Lister LPWS4 operating temperature range.

[Tony Brooks]

11 hours ago, jonathanA said:

 

I'm not sure I understand why the skin size is important with regard to the thermostat temp, if the skin tank isn't big enough , then it isn't big enough and the thermostat would be open anyway.  I wonder if there is an argument that says having a bigger difference between the coolant temp and the 'canal' temp on the skin tank will aid the transfer of more heat ?  My knowledge of thermodynamics is not up to that sort of question...

There is also no or little correlation between coolant capacity and running temperature as long as the system is full and has no airlocks.

 

You quoted the coolant capacity and some time later that was re-quoted. I know that other people read topics in an attempt to get help so I felt it was important to put on record that the coolant capacity in itself is not a component in overheating. The basic thing about adequate cooling is skin tank singe side area. That is why I posted as I did, to ensure no one  was mislead.

 

You are correct that the amount of heat transferred is proportional to the temperature difference so that suggests that running the engine hotter will transfer more heat BUT it is/should be well known that narrowboat builders are notorious for fitting undersized skin tanks and even if it the correct area poorly designed ones so without measuring the tank and assessing its design there is way forum members can know the cooling will be adequate under ALL circumstances. This, in my view, makes it prudent to run with a cooler thermostat so that in an emergency requiring high power  you have at least a little time before the engine actually boils. Also it is far from universal to have a thermostatic mixing valve fitted to the calorifier hot outer so again because we can never know the configuration of any particular boat it is safer to suggest a lower rather than higher temperature thermostat from the potential scalding point of view.

 

[jonathanA]

Thanks Tony - as usual a clear and insightful explanation much appreciated.

 

eta having looked at various pictures of lister thermostats I’m going to have see what I actually have fitted and what I took out before deciding to stick with what I have or change to a 74C one 

 

 

Edited September 17, 2019 by jonathanA