3S3P East, South and West

[ATX]

Hi All,
I have 3S2P West and South facing arrays. This is working well during the day and keeps the battery topped up before the sun goes down.


MPPT - 150V 15Amp
Solar Panel - 45VOC / 11amp per, so each South and West array has max 135VOC and together produce about 19amps total (because each array never peaks the same time)
Mounting angle - 45degree fixed (maximize production in winter)

Question - Can East facing array added without fuse? Since current is not going to exceed 25amp due to panels orientation.

What are trade off of adding a East facing array to the same MPPT?

 

[740GLE]

Why not add a combiner box with breakers for each string?

That way if you need to work on one array you can isolate its output.

Downside to east facing array is if you typically have early morning haze or fog, at our place the sun isn’t really doing much but burn off haze until 9-10am, so at that point it’s only 2-3 hrs of production.

Where as adding more panels to south facing will add more KWHr per day.

 

[ATX]

Why not add a combiner box with breakers for each string?

That way if you need to work on one array you can isolate its output.

Downside to east facing array is if you typically have early morning haze or fog, at our place the sun isn’t really doing much but burn off haze until 9-10am, so at that point it’s only 2-3 hrs of production.

Where as adding more panels to south facing will add more KWHr per day.

That’s insightful point about morning production.

 

[PVGeezer]

Question - Can East facing array added without fuse? Since current is not going to exceed 25amp due to panels orientation.

What are trade off of adding a East facing array to the same MPPT?

Not per the NEC. More than two parallel strings requires overcurrent protection, the Code doesn't make an exception for orientation, you just use the module Isc x 1.56 x number of parallel modules.

East and West facing arrays will have different max power voltages because they will run at different temps and irradiance levels. So you will have some voltage mismatch when you connect them in parallel. The MPPT will still find the best voltage to run the combined array at, but that will be a bit less than if you ran separate MPPTs. Will it be significant? Probably not more than a few percent.