Building Reserve and Using KWH

[bcroe]

I used to worry about all HVAC functions being centralized, both the propane furnace and
the air conditioner relied on that furnace blower. One failure there and I was SOL. That
problem is gone, with 4 mini split zones, backed up by some substantial resistance heaters
if ever needed. So the blower is never triggered by the central plant anymore.

BUT I have an electrostatic air filter I would like operated regularly. And a little air mixing
between zones could be useful. A brand new blower motor is in place, and the solar PV
provides plenty of energy to run the motor.

SO a new function is tagged onto the central furnace. The blower may be run for a set
time (12 to 60 minutes), and then paused a set time (12 to 120 minutes). This repeats,
unless set to OFF.

Here is the control, which just attaches to the 24VAC thermostat circuit. Next winter will
check it out. Bruce Roe


blowerF.JPGblowerR.JPG

[Ampster]

Most of the 4/0 cables I have done are DC cables with hydraulic crimps. They bolted to either a battery pack or the inverter. I did connect some 4/0 cable to a service entrance but it already had lugs. You would have to see what kind of connection devices are available at your local supply house. One West Coast supply house that I have used in the past, does have 4/0 cable connecting blocks.

Now that I am reminded it is direct burial and that you have inclement weather in the winter you might consider a 3 or 4 inch LB into the house and have the junction box inside if that works better. I don't know enough about the details of your house to offer anything more substantial. There are probably several mechanical solutions. As far as the aluminum to copper connection I use Noalox.

[bcroe]

You are not going to want pull 4/0 through more than a couple of long sweeps. I would
terminate in a big j box and go out the back of that to the building.

For direct burial the only pulling 4/0 will be through a couple feet bringing it out of
the ground. Tell me about a suitable aluminum/copper J box. On the very short
run into the house to a 100A breaker, I could use 2 gauge copper. Bruce Roe

[Ampster]

.....

The question then is how to terminate it. Could it come up through conduit, to an
outside box, then convert to smaller copper to the building? Bruce Roe

You are not going to want pull 4/0 through more than a couple of long sweeps. I would terminate in a big j box and go out the back of that to the building.

[bcroe]

One item of loss here, is the original 600 foot loop of 4 gauge wire my inverters feed
the line through. The wire is not operating near capacity. But besides high voltage
problems, this may be loosing around 1000 KWH a year in resistive heating. The
thought lately is use direct burial 4/0-4/0-2/0 aluminum cable instead, 24 inches deep.

The question then is how to terminate it. Could it come up through conduit, to an
outside box, then convert to smaller copper to the building? Bruce Roe

[bcroe]

At this point the annual energy device upgrades are in place and ready for another IL winter. The
3 mini splits installed 2018 have been able to cool the 2000 sq ft ranch plus the partially exposed
2000 sq ft basement, and keep it toasty down to 0 deg F outside. There are several resistance
heaters backing these up in case we see a repeat of -31 F. Backing that up is a propane furnace I
have not used in a while, but could be run by a gasoline genset if power went away. Surplus KWH
energy will again be monitored.

This summer the house mini split capacity was increased 50% by adding one larger unit, and
another of these was put in the car shop to keep it cooled in summer and hopefully at least above
freezing all winter. It is surprising how little these need to run in the summer. With 5 minis and
a dehumidifier on line, 80% of PV generation is still going toward net metering winter reserve. A
new blower motor in the central furnace will reliably aid circulating any uneven temp air, along
with the new electrostatic air filter.

Here is the last mini to go on line, rated effective to -20 F. Still some clean up work needed covering
the freon lines. Normally I consider it a very amateur thing to just coil up extra length, instead of
cutting it to exactly the length needed. But this unit specified a minimum 10 foot length, so a 10 foot
line set was installed unmodified.


Mini52.JPG


One thing learned this spring, is that any tubing joints need to be brazed,
not soldered. With the very high pressure and the thermal cycling, this
joint pulled apart after some 9 months of operation. Bruce Roe

MiniLineJoint.JPG

[azdave]

I want to be like Bruce! (sort of)

Mini-split installed here too but a cooling-only unit to maximize our solar reserve in the summer heat. Working out nicely now that it has hit 110 here in Phoenix. Keeps the master bedroom and bath a very comfortable temperature while we sleep. The rest of the house is not cooled overnight. Usually, this is the time of year where we start eating into the small reserve that unfortunately gets reset on May 1st. Yesterday was 110 and yet we still banked 20kWh. July and August, when the monsoon season is upon us, will reveal the real value of not cooling the entire house all night long.

[Ampster]

............
Just what is the right amount of annual
generation is hard to say, because winter weather is so variable. Bruce Roe

That is a good reason for an aggressive design.

[bcroe]

The mini split R410A inverter driven compressor technology has such a long list of
improvements over what proceeded it, it ought to be replacing equipment (where
applicable) on a huge scale. But there seems to be some resistance in the US HVAC
industry to them. I am doing some volunteer work on a century old solid concrete
mansion, now on the nat register. I just got the job of an extensive energy audit of all
the buildings. Have not started yet, but high on my hit list is a huge old AC unit sitting
on an intermediate roof, to supplement some rooms in the steam heat main building.

These units run 450psi high side, 240psi low side, more than double my R12 stuff.

My place has been highly experimental, but it feels like solutions to all main issues
have been found. Perhaps once all my HVAC equipment is updated and the rest of
the panels are remounted, it will be finished. Just what is the right amount of annual
generation is hard to say, because winter weather is so variable. Bruce Roe

[Ampster]

For most folks - not Bruce - rather than looking for ways to utilize overproduction, some might think it might be better yet to size the equipment so that the excess production isn't generated in the first place.

I don't get the impression that this project has been completed yet. I has been going for at least 15 months with a stated goal of being Net Zero. I think it is too early to say that long term there will be excess production.

[frankge]

jumping on the minisplit bandwagon. In Tampa we run AC 24x7 in the warmer months which is a good part of the year. I installed a 12000btu Pioneer minisplit for our master bedroom which allows me to basically turn off the new 2 stage heatpump with ECM blower I just installed. That along with a heatpump water heater has given me a net-zero electric consumption. They raised our rates and electric s still cheap compared to some of you - 14 cents per Kwh, but I've already seen it raise from 12 cents. Btw the cost to install the minisplit myself end to end was about $800.00

[J.P.M.]

Sounds like a good plan to utilize some of that 4 gWhrs of energy your system produces over and above your consumption..

For most folks - not Bruce - rather than looking for ways to utilize overproduction, some might think it might be better yet to size the equipment so that the excess production isn't generated in the first place.

[ButchDeal]

Sounds like a good plan to utilize some of that 4 gWhrs of energy your system produces over and above your consumption..

I think you mean 4MWhs not 4GWhs

4000kWh = 4MWh
4000MWh = 4GWh

[Ampster]

Sounds like a good plan to utilize some of that 4 MWhrs of energy your system produces over and above your consumption..

[bcroe]

Meantime the car shop is well along in the installation of a 16,000 BTU mini-split
heat pump, pictures soon. This 15RLS3H has a -25F degree operational capability,
achieved with some internal supplemental resistive heat at the very lowest outside
temps. This luxury will attempt to keep inside temps at least 40 F year around, as
opposed to just being really cold in Feb. This will make quick jobs (oil change) easy
and a quick blast from the propane furnace will get me 65 F for a transmission
overhaul. The occasional, automatic use of some resistance heat at extreme lows
is a huge improvement over using it continuously and manually.

The shop is 1080 sq ft, with basic level insulation. Bruce Roe

Here is the state of the 15RLS3H installation in the car shop, the inside work is
already finished. My house mini splits past winter left me with a generation
surplus of over 4000 KWH, so this winter will attempt to use some of it up on
this semi insulated building, which used to sit with no heat in winter. Damaging
levels of ice and snow slide off the high metal roof, so a small roof/shield will
be placed a foot or so above this equipment for protection.

The 15RLS3H will be the main energy experiment for the next winter. I do not see
it as being in its sweet spot, trying to maintain 40 F in a substantial area with
outside temps down to -25F, so it will be a test. It has more capacity than my
first minis, and the heater supplement will take energy, but nothing like a pure
resistance heater. Bruce Roe

RLS3H1.JPG