Rinnai RU199i and MC-601 Controller

Billinthemail

Hello,

I'm new to this forum. I am hoping to get some help from the friendly knowledgeable people here.

I have the subject system heating my cabin using radiant heat from the glycol that circulates through the baseboard radiators. The rinnai recirculates water through heat exchanger plates that heats the glycol that runs through the house.

I had set the temp to 165 F for winter, and the system got an error 54. Assuming that the inlet water temp was too high. I had to drive to the cabin in a snow storm for 2 hours and turn off and on the system.

I was not able to turn down the temp from 165 F to 160 F to prevent the error so I unplugged the MC-601 controller. Now I can't get the temp above 140 F needed to prevent the cabin from freezing and having the pipes burst. Temps here can go below -40 F.

Can someone please inform me on how to get the temp back up to 160 F? I cant leave the cabin and go home unless I fix this.

Thank you kindly.

Bill

Teemok

Hi bill, It's my understanding that 140F is the max temperature setting for a non commercial RU199. While I know nothing about your setup domestic water to flat plate to baseboard is generally not an good application for a thankless heater. Code 54 is a high flue temp. That's normally due to scale build up preventing good flame to water transfer. It might need a descale treatment and I would check all pumps operation and a look for possible flow problem. Obviously, make sure the Rinnai inlet filter, if still there, is clean.

Kaos

You need to plug the 601 back in, without that it won't go above 140F.

The issue is you are using baseboard heaters so the return water temp is too high. Ideally you would add more emitters or use higher output ones so you can run at much lower water temp and still heat the place.

Can't do this right now, so you need to get the return temperature down to avoid issues. The simplest is to reduce the flow rate a bit to get the return water temp going into the Rinnai to about 120F. This will reduce the amount of heat your are delivering to the place by a bit but not as much as turning the temp down. That is keep the supply temp at 165 and the return should be 120F.