Building Reserve and Using KWH

[J.P.M.]

I try to improve a weaker link every year, and there is opportunity in the hot water sys.
The PO was apparently an even worse plumber than me, pretty bad. I found one HW
copper pipe that actually wrapped around and crossed itself, and the leaks I have repaired.....

Part of the problem is a narrow ranch with a 37 deg bend in the middle, and a stairway at
that point make it difficult for utilities to pass there. So all the pipes have the furnace air
ducting passing underneath, making access extremely difficult. I may need to make the
ducts removable or just move the furnace to solve the problem, has not been used in a
while.

With only a couple people and limited laundry, I do not think the quantity of hot water used
can be reduced. Dishwasher runs 2 or 3 times a week. What I do think could improve is
pipe insulation. When I started out with a lot of resistance heat, the water just helped out
for many months, but now with Heat Pumps it is looking inefficient. The big box snap on
insulation is tightly wrapped to keep it in place, unlike that I removed. But it is quite warm
to the touch. I noted the 1 inch foam I attached to garage doors is never cold to the touch
despite outside cold. The thought is get the pipe straightened out, then mill a deep slot in
inches of that foam to push over the pipe. Then a flat foam piece would be friction fitted
into the grove. My recirculating return line would be strapped directly to the main pipe and
included in the foam groove. This is about as far as the thought has gotten to date.
Bruce Roe

Sounds (Reads) like you've got a cross between a rat's next and a Rube Goldberg system for some of your piping.

On the temps of insulation surfaces: The pipe insulation outside surface is hotter/warmer relative to the interior side of the garage door insulation most likely because:
1.) The DHW temp. is most likely a fair amount warmer than the conditioned space the pipe is running through compared to the temp. diff. between the garage interior and the outside environment.
2.) Unless it's the black, closed cell foam ("Armaflex" type stuff), the stuff on your pipes is probably the cheap "Frost King" stuff which is mostly crap. Additionally, it's probably ~ 1/2" thickness or less, or ~ 1/2 as thick as the 1" garage door insulation thickness. BTW, warping compressible insulation too tightly will reduce its thickness and so decrease its effectiveness. Just close the seams as best as possible but don't "snug up " compressible insulation. FWIW, I use 1" Armaflex on all the hot water runs and wrap it completely with aluminum tape (note: NOT duct tape).

My tank and piping are pretty well buttoned up - the piping as described above and an additional 6" fiberglass around the tank w/2" rigid polyurethane foam top and bottom. My total annual DHW load is ~ 2675 kWh/yr. (~ 9.1 MM BTU /yr.), with ~ 90-95 % of that load met with ~ 5.5 m^2 of solar thermal in any given year. Of the 2,675 kWh/yr. total DHW load, the tank standby losses and piping losses are ~ 1,250 - 1,300 kWh/yr. All that comes down to if your usage and piping lengths are somewhat like mine (which sounds likely), your tank standby losses and piping losses are probably as great or greater than your actual DHW loads.

[bcroe]

Any measures considered that would lower the DHW usage or lower
line or standby losses ? You won't heat what you don't use.

I try to improve a weaker link every year, and there is opportunity in the hot water sys.
The PO was apparently an even worse plumber than me, pretty bad. I found one HW
copper pipe that actually wrapped around and crossed itself, and the leaks I have repaired.....

Part of the problem is a narrow ranch with a 37 deg bend in the middle, and a stairway at
that point make it difficult for utilities to pass there. So all the pipes have the furnace air
ducting passing underneath, making access extremely difficult. I may need to make the
ducts removable or just move the furnace to solve the problem, has not been used in a
while.

With only a couple people and limited laundry, I do not think the quantity of hot water used
can be reduced. Dishwasher runs 2 or 3 times a week. What I do think could improve is
pipe insulation. When I started out with a lot of resistance heat, the water just helped out
for many months, but now with Heat Pumps it is looking inefficient. The big box snap on
insulation is tightly wrapped to keep it in place, unlike that I removed. But it is quite warm
to the touch. I noted the 1 inch foam I attached to garage doors is never cold to the touch
despite outside cold. The thought is get the pipe straightened out, then mill a deep slot in
inches of that foam to push over the pipe. Then a flat foam piece would be friction fitted
into the grove. My recirculating return line would be strapped directly to the main pipe and
included in the foam groove. This is about as far as the thought has gotten to date.
Bruce Roe

[J.P.M.]

My latest PoCo bill shows a winter reserve built up to 13,000 KWH, running with my best past
years. I was sort of hoping for a week of good sun to make it the highest ever, but that seems
unlikely. Rather optimistic, since the heat pump in the car shop is now on line. I collect energy
all year, but the reserve usually usually peaks about 1 Nov, with limited sun and increasing
heating load. System efficiency is as good as ever, now with my peak AC losses over the long
run from the inverters to the PoCo meter at around 1%, and with even better efficiency under clouds.

With annual generation running near 20% in excess of consumption here, the thought is of adding
an electric water heater. The 3rd water heater I have had in 16 years uses propane I paid $1.09
a gallon for this summer, avoiding any winter purchases at up to a manipulated $5 a gallon. The
propane heater is vented, and I note cold air back feeding through it into the house winters when
not running.

To begin the trial, cold water might come into the electric heater, then feed the input of the propane
heater. If I got hit with a supper cold winter eating my KWH reserve, the electric water could be
shut down for a while. Perhaps if this proves to be a very rare situation, the propane water heater
will disappear.

I would like to limit the too frequent heater replacement, maybe a glass tank like marathon 40
gallon lifetime electric water heater would be the answer? I read of heat pump water heaters, but
in winter I would just have to replace the heat inside the house anyway, is that really an advantage?
There is always the thought of an incoming pipe running just under the quite hot roof peak in my attic,
but that requires either seasonal management, or the big complications of a system with antifreeze.

Bruce Roe

Any measures considered that would lower the DHW usage or lower line or standby losses ? You won't heat what you don't use.

[azdave]

Seems like a logical use of excess kWh to pre-heat the water to the propane fired WH. I've been able to eek more years out of my water heater tanks by changing the sacrificial anode every 2 years regardless of whether I think they are due or not. Too many variables to know if that is really why mine last longer than the neighbors but some of them get leaks at 5-6 years and I've gone over 10 years so far.

Building kWh Reserve?
This was (and still is) a brutal summer here in Phoenix but we've made it though the worst of it without having any billable energy. We had less than 45kWh in reserve (1 day supply in the summer) as we ended August and only built up the reserve a measly 13kWh more after September. We've had 50 days over 110F and will very likely beat the all time record of 143 days above 100. Might not see a day below 100 here until Oct 11. Our mini-split in the master bedroom saved us for sure from purchasing energy this summer.

[bcroe]

My latest PoCo bill shows a winter reserve built up to 13,000 KWH, running with my best past
years. I was sort of hoping for a week of good sun to make it the highest ever, but that seems
unlikely. Rather optimistic, since the heat pump in the car shop is now on line. I collect energy
all year, but the reserve usually usually peaks about 1 Nov, with limited sun and increasing
heating load. System efficiency is as good as ever, now with my peak AC losses over the long
run from the inverters to the PoCo meter at around 1%, and with even better efficiency under clouds.

With annual generation running near 20% in excess of consumption here, the thought is of adding
an electric water heater. The 3rd water heater I have had in 16 years uses propane I paid $1.09
a gallon for this summer, avoiding any winter purchases at up to a manipulated $5 a gallon. The
propane heater is vented, and I note cold air back feeding through it into the house winters when
not running.

To begin the trial, cold water might come into the electric heater, then feed the input of the propane
heater. If I got hit with a supper cold winter eating my KWH reserve, the electric water could be
shut down for a while. Perhaps if this proves to be a very rare situation, the propane water heater
will disappear.

I would like to limit the too frequent heater replacement, maybe a glass tank like marathon 40
gallon lifetime electric water heater would be the answer? I read of heat pump water heaters, but
in winter I would just have to replace the heat inside the house anyway, is that really an advantage?
There is always the thought of an incoming pipe running just under the quite hot roof peak in my attic,
but that requires either seasonal management, or the big complications of a system with antifreeze.

Bruce Roe

[SunEagle]

Seems since the BIG OUTAGE, I no longer get email alerts to strings I thought I
was subscribed too.



.....Bruce Roe

I have noticed the lack of email alerts also and have passed that onto Solar Pete.

[bcroe]

Rodents eating car wiring is not a small problem. Check this out...........

Seems since the BIG OUTAGE, I no longer get email alerts to strings I thought I
was subscribed too.

Eating insulation seems to be a lot more interesting than insulation resistance. Can
the wiring easily be made a lot less tasty ?

Yea that link illustrates the latest ploys to force you to replace your car on a regular
basis. The latest Integrated Circuits use such fine geometry that cosmic rays may
knock out enough transistors after a while to kill them, probably that is why the first
Rover used a 70s 8085. All the intelligent solar equipment is probably in the same
boat, and there is no repairing a custom, short run, and unavailable IC.

Plastic parts went into car drive train, all these have been replaced on my 77. I do not
own a car containing a digital computer. Her new one is an electronic marvel, I am
overhauling the 2001 so it can come back to replace the 2020 when the electronics
become unmanageable. Bruce Roe

[DanS26]

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

Rodents eating car wiring is not a small problem. Check this out...........

http://www.synlube.com/IncredibleEdibleCar1.htm

[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