Monday, November 19, 2018

Failing first generation microinverters

I installed my first array of 26 solar panels back in 2009 using state of the art microinverters made by Enphase.  I was an early adopter of the new technology that has created a paradigm change in solar power systems.  Previously an array of solar panels was wired in to a single large inverter that converts DC power from the solar panels to 240VAC that feeds in to the building.  

Microinverters are mounted behind each individual solar panel.  This creates a granular system that allows precise monitoring of the power produced at each panel.  It also offers a more graceful failure mode, if a single microinverter or panel fails, the whole system does not go down as it would with a large central inverter.
Over the years several of these first generation microinverters have failed and Enphase have been very responsive about sending out replacement units, honoring their 15 year warranty.  Of the original 26 inverters, 4 have now required replacement.  More details here.

It is tedious to have to go up on the roof using 2 ladders with a helpful neighbor and remove one of the panels and replace the inverter below it.   I hope the replacements will last longer!  As an electrical engineer, I recognize that the electronics are operating in the harshest conditions of heat and cold up on the roof and clearly there has been a learning curve as they gather data from failed units and incrementally improve the design.

Sunday, October 28, 2018

Heating my bedroom - recovering chimney heat

In my last post I explored optimal ways to heat my bedroom using a small electric heater.  In this post I will detail how I have diverted trapped heat from around the chimney in the hallway to heat my room.  The chimney is cinder block and was exposed when my ex and I bought the house.  It was pretty ugly so I boxed it in with drywall on both floors, being careful to keep combustibles several inches from the hot surface.

The large wood stove in the basement is big enough to heat the whole house as heat rises from the open basement stairs and 2nd floor stairs to the bedrooms and bathroom.  The pictures below show the first floor boxed in chimney and the vents I installed to release the trapped heat.
By ventilating the closed space around the chimney I am releasing heat that could build up and prevent a chimney fire which is an added benefit.  But the primary goal was to recover this trapped heat.

My bedroom is adjacent to the chimney and I had used a similar scheme to ventilate the walled in chimney on the 2nd floor, but the vents both were in the hallway.  I decided to move the upper vent into my bedroom to divert the heat there.  This drawing shows the simple change I made:

Here's the bedroom wall before I cut the vent:
As you can see the area near the chimney is warmer than the other walls - through 2 layers of drywall!

After cutting the hole and closing off the vent in the hallway, I immediately felt warm air exiting the new vent in my bedroom.
With only a moderate fire going the heat coming from the vent is at least 10F hotter than the ambient room temperature. 

And after keeping the stove lit for a few days it's a lot warmer at the top vent (105F).

So I'm hoping this recovered heat will reduce the electricity needed to heat the bedroom.

Tuesday, October 23, 2018

Exploring efficeincy of electric heating my bedroom

This spring I moved into the smaller bedroom of my house so I could rent out the much larger bedroom full-time.  I had been renting the small room out on airbnb previously, but only during the warmer months .  While the large bedroom has an adequate Rinnai propane heater, the small room has no permanent heater.  As winter is approaching I have started using a small 1500W heater made by Pelonis.  

I bounght this neat little unit back in the 1980s.  It contains a ceramic disc heating element that was a spin-off from NASA space shuttle technology.  The clever feature of this unique heater is that it can continuously vary it's output in response to room temperature.  The temperature sensor is embedded in the power cord a few inches from the heater.
A simple knob lets you set the temperature, and a switch allows automatic (thermostatically controlled) or manual setting.  The manual setting just stays at a fixed power level.  Output power can range from 350 to 1500 Watts.

In use what happens in the automatic mode is that as the room approaches the set temperature, the heater and fan speed dial down across a continuous range.  The issue I have is that the fan can produce some odd harmonics at some speeds that can be annoying - it sounds like a jet engine winding down.

Recently I came across this clever programmable wireless thermostat that can switch power to a room heater plugged into its switching module.
wireless programmable thermostat
So I bought a couple of them (click image for details) since they were relatively inexpensive and appealed to my geek nature.  I like the programmable features that let you set up to 8 programs for specific days and time of days.  Of course actually programming it is very tedious, but I figured it out eventually. (And while the picture shows Centigrade, it can be set for Fahrenheit).

The obvious application was for my bedroom, so I could program the heater to set back during the day and warm up the bedroom at night before I go to bed.  As an interim solution I had been using a programmable timer to turn the heater on and off in its automatic mode, but this left the room too cold during the day if I wanted to take a nap.  I like these $10 timers from Harbor Freight (click image for details).
Like the thermostat, it takes time to figure out, but can be used to set multiple times of on/off cycles per day and has a manual override button.  

So I decided to test the new wireless thermostat with the Pelonis heater and compare it to the timer that would activate the heater in it's auto mode only at night.  With the wireless thermostat, I set the heater to switch on at full power of 1500 Watts and let it cycle on and off based on the temperature sensed at the thermostat on my bedside table.  This means that I would not hear the annoying whine of the heater at lower speeds, but it would switch off for periods which is better, and while loud when running it is less irritating.

So being a geek, I decided to see which mode is the most efficient from a power standpoint.  In theory using this heater to maintain a fixed temperature in the room should be the same either way.  But the devil is in the details.  I set up a data logger to record outside temperature, room temperature, heater power and outside ambient light (because why not!).  All the sensors are ones that I custom built for other projects.  I also used a Kill-A-Watt meter to record cumulative power.
Test setup with datalogger, sensors and Kill-A-Watt meter

 Here's what I learned.
click image to embiggen
On day 1 the wireless programmable thermostat switched the heater on and off and used 5.2kWh.  On day 2 the heater used its internal thermostat and used 6.5kWh.  Note that at the left end of the chart the wireless thermostat was activating the heater periodically to maintain the set-back temperature of 65F.  As the winter gets colder, this will be a bonus.

The outdoor temperatures were roughly the same averaging in the mid 30s, so it's a fair comparison and clearly the the external thermostat wins and will save me about 1kWh (at the utility rate of 15cents) a day in energy costs while also reducing my carbon footprint.  Maine's electric power is almost 40% renewable, and my solar power system provides much of my energy in the winter anyway so the carbon footprint aspect is relatively moot.  I have found that I prefer the sound of the heater switching on and off and sleep better not hearing the whine of the reduced power mode.  The only drawback is the wide temperature swings of over 5 degrees, but I can handle that.

I later replaced the heater with a more modern and much quieter unit. Then I upgraded to a Nest thermostat and built a custom interface for that so that it could switch power to the heater. This works extremely well for me and allows control of the heater from anywhere, any time via Alexa and my Echo Dots.

Saturday, August 18, 2018

The unsustainable world of computer printers - and what you can do

My multi-function computer printer started failing a few months ago.  The color LCD screen on the front went first - showing inverted colors, then finally the interface failed.  I tried switching from USB to wireless, and that worked for a day.  Tried a network setup and that didn't connect, all of which wasted a half hour of my time or more.  I had bought it in December 2013 so it is almost 5 years old and it cost me over $200 back then.  The thing is that there is no good reason for it to fail so soon.  I design electronic products for a living and a machine like this should last over 15 years or much more ideally.  But it is deliberate planned obsolescence by the manufacturers.  Over the last 30 years I have personally owned more than 8 printers as they evolved from "dot-matrix" to laser and inkjet technologies.  And from black to color and then photo quality.

I bought a replacement that is basically the same as the old one - but of course I can't use the same ink cartridges!  And of course it was packed in (non-recyclable) styrofoam, just like the last one.  The printer manufacturers want to keep making money on new designs and ink cartridges.  The folks at Staples wanted to sell me a 4 year "protection policy".  That just made me angry!  These things ALWAYS fail right after the policy expires.  In fact the staff person freely admitted that printers typically only last 3 years.  So I should count myself lucky that my last printer lasted 5 years?  When I took the new printer in it's box to the checkout counter, the gal there said "Oh, let me get some ink cartridges for that."  Apparently they only provide "starter" cartridges that just last long enough to align the print heads!  That's like selling a new car with only spare "donut" tires on it!  So that doubled the cost of the printer that I thought was reasonably priced as marked down old model.

I think about the millions of printers that the world has to replace every year and it boggles my mind!  Plastic comes from oil, so this is driving our global demand for oil - even if the plastic can be recycled.  

I tested the (Energy Star rated) printer with my Kill-A-Watt meter and found that it drops to less than 1 Watt in sleep mode and peaks at 6 Watts when printing.  If I were to leave it on like most people do, I would only be using up to .7 KWh/month.  While this may only cost about 7 to 10 cents each month, there is the environmental impact of the electricity source to consider.  Of course I'm on solar power, so this is moot for me.  But I have all my computer equipment plugged in to a switched outlet box with separate switches for each device.  This way I can kill all the phantom loads like the monitor and USB peripherals.  With this model printer, if I turn it off using the button on the printer, it does not seem to draw measurable phantom power unlike older models.  My last laser printer drew over 30 watts in "sleep" mode!  Most big office printers are sitting there all night drawing phantom power when they are not being used and that really adds up.

So what can we as responsible consumers do?  Well first, don't trash that printer!  Remove the old print cartridges and sell them on eBay (yes people buy used cartridges to re-fill) - or turn them in to the office supply store to be recycled.  And if you have spare unused ones, sell or return them too.  Most office supply stores will also recycle the old printer too.  Here is what Staples says about their electronics recycling program:

"Materials Staples collects from customers are kept in an employee-only area of the store for a short time until sufficient material has been collected to backhaul to our Staples® warehouse locations. The Staples warehouses consolidate the electronics into full truckloads and ship the material to the facilities of our national recycling partner, ERI Direct. There, the material is triaged based on potential for re-manufacturing or parts harvesting. Items that can be refurbished or that may have parts that can be reused are separated and processed separately."

Staples is an e-Stewards Enterprise, which means that we have committed to using certified e-Stewards recyclers whenever possible to handle the materials we collect. ERI Direct, a certified e-Stewards Recycler, is our primary recycling partner for electronics and therefore must be audited against stringent standards and disclose their downstream processing partners to ensure that they are using responsible e-waste recycling practices and not exporting or otherwise improperly handling electronic materials."

This is commendable and the ERI web site includes a good video that clearly shows how responsible they are about recycling.  But it would be a better world if printer manufacturers took responsibility to make better, longer lasting equipment.  They could also design around a standard ink cartridge that works across most models.

As I was writing this my new printer's screen lit up and showed:
Followed by the printer turning off, then on to install an update.

Ok, so that's impressive - it can update it's own software!  And this model can also order it's own ink cartridges when they run low.  They have got us right where they want us!  But this is all driven by corporate greed and not the common good.  This is just not sustainable in the long term.  We have one planet worth of resources and industry keeps using it up as if it was infinite.

Monday, July 30, 2018

Optimised water heating and upgrade for meeting house

I have been very involved in maintaining my Quaker Meeting House in Damariscotta, Maine for many years.  I have helped to "green" the building in many ways, from adding a modest solar power system, to many efficiency upgrades.  The building was constructed in 1995 and was built with "traditional" construction and heating system.  This means that it uses an oil fired boiler like many buildings and homes in New England.  So about 10 years ago we decided to switch to a B20 (20% biofuel) mix that became available in our area.  Higher biofuel ratios do not work well in frigid temperatures because it can congeal and also corrode seals.

But then we realized that the water heater is tied in to the huge oil boiler and the boiler was running during the warm seasons to heat a 30 gallon tank located in the cool basement.  In this environment the tank loses heat and needs to be "topped up" fairly often wasting a lot of fuel oil to heat water that was not being used.  So we came up with a work-around.  We had a small 4 gallon electric heater installed after the hot water tank.  Then we installed a timer that only runs the oil "boiler-mate" for hot water on Sundays when we need more for dish washing and events.  When the tank is not being heated by the boiler, the stored water is tempered by the ambient environment, thus raising the temperature of the well water from a nominal 45-50F to 50-60F.  This reduces the load on the small electric heater a little.

Now the modest weekday hot water needs are met by this small electric heater.  Due to the Regional Greenhouse Gas Initiative (RGGI) in New England, the electric supply is supplied from at least 45% renewable sources such as hydro, solar and wind.  So this is a win from a cost, carbon footprint and efficiency standpoint.

All this came up when someone noticed rusty water coming from the hot faucets.  I drained water from each tank and determined that the small electric unit had rusted out inside.  Our local plumbing company wanted $400 for a new heater, plus labor.  This seemed unreasonably high so I found a nice Bosch unit on Amazon Prime (free delivery of a 20+ lb package!) for under $200.  It took me about 20 minutes to replace the unit.

Tuesday, July 3, 2018

Time-lapse of nesting robins being fed by their mother

A robin decided to nest under the solar collectors on the south side of my workshop this year.  The nest is about 5ft off the ground and I have been watching since the first little blue egg was laid several weeks ago.

They all hatched a week or so ago.

It is now July 3, and they are coming along nicely.  I can watch the mother robin flying in and feeding them from the window in my utility room.  What surprised me is the long gaps as she foraged for food.  Up to 20 minutes could go by as they waited patiently with beaks open.  The video was shot at 1 frame per second (about 30X real time), it is edited down so it is not too boring.

Sunday, April 8, 2018

Metal detecting - my new hobby

Last year I binge-watched the British TV series "Detectorists" (available on Netflix and Amazon) which is a comedy/drama about 2 quirky English mates who share a passion for metal detecting.  Don't call them "detectors" - that is the machine, as you quickly learn!  I highly recommend watching the show and I was captivated by the idea of digging up history, relics, coins and just about anything including "can slaw".  (Can slaw is detectorist slang for a soda can that has been chewed up by a lawn mower.  These and pull tabs are the bane of our existence because a detector sees aluminum as precious metal and pull tabs could be a ring).  

Detector, tools, pinpointer and finds from December 2017
So last fall I bought a metal detector, pinpointer and the related equipment that includes digging tools, too belt and cleaning brushes etc.  I started by practicing on my rural property and quickly found some coins and assorted bits of metal, I was hooked!  Unfortunately the ground froze a few days later and snow covered the ground for most of the winter.  So I was stuck watching other detectorists on YouTube and learning skills from them.  I also joined several Facebook detecting groups.  Basically I was going to Detectorist University all winter!

Now it is April and the ground has thawed I'm starting to explore the historic sites around my small Maine town.  My first day was uneventful but enjoyable, all I found was a few rotted modern penies - known as "clad" to detectorists because they are plated and quarters are not solid silver like they quarters used to be.  Contemporary pennies are copper plated zinc and don't hold up well under ground, but old silver coins tend to come right out of the ground all shiny.  Oooh!

Then on my second day, the second hole I dug turned up an amazing find.  It is a silver flashed brass medallion honoring 300 year of ship building in the nearby town of Bath and dated 1907.  Wow!  I immediately offered it to the local Historical Museum and they were grateful to accept it.

So by now you may be wondering what does all this have to do with living sustainably?  Well it's not all treasure.  There is a code of ethics for metal detectorists that, among other things, requires that you remove everything you dig.  This makes it easier for the next person that might detect in the same area.  On almost every dig you tend to find a variety of trash that includes, nails, rusting steel parts from old farm equipment and fixtures, old beer and soda cans and pull tabs.  Also lead bullets dating back to muskets and lead flashing from roofs.  Much of this can be recycled!  So I plan to store this "scrap" until enough accumulates to take it to a recycling center.

Another basic ethic of the hobby is to leave the land the way you found it.  So all holes on public and private property are filled back in.  And we are assiduous about getting permission to dig on private land.   Beaches are different, and most public beaches allow metal detecting and filling holes is not that big a deal, but we do haul out all the trash - and the occasional gold ring or silver coin!

I have started a new blog called: "Guy Digs It Up" so you can follow my adventures there.

Wednesday, March 7, 2018

How I design an electronic product

I thought I would share the process I go through to design an electronic product.  I have been doing this type of work since the mid 1980s and while the tools and parts have changed, the process has remained much the same.  As an example I will show how I designed my own product which is a Differential Temperature Controller designed for solar heating systems.  

This device controls fluid circulation pumps that move heat from solar collectors to storage tanks.  I sell these products from my ART TEC Solar web site.

I begin by designing the schematic in CAD (Computer Aided Design).  This is the hard part that requires a lot of research to find the right components and then figure out how they interconnect.  In most products these days there is a microcontroller chip that is programmed to perform all the functions.  More on that later.  Selecting the right microcontroller begins by deciding how many things it needs to connect to or control.  These include buttons, LED indicators, LCD (Liquid Crystal) text display, and connections to external parts like pumps, sensors and power source.  The schematic drawing defines how all these parts connect to each other.
Next I design the circuit board (PCB) in CAD.  The layout software imports the signal connections from the schematic making it easier to ensure all the right connections are made.  This PCB is the physical embodiment of the schematic and involves carefully placing the parts such that the interconnections are optimized.  Key parts like the controls and screw terminals need to be placed for ergonomics and easy access.  For me, this is the fun part because it is a lot like creating an artwork and I enjoy making an aesthetically pleasing layout.
The location of every part has to adhere to electrical AND functional rules and the size of the circuit traces has to be scaled to the amount of power it has to carry.  Circuits that carry more current are wider like the green ones along the bottom in the design above. The green represents the conductive traces on the bottom side of the board, and the red are those on the top of the circuit board.  A great deal of thought goes into every minute detail to optimize size and cost.
The parts need to line up to make assembly by robot or hand easier.

Once the design is complete the file is sent to a fabricator that makes the bare circuit board.  This is a fiberglass board with plated copper traces connecting the holes where the components get inserted.  For volume production, they are tiled up into groups to facilitate machine assembly.  

Once an assembly machine has been programmed to insert all the parts, it can just copy the sequence to the rest of the boards on the panel.  For hand assembly, boards are separated and parts are inserted by hand and then hand soldered on the back.  In my design, parts are installed on both sides.

Once a prototype is assembled and tested, the next step is to write computer code for the microcontoller chip.
I write in BASIC language and have been coding in some form of that language for over 40 years.  The code defines the functions of how the device responds to inputs like buttons and sensors.  The heart of the code defines the functions of what the device does.  In this case how it responds to sensor readings and when it decides to activate a pump.  It also displays real-time temperatures on the LCD and all the interactive menu features.  The code is them compiled into machine code and downloaded into the flash memory in the chip in much the same way you save a file to a thumb drive.

Finally, I design the front panel and case.  Often for my clients projects, I work with a product designer who does 3D CAD design.  In this case, I used an off-the-shelf basic box and set up tooling to make cutouts using the woodworking equipment in my workshop.  It would have been prohibitively expensive for me to design a custom enclosure and have molds made for injection molding a low volume product like mine. 

The front panel of this product is a membrane that I designed and had fabricated.  It is flexible so that a light touch can move the membrane enough to actuate the switches behind.  It has clear windows for the LCD screen and a green LED indicator.

The final step is to assemble the whole product.  All the parts get screwed or glued together and the membrane is adhered on to the front.  Here is one that I use in the solar heating system for my workshop.

The process of developing this product took dozens of hours over several weeks.  Finally I have a product that has done relatively well in the niche market of the DIY solar heating world.  I set everything up to be scalable from making them by hand to volume contract assembly.  In boom years I contracted an assembly company to make batches of 100 pieces.  Otherwise I just build them by hand myself and it takes me about 30 minutes to assemble.  I call this my "get rich slow scheme" as orders come in almost every week. Over the years I have sold over 200 of this particular model and have two other models that have sold over 1000 pieces total. 

Many of my clients start out by ordering 1000 products for test marketing, then scale up once they have created a demand.  Most volume manufacturing is done off-shore, but for under 1000 pieces there are companies in the US that can be competitive.

If you have a great idea for an electronic product, visit my Product Design page and contact me.

Wednesday, February 28, 2018

Replacing the battery in my Kindle Fire HDX 8.9"

I have had my Kindle Fire HDX for over 4 years now and I like it a lot.  It is my go-to device for social media, email and web browsing while at home.  Recently the battery has been lasting only a few hours - previously it would last over a week of normal usage.  So I decided to replace it.  I found a deal on ebay for about $25.00 which is a LOT cheaper than replacing or upgrading to a new tablet!  I found a instructions on ifixit that shows how to open up the Kindle and replace the battery and it did seem a bit daunting, but I'm an engineer dammit!  It turned out to be quite challenging, but I got it done without ruining the tablet.  At one point I did puncture the batteries (there are 2) and smelled a strong solvent odor, but nothing exploded or got hot so I proceeded.  Those batteries are glued in there quite firmly, and it took about 15 minutes to pry them free.  Replacing them and re-assembling the case was relatively easy.

From a sustainability standpoint I'm pleased with the outcome.  I can responsibly recycle the old batteries at Lowe's.  Also I'm not contributing the the consumer culture that drives people to upgrade their devices every year or so.  Plus I have delayed the day that I will have to recycle this great tablet, and I saved a bunch of money.  I do wonder how these things are taken apart and recycled given how much trouble I had.

Here's a brief photo summary of what I did:
 Here is the replacement battery and the relatively useless tools that came with it.
The blue spudgers broke and I ended up using a flat blade screw driver and my trusty Swiss Army knife to pry the case open.  There was a tiny specialty screw driver tool that was needed to remove 4 small internal screws, but it was for a smaller screw.  I was able to grind down the tip to make it fit.

Here's the case opened up and the display disconnected and off to the left.

You can see that I had to do horrible things to remove the batteries!

Here's the back of the device after I got them out. 

I don't recommend this for the faint of heart or those not "tool enabled".

Thursday, February 8, 2018

Solar and snow

The first morning after a snow storm is often sunny.  This morning (Feb. 8, 2018) was a good example and I got up early so I can clear all the snow off my solar panels and collectors.  Yesterday's total was about 8" capped with a layer of ice.  I have a snow rake that can reach up about 25 feet with multiple extensions.  Each different type of snow requires a different strategy.  Sometimes I can just whack the panels and it all breaks loose in big chunks.  Other times I have to chip away at it.  Today I worked my way up from the bottom.  Some big areas broke loose and came down hitting me in the legs which is why I wear waterproof slickers.  That stuff is heavy!

Here's a time-lapse of the process:

Obviously the sooner I get everything cleared, the more free electricity and heat I get.  Maine is at the 43rd parallel and we get a lot less sun in the winter so I want to optimize every Watt.  My electric bill is at the minimum connection fee for most of the spring/summer, but jumps up quite a bit in the winter due to my increased use of electricity for heating and the reduced solar.

Sunday, January 7, 2018

Repairing the tankless propane boiler for my solar augmented heating system

4 solar collectors shown at right
When I moved to Maine in 2001 I converted the open barn on my property to a well insulated workshop.  I also designed and built a heating system that uses solar and propane to heat the radiant concrete slab on the ground floor and baseboard radiators on the 2nd floor office/lab spaces.

The system relies heavily on the Bosch Aquastar BS124 tankless propane boiler that has performed flawlessly since it was installed with only token maintenance.  (You can see a system diagram and live performance charts on my web site.)  Unfortunately it recently failed dramatically due to a prolonged period of extreme cold. 

In the images above you can see the storage tank that accumulates solar heated water during the sunny hours of the day.  Above left is the boiler that automatically brings the water temperature up to 140F when it is lower than that.  In the dead of winter I am lucky to get 140F in the tank so the propane boiler runs a lot.  To reduce the propane consumption, I use my wood stove.  The drawback to the wood stove is that when lit it pulls air into the building and that comes through the powered exhaust vent above the boiler.  Originally, the boiler vent had a flapper valve on the outside to prevent a back draft, but I had foolishly removed it.  So what happened this winter is we got a prolonged period of very low temperatures with night time temps dropping below zero a lot (see the red line below).
(lost data on Dec 28 for some reason)
So on December 30th when the wood stove was running and the heater was off - the cold back draft got down to -15F and eventually a pipe burst in the top of the heat exchanger:
Heater running AFTER repair - arrow shows location of the burst pipe
The arrow points to the section of pipe that blew open.  I immediately researched replacement parts and found a source for a complete replacement copper heat exchanger and in a panic - ordered one online for $350.  But then after calming down, I realized that the damage really wasn't that bad, and that I probably had the plumbing skills to repair it since I had plumbed the whole system myself!
Here is what the burst pipe looked like when I looked closely at it.  It was fairly simple for me to gently hammer the lips of the burst out section back together after draining the system down below the leak.  Then I carefully sanded the whole area around the cut to expose clean copper.  I wiped on a lot of paste flux and warmed it all up with a blow torch.  By gently applying solder, I was able to fill the crack and build a layer of solder over the whole area.  Problem solved and I canceled my order for a new heat exchanger!
There is no running water in the building so in order to re-fill and pressurise the system I had to drag a garden hose across the yard from the house.  This was challenging with 8" of snow on the ground and day time temperature peaking at 10F!  I had to pre-warm the 2 - 50ft lengths of hose in front of the wood stove to loosen them up first!  But it all worked out and it has been holding 50psi pressure for over a week now.  And of-course I made a new back draft flapper for the vent to prevent frigid air from being drawn in again.

Problem solved!  And I saved $350 in replacement parts!  Incidentally the whole building only uses about $200 gallons of propane a year at a cost of about $400 in a good year.  This is very inexpensive and due to the great insulation, interior storm windows and about 1 cord of firewood that I cut for free on my property.