My max PV string voltage (factoring in cold weather) is 150v. I’m pairing this with the above CC. Many of the SPDs out there are Uc 600v or 1000v which is more than enough for my string voltage but I’m concerned that they may not be low enough to protect my CC - which has a max input limit of 250v.
I’m still trying to understand the SPD concepts tbh.
I haven’t been able to find out whether the SmartSolar MPPT 250/100 has any built-in surge/transient tolerance, between for example 250v - 600v? Obvs the cont. input of 250v is a hard limit but can it be safely paired with a Type 2 PV SPD of Uc 600v for example?
Really difficult to find compatible SPDs with Uc of around 200v - which sits between the max string voltage (150v) and the Maximum PV open circuit voltage supported by the CC (250v).
However, I’m not even sure if that’s what I need for adequate protection!
Fundamentally the goal of the spd is not to protect above the max voltage limit of the scc but to minimise the differences between the wires to avoid breaking thru the insulation limits is how I understand it.
In the case of a 150V pv circuit I would suggest a Midnite SPD 300 DC:
You could potentially use an spd-115 but may be too close to MCOV voltage of 180V:
I also had this thoughts back then when I installed my system. My conclusion was, that (in best case) I need something below the max. rated MPPT PV input voltage. In my case the PV modules delivers max 110V in cold weather, so I chose a SPD with 150VDC rating. It was hard to get one in Europe, so in the end I ordered some in China from LSP. This company has several unusual rated devices like e.g. a 180V version that could fit for you.
In the meanwhile there are more companies that discovered this market gap and started with corresponding products. CITEL or Dehn are two I can mention.
In general, Victron is not giving any information if there is any special SPD device in the MPPT chargers, or how much energy or peaks it can handle without any damage. So if you want to be sure, you have to stay below the rating. Although the rating is a continuous max working voltage, every MPPT has big capacitors and inductors on the PV input, that can absorb short peaks without any damage.
In your case I would also choose a SPD with a rating that is slightly higher than the max PV voltage, but still below the MPPT voltage rating. But keep in mind, the SPDs have a tolerance, so be sure to not cross the lower limit with the PV voltage rating.
On the roof the big ones in the generator junction box to protect the line (if longer than 10m this is mandatory).
In front of the regulator or inverter the suitable smaller ones.
Also you need grounding of the frame on the roof, but be careful, there is/could be also functional grounding possible (detection of isolation faults of Inverters )
As a good installation, the cables are installed in metal shielded compartments or structures (on the roof in the c-like profiles) so the naked parts are as short as possible. Check local regulations and ask local companies spezialized in constructing lightning protection systems.
