[RFI] Trying to avoid Solar RFI

[Michael Carter]

Hi Gordie,

I advise separating the decision about your
PV array DC bus voltage from the decision
about the battery bank bus voltage.  The
Trina PV modules you acquired have an
open-circuit voltage of 37 V - the maximum
power point voltage is 29 V, but the true
maximum power point of any PV module
varies over the course of the day as the
illumination angle changes.  Unless you
plan to add microinverters or optimizers
to each module, you should consider a
high array DC bus voltage  consistent
with the allowable input voltage of the
battery charge controller you select.

On the well pump question: at the well
depth you cite, a typical pump size is
½ hp (assuming 240 VAC pump) and
8 A running current.  Starting current
is typically 80% higher or about 14-15 A.
You should check your well pump
to see what type it might be (e.g. capacitor
start).

You'll also want to consider peak current
demand on your battery bank if the
well pump, freezer compressors, and
refrigerator compressors all decide
to start up concurrently (unlikely, and
your circuit breaker may not trip
even if they do conspire against you),
but your inverter may not deliver that
peak current unless sized for it.

The configuration of PV modules into
an array with desired array bus voltage
and combined module string currents needs
to account for both the battery charge
controller input voltage and current
ranges if you're going to draw all power
from the battery bank/inverter.

Jim, K9YC has commented elsewhere
on preferred battery charge controllers
that are (mostly) RFI-quiet or can be
tamed with his choke/twisted pair
recommendations.

73,
Mike, K8CN



________________________________
From: RFI <rfi-bounces+mike.carter=unh.edu at contesting.com> on behalf of James Gordon Beattie Jr <w2ttt at att.net>
Sent: Friday, December 16, 2022 3:45 PM
To: Hare, Ed, W1RFI <w1rfi at arrl.org>; w6ya at arrl.net <w6ya at cox.net>; RFI List <rfi at contesting.com>; James Gordon Beattie Jr <w2ttt at att.net>
Subject: [RFI] Trying to avoid Solar RFI

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Hi Folks!
I picked up 23 Trina 230 Watt solar panels and plan to install 20-22 of them to power our 230 VAC well pump, the ham shack and in emergencies, the freezers and refrigerators.

These are 29 VDC panels are ideal for ground or rooftop mounting.  I would like to run 48 VDC from the solar array to an adjacent ventilated shed where I can place batteries and convert it to 230 VAC for the nearby well.  I can also split that into two 115 VAC legs from a breaker panel to feed the freezers and refrigerators when needed.  I'll also run a 230 VAC line to the ham shack and use a manual transfer switch.  The ham shack already has a small 14.2 VDC LiFePO4 battery array and charger for the DC gear in the shack.  The only thing in the shack that doesn't run on this voltage are the high power amplifiers, the air conditioner and some of the lights.  We can live with 100 W radios if needed, but if the 230 VAC feed from the solar array and its batteries and inverter are capable, then I might be able to run the AC or the amplifier.  We don't need heat, as the ham shack is insulated and the gear keeps it snug!

Noise suppression is my first consideration for the system, so what are my options for a solar charge controller/charger combo or separate units?

I'm prepared to configure the system in the shed for a 48 VDC battery array near the solar panels, but it needs to put out 230 VAC.  I KNOW that the next question will be how big is the well pump?  I don't know, but it has enough power to lift water 140 feet.

Thoughts?

73,
J. Gordon "Gordie" Beattie, Jr., W2TTT
201.314.6964
W2TTT at ATT.NET
Gordon.BeattieJr at VIAVISolutions.com


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