Originally Posted by a64pilot
A way to run probably rather large heaters off of an engine would be to bypass the engines heat exchanger, using the heaters of course to cool the engine.
Really bad things could happen if you don't watch the engine temp close of course.
Technically possible is the addition of a thermostat in the heat exchanger, making water bypass it to the heaters until a certain temp was reached, you would want this t stat set higher than the engines primary one, and it's function would be different, current
engine t stat restricts flow, this one would bypass, not restrict.
Not worth the considerable work
to do though, unless you just want a really neat project
I would not go to a higher pressure cap, lord knows what possible weak links you could find doing that, it won't raise temp either as was posted, just raise boiling point of the coolant.
Water is about the best coolant there is, interestingly anti-freeze isn't as good a coolant as water, the higher the percentage of anti-freeze, the less heat the coolant can absorb, but you need the anti-freeze for corrosion
protection more than anything else. I only bring this up as I have seen people run very high percentages of anti-freeze thinking that's best, but have engines that overheat or very nearly so.
I hooked up the heaters last night and was a little apprehensive quite honestly. The apprehension was not well founded however and the heaters both work superbly, while at the same time, the engine temp stayed the same. As Jim mentions though, it's a dynamic system and I wonder about the summer temps and what that will do to it. I will continue to monitor
it and look for deviations. These are truck, bus, tank heaters, so ya, engine coolant driven. An interesting note, while looking at the shop manual for the engine I noticed that the thermostats in the land based engines are all 10*f higher than the marine
engine thermostat. Haven't figured out why yet, they have a different cooling
system (all fresh water), and a heater
system. Can anyone think of why else they would be different?
Originally Posted by jimbunyard
I suppose the most important thing to realize and remember is that the
system is dynamic and operates within a variable set of environmental conditions. If the raw water
is at 45F and the ambient temp is at 90F the engine operating temp, even with all other factors controlled for, will be different than if those two values are reversed. The main reason for the t'stat is to keep the engine operating at as close to a specific temperature as possible.
I didn't mean to give the wrong impression; given the time of year (if you're in the Pacific Northwest), I'd say the temperatures you're running at are at the upper end, in the summer they'll almost certainly run hotter. As A64 says, consider it a little reserve cooling capacity.
As for increasing the operating temperature of the engine there are two sure ways; increasing the load and changing the temperature rating of the t'stat. I would strongly recommend against going to a hotter t'stat, efficiency is one thing, running on the ragged edge between efficiency and overheating
is quite another. Increasing the pressure rating on the cap will increase the boiling point of the coolant, but unless the transfer or production of heat within the engine is changed, the operating temperature will remain the same.
If the heaters you plan to install use engine coolant to heat them, I would expect them to make a difference in the engine operating temp, how much depends on the heaters efficiency. It is conceivable that you'd have to change the t'stat to compensate and if so the radiator cap too, but I'd be very leery. My experience with aluminum head
engines is that they don't like overheating
, so a comfortable temperature cushion is prudent. Better some kind of volume modulating valve (if the heaters don't already have one) and an extra sweater....
Can't imagine any problem (other than forgetting to close them) with a drain valve instead of a plug
, I've got 1/4" ball valves on the block, the exhaust
riser and the muffler
So far it looks like I won't have to change the the radiator cap or the thermostat. We'll see what happen as some of those variables change.
The Dickinson stove
adds a variable as well. After running the system and playing with it all night, it would appear that the Dickinson
has little impact on system temps. The run is so far un-insulated, and far enough away from the engine to have little to no impact. Although it does boost the heat for the final heater
in the system.
I believe I'm starting to get this system working, but have learned to be cautious in my celebrations of my accomplishments
Time to put anti freeze back in, and go for some more sea trials. I'll keep you posted.