Plumbing is a *system* and can be quite complex!
Basically the water entering the water heater needs to be hot when it enters.
As you use hot water, you wouldn't want to be drawing water from the OWB pipes unless it was hot. If there is 100 ft. to the OWB, then maybe the water in the pipes in-between is cold?
One way to solve this problem is for the cold water supply (city/well water) to the hot water heater be just before the OWB or on the cold side of the OWB. And a check valve so that this water can only flow to the water heater via the coils in the OWB. Not back through the return from the water heater.
Then the water from the OWB would be routed to the cold inlet on the water heater. And from there a check valve, then the city cold water supply connection, then return to the OWB. So cold city water would enter the return pipe, and the check valve would force it to go through the OWB before it could get to the hot water heater.
Then run your pump before taking a shower. This will circulate the water in the 100 ft of pipe and heat fill it with hot water.
Then turn off pump and take your shower. Cold water will flow through the OBW first, be heated, and hot water will then enter the cold side of your hot water heater.
The test will be to feel the pipes at the cold entry to the hot water heater...
Turn on the pump, then after awhile the feed and return from the OWB will be hot, but the cold entry to the hot water heater will remain cooler.
Then turn off the pump and run the shower. Then the hot water will then enter the cold inlet of the hot water heater.
..............................................................Cold City water
WH cold inlet: _____Check Valve ->_________|_______>________
...................T_____________________<________pump________| OWB coil
Basically the water entering the water heater needs to be hot when it enters.
As you use hot water, you wouldn't want to be drawing water from the OWB pipes unless it was hot. If there is 100 ft. to the OWB, then maybe the water in the pipes in-between is cold?
One way to solve this problem is for the cold water supply (city/well water) to the hot water heater be just before the OWB or on the cold side of the OWB. And a check valve so that this water can only flow to the water heater via the coils in the OWB. Not back through the return from the water heater.
Then the water from the OWB would be routed to the cold inlet on the water heater. And from there a check valve, then the city cold water supply connection, then return to the OWB. So cold city water would enter the return pipe, and the check valve would force it to go through the OWB before it could get to the hot water heater.
Then run your pump before taking a shower. This will circulate the water in the 100 ft of pipe and heat fill it with hot water.
Then turn off pump and take your shower. Cold water will flow through the OBW first, be heated, and hot water will then enter the cold side of your hot water heater.
The test will be to feel the pipes at the cold entry to the hot water heater...
Turn on the pump, then after awhile the feed and return from the OWB will be hot, but the cold entry to the hot water heater will remain cooler.
Then turn off the pump and run the shower. Then the hot water will then enter the cold inlet of the hot water heater.
..............................................................Cold City water
WH cold inlet: _____Check Valve ->_________|_______>________
...................T_____________________<________pump________| OWB coil
