Battery installations with Supply side Point of interconnection.

[msi99]

In last year's SPI, Mr. Bill Brooks made a few comments while he was presenting that performing supply side point of interconnection to a service when the system involves a battery is not a good idea since all it will do is an energy arbitrage and the battery cannot be used for backup.
Sharing this with the community to shed some clarity.

Irrespective of the point of interconnection( load/supply side) the battery will still be involved in arbitrage and backup right?

 

[winnie]

A battery used for _backup_ must have something the equivalent of a transfer switch or isolation device to permit the battery to function when the grid is down.

A supply side connection means a connection 'upstream' of the main disconnect. How do you provide the necessary isolation functionality without it becoming the main disconnect?

-Jon

 

[jaggedben]

You could install an additional service disconnect, and move the backed up loads to that connection. It's just the same thing by another name. Otherwise, Jon is right; you can't use the battery for backup if it's connected to the utility separately from the loads you want to back up. You need equipment to isolate them together.

If you can't backfeed the existing equipment due to code restrictions, or if the loads you want to back up are in a meter main combo, then you're going to have to find a way to reconfigure the existing equipment or wiring if you want to do backup.

 

[msi99]

Yes most of the battery manufacturers out there have transfer switches like backup interface/general inverter relay switches/auto transformer to isolate the grid during a power outage and kick the system into backup mode. So battery systems with line side should not be an issue.

 

[don_resqcapt19]

Yes most of the battery manufacturers out there have transfer switches like backup interface/general inverter relay switches/auto transformer to isolate the grid during a power outage and kick the system into backup mode. So battery systems with line side should not be an issue.

A line side connection has no way to supply any loads that are supplied by the service.

 

[jaggedben]

A line side connection has no way to supply any loads that are supplied by the service.

Well, not unless you re-wire the loads to the system connected to the 'line side' and call it a regular service disconnect.

At least the code and the CMPs are increasingly recognizing that the difference between a 'supply side connection' and an 'additional service disconnect' is just semantics, at least if you have six handles or less, total.

 

[msi99]

A line side connection has no way to supply any loads that are supplied by the service.

When you perform a line side connection, have an autotransformer or backup transfer switch, and have installed a backup load panel ( emergency loads), the battery can provide electricity for the backup loads. The backup interface will isolate the solar system from the grid during a grid outage.
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[don_resqcapt19]

When you perform a line side connection, have an autotransformer or backup transfer switch, and have installed a backup load panel ( emergency loads), the battery can provide electricity for the backup loads. The backup interface will isolate the solar system from the grid during a grid outage.

If you have any kind of load panel between the output of the battery system and the "line side" connection to the utility, you do not have a line side connection.

 

[jaggedben]

If you have any kind of load panel between the output of the battery system and the "line side" connection to the utility, you do not have a line side connection.

He's talking about a load panel on the other side of the power source outputs, not in between.

 

[don_resqcapt19]

He's talking about a load panel on the other side of the power source outputs, not in between.

Are there parallel connections at the parallel source outputs?

 

[jaggedben]

Are there parallel connections at the parallel source outputs?

Yes.

(But they could be internal to equipment.)

 

[don_resqcapt19]

Yes.

(But they could be internal to equipment.)

I guess I need to see a one line as I am not understanding how that is code compliant.

 

[jaggedben]

You said:

If you have any kind of load panel between the output of the battery system and the "line side" connection to the utility, you do not have a line side connection.

In other words you described
Service conductors <---> Distribution Panel <---> Solar and/or ESS equipment
I agree that's not a line side connection for the Solar/ESS.
Also it's not possible to provide backup power to the Distribution Panel in this arrangment.

But the post you responded to, I believe, was describing the following:
Service conductors <---> Solar and/or ESS Equipment (with MID) <---> Distribution Panel
In this case the power source equipment is connected directly to the service, which one might say is a line side connection, and the distribution panel can be backed up. The 'Solar and/or ESS equipment with MID' might merely contain connections for inverters (e.g. the Enphase System Controller or Tesla Gateway) or it might have the inverter in it with DC coupled battery (like an Outback or Sunny Island or SonnenCore).

In either example there could be splices to another set of service entrance conductors upstream, not shown, to another normal service disconnect that isn't backed up. For simplicity's sake I've also left out the location of the service disconnect and overcurrent protection, but that doesn't affect the issue under discussion. It might either be a separate fused disconnect in between, or part of SUSE equipment (Distribution Panel or Solar/ESS equipment in each example respectively).