First - Thanks to all that replied.
I agree with RSI. If I hook up a plate HX, it needs to be before the HWH. Otherwise, why have a HWH? If I preheat the water GOING to the HWH my electric use in winter time will be very little. If after the HWH I still have to heat the water in the tank unless I leave the breaker off. I need to price and size a Plate HX.
Comments?
Yes, I have a comment.
When you have a fire in the OWB, you turn OFF the HWH. That is the whole idea. People want to heat water, let it sit in a tank to "cool" then heat water to mix into 30, 40, or 50 gals of "cooled" water. Why folks do this is beyond me. You "loose" heat from the water coming out of the HX to the tank water. Leaving the HWH ON and "pre-heating" the water going in with a HX is missing the whole point also. If you put in a HX before the tank AND a side arm to keep it hot is just a waste of money.
I have a propane HWH that is turned OFF during my burning season. If for some reason my OWB stops producing hot water, I just light my HWH. Yes, it may take 15 mins to heat the tank but I have never in my life needed hot water faster than that. TRUST me, in the summer when OWB is off and circulater pump is off, my HWH water going through my HX is NOT affected by it.
One last question, if you put 175 degree water from your HX "into" your tank..........you are using "lots" of hot water.....so all the water is replaced with nice fresh HOT water........what is your tank safety valve temp setting? I'll bet it's not more than 175
In any case, enjoy your OWB........