yesterday to reset my Solic Water diverter which had gone weird (sidenote: It's dead after only 12 months - would not recommend one!)
Pulling the battery fuses (the MCBs were notorious back then for being a bit... "melty") with the battery still "on" and the BMS still talking to the inverter causes the SOC to drop to 0.
So it can detect a trip (presumably by either seeing the voltage on the terminals drop to zero or some sort of resistance test it does - i know it kicks out about 5V from the "inverter" side to my fuse terminals in this state which may or may not be used to ascertain if a battery has tripped or not)
Push notifications would be nice for those hard trips.
Not so keen on push notifications for other stuff people have asked for like "your exporting now" - I really don't care and constant alerts for that would annoy the hell out of me (so make them toggleable!)

All these DC MCBs failing. Are they 60A or 100A?

Mine is a 100A one, never seen this happen, Inverter can pull 70A at 3.3kw DC, So may explain why so many are tripping

TheDragon (GivEnergy) After I emailed my installer on Sunday, his chaps were at my door just before 9am today and had left by 9.10 having swapped out the faulty isolator. They said they've had to change a few recently and think it's the contacts (or internal terminals) on the isolator rather than the DC connections made by the installer. I checked with them that it is a DC isolator (rated to break a current of 100A, so above normal full load, if necessary) and not a circuit breaker which trips on over-current. It's design duty is simply to isolate the energy stored in the battery from the inverter during maintenance. If it trips, as mine did, it's just plain faulty as Zakalwe reported.

Interesting stuff,

It looks like my Givenergy 100A DC isolator between my battery and inverter has died also...... or at least thats what im hoping it is! SOC crashed from 100% to zero after a large consumer in the house was turned on. Just waiting for it to get replaced now, having no working battery for 2 weeks has not been ideal.

Just for reference I have a Keto fused isolator
Yes it's not Givenergy preferred design of MCB but it does use M8 terminals so you can use proper cable crimps rather than just ramming cores into an MCB like some sort of savage... (sorry - work on powerstations and old habits die hard!)

My GE 100A breaker was dodgy, it kept dropping the battery connection.

Eventually tracked it down if I very lightly touched the breaker it would disconnect the battery - not even enough pressure to take the backlash out of the mechanical part of the switch.

New one fitted and aside from the occasion battery SoC plunge thing it's been fine since.

Tim I have had a similar issue on my battery isolator. It has been installed for since April however the breaker has a "loose connection" and had melted on one side when checked by the installer over the weekend. Interestingly I note your post is in April similar time to when mine was installed. Do you think perhaps some of these Isolators in and around that time could potentially be faulty? The installation guide just states to "tug test" the cables however the official response from GE support is that the cable should be tightened and then left to rest and then re tightened 20 minutes later. This is not in their manuals so I wonder where I stand with the long term damage potentially caused to the inverter components and battery internals due to this? My warranty may be potentially void and the performance reduced but where do I stand? Is this the installer or lack of info from GE in their manuals or GE having a faulty product? Either way I feel stuck in the middle through no fault of my own and nobody prepared to accept any liability.

Jonny_Springall

This is caused by a loose connection, or accidently nipping the insulation. Had your installer used the provided Ferule lugs, you wouldn't have had this issue. 100% installer issue.

Jonny_Springall should be tightened and then left to rest and then re tightened 20 minutes later

Agee with @TheDragon (GivEnergy) that terminating cables, especially power cables, in switches/MCBs/Isolators etc is a bread and butter skill for competent electricians. Most these days seem to use torque drivers but ensuring that there is an adequate connection, rechecking after some time if necessary, just isn't a specialist skill.