Faster hot water

[RoyS]

Wondering if anyone has attempted to install an automotive type thermostat and associated housing to by-pass the heat exchanger while the engine heats up. In my case this would direct all heated coolant through the water heater only while the engine warms up and then through the water heater and the heat exchanger when the engine is fully up to operating temperature. Using this scheme hopefully hot shower water may be generated at anchor with only a short engine running time. Anyone attempted this?

 

[kloudie1]

The old GMF series Yanmar engines do that by design.. The thermostat on those and newer Yanmars have a positive bypass that circulates block water through the water heater and not the heat exchanger until the block water gets hot enough to open the flow to the exchanger.. It does heat the water tank inside of about 15 minutes.
Which engine do you have, Roy?

 

[centerline]

Most motors with an enclosed cooling system use a basic automotive type water circulating pump for the engine cooling loop, and the nipples that would normally have the heater hoses connected to them, will go to the water heater on the boat... this circuit loops behind the thermostat for the quickest heating period...
a good working thermostat in the proper heat range makes a difference also.

 

[RoyS]

Thank you for your inputs. My engine is a Yanmar 2QM15 that was converted to fresh water cooling with a Sendur heat exchanger and additional pump before I bought the boat. The raw water pump draws sea water and pumps it through the heat exchanger and out through the exhaust system. The fresh water pump recirculates coolant from its pump to a T fitting on the engine block to the thermostat to the hot water tank to the heat exchanger and back to the pump. The T fitting permits coolant to either go directly to the thermostat housing or when the thermostat opens to pass through the head and exhaust manifold casting and then to the thermostat. My intent here is to bypass the heat exchanger until the engine reaches operating temperature.

 

[Jim Legere]

I suspect one issue with those old Hunter conversions of the Yanmar QMs using the Sendure exchangers is that the thermostat used is still the older, colder version specified for raw water cooling.

 

[tmjb]

Thank you for your inputs. My engine is a Yanmar 2QM15 that was converted to fresh water cooling with a Sendur heat exchanger and additional pump before I bought the boat. The raw water pump draws sea water and pumps it through the heat exchanger and out through the exhaust system. The fresh water pump recirculates coolant from its pump to a T fitting on the engine block to the thermostat to the hot water tank to the heat exchanger and back to the pump. The T fitting permits coolant to either go directly to the thermostat housing or when the thermostat opens to pass through the head and exhaust manifold casting and then to the thermostat. My intent here is to bypass the heat exchanger until the engine reaches operating temperature.

Not sure if it helps and/or if you need it but you might check out Indigo Electronics who make a bronze thermostat housing that accepts standard auto thermostats plus other related gear. They are intended for use on Aromic 4's but I think might possibly be useful in this application.

 

[centerline]

My intent here is to bypass the heat exchanger until the engine reaches operating temperature.

all it will take is one time forgetting to open the bypass valve will show you how bad and expensive of an idea that is....

beside, you already have an automatic valve that does this called a thermostat.

its NOT the heat exchanger that causes the speed at which the engine heats up. its the thermostat within the engines cooling loop that does this.... as long as there is water in the block, nothing else in the system matters until this water comes up to temp and the thermostat opens... if the thermostat FAILS to close, the water will freely circulate thru the block and will take much longer to heat up. if its closed, the water will remain stationary against the heat producing parts of the block and will be heated as quickly as the heat is generated.... it does NOT even reach the heat exchanger UNTIL it becomes too hot for it to be effective in cooling the hot engine down....

Dont ever restrict the heat exchanger...

 

[RoyS]

Thank you TMJB. I checked out the Indigo Electronics site that you suggested and they have exactly what I am looking for. I called the site owner and he was very helpful. Should this faster hot water scheme work I will report the results here next Spring when my boat is uncovered and back in the water. Thanks again.

 

[RoyS]

Jim Legere is also correct, the Sendur kit originally came with a 160F thermostat. That thermostat is no longer available (at least I cannot find one). The original raw water cooled Yanmar 2QM15 thermostat is 107F and that is all that is available. I not only have that 107F thermostat, I also have a heat exchanger in the cooling circuit. Hot water for showers requires the boat to operate under load for a considerable time at present. I hope to raise the engine operating temperature to 160F and to bypass the heat exchanger until the engine reaches full temperature. Work in progress.