Rinnai REU-V2520FFU-US Tankless Water Heater

[user 25755]

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?

 

[Mitchell-DIY-Guy]

Hey, just shooting from the hip here, but asking the question, do you really need to constantly fiddle with the temperature? The Rinnai, as all tankless I believe, have a digital temperature setting at the unit. Seems to me you set it and forget it; figure out what set point you need, and leave it alone. These controllers you mention allow remote control (at the bathroom or kitchen for example, instead of at the tankless unit) of the unit.

Go to your bathroom sink, turn on only the hot, and let it run for a few minutes. It should be "too hot" coming out of the faucet (don't we always mix hot and cold to get a comfortable warm, both at a sink and at a shower?). Make sure your Rinnai is firing, and check the set point. Adjust as necessary. From what the controller manual says, you have limited control of temperature WHILE the unit is working.

You may find, for example, that the setpoint is say, 100 degrees. That may simply be too low to get a good shower; you may need it higher. If the setpoint is 120 degrees and only 100 degree water is coming out after a few minutes of running, well you'll have to go higher to compensate for this heat loss along the way.

I have a conventional gas water heater, tank style. We don't fiddle with the temperature. It's set for probably about 120 degrees, and the only time we change that is if we go away, and then we'll turn it down to the vacation setting.

Good luck!

 

[Twowaxhack]

Without the controller the only way to set temp is with changing wiring connectors inside the unit. You can’t get the trouble codes either.

The controller is optional. The unit will operate without it.

Just connect the two wires from the controller to the terminals marked for remote control. They’re screw terminals.

It’s all in the installation manual. It’s really as simple as it sounds.

 

[Mitchell-DIY-Guy]

I guess someone installed it w/o wiring in the INCLUDED controller? Wow.

 

[Twowaxhack]

I guess someone installed it w/o wiring in the INCLUDED controller? Wow.

That unit is sold with or without the controller. The OP might have called Rinnai and according to his serial number they told him it was sold with the remote.

But since the OP isn’t the original owner, it’s not known if the original installer included the remote in the price.

For example,I’ve purchased a tankless with the remote but the customer didn’t want to pay for the remote so I price the job without the remote and keep it.

Installing the remote is not required.

The Only way to get max performance water over 140 is with the remote on some models. I’d have to read the install book on this model to know if this is the case with his.