Single Points of Failure

Over the weekend, my family had an annoying lesson in one of the basic principles of software engineering, the "Single Point of Failure". 

You see, when we built our house, we decided to go with a "hai-tekku" heating solution, and we're paying the price for it.

Normally, when you build a house you get two units installed - a hot water heater and a furnace.  For a house heated with natural gas, that means that you need to have two chimneys - one for the water heater and another one for the furnace.  That means you (a) need to have two holes punched in your roof, and (b) you send a ton of heat up the chimney of your furnace (because air is a lousy thermal conductor).  Hot water heaters are WAY more efficient than furnaces (because water is a pretty good thermal conductor, and thus retains heat better).

Instead of relying on a more traditional hot water header/forced air heater combination, we chose to go with a Polaris hot water heater, which allowed us eliminate the furnace - instead, the hot water from the hot water heater is pumped into a heat exchanger and the residential air is warmed by the heat exchanger.

This system works great - we get a huge amount of hot water (as a result of the large capacity tank and it's relatively quick charge time) and it usually "just works".

Until Saturday afternoon.  Valorie came back from riding and discovered, much to her chagrin that we didn't have any hot water.  I went down and checked the tank and sure enough, the "Igniter" light was out - the igniter had died on the hot water heater.

Well, having no hot water's not THAT big a deal - it's somewhat annoying, but it's no big deal.  We called the repair people and they came out today to repair the system.

Remember above where I talked about our not having a furnace and instead using a heat exchanger to heat our house?  Well when the hot water heater went out, so did the heat inside our house.  When I left for work this morning, it was 52 degrees Fahrenheit inside the house - a bit nippy.

Our hot water tank acted as a single point of failure for our homes environmental systems - not only did its failure take out the hot water, it also took out our heating system as well.

Fortunately, we had power and so we were able to heat water, and throwing on a couple of sweatshirts fixed things.  It was also fortunate that Microsoft has lockers with showers in them so we were all able to get showered before we went to theater on Sunday :).

For our next house, we need to consider if we need a backup heating solution or not.

Edit: Fixed awful transliteration, thanks Norman.