Rinnai REU-V2520FFU-US Tankless Water Heater

Old 04-04-21, 10:41 PM
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Rinnai REU-V2520FFU-US Tankless Water Heater

Previous homeowner was the one who had a Rinnai REU-V2520FFU-US installed. I wasn't aware until a month ago that it came with a controller which should have been installed. Bought the house 3 years ago with no controller installed or left behind. Only 1 shower got hot water initially but not that hot. Everything else in the house (minus maybe the washing machine?) got cold water. I bought the mc-601-bk controller since I was told it replaced the mc-91-2-us controller. I don't know how to 100% sync it to the tankless water heater even after finding a manual online. After reading the manual, it's saying a max of 4 controllers could be installed but more than the single master controller is optional. I don't THINK I have warranty on my tankless water heater either. (Serial # 05.06-120823) Rinnai takes a while (2 weeks min) to respond. So I’m wondering if a technician installs the controller, would that controller most likely fix my issue? Should I be going about this a different way?
Old 04-05-21, 09:42 PM
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Welcome to the forums.

I'm not a pro with Rinnai products. I can't for the life of me see why you'd need 4 controllers for the water heater. Regardless of the quantities of remotes.... only one temperature can be set. They show different temps for different areas. That makes absolutely no sense.

You don't need any remote for the water heater to work properly. Having hot water at one location and not others is not a typical water heater issue. The water heater should start instantly as soon as any hot water tap is opened. Is that occurring ?

The remote connects to the heater with two wires. It is polarity sensitive. The unit should be off when the remote is connected. When the unit is repowered.... the remote should be working.

Rinnai manual (pdf)

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