Dual xwpro main loads breaker

[hogback]

So I'm soon to replace a single xw+ with dual pros. No external transfer switch. Because of the inverter internal relay (I'm off grid but have a generator for low battery (rare) and it does exercise monthly), the combined load during a switch cannot be above 60A. So, by having two pros instead of one, I can use what would have been the surge capacity of a single inverter, but continuously, but I cannot take advantage of the surge capacity of the combined system. If the system happened to switch to generator during a surge with more than 30A/inverter.... this is no good for the relays. 30A is 7200W, so not much into the surge realm above 6800W.

Am I missing something? I need to decide on wire awg to service panel and main breaker size. 60A would trip before endangering a switch during surge, but then I loose most surge capacity. 100 or 120A would get me full surge, but the danger of a switch and frying the relays.

I have 52kWh batteries now, so not likely to need generator, and I can disable the genny exercise and only do it manually when I know the loads are low. But.... what if I add more loads over time, and somebody turns on a hairdryer when the car is charging and I'm cooking on induction.... maybe still there is battery soc but the V sag causes the generator to click on. I am open loop so no soc info is on xanbus.

On one hand, I think I can just disable the ags and keep an eye on things when it been raining for days, but on the other, Murphy is out there....

Opinions?

Thanks,

 

[hogback]

And if I wired the combined 2x 60A load breakers to a main lug load center, this would essentially be a 120A breaker back at the pdp. I'm sure that's not code but not sure why it wouldn't work. If I wanted to derate below 120A, I should probably put a 60/80/100A breaker right after the combined 60A load breakers in the pdp, and skip the main breaker (and just use direct lugs) in the house panel (about 40' away). What do you all think?

 

[hogback]

Ok, simple question: What size breaker would you use on the combined output of a dual xwpro?

 

[GRMRC]

So I'm soon to replace a single xw+ with dual pros. No external transfer switch. Because of the inverter internal relay (I'm off grid but have a generator for low battery (rare) and it does exercise monthly), the combined load during a switch cannot be above 60A. So, by having two pros instead of one, I can use what would have been the surge capacity of a single inverter, but continuously, but I cannot take advantage of the surge capacity of the combined system. If the system happened to switch to generator during a surge with more than 30A/inverter.... this is no good for the relays. 30A is 7200W, so not much into the surge realm above 6800W.

Am I missing something? I need to decide on wire awg to service panel and main breaker size. 60A would trip before endangering a switch during surge, but then I loose most surge capacity. 100 or 120A would get me full surge, but the danger of a switch and frying the relays.

I have 52kWh batteries now, so not likely to need generator, and I can disable the genny exercise and only do it manually when I know the loads are low. But.... what if I add more loads over time, and somebody turns on a hairdryer when the car is charging and I'm cooking on induction.... maybe still there is battery soc but the V sag causes the generator to click on. I am open loop so no soc info is on xanbus.

On one hand, I think I can just disable the ags and keep an eye on things when it been raining for days, but on the other, Murphy is out there....

Opinions?

Thanks,

Your approach is a really expensive way to get one xwpro worth of power. Might want to think this one through again. See signature below.

 

[BentleyJ]

And if I wired the combined 2x 60A load breakers to a main lug load center, this would essentially be a 120A breaker back at the pdp. I'm sure that's not code but not sure why it wouldn't work. If I wanted to derate below 120A, I should probably put a 60/80/100A breaker right after the combined 60A load breakers in the pdp, and skip the main breaker (and just use direct lugs) in the house panel (about 40' away).

The PDP is has finger style bus bars to take a single set of input wires and distribute to 2 or 3 inverters via a 60A or less individual breakers. Maybe downgrade the AC Input breakers to 50A each. I believe those internal relays are technically rated at (3 x 30A = 90A) because they have 3 contacts. In any case, you definitely don't want the contacts to get welded closed, your concern is valid.

If the house meter panel is 40' away there should either be a main breaker or a fused disconnect. Wire gauge is determined by the rating of the Over Current Protection Device and can be found in many available online tables.

I have 52kWh batteries now, so not likely to need generator, and I can disable the genny exercise and only do it manually when I know the loads are low. But.... what if I add more loads over time, and somebody turns on a hairdryer when the car is charging and I'm cooking on induction.... maybe still there is battery soc but the V sag causes the generator to click on. I am open loop so no soc info is on xanbus.

Not an AGS expert but doesn't it have various voltage-time settings that can ignore short term sags and only start the gen after the voltage has been below for an extended period of time or reaches a lower critical level.

52kWh is a 1,000Ah battery. Even with 2 inverters in full surge mode they can't pull more than 0.5C. Should be much voltage sag if the wiring is all good.

 

[hogback]

Thanks Bentley. I haven't looked much at the ags since I set it up five years ago. For the majority of that time I was on 14kWh bank, and did see the occasional gen start from a new load near, but before it was really called for. This was with just a single xw+. Will have a peek at the ags menu in more detail.

I was planning on upping the awg between batt/inverter shed and house. I think I pulled 6 originally.

I'm thinking more of the ac output. Ac input would only be the genny (14kw kohler), which I can limit via the inverter charger via the "breaker size" (80% of) setting. The output without any addition/modification is two parallel 60A breakers in the pdp. They are bridged like you say with the finger bus. It seems like a good thing to do (although sort of redundant) is to have another breaker just past the bridged 60A breakers in the pdp. I could have another at the house of the same size, but I don't see it really being needed.

A single xw+ is clearly fine with 60A breaker on the output, as is in the current minipdp. Just trying to wrap my head around why two xwpros might also need to feed into a single 60A past the bridged 60A output.

 

[hogback]

Thanks Bentley. I haven't looked much at the ags since I set it up five years ago. For the majority of that time I was on 14kWh bank, and did see the occasional gen start from a new load near, but before it was really called for. This was with just a single xw+. Will have a peek at the ags menu in more detail.

I was planning on upping the awg between batt/inverter shed and house. I think I pulled 6 originally.

I'm thinking more of the ac output. Ac input would only be the genny (14kw kohler), which I can limit via the inverter charger via the "breaker size" (80% of) setting. The output without any addition/modification is two parallel 60A breakers in the pdp. They are bridged like you say with the finger bus. It seems like a good thing to do (although sort of redundant) is to have another breaker just past the bridged 60A breakers in the pdp. I could have another at the house of the same size, but I don't see it really being needed.

A single xw+ is clearly fine with 60A breaker on the output, as is in the current minipdp. Just trying to wrap my head around why two xwpros might also need to feed into a single 60A past the bridged 60A output

Your approach is a really expensive way to get one xwpro worth of power. Might want to think this one through again. See signature below.

Your approach is a really expensive way to get one xwpro worth of power. Might want to think this one through again. See signature below.

@GRMRC how do you combine (breaker-wise the output of your two inverters? Thx,

 

[GRMRC]

Thanks Bentley. I haven't looked much at the ags since I set it up five years ago. For the majority of that time I was on 14kWh bank, and did see the occasional gen start from a new load near, but before it was really called for. This was with just a single xw+. Will have a peek at the ags menu in more detail.

I was planning on upping the awg between batt/inverter shed and house. I think I pulled 6 originally.

I'm thinking more of the ac output. Ac input would only be the genny (14kw kohler), which I can limit via the inverter charger via the "breaker size" (80% of) setting. The output without any addition/modification is two parallel 60A breakers in the pdp. They are bridged like you say with the finger bus. It seems like a good thing to do (although sort of redundant) is to have another breaker just past the bridged 60A breakers in the pdp. I could have another at the house of the same size, but I don't see it really being needed.

A single xw+ is clearly fine with 60A breaker on the output, as is in the current minipdp. Just trying to wrap my head around why two xwpros might also need to feed into a single 60A past the bridged 60A output



@GRMRC how do you combine (breaker-wise the output of your two inverters? Thx,

If you read the installation manual for the BCS it lays it all out. AC1 60 amp breaker. Grid AC comes in, Excess AC power produced goes out. Grid goes down the BCS disconnects the 200 amp service not the relays in the XW pros. Works great. I am whole house backup, no critical loads panel.

 

[hogback]

My plan now is to take the loads output from the pdp and combine them into a single 60A breaker right next to the pdp. That way, if both inverters are sharing load equally, which I understand they won't perfectly, then neither inverter will be able to use surge capacity. Together, they will act like one xwpro, but with indefinite "surge" (13kW) capability.

I'm not sure how I'm going to handle the ags settings and wiring. Currently with one xw+ I have a 14kw kohler with "breaker setting" in the charger menu set to 60A, which limits the draw on the generator to 48A. This has worked fine. Should I use both chargers? I bought the wiring to run from the pdp to AC2 on each pro, but thinking of only using one pro for charging. Or - use both but set "breaker setting" to 30A each?

 

[BentleyJ]

I bought the wiring to run from the pdp to AC2 on each pro, but thinking of only using one pro for charging. Or - use both but set "breaker setting" to 30A each?

I would wire up both inverters then you have built in redundancy if either inverter has an issue in the future.

Charging can be disabled on the bad one and the other is already set up and working. Its a lot easier to change menu settings then to mess around with wiring if you need to use the other Inverter-Charger.

 

[hogback]

Thanks Bently. Do you imagine that there could be any funny business with them qualifying (and ending charge) at slightly different times?

 

[BentleyJ]

Good question, I believe that while the 2 inverters are synchronized with regard to power output, AC sine wave and Voltage. They will act independently with regard to other functions such as as battery charging. In other words, each inverter will choose independently when to exit Bulk and go into Absorb and then Float if 3 Stage is set Etc. The idea is to dial in the settings to get them to act in the same manner.

JBertok has posted about this in the recent past. Suggesting that the inverters are not calibrated to super fine detail. Say the the actual battery voltage is 53.6V as measured by a meter but one inverter reads 0.3V High at 53.9V and the other reads 0.4V Low at 53.2V. Unfortunately there is no way "offset" the readings in the software so the way you compensate is with the set points.

If the goal is to have a true Absorption Voltage of 56.0V The one inverter that reads High will be set for absorption to be 56.3V (Which is actually 56.0V) and the other inverter that reads Low would have Absorption set at 55.6V (which is actully 56.0V)

Hope this makes sense.

 

[hogback]

I have the charger set to 2-stage, no float on my single unit installation right now. Bulk and absorb are same voltage. So in the dual inverter/charger setup, the first charger to stop shouldn't cause any issues with the second.

Perhaps the problem I see is that the first unit to start charging could bring the batteries up enough so that the second doesn't see a V low enough to charge. Perhaps the best way around this is to mess with the delay settings rather than DC V offsets, although fine tuning those could help. I wonder if the decimal precision of the internal V meter/reading is enough though to make manual offsets effective. Thanks for the mention of JBertok's post. I had read it but will read it again.

 

[BentleyJ]

Yes, its quite possible that one of the chargers will activate first and the other would not. Most likely the inverter with the gen start attached to the Aux relay is the one that would always be used.

In the original post you noted that it was rare for the generator to be needed to charge batteries. If that's the case, its not difficult to manually activate a force charge through the user menu. This charging issue is even more of a problem for those of us with AC coupled systems. There is a charge block timer but no charge start timer built into these inverters. The work around is to use Node-Red or some other means of external control via the Modbus TCP or RS-485 interface.

 

[hogback]

Thanks, and yes, I have done the force charge a couple of times from the ags menu. We'll, I guess it's just a "turn on generator" signal and then the thing qualifies as usual.

 

[GRMRC]

If you read the installation manual for the BCS it lays it all out. AC1 60 amp breaker. Grid AC comes in, Excess AC power produced goes out. Grid goes down the BCS disconnects the 200 amp service not the relays in the XW pros. Works great. I am whole house backup, no critical loads panel.

Lost grid power for 3.5 hrs today. System worked without any problems. See sig below. BCS handled 200amp service when grid went down.

 

[goodoleme]

Lost grid power for 3.5 hrs today. System worked without any problems. See sig below. BCS handled 200amp service when grid went down.

Nice, no CLP and 125amp back feed to main panel...

 

[GRMRC]

Nice, no CLP and 125amp back feed to main panel...

Whole house backup. No CLP. The BCS is a nice bit of hardware.