My boat has a separate pair of coolant lines for the heat exchanger and a separate pair of coolant lines for the hot water tank, (supply and return lines for each), that is.
So by closing the manual valve that I installed to the heat exchanger, the engine's internal coolant pump is forced to send hot coolant through the coil inside the hot water tank and the cold water in that tank acts for a short time like a heat exchanger. In fact if I carried an unlimited supply of fresh cold water so that I could leave the domestic hot water faucet running continuously that would probably be adequate to keep the engine running cool, but unless there is a separate thermostat somewhere in that loop the engine might run too cold. I always wondered why the domestic hot water set up worked so poorly when I first got the boat but now I am thinking that there is a faulty thermostat somewhere in the line to the hot water tank, if so and it were functioning properly, then while motoring I would always have hot water at some thermostatically controlled temp. I guess most boats with engine coolant heated domestic hot water are like that but I don't know. Now, I think I will start with looking for a thermostat on the hot water tank. Maybe I can get rid of that manual valve that I installed. But if I find a thermostat in the line that is heating the domestic hot water, and it is stuck closed, I don't understand how I could produce hot water better by closing the manual valve to the heat exchanger...there should still be a closed loop to the heating coil inside the hot water tank. More stuff to investigate...more convenience systems onboard means more work, lucky I got time but the spaces where this stuff is located are getting tighter as I get older. Dwight Veinot C&C 35 MKII, Alianna Head of St. Margaret's Bay, NS -----Original Message----- From: cnc-list-boun...@cnc-list.com [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of djhaug...@juno.com Sent: August 24, 2012 9:55 AM To: cnc-list@cnc-list.com Subject: Re: Stus-List Hot water heater Dwight, Greg Just some insights to consider...I hope it helps A thermostat would regulate the flow of heating fluid to the hot water tank. I'm not sure of your setup, but it sounds like you may have a hot water tank with a heating water coil submerged in the tank that the engine coolant runs through to heat the water. Typically, the thermostat on the water heater will open or close a circuit to either a pump (not your case) or an actuated valve (would be your case as you only get heating water when the engine is running and your fresh water pump is always on when the engine running). So if your potable hot water tank had a thermostat regulating it's water temp, there should be some kind of actuated valve in the hose running from your heater to where it ties into the engine coolant line. Now, it could tied in series, in other words, it could be part of the engine coolant loop and gets hot water through the Hot water heating coil constantly when the engine is running (which is probably not a good idea and doesn't sound like what you have), or there is a tee somewhere in the coolant hose that the hot water heater gets its heating water from. Anyway, all this dribble to try and help you determine whether or not your hot water tank is thermostat controlled. If the Water Heater is electric it will have a submerged electric heating element, sometimes 2 of them. They do go bad and sometimes produce luke warm water. Especially if there are 2 electric elements and one goes bad. ---------- Original Message ---------- From: dwight veinot <dwightvei...@hfx.eastlink.ca> To: cnc-list@cnc-list.com Subject: Re: Stus-List Hot water heater Date: Fri, 24 Aug 2012 09:25:14 -0300 Rich The hot water on my boat is also heated by the engine coolant, which passes through a coil in the hot water tank. I have installed a manual valve in the coolant line from the engine to the salt water heat exchanger. I can adjust that valve to control the flow of coolant to the hot water tank, mostly I leave it full open to the heat exchanger but when I want faster hot water I adjust it to force more coolant through the heater and less through the engines salt water cooled heat exchanger. I was not aware that a thermostat controlled engine coolant flow to the hot water tank but maybe my boat has such a setup which was not functioning when I first got the boat. I did not produce much hot water in the tank by running the engine until I installed that manual valve which allowed me to divert more engine coolant to the coil in the hot water tank. Maybe I had a malfunctioning thermostat in the line but it I did not see one. Based on your advice to Greg, I'll look harder now because that would be preferable to using the manual valve. Is the thermostat that would control this usually found on the engine or the hot water tank? Thanks Dwight Veinot C&C 35 MKII, Alianna Head of St. Margaret's Bay, NS -----Original Message----- From: cnc-list-boun...@cnc-list.com [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Rich Knowles Sent: August 23, 2012 11:35 PM To: cnc-list@cnc-list.com Subject: Re: Stus-List Hot water heater Thermostat? Rich (mobile) On 2012-08-23, at 22:57, "Greg Sutherland " <bluenosesail...@hotmail.com> wrote: We are anchored off of Masons island in Mahone Bay and just finished a nice bbq supper. Have been running the diesel for a good 60 minutes to charge the batteries and electronics. when we turned the tap to clean the dishes the water is lukewarm. It typically takes 10 to 15 and the water will scald you. Any ideas what the issue may be? Thanks group Greg 87' 33 mk2 Sent wirelessly from my BlackBerry _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2197 / Virus Database: 2437/5219 - Release Date: 08/23/12 _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.2197 / Virus Database: 2437/5220 - Release Date: 08/23/12 _______________________________________________ This List is provided by the C&C Photo Album http://www.cncphotoalbum.com CnC-List@cnc-list.com
