Hydronic Cabin Heating and Domestic Hot Water

An early requirement for the boat is cabin heat and hot fresh water using a hydronic heater. With that as the plan, there are hose runs through bulkheads and settee structures. Installed quite sometime ago. Well, we realized the finished system. Here are the details.

ITR Zephyr Hydronic Boiler

Boiler unit mounted in the purpose built settee cabinet

The primary unit is an ITR Zephyr HW. It is a diesel fired boiler that includes domestic hot water, AC element and propulsion engine heat assist.  The boiler unit is in the purpose built aft dinette settee base cabinet, on the port side, just to the left of the companionway door.

Fuel Filter and Coolant Access 

The fuel filter, coolant reservoir, pump and overflow tanks are below the companionway door threshold, covered by cabinetry (eventually), for easy access.  Coolant hoses and fuel lines lead from to the port side, secured against the bulkhead and behind the settee base cabinet. All hoses either terminate at the top of boiler unit, or through the bulkhead to underneath the workbench in the engine room, where fittings have easy access. 

The coolant expansion and overflow tank

Coolant plumbing (and diesel fill plumbing) against the engine room bulkhead.


Intake and Exhaust

The air intake, muffler and exhaust flue rise up almost vertically from the boiler unit, behind the aft settee backrest. A small space contains the combo air intake/exhaust vent. With that, in this small space is a 24VDC fan to push warm air into the engine room to keep the temperature in the space relatively cool. The fan activates when the coolant circulation pump is active.

Exhaust/Intake ducting

There are three radiators, with 12V fans, in the aft cabin, main cabin, and forward head, with electronic thermostats near each. The main control unit is in the engine room on an overhead console accessible while sitting at the workbench.  The primary touch screen control unit is near the dinettee settee where it will be mounted in the nav station table.

Innards of the hydronic control system.

After chasing a couple coolant leaks at the hose clamp joints, and purging the fuel lines of air, the boiler fired up without issue. 

Burner working. All systems go.

The aft cabin radiator.

Main control head at the nav station.

Muffler, exhaust, intake ducting.

Exhaust/intake ducting with space cooling fan.

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