Rinnai tankless heaters

I'm getting a Rinnai tankless water heater installed by the Gas company in our area. Our bathroom is on the second floor on the opposite wall from the heater and will take quite a while for hot water to get there. These things are supposed to have a circulating pump that takes care of that problem. Or so they tell me. I had a gravity circulating system many years ago in a basement with a standard tank type heater and it worked perfect. However it required a return line.

I am getting all kinds of explanations about how this circulator system on the Rinnai works. Anywhere from a loop in the farthest bathroom between the hot and cold water lines to the unit just having a small expansion tank internally. Now, I'm a Well Driller not a genius, but can anyone explain how these things work if at all, or am I being lied to?

The only one of these that I have installed I had the option to put in a proper recirc line while the walls and ceiling were open, which I did.

The unit that I installed had an onboard recirc pump, which "learned" the habits of the users. The system will also work with a crossover valve on the farthest sink, which will shut down the recirc when there is a rise in water temperature at that point.

Don't be surprised if there is a little bit of warm water in the cold water piping when you first turn on the faucet.

I wonder if the recirc pump that supposedly build into the one I have can be used to resurc through a return line because I do have that if needed.

Let me know the model #, and I will look into it a little bit.

But my guess is that it can. No reason that I can think of that it would *have* to use a crossover recirculation setup.

But if it is plumbed into a dedicated recirc line, it needs to be done correctly, or you can run into problems.

Phish,

The model # is Rinnai RUR98EP- tankless, outdoor, recirculating, water heater. The tank is in the ground but the heater hasn't been installed yet, so it isn't too late to change models if necessary.

Thanks...

I installed one of those late last year, exact same model except it was a natural gas unit. It works just fine with a dedicated recirculation line. It needs to have a check valve on the cold water inlet, and a check valve on the recirc line before it ties back into the cold. And, since that creates a closed system, Rinnai requires that a thermal expansion tank is installed.

That helps make me feel a lot better. I can understand the check valves. When tying back into the unit. Where do I actually tie in?

Cold feed between the main check valve and the unit.

Ok got it. Thanks

I had heard a few issues arising with the Rinnai, not sure to what extend. I hope yours doesn't come up with any issue.
Best wishes with the new install.

We are still in the renovation however things are getting close to a finish. The Rinnai heats water just fine. I have finally figured out how to make it heat on a schedule by using the hand held mini Ipad or whatever it's called. One morning the cold water was quite warm for quite a while. Can't explain that any other way other than the swing check isn't seating completely. We are using a dedicated loop which seems to work great for the most part except for the few unexplained glitches. I will probably change the swing check just to see if the hot/cold stops occurring.

I thought it was odd that the installers from the Gas company knew about as much about this thing as I did. We kind of learned together. Good thing they were nice guys and had a sense of humor.

Thsnks for the help Phish and the good wishes from Orbster89.