The tax man cometh... and brings gifts

    Yes it is that time of the year again, yet some of us are looking forward to it for a change.  Tax season.

  Agree or disagree, the federal government is willing to pay for 30% of the installed cost of solar hot water systems.  And if the government is offering, then surely I am going to take them up on it.

  Having spent just shy of $12,500 (I know it is a lot!) on my hot water system, the government has sent me a check for $3,750.  Not too bad.  That leaves me $8,750 out of pocket for the system.  We will see, in the months and years ahead, whether that was a good or bad investment.  However, considering (a) I heat with oil and (b) I lived through the 1974 OPEC oil embargo, I think the peace of mind will be well worth it.

   Next up, more 2" thick foam insulation for my basement walls to save even more oil.

How Much is 80 Gallons of Hot Water Worth?

Winter is finally giving way to spring, and the sun is now clearing more of the trees that have been shading the solar panels.  The result is that for two straight days in a row, the system has produced 80 gallons of 160 F water.  That leads me to this question, how much is that really worth.  Time to break out Excel.

So the water starts out (at this time of year) at 52 F and is heated to 160 F, for a delta T of 108 F.  The 80 gallons of water weighs 668 lbs and given that a BTU is the energy needed to raise 1 pound of water by 1 degree, this totals 668*108=72,144 BTU.    But what does that really mean?

If that water had not been heated by the sun, it would need to be heated by home heating oil burning in the furnace.  Let's assume that the furnace is only 80% efficient, so in stead of 72,144 BTU, we would need 90,126 BTU from the fuel.  Looking up on the internet, we see that there is 139,000 BTU in one gallon of home heating oil.  Thus we saved 0.65 gallons/day or (at $4/gallon) $2.59/day.

Well that hardly seems worth the thousands of dollars that I spent on the solar hot water system.  But before we conclude that, let's look at how much this adds up to over the course of the year.

Let's assume that half the time, the system will produce a tank full of hot water.  That is 182.5 days per year.  So, I will save 118 gallons/year or $473/year. 

At that rate, it will take a depressing 17 years to pay back the $8000 of out of pocket expenses (after federal 30% tax credit.)  However, there are two more things to consider.  First, it may be possible for me to shut off the furnace during the summer which might double the savings.  Second, perhaps over the next 10 or 20 years, oil might cost a lot more than $4/gallon, accelerating the payback.  That may make facing the future just a little bit more bearable.

Solar PV Panel on the move

Rather than make the sensible choice and plug my solar differential controller and pump into the "mains" AC power, I chose to use a solar PV (photovoltaic) panel to supply this electricity.  This choice continues to cause issues.

The latest issue is that sometimes I find that the Taco zone valves fail to open and the solar hot water system overheats because the pump cannot pump the fluid past a closed valve.  The problem with the Taco zone valve is not clear.  I have tried to duplicate the problem by turning on and off a power supply connected to a spare zone valve.  The valve seems to work flawlessly.

On the actual solar hot water system, however, on a few occasions, I have seen the valve fail to open.  The problem is that the power available to open the valve is inadequate in the morning.  This causes continuous cycling and resetting of the solar controller and the valve.  When the solar fluid gets hot enough, the solar controller attempts to turn on the valve and the pump.  This causes too much load on the batteries and PV panel and the 24 VDC power drops below the cutout voltage of the controller (about 22 volts) and the controller shuts off and the valve closes.  With this load removed, the battery voltage quickly recovers to 24 VDC and the system turns on, only to repeat the same reset cycle.

The problem seems to be largely caused by my chosen location for the solar PV panel which is on the right of the Heliodyne solar hot water panels.  In this location, the solar PV panel is getting shade in the morning even when the hot water panels are in the sun.  The result is that there is inadequate electrical current to turn the system on when needed in the morning.  Usually this just means that the system continues to cycle and reset for 10 or 15 minutes until adequate PV power is available.  This would be no big deal.  However, the weakness in the zone valve means that under some combination of reset cycling, the valve ends up closed for the whole day.  That is bad.

To work around this problem, I have decided to relocate the PV panel to a location with less shading.  Specifically, I decided to put the panel at the top center of the hot water panels.  The picture below shows the old PV panel location.

And the next picture shows the new location.

Initially, I had rejected that location for the PV panel because I didn't want it to block the view from the window.  However, I think it looks fine at that location and the symmetry looks nice.

To hold the panel in place, I used about $100 worth of aluminum extrusions and other part from Misumi.  The aluminum extrusions are HFS8-4040 from Misumi which is 40x40 millimeters or about 1.5 inch square.  These are coupled into the Misumi frame that I used to hold up the solar hot water panels.  All the fasteners are stainless steel so the frame and fasteners should not rust.

As typical, I laid this all out in Pro/Engineer before hand to make sure everything would fit.

The first sunny day showed that this location works much better and the controller was able to turn on the valve and pump with no problem early in the morning.  Ultimately, the choice of solar PV based electricity over mains power may ultimately prove to be the right one.

Battery Pack Woes

My battery pack and I are having relationship problems.  I think it should work every day, but it thinks it deserves a day off once in a while.  So I have fired it from its job.  Let me back up for a moment.

The solar hot water system needs a small amount of electricity to run the pump, valves, and controller.  You can get this electricity from the wall outlet, but I decided to get it from a separate 40 watt photovoltaic solar panel.  But if the sun ever ducks behind a cloud, even for a moment, that power is lost, valves start closing... and repeated cloud passing can make the system cycle on and off repeatedly.  So to stabilize the system I am using a charge controller and a battery.

Charge controllers mix together electricity from the solar panel and the battery to optimize the power output.  If excess power is available, the system charges the battery.  If solar output drops, the power can be supplied from the battery, at least for a short while, and prevent valves from closing.

Charge controllers are built assuming that you are going to use either one 12 volt lead acid battery or two together (24 volts).  I have no interest in using lead acid batteries because they only last about 3 years.  So I decided to make my own 24 volt battery from AA Sanyo Eneloop NiMH batteries.

The first challenge was how many batteries did I need to mimic the 24 volts that the charge controller is expecting.  Each NiMH cell is about 1.25 volts so twenty batteries would produce a theoretical 25 volts.  This seems close enough.

Next challenge is to find a battery holder for 20 AA cells.  Since I could not find one,  I decided to put together three holders, two 8 cell (2×4) and one 4 cell (2×2).  The photo below shows what I came up with.

At the top of the battery holder is three 9V style connectors that I had to connect together to get the total 24V output.  To hold this assembly together, I bent some sheet metal and glued it to the outside.  Of course I needed to be careful that the metal did not short out any of the electrical contacts.

The Problem

Shortly after installing the system I started noticing problems with the battery.  Sometimes when I touched the battery holder, the voltage would drop to zero.  After some fiddling, the voltage would be back to normal with no clear reason way.  Other times, I would find the battery pack completely dead with the cells reading 0V each.  Upon removing the batteries from the pack they would slowly recover to about 1V suggesting they were being loaded in the pack.  I am not sure why these problems were happening, but decided a new, cleaner, battery holder might help.

I found batteries holders on the web that could hold 10 cells, so I only needed two of them rather than three holder used in the last system.  By placing them back to back, I would make one nice twenty cell holder.  I just needed to solder two terminals at the top, solder some leads, and tape the outer edges with electrical tape.

The new battery holder is installed and working well. 

I have had a discussion with my new battery pack and it has agreed to work every day and not just occasionally.  Hope springs eternal and I believe it. (for now).

Plumber makes final connection, Impressed me, not so much

Generally I am a fan of building codes that keep the public safe.  It is great that only qualified people do things like install foundations, chimneys, high voltage lines, etc.  So I was not that disappointed when I learned that I had to hire a professional plumber to make the final potable water connections for solar hot water system.

I have changed my opinion.

The idea sounds great in practice, but the execution is not always a guaranteed success.  Let me share with you my experience with the plumber.

Firstly, the task was very simple.  Break open the feed to the existing fossil fuel hot water heater, route it to the solar hot water tank, then route it back.  The idea is that the solar hot water system acts as a preheat for the existing furnace based tankless heater.

My preferred plumber (Plumber 1) wanted $1100 to do the job.  This is impressively expensive for a couple of hours of work.  I tried to hire him, but he stopped returning my phone calls due to many "no-heat" calls from a freak fall snow storm that knocked out power to many homes in the area (including mine for 28 hours).  After a while, I called on Plumber 2 that only wanted $700 to do the job, fine, I hired him.  By the time it was done, he charged me $1000 for a crappy job, but I paid him anyway.  I really should have waited from Plumber 1 due to past good experience with him.

The best thing that can be said is that the system "worked" after the plumber left and the job site was left very clean.  Unfortunately, the quality of the work could have been much better.  Let me enumerate the ways that the plumber "failed" (in my humble opinion).

FAIL 1: The Backflow Preventer
The plumbing inspector required the plumber to install a backflow preventer for some unknown reason.  Perhaps there was concern that the non-toxic propylene glycol might work itself back to the street under some impossible scenario.  Of course, that would not help us here in the house.  If the propylene glycol leaks, it will come right in to the hot water supply and we will likely drink it.  That is not much of a problem since it is non-toxic, so I don't know why a backflow preventer was needed.  Also, if this had been a fossil-fuel fired heater, no backflow preventer would have been required.  This is clearly a case of fear of the unknown, but shouldn't have been a big deal, if it was installed correctly.
  The backflow preventer should have been installed for the whole house water supply, however it was installed just in the hot water feeder line.  The resulting back-pressure made the hot water supply pressure very low while leaving the cold water supply pressure high.  The result was that it was impossible properly adjust the temperature of the shower without micron precision on the hot and cold water taps. 

So I removed the backflow preventer and installed a short length of pipe instead.

Upon removing the backflow preventer, it became clear that it was plugged with plumbing putty or some such material as can be seen in the image.  It was almost completely plugged.  What kind of plumber does such lousy work?  I thought this might have flushed out of the new hot water tank and then perhaps be the fault of the tank manufacturer.  However the backflow preventer is before the hot water tank.  So this material must have come from the plumbers new work.

FAIL 2: Can't close 1/4 valve.
If there is a 1/4 turn ball valve in the existing plumbing, you would think the plumber would know not to run pipes in such a way that the valve cannot be closed.  As can be seen in the image, the yellow handled full port ball valve cannot completely close because it now hits a pipe.  Nice work.

FAIL 3: Tempering valve defeated
If you are not a plumber, you might not have heard of a tempering valve.  This is an important piece of safety equipment in your home.  If you have a furnace (or boiler) then it is possible that it could malfunction and produce seriously hot water, e.g. 210F.  If this came up your pipes into your shower you might be badly scalded.
   To prevent this, a tempering valve is installed.  The tempering valve takes in both hot and cold water, as shown in the picture.  If the hot water is above a certain temperature, the tempering valve mixes in a small amount of cold water to reduce, or temper, the water temperature so you are not scalded.

However, my plumber managed to connect hot water to both sides of the tempering valve making is dangerously useless.  He plumbed the solar hot water into the cold port of the valve, and furnace hot water into the hot port of the valve.  The result is that the tempering valve cannot function as intended.  This is probably due to the plumber's lack of familiarity with solar hot water systems.  Alternatively, perhaps I should had developed a plumbing diagram and given it to the plumber.  That seems a little silly for someone that is supposed to know how to do this, but there you have it.

This is really a double fail because the inspector didn't catch this error either.

FAIL 4: No Unions or 1/4 turn shut off valves
This might be a bit of a nitpick, but here goes.  As recommended by the manufacturer of the hot water tank, I installed unions and 1/4 ball valves  just above the hot water tank on the solar loop.  This allows the tank to be disconnected if service is needed.

However, the plumber defeated my efforts by not installing them on the potable water side of the tank.

So if service is needed on the tank, I will need to cut the copper lines on the potable water side.

Fail 5: Pretzel Plumbing
There is a certain art to plumbing.  A well done job not only works, but it looks neat and clean.  The plumber only had to run two lines and inexplicably he didn't run them along the same path.

As can be seen in the image, the cold line (blue) and the hot line (red) are not run along the same path even though they easily could have.  This would also have avoided the cold line running into the 1/4 turn shutoff valve.


All in all, the whole job was pretty disappointing and only barely functional.  The work was neat and clean, but the plumber failed in the five ways shown above.  He also seemed quite uncertain about whether or not an expansion tank was needed and ultimately installed one even though he worked to try to convince me that a tank was not needed.  All this difficulty occurred despite A) hiring a pleasant experienced plumber and B) getting a personal recommendation to hire this plumber.

I guess tradesman, in general, are not big thinkers.  They do what their fathers and grandfathers have always done, no matter if it is good or bad, unless it totally and utterly fails to work or the law requires something new to be done.

Wish I had done the plumbing myself and ultimately will probably remove all of it and install my own plumbing correctly.