Heat cabin with gen coolant? anyone replumb for?

[BluewaveRV]

Our 1994 37'DP HR has a diesel 3 cylinder coolant cooled 7.5KW generator.
Sure would be great to use the waisted heat to heat the cabin when it is running.
HAS ANYONE DONE THIS???
I was thinking I could use the dash heater but would require two check valves & rewiring the fan motor to run off the cabin batteries that would be charged by the generator. But that would heat the front & leave the bedroom cold.
ANY IDEAS???

PS our ONAN diesel gen is a sweet running reliable unit. I have seen & heard the gasoline ONAN gen are just the opposite & the people that I know have replaced them.

John

[Roy-c]

Not enough engine, creating not enough heat to make a real difference. Think about how much heat the front heater/ defroster puts out. And that is from a big block engine. Great idea but a genset engine just isn't big enough. I wish it were.

[Bylandorsea]

I like the way you are thinking, I am not sure how cost effective it would be

[BonS]

Roy-c is correct if you use both the external radiator as well as the dash heat exchanger. Too much of the available heat will be wasted in the radiator. If most, if not all, of the waste heat were able to be directed into the cabin, and if your gen is actually producing 7.5kw of energy and it's around 40% efficient then there is 4500 watts of wasted, heat, energy to be scavenged. That's about 3, 1500 watt, space heaters. Not bad. But, if the radiator is throwing off 2/3-3/4 of the heat then you're down around 1000-1500 watts of energy as heat. It's certainly a lot easier to plug in a space heater or two into that 7.5kw generator and get the heat where you want it.

[Stevens10]

Originally Posted by BluewaveRV

Our 1994 37'DP HR has a diesel 3 cylinder coolant cooled 7.5KW generator.
Sure would be great to use the waisted heat to heat the cabin when it is running.
HAS ANYONE DONE THIS???
I was thinking I could use the dash heater but would require two check valves & rewiring the fan motor to run off the cabin batteries that would be charged by the generator. But that would heat the front & leave the bedroom cold.
ANY IDEAS???

PS our ONAN diesel gen is a sweet running reliable unit. I have seen & heard the gasoline ONAN gen are just the opposite & the people that I know have replaced them.

John

As a general rule the energy input to an internal combustion engine goes 1/3 to output power, 1/3 to exhaust heat, and 1/3 to radiator. Given that the diesel is probably around 38% efficient compared to a gas engine at 32% you should be able to capture 30/38 x7500 watts 3.4 BTU/watt or approximately 20K BTU. This is assuming that you can divert the flow entirely from the radiator and that the genset is at full load. Since both of these things are probably not true, your available heat would be more likely to be 10K BTU or less.

The plumbing to divert the coolant and to get the flow back to the bedroom area would be major, then you would have to find a location to put the coil and fan and controls.

I am fearless when it comes to engineering out of the box solutions, (check out some of my other posts), as a result of spending a long career as a mechanical engineer in the HVAC and process piping field, but even I would hesitate to do this.

I will admit the idea intrigued me at first glance but after I started thinking about the application I quickly decided that it was not a great idea.