Lightning Arrestor/Capacitors

phoenixfire · May 2010

Hello again,
I am seriously considering putting a Delta Lightning Arrestor and/or Delta Surge Capcitor on my AC circuits.

I am fully off-grid. I have two inverters, one is a modified sine wave (altho it is actually in between the normal square wave and a pur sign wave) the other is a Pure Sine wave inverter.

My question is, both the products above have two 'hot' line and a neutral or ground depending on which product you are talking about. For both products they are designed to be connected to both legs of a 220/250v household current system. My question is can either or both of these devices be connected to both inverters? Both inverters are isolated with exception to system ground. Their neutrals and Hots are both completely isolated from one another.

in the case of the lightning arrestor is it possible to connect the hot from one inverter to the arrestor and the hot from the other inverter to the other leg on the arrestor and the ground lead to ground.

Both inverters have 0v on neutral so at least that isnt an issue. I have read everything there is on Delta's website and can find no information outside of connection to a power panel.

This statement "For two-wire (single 115 volt) systems and inverters you can tie the white and black wires to the same side, or the white to the input side, such as from a generator or grid, and the black to the output side. The Green should be well grounded. For dual inverter systems that operate from the grid for battery standby systems, you can put one on the input and one on the output.
" from the NAWS store makes no sense to me really hence why I am asking here.

Cheers

Scott

Cariboocoot · May 2010

Re: Lightning Arrestor/Capacitors

As you're probably already guessed, no you can't connect one lightning arrestor to the outputs of two separate (much less different type) inverters. If the inverters are 'stacked' (outputs connected in synch, possible on some) it will work because they act as one. It's a matter of not connecting unsynchronized AC waveforms. Bad things happen if you do that!

So it's a separate arrestor for each inverter.

To explain this from NAWS:

"For two-wire (single 115 volt) systems and inverters you can tie the white and black wires to the same side, or the white to the input side, such as from a generator or grid, and the black to the output side. The Green should be well grounded. For dual inverter systems that operate from the grid for battery standby systems, you can put one on the input and one on the output."

They're talking about the two 'input' wires of the arrestor; you can hook them together on the hot of a 115 (120) inverter output, or use on on the inverter hot and one on the gen hot to provide protection for both. Otherwise you'd use one on each leg of a 230 (240) output; there's no need to 'lightning protect' the neutral as it should be connected to ground anyway (in one place only).

RCinFLA · May 2010

Re: Lightning Arrestor/Capacitors

First question is why you think you need surge suppressor on an off grid AC output. If you have runs outside, like to a light post, then maybe. If confined to within house there is not too high a probability of having any lightning risk.

It is a bad idea to put a large cap on output of MSW inverter. It causes high surge currents during square edge transitions that increase the power dissipation on the H-bridge output MOSFET's. In extreme case it can blow them out.

A typical breaker box surge suppressor has three MOV's or equivalent ZNR's. One on each side (L1,L2 to neutral) of 240 AC to neutral and one across 240 AC (across L1, L2).

phoenixfire · May 2010

Re: Lightning Arrestor/Capacitors

Honestly The only reasson I was considering them was EMP. SInce there is no access to the AC side of the inverter from anywhere except inside the house I would agree it seems unlikely. I do understand that EMP normally only affects low voltage devices like rs232, UTP, Ham, Cell/pcs booster/repeaters and the like.

I had already considered the cap issue with the MSW inverter and had not planned to connect one to that anyway. I would expect some very interesting waveforms on the scope if I had tried and also wouldnt expect the cap to last very long al all.

I was still planning to put a DC arrestor on the line in from the PV array Though.
Scott

mike95490 · May 2010

Re: Lightning Arrestor/Capacitors

phoenixfire wrote: »

Honestly The only reasson I was considering them was EMP.

Consumer grade Arrestors will do little for high altitude EMP, and not needed for local lightning induced EMP (unless lightning hits you house directly).

Lightning Arrestor/Capacitors

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