Last year I installed a complete hydronic heating system in our 42 footer. The heat source is either an Espar "boiler" or the engine coolant.
As part of the project I put in a heat exchanger and circulation pump system that has greatly reduced the time to make hot water in our 11 gallon Seaward compared to the standard u-loop inside the water heater tank. The pump circulates the domestic water from the tank through one side of a double-wall heat exchanger with the heating system fluid on the other side.
Based on some recent tests using the engine as a heat source the time to heat the 11 gallons from 60° to 130° went from 3+ hours with the u-tube only to less than 30 minutes with the heat exchanger/pump. This was with the engine running 1500 rpm in reverse at the slip.
It would be fairly simple to add this type of water-heating portion to an existing water heater. I am planning to write up a DIY project with information on how to do it. Many years ago I subscribed to Practical Sailor and recall a report they did on tests of various heaters part of which compared the heat-up rates when connected to an engine. On the PS website I see they did an update in December 2013. Specifically what I am looking for is data on the heating rates. Before I get too far ahead of myself I want to see if other makes of water heater are as slow to come up to temperature as my Seaward. Does anyone here have that article and would consider sharing an excerpt with the data? I believe it is permitted to extract portions from publications without violating copyrights (and fair play).
As part of the project I put in a heat exchanger and circulation pump system that has greatly reduced the time to make hot water in our 11 gallon Seaward compared to the standard u-loop inside the water heater tank. The pump circulates the domestic water from the tank through one side of a double-wall heat exchanger with the heating system fluid on the other side.
Based on some recent tests using the engine as a heat source the time to heat the 11 gallons from 60° to 130° went from 3+ hours with the u-tube only to less than 30 minutes with the heat exchanger/pump. This was with the engine running 1500 rpm in reverse at the slip.
It would be fairly simple to add this type of water-heating portion to an existing water heater. I am planning to write up a DIY project with information on how to do it. Many years ago I subscribed to Practical Sailor and recall a report they did on tests of various heaters part of which compared the heat-up rates when connected to an engine. On the PS website I see they did an update in December 2013. Specifically what I am looking for is data on the heating rates. Before I get too far ahead of myself I want to see if other makes of water heater are as slow to come up to temperature as my Seaward. Does anyone here have that article and would consider sharing an excerpt with the data? I believe it is permitted to extract portions from publications without violating copyrights (and fair play).