Nice set up! Do you have all your coolant forced through your HE from the water pump or does it "T" before? I'm asking as forcing it through will make the HE way more efficient but might not work if your in-cab heater isn't turned on hence the possible need to "T" it before the HE...
I'm using a very similar set up but to warm up my veggie oil (WVO powered truck) and might consider adding a second HE in line for hot water.
Well done!
Cheers,
Mr. D