We have a Tankless Hot water heating system, in fact we have two units, home is approx 3400 sq.ft. our problem hot wate not hot, we keep getting cool water, then warm to hot, back to cooler water. Showers, start cool, to luke warm to hot back to cool then again back to hot and staying hot rest of shower. Someone told me this is called "Sandwich water flow. The home is two years old, but Brand new, was up for Sale, so no one actually lived in it until now. HOW CAN WE CORRECT THIS SITUATION? HELP!

When they work, there will be a endless supply of hot water,
Most have a flow switch that requires a volume and/or pressure to be passing though the system before the heat will kick in. If the water going though is not meeting that requirement, often the system will not come on.

Most are gas operated, since you moved in, was the system cleaned and adjusted.

Hi, Fr_Chuck, thanks for your response, as far as I know no one checked or clean out anything in the units. You talk about a flow switch... where would this flow switch located?
It much be a switch that is programed, is that it?

Brand and Exact model.

What you mentioned is not unusual for tankless and there can be a few reasons. If the home is essentially new then you should have some kind of warranty. Have the builder, or their plumber that subs, come back and address this issue.

Hi HVAC1000 thanks for your response, the units are Rinnai. Model R85e (2532W)

Incoming hot water inconsistent, starts cool/cold to warm to hot but not scalding, then back to cool, for a while (?seconds) then hot again. Sink faucets similar, but once in while, one coulf turn on the faucet and receive warm to hot immediately. It is very, inconsistent.

The E in the model number indicates it is a exterior model only is that correct and it is on the exterior of the home?

Try and get the error codes that are in memory
Press on/off button once then hit the up temperature arrow. Post the codes on your reply.

One last item are the heaters piped together outside? Side by side etc.

Here is the factory install manual.

http://www.foreverhotwater.com/pdf/r85e-io.pdf

I also suggest you read the warranty. Since you are the first owner the warranty should start with you. If that is the case you are under warranty so I would call the company and have them recommend a service person in your area for warranty service.

Hi, HVAC1000, I sent this message and not sure it was received so Please forgive me if this is duplicated.

The E in the model number indicates it is a exterior model only is that correct and it is on the exterior of the home?

Try and get the error codes that are in memory
Press on/off button once then hit the up temperature arrow. Post the codes on your reply.

One last item are the heaters piped together outside? Side by side etc.


Yes, these models are Exterior units, installed on outer wall of house.

I followed you instructions and no Error message, screen was Blank, after I clicked on/off once then the up arrow button... no error messages on both units.

Thanks

Havc1000

Thanks for your help, shall do, we are working on it, I just wanted to have some information so I could speak with some knowledge... Thanks again.