question

tbratten avatar image

Parallel Quattros split phase ground relay setting

I have an off-grid system (in US) using (2) Quattros (48/5000/70-100/100 120V) configured for split phase parallel operation. Hence, each Quattro is providing a 120V leg which creates a 240V system.

My question concerns the NEC (National Electric Code) requirement for bonding the ground and neutral. NEC requires the ground and neutral to be bonded at the "service entrance" and that this bonding should only be done in 1 place. Each Quattro contains a relay that bonds the ground and neutral by default. If both Quattros are configured to enable the relay (i.e. the "Ground relay" box is checked) this would seem to bond the ground and neutral in 2 places. Should I enable the Ground Relay on both Quattro's or only on 1 Quattro?

MultiPlus Quattro Inverter Chargerparallelsplit phase
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2 Answers
pigwet avatar image
pigwet answered ·

This video explains (10min -17min) you only check the ground relay box for the master inverter. https://www.youtube.com/watch?v=twLjlpeibdA&ab_channel=OptingOutofNormal

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snoobler avatar image
snoobler answered ·

I'm following this because I'll eventually be where you are.


I swear I read somewhere that units in parallel operation must be set the same.


I think this is also an interpretation issue. Each Quattro is half the source, so each has to provide its own ground as the source. Q1 is L1/N and Q2 is L2/N, so each N has to be grounded at each "source."

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