Summer Heating

Unless we are looking to heat a swimming pool, heating is not foremost on too many minds.  From what I have seen, most homeowners that can afford to heat their pools have a central heating system for their house and a separate pool heater for their pool.  Did you know that one boiler can do both?

How does a boiler heat a swimming pool?  Essentially, the pool would be a separate zone piped to a heat exchanger where boiler water would flow through one end and pool water through the other end.  It would be ideal if the pool filter and exposed piping were located next to the house on the same wall as the boiler.

The main advantages of using one boiler are these:

  1. There would not be a separate pool heater exposed to the elements.  Pool heaters that are not properly winterized last only a few years.  Even with proper care, pool heaters located outdoors rarely last as long as boilers located indoors.
  2. Less maintenance is required.  There is only one burner and one fuel line to worry about.  Freeze ups from improper winterizing would not be as costly since the heating unit is inside.   

The main disadvantages are these:

  1.  With an average sized house, the boiler would likely take two to three times longer to heat up the pool than a separately installed pool heater sized for the pool.  Once the pool is up to temperature, the undersized boiler would probably be able to maintain it for most of the swimming season.  Covering the pool would help when no one is using it.
  2. If the pool filter and piping are located away from the house, long piping runs from the pool to the house could diminish the versatility gains of having one unit.  If 200 feet of piping needs to be installed, there would be a long payback for the installation and some heat would be lost through the piping.

Let’s say that a guy needs to install a pool heater.  His boiler is 20 years old and inefficient.  Should he replace his boiler with one that is the right size for the pool even though it is way more than he needs for the house?  It depends.  A lot of fuel is wasted because heating systems are over-sized. The biggest reason is what is referred to as “idle loss”.  When there is no heating load, heat is lost in a variety of ways.  If a boiler maintains a certain temperature, the burner will run numerous times per day just to keep the boiler warm.  That fuel is wasted the same way as if a car were left running all day just so the person wouldn’t have to start it when he needed to go somewhere.  If idle losses are negligible, one heating unit might make sense for him.   More on that next time.


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