Rinnai I-series tankless combi intermittent E430

[Nhandojo]

Boiler is piped wrong heat side. It needs hydraulic separation and constant flow through it. The built in pump flows enough for one small zone but not the three or four. Primary secondary loop is needed with built in pump just for the boiler another for the zones with some headers instead of all the tees. Are there zone valves?

As much as I don't trust the contractor that installed this system (and I did find mistakes in how they wire the boiler to my existing air handler/thermostat), I think they actually did plumb the CH side correctly. Due to the limited space, the piping is a bit convoluted, and hard to follow from the pics I posted. I drew a diagram to clarify the CH piping (and convince myself that the plumbing is indeed correct).

Closely-spaced tees used provide hydraulic separation between the boiler and the air handler (this is a small system with only a single zone). And water have been circulating to the air handler with no issues.

 

[Nhandojo]

Well my luck ran out (or came in, depending on your perspective). The water heater started acting up a few weeks ago, and rinsing the sensor with tap water only make the problem go away for a week or so.

So I purchased a new sensor (out of pocket, don't have time to spend to convince Rinnai), and voila transient pressure dips go away completely.

Given I now have a completely redundant sensor, I decided to open it up and found that the pinhole was almost completely covered in scale, so much that I originally thought the scale was part of the sensor itself.

There was no component marking on the PCB, but if I have to guess, the pressure sensor part is this (based on looks): Digikey

In 1.5 year or whenever the new sensor starts acting up again, I'll put this old sensor back and see if I'd broken it.

 

[Sponsor]

 

[TonyaGilmore]

Hello! Your Rinnai water heater appears to be having a problem. It's excellent that you have already conducted preliminary examinations and observations to compile data on the issue. One possibility could be a damaged pressure sensor or a cabling or connection issue between the controller and the pressure sensor. Even when the water pressure is within the standard range if the sensor gives erroneous data or does not communicate properly it could still cause the error. Contacting a plumber or a technician experienced with Rinnai water heaters would be preferable. They will be better skilled and equipped to identify the problem.

 

[Fitter30]

Need a piping diagram of both dhw and ch with brand ,model of pumps and type of heat emitters. The gpm flow sensor normally is used just for dhw not ch. Has dhw side been cleaned with vinegar since system is 1.5 years old?

 

[Nhandojo]

To be clear, problem was solved. Pressure sensor was dirty, the transducer hole was caked with what I presume is dissolved minerals. Purchased a new sensor and the problem went away. I then thoroughly cleaned the old sensor, and tried to identify the pressure transducer part so if this happens again I can reuse the old sensor.

Nothing to do with plumbing arrangement, though perhaps related with the use of black iron fittings..

 

[Fitter30]

Dhw side? Needs to be cleaned with vinegar details on you tube and manual. Mineral build up will cause heat exchanger to fail.