Enough heat that I had to add a tempering valve. I've never measure the temp with the espar off and the engine running. I don't know why it wouldn't keep the temps up but I also have a circulation pump in the loop to increase coolant flows when the Espar is off.
2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer
Thanks guys. I didn't even think about a gas fired heater. I'm still not sure which way to go. My pump will do 15 GPM so I suspect the flat plate will cope better with the higher flow. Also the smaller space needs are nice.