A high-efficiency boiler was used to heat this year-round outdoor pool, resulting in less maintenance and lower Btu.

In November 2009, the original pool heater at the L’Arbre Croche resort finally ended its career. A new pool heater was needed, but more importantly, it was needed fast.

L’Arbre Croche (French for “Crooked Tree”) is a beautiful resort community on the shores of Little Traverse Bay of Lake Michigan. L’Arbre Croche is nestled beside soft, white sand beaches and is a short drive from ski resorts to provide year-round outdoor activity.

A high-end resort, L’Arbre Croche was known for heating its all-season outdoor pool. A time crunch was on to install a new pool heater in time for the Christmas holiday, when the resort would be full with members and their guests.

Enter Rich Murphy, Lochinvar’s national pool sales manager. Rich was approached about Lochinvar’s Copper-fin pool heater. But Rich had another way. Rich consulted with Mike McElroy, the Club’s property manager at L’Arbre Croche and presented the new XLP pool heater series. 


The XLP system features a Knight heating boiler skid-mounted and pre-piped to a secondary pool heat exchanger. From the Knight XL heating boiler, hot water flows into the heat exchanger vessel. Pool water flows through copper-nickel tubes mounted inside the vessel. The pool water is separated from and indirectly heated by the boiler water, which is important due to the high flow rates in the pool loop.

McElroy was impressed with the XLP package but was surprised by the model chosen. Rich offered the 399,999 Btuh XLP to replace a pool heater originally firing at 1,000,000 Btuh. Due to the high efficiency of the indirect heating method, a lower Btuh input boiler could be used.

In addition, the 5:1 turndown of the boiler’s input rate allowed the XLP to track the heat loss of the pool and modulate the input rate to match the load. Operating at lower input rates reduced operating costs.

Local installer Ballard’s Plumbing and Heating was contracted to install the XLP and the installation proved easier than anticipated. First, XLP Package took less floor space than the original pool heater. The original metal vent pipe was replaced was also used for the combustion air which supplied the boiler with clean air, free of destructive pool chemicals. The simple water piping routed pool water straight through the XLP pool heat exchanger. 


The L’Arbre Croche 35,000-gal pool was open and operating by the Christmas holiday. The pool temperature was kept at 101°F during daylight hours that often dropped as low as 0°F ambient. “The Knight XLP System was the best investment I made, and my staff loves the simplicity and ease of maintenance,” said McElroy.ES