Voltage Selection

Started by mark, March 20, 2012, 04:25:03 PM

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I purchased the 300 volt MNSPD last year before the 115 volt unit was available to protect the DC side of my system.
I would like to inquire as to which voltage MNSPD I should use on the DC side where the voltage is between 125 and 145 volts max. Do I stay with the 300 volt that is installed or purchase the 115 volt unit for a closer voltage match?



Yes for anything over say 60 volts I would recommend the SPD-300
Changing the way wind turbines operate one smoke filled box at a time


now that perks my curiosity as to why that would be when the 115 is listed as being able to use between 0 and 150v.


  Thanks for the advice,
Anyone else have an opinion on MNSPD voltage before I order 2 more to protect  at the combiner box and submersible pump?



On my system I have an SPD115 on the inverter's DC input since I want to protect it from any spikes even more,  and the rest of the system I have SPD 300's on  DC  combiners. Since these all are connected, in an electric storm what would happen is that all the peripheral SPD's would clamp the spike to 900V and then it would travel to the inverter at 900 volts where it would be clamped to even lower by the 115.

My max system VOC is around 85V so there is no issue with the SPD115 clamping under normal operation. But your voltages are pretty high, so like Ryan/Halfcrazy says you should probably go with the 300 to be safe.

4.6KW offgrid PV system, Classic 200, MX60, dual Magnum PAE 4448 inverters, Midnite combiner and disconnect boxes, e-panel,  WBJr, and 8 MN SPDs


Thank you,
My original question did not have enough detail about my system for Halfcrazy to give me a complete reply, but your reply explaining your system's protection is exactly what I was looking for.

Please correct me if I am wrong:

MNSPD 300volt on the combiner box.
MNSPD 115volt at the DC input to the 48 volt Magnum Inverter.
MNSDP 300volt at the well head for the 240volt Grundfos pump 120 feet from the Power Panel.

I'm off grid.  Does anyone recommend any more MNSPD protection?
Should I protect the Outback Charge Controller?
Should I protect the Inverter AC output or input (generator) in the Power Panel?


So far that looks good. My rule of thumb is to put an SPD on each end of any wire run of 150ft or more if there is anything on that end of the wire worth protecting. The real killer in these systems is induced voltage in wiring from a near by lightning strike. Any wire around 100-150ft makes a nice antenna to pick this up. So I usually do PV+ and - on the incoming and all AC hots in and out of my inverter. I also dot he Mains panel with the well pump in it. I basically put them anywhere something is happening IE all sub panels if a ways from the main panel etc.

Changing the way wind turbines operate one smoke filled box at a time


Ryan, I assume you mean any line or multiple lines combined > 100 ft  between SPD's.
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The maximum allowable DC voltage for the MNSPD is 150VDC as mentioned. However, things like a 150V charge controller can and do go above 150V. That is why we recommend the 300. It clamps to a higher voltage, but remember all UL and ETL listed devices get tested at the factory to withstand at least 1800V. As long as the clamping is less than 1800V, you are good to go.
Another question asked if they needed to have an SPD on their OutBack controller?The Outback controller does not need any lightning protection. Of course when it does blow up from lightning, you will want to add an SPD300 to your nice new shiny Classic150 replacement. TeeHee.
Robin Gudgel