European installation standards for US based installer

I'm looking for some input on minimum installation standards for an installation that is a hybrid of US and EU equipment for an installation I am working on.
The project is located in a Caribbean island that uses 230/400V 60Hz. My solar training is all US focused although I am originally a UK trained electrician, many years ago.
The island has very confused electrical standards, most of the electrical equipment is American but the conduit and boxes are often British. High voltage customers with recently built plant typically use 120/208V US based designs and so everything would be US equipment and standards.

This customer has a lot of US sourced refrigeration equipment running 480V compressors on 420V to 440V supply through booster trafos.

The project is pretty large, multiple roofs in multiple locations, all 3 phase 230/400V. As no US inverter manufacturer could offer a suitable inverter, we decided to use SMA inverters sourced from Germany, and we went with a multiple string inverter design with as many as 8 inverters on the largest installation. The most common inverter we are using is a Sunny Tripower 20000TL and 17000Tl, which I think are beautiful pieces of equipment.

The standard US design would include a fused DC string combiner, DC disconnect and single connection to the inverter in conduit. As far as I can determine, the design that the inverters are intended to use involve direct connection of the strings to the inverter with no fusing or disconnects. They have an Electronic Solar Switch that protects the inverter from reverse current by shorting the strings to make them safe. From the manual, SMA's preferred method to disconnect the strings seems to be to turn off the AC disconnect, in which case the DC current is near zero and therefore safe to unplug the strings. I can see why these inverters are not available in the US where the NEC likes to see a big DC disconnect before the inverter, however, I can also see why SMA would not see that as necessary as disconnecting the AC does reduce the input current to near zero.

I don't have any code requirements to consider, there is no code to cover solar pv, so I am having to make this up as I go. I want to take advantage of the features of the inverter such as Intelligent String Failure Detection which monitors the strings, builds a profile over several days and can detect loss of strings.

I'm looking for advice on how to implement a common sense design using available components. All our electrical supply comes from the US. My biggest issue is on the DC side, I believe that a non-fusible 600V 60A 3 phase disconnect on the AC side covers the bases. I love the idea of being able to safely test the strings at the inverter with our Seaward Solar PV150 test set, something you can't do on an American system as the strings are hard wired at the combiner.

What advice can the members offer on best practices we should follow?

Use true DC isolators per string rated for the current/voltage that you have per string.

Just Google it in images.

Excellent. Any suggestions for a source? UK based is fine.

Contact Andy at Sibert on 07775 427243 Andy O'Leary [[email protected]]

The SMA inverters can have string fuses built in to them, download this free guide to (almost ) best practice for solar pv : http://www.microgenerationcertification.org/images/PV Book ELECTRONIC.pdf


Other useful (well some of it ) here Microgeneration Certification Scheme - Installer Standards

p.s. also hook the SMA inverters up via the RS485 module to sunny Webbox (RS485 version) to Sunny Portal via the internet - invaluable for on-line and remote monitoring of systems.

You'll end up with something like this:

masonc said:

I don't have any code requirements to consider, there is no code to cover solar pv, so I am having to make this up as I go. I want to take advantage of the features of the inverter such as Intelligent String Failure Detection which monitors the strings, builds a profile over several days and can detect loss of strings.

I'm looking for advice on how to implement a common sense design using available components. All our electrical supply comes from the US. My biggest issue is on the DC side, I believe that a non-fusible 600V 60A 3 phase disconnect on the AC side covers the bases. I love the idea of being able to safely test the strings at the inverter with our Seaward Solar PV150 test set, something you can't do on an American system as the strings are hard wired at the combiner.

What advice can the members offer on best practices we should follow?

Click to expand...

don't use the string failure tool if there is any seasonal shading, as it sees this as a string failure - only use in unshaded situations.

the 20,000TL has a fairly narrow voltage range, and single string - the 17,000 dual MPPT option has much wider voltage range and dual MPPT so could be better for multi roofs etc. you also don't usually need to worry about fusing the strings due to the split MPPT set up, as long as you size the cables to take possible reverse current from the strings connected to that side of the dual MPPT set up.

they do optional add in string fuses and surge protection.

talk to SMA technical design team, they know their stuff and you should be able to configure the inverters properly with their help.
Please call +44 001908 304899
[email protected]

One of the useful triggers from the Sunnyportal is the relative inverter performance, where there are multiple inverters on a site we have found that this highlights any string or invereter problems. Also by plotting multiple sites against each other (which we site up as the first screen we see on login) it's easy to pick up unusual variances so that we can then investigate remotely (in our case from a warm office, in your case from a nicely air-conditioned / beer cooled office)

Dont need any help fitting them, do you?

Caribbean island?? I'm in :disguise:

Worcester said:

p.s. also hook the SMA inverters up via the RS485 module to sunny Webbox (RS485 version) to Sunny Portal via the internet - invaluable for on-line and remote monitoring of systems.

Click to expand...

I offer that to clients, here is a system with 6 x 10KW SB
Hughes Medical Center Plant overview

However on this project, it was not in the bid as it was a competitive bid. We will discuss that later.

Gavin A said:

don't use the string failure tool if there is any seasonal shading, as it sees this as a string failure - only use in unshaded situations.

Click to expand...

THanks. There's no shading on this project, just huge steel warehouse roofs. We don't get a lot of shading concerns in the Caribbean locations, not a lot of tall trees, no chimneys, lots of flat concrete roofs.

- - - Updated - - -

moospark said:

Dont need any help fitting them, do you?

Click to expand...

I might have space for an intern, yes.

Worcester said:

You'll end up with something like this:

Click to expand...

That's very useful for me to to see. We don't get to use flexible cables and plastic trunking, so a lot of our installation time is on bending conduit, fabricating gutter, etc. I'm jealous.

This is what our multi-inverter setups look like.

"the 20,000TL has a fairly narrow voltage range, and single string"
We are using mostly 20000TLEE with 1000V SolarBOS fused combiners with disconnect. I only have one 17000 specified, but when I went to install it I was very impressed with the features. We don't have those advanced SMA products in the US market.

Worcester said:

download this free guide to (almost ) best practice for solar pv : http://www.microgenerationcertification.org/images/PV%20Book%20ELECTRONIC.pdf

Click to expand...

That link made my day. It is exactly what I am looking for a relatively simple guide with diagrams.
I read the string fusing requirements, so much more complex than NEC. Under NEC, 1 or 2 strings, no fuse. 3 up, fuses are required.