Yanmar 4JH57 water heater (calorifier) shutoff

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   Marsella
The reference to a yacht chandler selling accumulators from 0.6l upwards, was just to answer your question as to whether accumulators smaller than 5l were available. It was not a sizing recommendation. 

People can just use the sizing calculator as a starter. 

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Martin&Rene Members Profile Send Private Message Find Members Posts Add to Buddy List Vice Admiral Joined: 06 December 2009 Location: United Kingdom Status: Offline Points: 967	Post Options Post Reply Quote Martin&Rene Report Post Thanks(0) Quote Reply Posted: 28 November 2025 at 15:40
	Marsella The reference to a yacht chandler selling accumulators from 0.6l upwards, was just to answer your question as to whether accumulators smaller than 5l were available. It was not a sizing recommendation. People can just use the sizing calculator as a starter.
	Martin&Rene Hanse 341 Dipper Wheel steering, 3 cabin layout, normally based in Scotland

marsella Members Profile Send Private Message Find Members Posts Add to Buddy List Rear Admiral Joined: 21 June 2022 Location: Antigua Jolly H Status: Offline Points: 592	Post Options Post Reply Quote marsella Report Post Thanks(0) Quote Reply Posted: 05 March 2026 at 21:10
	Just for the record of this thread, as some admirals advised, I finally installed the expansion tank on my 458. I went for Zilmet ZS2 with acceptance volume of 1.13L. It went under sink in saloon bathroom. On this boat we have 22L water heaters, which produces about 0.53L of excess volume when heating the water from 20 to 80C, therefore 1.13L should be ok. I also plumbed two pressure gauges showing the water pressures in cold and hot lines. I can confirm that the expansion tank stabilizes the hot water pressure when either engine is working or electric heater is turned on. The pic below illustrates hot water pressure reaching 70 PSI, while cold water line stays at 40PSI (expansion tank is seen below) I can also confirm that the hot water pressure goes thru the roof at the absence of expansion tank, dont know how high since my pressure gauge is limited by 100PSI but it definitly exceeds it. Here is the pic of hot water pressure without the expansion tank:

perry Members Profile Send Private Message Find Members Posts Add to Buddy List Captain Joined: 13 October 2015 Location: IOW Status: Offline Points: 318	Post Options Post Reply Quote perry Report Post Thanks(0) Quote Reply Posted: 06 March 2026 at 09:25
	Thanks your work and the informaton. I was aware that the pressures go high [somewhat dependant on the stiffness of plumbing etc] without a accumulator in the circuit, but seeing your gauge at close to 100 psi reinforces my theory that the isotherm vitreous lined calorifiers are prone to fail early; not to mention the poor quality of the isotherm pressue release valve? With pressure expansion of the pressure vessel and the brittle vitreous coating cracking. Either way the quality alternatives of a copper [Surejust UK] or Duplex SS pressure vessel is a better solution, and of course a pressure accumulator to limit the peak pressures. Perry
	Current Yacht Hanse 315 2007 Last Yacht Hanse 301 Round GB in 2017



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