Unless you're on the West Coast of the U.S.. Ocean Options is the largest U.S. dealer and an expert in both Hydronic and Forced Air Systems.

http://www.oceanoptions.com/catalog/heating/hydronic-heaters

Michael Bowden is their President and founder. You can call him. He's worked on all kinds of boats, yachts, work boats, etc. (401) 624-8091

P.S. - About 30 years ago, our Sabre 42 had just been delivered with the first Espar system ever installed on a Sabre sailboat. Mike had helped "Plan" the system, but Sabre had installed it.

After a long weekends' use, I noticed that it seemed to failing to put-out heat. I called Sabre, they said that someone from Espar would stop by our boat in Annapolis because the master dealer was at Annapolis' US Boat Show.

At about 8:00 on a Saturday morning along comes a guy in slacks, sport coat and a white "dress" shirt. He introduced himself as the President of Ocean Options and asked me what my problem was. After I described it, he checked the controls to see what the heater wasn't doing.

He muttered, I asked them, "Not to connect the two stage switch option! Just have one fan speed." Then he found a bad connection at the controls, he said that I should have the glow plug changed to be secure that it would work through the Fall and over the Winter. Asked if I had some tools. Then Mike took his jacket and shirt, and shoes off; and, then climbed down into our stern locker. He changed the glow-plug with a spare that we were given, said our previous glow-plug would work, but he wanted to make sure (he found a couple of connections he tightened). Mike climbed out of the stern locker, got redressed, shook my hand, and went off to the boat show.

He's still the same guy he was almost 30 years ago -- running a small, company, and doing as good a job as he can.