Building Reserve and Using KWH

[Ampster]

.......... I still don't understand why a mouse would have the desire to gnaw on an electrical wire.
.........

I have heard some electrical wire insulation is Soy base. It was a problem for my nephews car.

[badwithusernames]

regarding animals chewing wires, I have been told that there are certain brands of wire that come covered with what is essentially rat poison. I've seen a few fires from chewed wires and the idea is sound. A quick search yields little info, but I did fond this. Apparently some USE-2 wire is or has been available with it

https://solareducational.blogspot.com/2011/09/use-2-and-thhn-wire-insulation-types.html

[SunEagle]

I don't know how much nutrition they get out of that stuff but they persist. I found a dead mouse in my old service panel.

I have had a bad experience with a rat gnawing through Schedule 40 pvc sink drain pipe just to get some moisture but I still don't understand why a mouse would have the desire to gnaw on an electrical wire.

Maybe the electrical wire company should infuse some bad tasting fluid into the insulation. That may stop an animal from chewing on one.

[Ampster]

I don't know how much nutrition they get out of that stuff but they persist. I found a dead mouse in my old service panel.

[bcroe]

In the dead of the night 30 JULY, my house lost power, my neighbors did not. Called
the PoCo and was operational by sunrise, after they removed the dead raccoon and
replaced the fuse. No solar generation time lost.

The more efficient wiring buried between my inverters and my house meter has been in
service since 14 July. The loop of 600 feet of mostly direct burial 4/0 aluminum, some
1/0 copper in the house, at 60A (250VAC, 15KW) is running nice and cool, unlike my
original 4 gauge copper wiring. I am not generating any more power, but more of it is
getting to the meter to be credited.

Since then partially cloudy weather has prevailed. Despite that my energy reserve
buildup (for winter heating) is running at the second highest in 7 years. I was hoping
with some good sun, to set a new record. But when the sun does shine, I do
enjoy seeing my spinning disc reserve meter crediting me at 36 rpm. At night it
barely creeps backwards.

Someone questioned the integrity of my direct burial 4/0 aluminum wire. Put in
parallel with the original 4 gauge circuit, the current split just about the way it
should, telling me there are no high resistance points. At night I opened the 4/0
breakers at both ends to make insulation checks, after being buried a month.

My capacity meter says each wire is about 0.033 ufd to ground, that is fine.
120VDC was applied to check insulation leakage current (AC would be impacted
by the capacity currents). Voltage across a 1K ohm series resistor did not give
a meaningful reading, I upped it to 100K. Both polaritys applied to each wire gave
around 8 mv across the resistor, or around 0.08 micro amp plus or minus 20%.
The resistance is about 1,500 megohms to ground. Power consumed over a year
is about 8766 hrs X 2 X 120V X 120V X (1/1500,000,000 ohms) = 0.00017KWH
per year. I am not calculating the power factor.

0.033 ufd gives 0.0015A reactive current from each feed to ground. No doubt
some restive element in this element will add a tiny bit more loss.

Array wiring issues continue to develop. After 7 years the original cabling has been
modified, added to, and just aged. I saw a couple wires on the ground BEFORE I
hit them with the mower. It does appear, Bambi ignored my DANGER 400VDC sign
and bit one, which was fatal though not affecting operation. So I set up my work
lights, and under a black night sky revamped the largest, original section. Wires
adjusted, tied down, a few needed to be shortened or replaced. The wire pictured
apparently was attacked by a mouse inside a cable guide, but again did not affect
operation.

Bruce Roe

WireInsulation.JPG

[SunEagle]

I believe mine is entirely within code, but going direct burial cable eliminated conduit
in the 230 foot trench, but required it to be deeper at 2 feet. That is more work, DIY
for free. My 18 inch deep trencher was only 3 inches wide, I converted it to 24 inches
deep but kept the 3 inch width. I believe that saved me moving a substantial amount
of dirt, sometimes a bit close quarters, compared to a standard 4 inch wide trencher.

Using aluminum wire knocked the delivered price from close to $3K down to
$650. I see this year it went up to $750. The 200A box next to the inverters was
around $200. A 100A (huge, 4 position) feed breaker was repurposed from my old
electric furnace feed. Bruce Roe

Sounds like you saved some money yet kept within the code.

I looked at direct burial and AL wire but the guys who helped me convince me to go with pvc conduit under the house which saved about 60 feet. Also I could not easily find 100amp AL wire so went with the CU instead.

It all worked out for me and now I no longer have all those 50amp extension cords that were starting to see degradation due to the elements.

[bcroe]

Wow. I just spent about $1600 to DIY a 100amp U/G feed to a remote panel about 160 feet from my main one. One of the big costs was the wire at $800. The next was about $500 for the Sh 80 PVC pipe and fittings, about $200 for the trencher and $100 for the panel and 100A CB. I know I saved some money with DIY but staying withing code still cost me.

I believe mine is entirely within code, but going direct burial cable eliminated conduit
in the 230 foot trench, but required it to be deeper at 2 feet. That is more work, DIY
for free. My 18 inch deep trencher was only 3 inches wide, I converted it to 24 inches
deep but kept the 3 inch width. I believe that saved me moving a substantial amount
of dirt, sometimes a bit close quarters, compared to a standard 4 inch wide trencher.

Using aluminum wire knocked the delivered price from close to $3K down to
$650. I see this year it went up to $750. The 200A box next to the inverters was
around $200. A 100A (huge, 4 position) feed breaker was repurposed from my old
electric furnace feed. Bruce Roe

[SunEagle]

Good question, hope I have a good answer. First, there was already a 4 gauge feed from the
shed to the house, which would be run at 75% of capacity with the inverters in the shed. If
I had put the inverters at the house near the PoCo meter, I would have needed to trench the DC
wires all the way to the house, doing this same trench in 2013 (when I had less experience). So
I would still have had to dig the trench. Later I saw that my AC transmission efficiency was poor,
and the very high line voltage (well above the legal limit) was going to cause alarms.

The DC wiring is still trenched from the array 230 feet to the shed, through a less difficult area. I
was just as happy to have total control of this 2020 wire upgrade, as opposed to letting an installer
do it. As usual, with the needed tools on hand, DIY reduces the cost to parts wholesale, I think less
than $1K. Maybe I should add a few hundred for a replacement trencher belt, this one survived the
rock but is pretty beat. The other thing is, I want the solar stuff completely separate from the house.
For example there are spare inverters in the shed. Bruce Roe

Wow. I just spent about $1600 to DIY a 100amp U/G feed to a remote panel about 160 feet from my main one. One of the big costs was the wire at $800. The next was about $500 for the Sh 80 PVC pipe and fittings, about $200 for the trencher and $100 for the panel and 100A CB. I know I saved some money with DIY but staying withing code still cost me.

[bcroe]

Why did you not mount those Fronius string inverters next or close to the service and run high voltage DC to the inverters? Seems like you could have avoided a lot of time, expense and aggravation.

Good question, hope I have a good answer. First, there was already a 4 gauge feed from the
shed to the house, which would be run at 75% of capacity with the inverters in the shed. If
I had put the inverters at the house near the PoCo meter, I would have needed to trench the DC
wires all the way to the house, doing this same trench in 2013 (when I had less experience). So
I would still have had to dig the trench. Later I saw that my AC transmission efficiency was poor,
and the very high line voltage (well above the legal limit) was going to cause alarms.

The DC wiring is still trenched from the array 230 feet to the shed, through a less difficult area. I
was just as happy to have total control of this 2020 wire upgrade, as opposed to letting an installer
do it. As usual, with the needed tools on hand, DIY reduces the cost to parts wholesale, I think less
than $1K. Maybe I should add a few hundred for a replacement trencher belt, this one survived the
rock but is pretty beat. The other thing is, I want the solar stuff completely separate from the house.
For example there are spare inverters in the shed. Bruce Roe

[DanS26]

Why did you not mount those Fronius string inverters next or close to the service and run high voltage DC to the inverters? Seems like you could have avoided a lot of time, expense and aggravation.

[bcroe]

FWIW, there is a mini-split brand by the name of "Mr Cool" that is aimed at DIYers. Unit comes precharged with special fittings so that you just plumb the lines together, then open the internal valves in the fittings and you are done. No HVAC serviceman required. Very simple to install. Limited to 25 feet between units though.

I saw that, wonder if it was primarily for DIYers, or installation ease for all? Now
wait to see if it becomes universal. I could not consider that for my units, the
paramount consideration was their ability to operate at outside temps far below
0 deg F. Bruce Roe

[solarix]

FWIW, there is a mini-split brand by the name of "Mr Cool" that is aimed at DIYers. Unit comes precharged with special fittings so that you just plumb the lines together, then open the internal valves in the fittings and you are done. No HVAC serviceman required. Very simple to install. Limited to 25 feet between units though.

[bcroe]

Meanwhile, the weather is improving, and the project to trench 4/0 aluminum wire
out to the inverters may start soon. Conduit coming out to a trench is near
complete, and some dirt has already been moved. Bruce Roe

Perhaps the second biggest disadvantage of a ground mount array (after cost) is the
distances power must be conducted to the destination. The trade off between cost
of large enough conductors and efficiency becomes significant.

At startup in 2013, the 600 foot (mostly buried) loop of 4 gauge wire connecting my shed
with my solar inverters to my electric meter, was burning up too much power. It was causing
unacceptable high voltage at my converters, and running a higher risk of failure with daily
heating up and cooling down. In 2018 the section running half the length of my house
section was replaced with 1/0 wire. Last year I started planning to bury a new feed of 4/0
aluminum wire for the rest. 2/0 copper would accomplish the same but would cost $2600
instead of aluminum for $600.

When the weather was finally favorable, I started a 235 foot trench 2 feet deep for the direct
burial 4/0, 4/0, 2/0 triplex wire. This can be difficult here because of all the rocks, here by the
Rock River. After the better part of a month I finally got the trench ready, frequent rain did not
help. Here is the biggest rock dug out, one of many removed or broken up with my hammer
drill. My rock pile grows with every project.


BigRock.JPG

7 July I got the (really big) wire hooked up to the house, and by 14 July had the shed
hooked up and running. Also in the trench is a ground wire, something the 70s installation
did not have.

Use of 200A dist boxes at both ends as sub panels really simplified the termination of the
big wires. The terminations worked out at the sub panel level for 4/0 aluminum (2/0 neutral)
looked like this going operational.


2ndBox11Jly3.JPGShedBoxAL2.JPG


The new wiring reduces AC loop resistance approximately from an original 0.15 ohms, to
0.045 ohms. At max inverter output of 15.2KW, power lost in the loop drops from about
560 W to about 170 W. While inverter output does not change, the rate of reserve registered
at the PoCo meter goes up by nearly 400W any sunny day. My estimate is its a few KWH a
day, over 1000 a year. My spinning disc reserve meter speeds up from 32 rpm to 33 rpm.
No more warm wiring at the end of a sunny day.

BiDirMtr.JPG

Here are a few pics of the operation in progress. Remaining is to get the last of the dirt
back in place. I put another (spare) internet cable near the surface of the trench, from
my tower dish. The old furnace blower made 95 F temps more tolerable. No propulsion
on this bottom end trencher, a boat winch pulls it along even better.

Trn4Jly.JPG
2ndBox7Jly3.JPG


Bruce Roe

[bcroe]

The PoCo bill came, I looked over the first 2 months of this net metering period. 2 years ago I was not
running the 5 mini split heat pumps. By subtracting reserve built up from inverter generation, I have a
pretty good idea of my KWH consumption. Going back 2 years, the consumption for April-May was
about 46.3 KWH a day. The past 2 months consumption was about 31.6 KWH a day. I am going to
credit this 32% reduction in use to the increased efficiency of the mini-split heat pumps, over the other
heaters. It would be even more, except an additional building is now being temp controlled.

Had a brief issue 29 May, both inverters went off and were having trouble getting back in service. Half
an hour later things were normal again, doing about 50% of capacity under some clouds. I guess there
must have been some kind of line fault, later I noted it was about 120/240VAC even with the inverters
pushing, think that has dropped a bit.

Meanwhile the new AC feed trenching is inching along. With all the rocks, that
term may be too optimistic. Millimeters? Bruce Roe

[bcroe]

Generally by 9am this time of year, a visit to the inverter shed reveals the twin 7.5KW
solar systems are both saturated at full power. That even if a slight bit of cloud is
present, with this arrangement. But a couple days ago one system was down some
hundreds of watts from the other. I decided to wait a day for better sun, got the same result.

OK, a quick walk around with the clamp on DC ammeter revealed, String 9 was putting
out ZERO current. I actually had been a bit suspect of somewhat reduced output from
S9 before winter, but tests had not revealed any fault. I went to the combiner and pulled
the S9 fuse, S9 was delivering zero volts.

At the array, some test points I had left in place revealed substantial S9 output available.
Apparently the string was not connected to the combiner. More checking revealed this
failed MC4 connection of the string return connection.

String9rtn2.JPG


Why is that a 3 way connection? This 2 sided array has strings facing East and strings
facing West. To save wire an E and a W string share a common return, since they could
not both deliver peak output at the same time. Even if they had, the return wire would
not be overloaded. I decided to wait for dark for a simpler and safer repair job, an
outdoor outlet on the end of this array would power a light.

So what was to be learned from the 7 years of experience with several hundred MC4s?
First my ability to compare the 2 systems at a glance had immediately demonstrated this
serious fault.

2nd the output difference between the saturated system and the faulted system showed
that the total number of panels facing E (in this case) was about right. A properly
operating system generated enough power to saturate the inverter, but not enough to
mask the loss of any section.

3rd my past warnings about MC4s were not excessive. Perhaps this one got a bit
of weather exposure, and/or perhaps the seals were not moisture tight, and the
heating/corroding daily cycle finally escalated and destroyed it. In the future all
MC4s here will receive a dab of anti-oxidant compound as insurance.

4th this will probably not be my last MC4 failure.

Meanwhile, the weather is improving, and the project to trench 4/0 aluminum wire
out to the inverters may start soon. Conduit coming out to a trench is near
complete, and some dirt has already been moved. Bruce Roe